qopenglpaintengine.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
/*
    When the active program changes, we need to update it's uniforms.
    We could track state for each program and only update stale uniforms
        - Could lead to lots of overhead if there's a lot of programs
    We could update all the uniforms when the program changes
        - Could end up updating lots of uniforms which don't need updating
 
    Updating uniforms should be cheap, so the overhead of updating up-to-date
    uniforms should be minimal. It's also less complex.
 
    Things which _may_ cause a different program to be used:
        - Change in brush/pen style
        - Change in painter opacity
        - Change in composition mode
 
    Whenever we set a mode on the shader manager - it needs to tell us if it had
    to switch to a different program.
 
    The shader manager should only switch when we tell it to. E.g. if we set a new
    brush style and then switch to transparent painter, we only want it to compile
    and use the correct program when we really need it.
*/
 
// #define QT_OPENGL_CACHE_AS_VBOS
 
#include <private/qopenglgradientcache_p.h>
#include <private/qopengltexturecache_p.h>
#include "qopenglpaintengine_p.h"
#include "qopenglpaintdevice_p.h"
 
#include <string.h> //for memcpy
#include <qmath.h>
 
#include <private/qopengl_p.h>
#include <private/qopenglcontext_p.h>
#include <private/qopenglextensions_p.h>
#include <private/qpaintengineex_p.h>
#include <QPaintEngine>
#include <private/qpainter_p.h>
#include <private/qfontengine_p.h>
#include <private/qdatabuffer_p.h>
#include <private/qstatictext_p.h>
#include <private/qtriangulator_p.h>
 
#include <private/qopenglengineshadermanager_p.h>
#include <private/qopengl2pexvertexarray_p.h>
#include <private/qopengltextureglyphcache_p.h>
 
#include <QDebug>
 
#include <qtopengl_tracepoints_p.h>
 
#ifndef GL_KHR_blend_equation_advanced
#define GL_KHR_blend_equation_advanced 1
#define GL_MULTIPLY_KHR                   0x9294
#define GL_SCREEN_KHR                     0x9295
#define GL_OVERLAY_KHR                    0x9296
#define GL_DARKEN_KHR                     0x9297
#define GL_LIGHTEN_KHR                    0x9298
#define GL_COLORDODGE_KHR                 0x9299
#define GL_COLORBURN_KHR                  0x929A
#define GL_HARDLIGHT_KHR                  0x929B
#define GL_SOFTLIGHT_KHR                  0x929C
#define GL_DIFFERENCE_KHR                 0x929E
#define GL_EXCLUSION_KHR                  0x92A0
#endif /* GL_KHR_blend_equation_advanced */
 
#ifndef GL_KHR_blend_equation_advanced_coherent
#define GL_KHR_blend_equation_advanced_coherent 1
#define GL_BLEND_ADVANCED_COHERENT_KHR    0x9285
#endif /* GL_KHR_blend_equation_advanced_coherent */
 
QT_BEGIN_NAMESPACE
 
 
Q_GUI_EXPORT QImage qt_imageForBrush(int brushStyle, bool invert);
 
////////////////////////////////// Private Methods //////////////////////////////////////////
 
QOpenGL2PaintEngineExPrivate::~QOpenGL2PaintEngineExPrivate()
{
    delete shaderManager;
 
    vertexBuffer.destroy();
    texCoordBuffer.destroy();
    opacityBuffer.destroy();
    indexBuffer.destroy();
    vao.destroy();
 
    if (elementIndicesVBOId != 0) {
        funcs.glDeleteBuffers(1, &elementIndicesVBOId);
        elementIndicesVBOId = 0;
    }
}
 
inline QColor qt_premultiplyColor(QColor c, GLfloat opacity)
{
    qreal alpha = c.alphaF() * opacity;
    c.setAlphaF(alpha);
    c.setRedF(c.redF() * alpha);
    c.setGreenF(c.greenF() * alpha);
    c.setBlueF(c.blueF() * alpha);
    return c;
}
 
 
void QOpenGL2PaintEngineExPrivate::setBrush(const QBrush& brush)
{
    if (qbrush_fast_equals(currentBrush, brush))
        return;
 
    const Qt::BrushStyle newStyle = qbrush_style(brush);
    Q_ASSERT(newStyle != Qt::NoBrush);
 
    currentBrush = brush;
    if (!currentBrushImage.isNull())
        currentBrushImage = QImage();
    brushUniformsDirty = true; // All brushes have at least one uniform
 
    if (newStyle > Qt::SolidPattern)
        brushTextureDirty = true;
 
    if (currentBrush.style() == Qt::TexturePattern
        && qHasPixmapTexture(brush) && brush.texture().isQBitmap())
    {
        shaderManager->setSrcPixelType(QOpenGLEngineShaderManager::TextureSrcWithPattern);
    } else {
        shaderManager->setSrcPixelType(newStyle);
    }
    shaderManager->optimiseForBrushTransform(currentBrush.transform().type());
}
 
 
void QOpenGL2PaintEngineExPrivate::useSimpleShader()
{
    shaderManager->useSimpleProgram();
 
    if (matrixDirty)
        updateMatrix();
}
 
/*
    Single entry-point for activating, binding, and setting properties.
 
    Allows keeping track of (caching) the latest texture unit and bound
    texture in a central place, so that we can skip re-binding unless
    needed.
 
    \note Any code or Qt API that internally activates or binds will
    not affect the cache used by this function, which means they will
    lead to inconsistent state. QPainter::beginNativePainting() takes
    care of resetting the cache, so for user–code this is fine, but
    internally in the paint engine care must be taken to not call
    functions that may activate or bind under our feet.
*/
template<typename T>
void QOpenGL2PaintEngineExPrivate::updateTexture(GLenum textureUnit, const T &texture, GLenum wrapMode, GLenum filterMode, TextureUpdateMode updateMode)
{
    static const GLenum target = GL_TEXTURE_2D;
    bool newTextureCreated = false;
 
    activateTextureUnit(textureUnit);
 
    GLuint textureId = bindTexture(texture, &newTextureCreated);
 
    if (newTextureCreated)
        lastTextureUsed = GLuint(-1);
 
    if (updateMode == UpdateIfNeeded && textureId == lastTextureUsed)
        return;
 
    lastTextureUsed = textureId;
 
    funcs.glTexParameteri(target, GL_TEXTURE_WRAP_S, wrapMode);
    funcs.glTexParameteri(target, GL_TEXTURE_WRAP_T, wrapMode);
 
    funcs.glTexParameteri(target, GL_TEXTURE_MAG_FILTER, filterMode);
    funcs.glTexParameteri(target, GL_TEXTURE_MIN_FILTER, filterMode);
}
 
void QOpenGL2PaintEngineExPrivate::activateTextureUnit(GLenum textureUnit)
{
    if (textureUnit != lastTextureUnitUsed) {
        funcs.glActiveTexture(GL_TEXTURE0 + textureUnit);
        lastTextureUnitUsed = textureUnit;
 
        // We simplify things by keeping a single cached value of the last
        // texture that was bound, instead of one per texture unit. This
        // means that switching texture units could potentially mean we
        // need a re-bind and corresponding parameter updates.
        lastTextureUsed = GLuint(-1);
    }
}
 
template<>
GLuint QOpenGL2PaintEngineExPrivate::bindTexture(const GLuint &textureId, bool *newTextureCreated)
{
    if (newTextureCreated)
        *newTextureCreated = false;
 
    if (textureId != lastTextureUsed)
        funcs.glBindTexture(GL_TEXTURE_2D, textureId);
 
    return textureId;
}
 
template<>
GLuint QOpenGL2PaintEngineExPrivate::bindTexture(const QImage &image, bool *newTextureCreated)
{
    QOpenGLTextureCache::BindResult result = QOpenGLTextureCache::cacheForContext(ctx)->bindTexture(ctx, image);
    if (newTextureCreated)
        *newTextureCreated = result.flags.testFlag(QOpenGLTextureCache::BindResultFlag::NewTexture);
    return result.id;
}
 
template<>
GLuint QOpenGL2PaintEngineExPrivate::bindTexture(const QPixmap &pixmap, bool *newTextureCreated)
{
    QOpenGLTextureCache::BindResult result = QOpenGLTextureCache::cacheForContext(ctx)->bindTexture(ctx, pixmap);
    if (newTextureCreated)
        *newTextureCreated = result.flags.testFlag(QOpenGLTextureCache::BindResultFlag::NewTexture);
    return result.id;
}
 
template<>
GLuint QOpenGL2PaintEngineExPrivate::bindTexture(const QGradient &gradient, bool *newTextureCreated)
{
    // We apply global opacity in the fragment shaders, so we always pass 1.0
    // for opacity to the cache.
    GLuint textureId = QOpenGL2GradientCache::cacheForContext(ctx)->getBuffer(gradient, 1.0);
 
    // QOpenGL2GradientCache::getBuffer() may bind and generate a new texture if it
    // hasn't been cached yet, but will otherwise return an unbound texture id. To
    // be sure that the texture is bound, we unfortunately have to bind again,
    // which results in the initial generation of the texture doing two binds.
    return bindTexture(textureId, newTextureCreated);
}
 
struct ImageWithBindOptions
{
    const QImage &image;
    QOpenGLTextureUploader::BindOptions options;
};
 
template<>
GLuint QOpenGL2PaintEngineExPrivate::bindTexture(const ImageWithBindOptions &imageWithOptions, bool *newTextureCreated)
{
    QOpenGLTextureCache::BindResult result = QOpenGLTextureCache::cacheForContext(ctx)->bindTexture(ctx,
                                                                                                    imageWithOptions.image,
                                                                                                    imageWithOptions.options);
    if (newTextureCreated)
        *newTextureCreated = result.flags.testFlag(QOpenGLTextureCache::BindResultFlag::NewTexture);
    return result.id;
}
 
inline static bool isPowerOfTwo(int x)
{
    // Assumption: x >= 1
    return x == (x & -x);
}
 
void QOpenGL2PaintEngineExPrivate::updateBrushTexture()
{
    Q_Q(QOpenGL2PaintEngineEx);
//     qDebug("QOpenGL2PaintEngineExPrivate::updateBrushTexture()");
    Qt::BrushStyle style = currentBrush.style();
 
    bool smoothPixmapTransform = q->state()->renderHints & QPainter::SmoothPixmapTransform;
    GLenum filterMode = smoothPixmapTransform ? GL_LINEAR : GL_NEAREST;
 
    if ( (style >= Qt::Dense1Pattern) && (style <= Qt::DiagCrossPattern) ) {
        // Get the image data for the pattern
        QImage textureImage = qt_imageForBrush(style, false);
 
        updateTexture(QT_BRUSH_TEXTURE_UNIT, textureImage, GL_REPEAT, filterMode, ForceUpdate);
    }
    else if (style >= Qt::LinearGradientPattern && style <= Qt::ConicalGradientPattern) {
        // Gradiant brush: All the gradiants use the same texture
 
        const QGradient *gradient = currentBrush.gradient();
 
        GLenum wrapMode = GL_CLAMP_TO_EDGE;
        if (gradient->spread() == QGradient::RepeatSpread || gradient->type() == QGradient::ConicalGradient)
            wrapMode = GL_REPEAT;
        else if (gradient->spread() == QGradient::ReflectSpread)
            wrapMode = GL_MIRRORED_REPEAT;
 
        updateTexture(QT_BRUSH_TEXTURE_UNIT, *gradient, wrapMode, filterMode, ForceUpdate);
    }
    else if (style == Qt::TexturePattern) {
        currentBrushImage = currentBrush.textureImage();
 
        int max_texture_size = ctx->d_func()->maxTextureSize();
        QSize newSize = currentBrushImage.size();
        newSize = newSize.boundedTo(QSize(max_texture_size, max_texture_size));
        if (!QOpenGLContext::currentContext()->functions()->hasOpenGLFeature(QOpenGLFunctions::NPOTTextureRepeat)) {
            if (!isPowerOfTwo(newSize.width()) || !isPowerOfTwo(newSize.height())) {
                newSize.setHeight(qNextPowerOfTwo(newSize.height() - 1));
                newSize.setWidth(qNextPowerOfTwo(newSize.width() - 1));
            }
        }
        if (currentBrushImage.size() != newSize)
            currentBrushImage = currentBrushImage.scaled(newSize, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
 
        GLuint wrapMode = GL_REPEAT;
 
        updateTexture(QT_BRUSH_TEXTURE_UNIT, currentBrushImage, wrapMode, filterMode, ForceUpdate);
    }
    brushTextureDirty = false;
}
 
 
void QOpenGL2PaintEngineExPrivate::updateBrushUniforms()
{
//     qDebug("QOpenGL2PaintEngineExPrivate::updateBrushUniforms()");
    Qt::BrushStyle style = currentBrush.style();
 
    if (style == Qt::NoBrush)
        return;
 
    QTransform brushQTransform = currentBrush.transform();
    bool isCosmetic = false;
 
    if (style == Qt::SolidPattern) {
        QColor col = qt_premultiplyColor(currentBrush.color(), (GLfloat)q->state()->opacity);
        shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::FragmentColor), col);
    }
    else {
        // All other brushes have a transform and thus need the translation point:
        QPointF translationPoint;
 
        if (style <= Qt::DiagCrossPattern) {
            QColor col = qt_premultiplyColor(currentBrush.color(), (GLfloat)q->state()->opacity);
 
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::PatternColor), col);
 
            QVector2D halfViewportSize(width*0.5, height*0.5);
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::HalfViewportSize), halfViewportSize);
 
            isCosmetic = !q->painter()->testRenderHint(QPainter::NonCosmeticBrushPatterns);
        }
        else if (style == Qt::LinearGradientPattern) {
            const QLinearGradient *g = static_cast<const QLinearGradient *>(currentBrush.gradient());
 
            QPointF realStart = g->start();
            QPointF realFinal = g->finalStop();
            translationPoint = realStart;
 
            QPointF l = realFinal - realStart;
 
            QVector3D linearData(
                l.x(),
                l.y(),
                1.0f / (l.x() * l.x() + l.y() * l.y())
            );
 
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::LinearData), linearData);
 
            QVector2D halfViewportSize(width*0.5, height*0.5);
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::HalfViewportSize), halfViewportSize);
        }
        else if (style == Qt::ConicalGradientPattern) {
            const QConicalGradient *g = static_cast<const QConicalGradient *>(currentBrush.gradient());
            translationPoint   = g->center();
 
            GLfloat angle = -qDegreesToRadians(g->angle());
 
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::Angle), angle);
 
            QVector2D halfViewportSize(width*0.5, height*0.5);
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::HalfViewportSize), halfViewportSize);
        }
        else if (style == Qt::RadialGradientPattern) {
            const QRadialGradient *g = static_cast<const QRadialGradient *>(currentBrush.gradient());
            QPointF realCenter = g->center();
            QPointF realFocal  = g->focalPoint();
            qreal   realRadius = g->centerRadius() - g->focalRadius();
            translationPoint   = realFocal;
 
            QPointF fmp = realCenter - realFocal;
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::Fmp), fmp);
 
            GLfloat fmp2_m_radius2 = -fmp.x() * fmp.x() - fmp.y() * fmp.y() + realRadius*realRadius;
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::Fmp2MRadius2), fmp2_m_radius2);
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::Inverse2Fmp2MRadius2),
                                                             GLfloat(1.0 / (2.0*fmp2_m_radius2)));
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::SqrFr),
                                                             GLfloat(g->focalRadius() * g->focalRadius()));
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::BRadius),
                                                             GLfloat(2 * (g->centerRadius() - g->focalRadius()) * g->focalRadius()),
                                                             g->focalRadius(),
                                                             g->centerRadius() - g->focalRadius());
 
            QVector2D halfViewportSize(width*0.5, height*0.5);
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::HalfViewportSize), halfViewportSize);
        }
        else if (style == Qt::TexturePattern) {
            const QPixmap& texPixmap = currentBrush.texture();
 
            if (qHasPixmapTexture(currentBrush) && currentBrush.texture().isQBitmap()) {
                QColor col = qt_premultiplyColor(currentBrush.color(), (GLfloat)q->state()->opacity);
                shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::PatternColor), col);
            }
 
            QSizeF invertedTextureSize(1.0 / texPixmap.width(), 1.0 / texPixmap.height());
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::InvertedTextureSize), invertedTextureSize);
 
            QVector2D halfViewportSize(width*0.5, height*0.5);
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::HalfViewportSize), halfViewportSize);
        }
        else
            qWarning("QOpenGL2PaintEngineEx: Unimplemented fill style");
 
        const QPointF &brushOrigin = q->state()->brushOrigin;
        QTransform matrix;
        if (!isCosmetic)
            matrix = q->state()->matrix;
        matrix.translate(brushOrigin.x(), brushOrigin.y());
        if (!isCosmetic)
            matrix = brushQTransform * matrix;
 
        QTransform translate(1, 0, 0, 1, -translationPoint.x(), -translationPoint.y());
        qreal m22 = -1;
        qreal dy = height;
        if (device->paintFlipped()) {
            m22 = 1;
            dy = 0;
        }
        QTransform gl_to_qt(1, 0, 0, m22, 0, dy);
        QTransform inv_matrix = gl_to_qt * matrix.inverted() * translate;
 
        shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::BrushTransform), inv_matrix);
        shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::BrushTexture), QT_BRUSH_TEXTURE_UNIT);
    }
    brushUniformsDirty = false;
}
 
 
// This assumes the shader manager has already setup the correct shader program
void QOpenGL2PaintEngineExPrivate::updateMatrix()
{
//     qDebug("QOpenGL2PaintEngineExPrivate::updateMatrix()");
 
    const QTransform& transform = q->state()->matrix;
 
    // The projection matrix converts from Qt's coordinate system to GL's coordinate system
    //    * GL's viewport is 2x2, Qt's is width x height
    //    * GL has +y -> -y going from bottom -> top, Qt is the other way round
    //    * GL has [0,0] in the center, Qt has it in the top-left
    //
    // This results in the Projection matrix below, which is multiplied by the painter's
    // transformation matrix, as shown below:
    //
    //                Projection Matrix                      Painter Transform
    // ------------------------------------------------   ------------------------
    // | 2.0 / width  |      0.0      |     -1.0      |   |  m11  |  m21  |  dx  |
    // |     0.0      | -2.0 / height |      1.0      | * |  m12  |  m22  |  dy  |
    // |     0.0      |      0.0      |      1.0      |   |  m13  |  m23  |  m33 |
    // ------------------------------------------------   ------------------------
    //
    // NOTE: The resultant matrix is also transposed, as GL expects column-major matracies
 
    const GLfloat wfactor = 2.0f / width;
    GLfloat hfactor = -2.0f / height;
 
    GLfloat dx = transform.dx();
    GLfloat dy = transform.dy();
 
    if (device->paintFlipped()) {
        hfactor *= -1;
        dy -= height;
    }
 
    // Non-integer translates can have strange effects for some rendering operations such as
    // anti-aliased text rendering. In such cases, we snap the translate to the pixel grid.
    if (snapToPixelGrid && transform.type() == QTransform::TxTranslate) {
        // 0.50 needs to rounded down to 0.0 for consistency with raster engine:
        dx = std::ceil(dx - 0.5f);
        dy = std::ceil(dy - 0.5f);
    }
    pmvMatrix[0][0] = (wfactor * transform.m11())  - transform.m13();
    pmvMatrix[1][0] = (wfactor * transform.m21())  - transform.m23();
    pmvMatrix[2][0] = (wfactor * dx) - transform.m33();
    pmvMatrix[0][1] = (hfactor * transform.m12())  + transform.m13();
    pmvMatrix[1][1] = (hfactor * transform.m22())  + transform.m23();
    pmvMatrix[2][1] = (hfactor * dy) + transform.m33();
    pmvMatrix[0][2] = transform.m13();
    pmvMatrix[1][2] = transform.m23();
    pmvMatrix[2][2] = transform.m33();
 
    // 1/10000 == 0.0001, so we have good enough res to cover curves
    // that span the entire widget...
    inverseScale = qMax(1 / qMax( qMax(qAbs(transform.m11()), qAbs(transform.m22())),
                                  qMax(qAbs(transform.m12()), qAbs(transform.m21())) ),
                        qreal(0.0001));
 
    matrixDirty = false;
    matrixUniformDirty = true;
 
    // Set the PMV matrix attribute. As we use an attributes rather than uniforms, we only
    // need to do this once for every matrix change and persists across all shader programs.
    funcs.glVertexAttrib3fv(QT_PMV_MATRIX_1_ATTR, pmvMatrix[0]);
    funcs.glVertexAttrib3fv(QT_PMV_MATRIX_2_ATTR, pmvMatrix[1]);
    funcs.glVertexAttrib3fv(QT_PMV_MATRIX_3_ATTR, pmvMatrix[2]);
 
    dasher.setInvScale(inverseScale);
    stroker.setInvScale(inverseScale);
}
 
 
void QOpenGL2PaintEngineExPrivate::updateCompositionMode()
{
    // NOTE: The entire paint engine works on pre-multiplied data - which is why some of these
    //       composition modes look odd.
//     qDebug() << "QOpenGL2PaintEngineExPrivate::updateCompositionMode() - Setting GL composition mode for " << q->state()->composition_mode;
    if (ctx->functions()->hasOpenGLFeature(QOpenGLFunctions::BlendEquationAdvanced)) {
       if (q->state()->composition_mode <= QPainter::CompositionMode_Plus) {
           funcs.glDisable(GL_BLEND_ADVANCED_COHERENT_KHR);
           funcs.glBlendEquation(GL_FUNC_ADD);
       } else {
           funcs.glEnable(GL_BLEND_ADVANCED_COHERENT_KHR);
       }
       shaderManager->setCompositionMode(q->state()->composition_mode);
    } else {
        if (q->state()->composition_mode > QPainter::CompositionMode_Plus) {
            qWarning("Unsupported composition mode");
            compositionModeDirty = false;
            return;
        }
    }
    switch(q->state()->composition_mode) {
    case QPainter::CompositionMode_SourceOver:
        funcs.glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
        break;
    case QPainter::CompositionMode_DestinationOver:
        funcs.glBlendFunc(GL_ONE_MINUS_DST_ALPHA, GL_ONE);
        break;
    case QPainter::CompositionMode_Clear:
        funcs.glBlendFunc(GL_ZERO, GL_ZERO);
        break;
    case QPainter::CompositionMode_Source:
        funcs.glBlendFunc(GL_ONE, GL_ZERO);
        break;
    case QPainter::CompositionMode_Destination:
        funcs.glBlendFunc(GL_ZERO, GL_ONE);
        break;
    case QPainter::CompositionMode_SourceIn:
        funcs.glBlendFunc(GL_DST_ALPHA, GL_ZERO);
        break;
    case QPainter::CompositionMode_DestinationIn:
        funcs.glBlendFunc(GL_ZERO, GL_SRC_ALPHA);
        break;
    case QPainter::CompositionMode_SourceOut:
        funcs.glBlendFunc(GL_ONE_MINUS_DST_ALPHA, GL_ZERO);
        break;
    case QPainter::CompositionMode_DestinationOut:
        funcs.glBlendFunc(GL_ZERO, GL_ONE_MINUS_SRC_ALPHA);
        break;
    case QPainter::CompositionMode_SourceAtop:
        funcs.glBlendFunc(GL_DST_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
        break;
    case QPainter::CompositionMode_DestinationAtop:
        funcs.glBlendFunc(GL_ONE_MINUS_DST_ALPHA, GL_SRC_ALPHA);
        break;
    case QPainter::CompositionMode_Xor:
        funcs.glBlendFunc(GL_ONE_MINUS_DST_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
        break;
    case QPainter::CompositionMode_Plus:
        funcs.glBlendFunc(GL_ONE, GL_ONE);
        break;
    case QPainter::CompositionMode_Multiply:
        funcs.glBlendEquation(GL_MULTIPLY_KHR);
        break;
    case QPainter::CompositionMode_Screen:
        funcs.glBlendEquation(GL_SCREEN_KHR);
        break;
    case QPainter::CompositionMode_Overlay:
        funcs.glBlendEquation(GL_OVERLAY_KHR);
        break;
    case QPainter::CompositionMode_Darken:
        funcs.glBlendEquation(GL_DARKEN_KHR);
        break;
    case QPainter::CompositionMode_Lighten:
        funcs.glBlendEquation(GL_LIGHTEN_KHR);
        break;
    case QPainter::CompositionMode_ColorDodge:
        funcs.glBlendEquation(GL_COLORDODGE_KHR);
        break;
    case QPainter::CompositionMode_ColorBurn:
        funcs.glBlendEquation(GL_COLORBURN_KHR);
        break;
    case QPainter::CompositionMode_HardLight:
        funcs.glBlendEquation(GL_HARDLIGHT_KHR);
        break;
    case QPainter::CompositionMode_SoftLight:
        funcs.glBlendEquation(GL_SOFTLIGHT_KHR);
        break;
    case QPainter::CompositionMode_Difference:
        funcs.glBlendEquation(GL_DIFFERENCE_KHR);
        break;
    case QPainter::CompositionMode_Exclusion:
        funcs.glBlendEquation(GL_EXCLUSION_KHR);
        break;
    default:
        qWarning("Unsupported composition mode");
        break;
    }
 
    compositionModeDirty = false;
}
 
static inline void setCoords(GLfloat *coords, const QOpenGLRect &rect)
{
    coords[0] = rect.left;
    coords[1] = rect.top;
    coords[2] = rect.right;
    coords[3] = rect.top;
    coords[4] = rect.right;
    coords[5] = rect.bottom;
    coords[6] = rect.left;
    coords[7] = rect.bottom;
}
 
void Q_TRACE_INSTRUMENT(qtopengl) QOpenGL2PaintEngineExPrivate::drawTexture(const QOpenGLRect& dest, const QOpenGLRect& src, const QSize &textureSize, bool opaque, bool pattern)
{
    Q_TRACE_PARAM_REPLACE(QOpenGLRect, QRectF);
    Q_TRACE_SCOPE(QOpenGL2PaintEngineExPrivate_drawTexture, dest, src, textureSize, opaque, pattern);
 
    // Setup for texture drawing
    currentBrush = noBrush;
 
    if (snapToPixelGrid) {
        snapToPixelGrid = false;
        matrixDirty = true;
    }
 
    if (prepareForDraw(opaque))
        shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::ImageTexture), QT_IMAGE_TEXTURE_UNIT);
 
    if (pattern) {
        QColor col = qt_premultiplyColor(q->state()->pen.color(), (GLfloat)q->state()->opacity);
        shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::PatternColor), col);
    }
 
    GLfloat dx = 1.0 / textureSize.width();
    GLfloat dy = 1.0 / textureSize.height();
 
    QOpenGLRect srcTextureRect(src.left*dx, src.top*dy, src.right*dx, src.bottom*dy);
 
    setCoords(staticVertexCoordinateArray, dest);
    setCoords(staticTextureCoordinateArray, srcTextureRect);
 
    setVertexAttribArrayEnabled(QT_VERTEX_COORDS_ATTR, true);
    setVertexAttribArrayEnabled(QT_TEXTURE_COORDS_ATTR, true);
 
    uploadData(QT_VERTEX_COORDS_ATTR, staticVertexCoordinateArray, 8);
    uploadData(QT_TEXTURE_COORDS_ATTR, staticTextureCoordinateArray, 8);
 
    funcs.glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
}
 
void QOpenGL2PaintEngineEx::beginNativePainting()
{
    Q_D(QOpenGL2PaintEngineEx);
    ensureActive();
    d->transferMode(BrushDrawingMode);
 
    d->nativePaintingActive = true;
 
    d->funcs.glUseProgram(0);
 
    // Disable all the vertex attribute arrays:
    for (int i = 0; i < QT_GL_VERTEX_ARRAY_TRACKED_COUNT; ++i)
        d->funcs.glDisableVertexAttribArray(i);
 
#if !QT_CONFIG(opengles2) && !defined(QT_OPENGL_DYNAMIC)
    Q_ASSERT(QOpenGLContext::currentContext());
    const QOpenGLContext *ctx = d->ctx;
    const QSurfaceFormat &fmt = d->device->context()->format();
    if (fmt.majorVersion() < 3 || (fmt.majorVersion() == 3 && fmt.minorVersion() < 1)
        || (fmt.majorVersion() == 3 && fmt.minorVersion() == 1 && ctx->hasExtension(QByteArrayLiteral("GL_ARB_compatibility")))
        || fmt.profile() == QSurfaceFormat::CompatibilityProfile)
    {
        // be nice to people who mix OpenGL 1.x code with QPainter commands
        // by setting modelview and projection matrices to mirror the GL 1
        // paint engine
        const QTransform& mtx = state()->matrix;
 
        float mv_matrix[4][4] =
            {
                { float(mtx.m11()), float(mtx.m12()),     0, float(mtx.m13()) },
                { float(mtx.m21()), float(mtx.m22()),     0, float(mtx.m23()) },
                {                0,                0,     1,                0 },
                {  float(mtx.dx()),  float(mtx.dy()),     0, float(mtx.m33()) }
            };
 
        const QSize sz = d->device->size();
 
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(0, sz.width(), sz.height(), 0, -999999, 999999);
 
        glMatrixMode(GL_MODELVIEW);
        glLoadMatrixf(&mv_matrix[0][0]);
    }
#endif // !QT_CONFIG(opengles2)
 
    d->resetGLState();
 
    // We don't know what texture units and textures the native painting
    // will activate and bind, so we can't assume anything when we return
    // from the native painting.
    d->lastTextureUnitUsed = QT_UNKNOWN_TEXTURE_UNIT;
    d->lastTextureUsed = GLuint(-1);
 
    d->dirtyStencilRegion = QRect(0, 0, d->width, d->height);
 
    d->shaderManager->setDirty();
 
    d->needsSync = true;
}
 
void QOpenGL2PaintEngineExPrivate::resetGLState()
{
    activateTextureUnit(QT_DEFAULT_TEXTURE_UNIT);
 
    funcs.glDisable(GL_BLEND);
    funcs.glDisable(GL_STENCIL_TEST);
    funcs.glDisable(GL_DEPTH_TEST);
    funcs.glDisable(GL_SCISSOR_TEST);
    funcs.glDepthMask(true);
    funcs.glDepthFunc(GL_LESS);
    funcs.glClearDepthf(1);
    funcs.glStencilMask(0xff);
    funcs.glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
    funcs.glStencilFunc(GL_ALWAYS, 0, 0xff);
    setVertexAttribArrayEnabled(QT_TEXTURE_COORDS_ATTR, false);
    setVertexAttribArrayEnabled(QT_VERTEX_COORDS_ATTR, false);
    setVertexAttribArrayEnabled(QT_OPACITY_ATTR, false);
    if (!QOpenGLContext::currentContext()->isOpenGLES()) {
        // gl_Color, corresponding to vertex attribute 3, may have been changed
        float color[] = { 1.0f, 1.0f, 1.0f, 1.0f };
        funcs.glVertexAttrib4fv(3, color);
    }
    if (vao.isCreated())
        vao.release();
 
    funcs.glBindBuffer(GL_ARRAY_BUFFER, 0);
    funcs.glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
}
 
void QOpenGL2PaintEngineEx::endNativePainting()
{
    Q_D(QOpenGL2PaintEngineEx);
    d->needsSync = true;
    d->nativePaintingActive = false;
}
 
void QOpenGL2PaintEngineEx::invalidateState()
{
    Q_D(QOpenGL2PaintEngineEx);
    d->needsSync = true;
}
 
bool QOpenGL2PaintEngineEx::isNativePaintingActive() const {
    Q_D(const QOpenGL2PaintEngineEx);
    return d->nativePaintingActive;
}
 
void QOpenGL2PaintEngineExPrivate::transferMode(EngineMode newMode)
{
    if (newMode == mode)
        return;
 
    if (newMode == TextDrawingMode) {
        shaderManager->setHasComplexGeometry(true);
    } else {
        shaderManager->setHasComplexGeometry(false);
    }
 
    if (newMode == ImageDrawingMode) {
        uploadData(QT_VERTEX_COORDS_ATTR, staticVertexCoordinateArray, 8);
        uploadData(QT_TEXTURE_COORDS_ATTR, staticTextureCoordinateArray, 8);
    }
 
    if (newMode == ImageArrayDrawingMode || newMode == ImageOpacityArrayDrawingMode) {
        uploadData(QT_VERTEX_COORDS_ATTR, (GLfloat*)vertexCoordinateArray.data(), vertexCoordinateArray.vertexCount() * 2);
        uploadData(QT_TEXTURE_COORDS_ATTR, (GLfloat*)textureCoordinateArray.data(), textureCoordinateArray.vertexCount() * 2);
 
        if (newMode == ImageOpacityArrayDrawingMode)
            uploadData(QT_OPACITY_ATTR, (GLfloat*)opacityArray.data(), opacityArray.size());
    }
 
    // This needs to change when we implement high-quality anti-aliasing...
    if (newMode != TextDrawingMode)
        shaderManager->setMaskType(QOpenGLEngineShaderManager::NoMask);
 
    mode = newMode;
}
 
struct QOpenGL2PEVectorPathCache
{
#ifdef QT_OPENGL_CACHE_AS_VBOS
    GLuint vbo;
    GLuint ibo;
#else
    float *vertices;
    void *indices;
#endif
    int vertexCount;
    int indexCount;
    GLenum primitiveType;
    qreal iscale;
    QVertexIndexVector::Type indexType;
};
 
void QOpenGL2PaintEngineExPrivate::cleanupVectorPath(QPaintEngineEx *engine, void *data)
{
    QOpenGL2PEVectorPathCache *c = (QOpenGL2PEVectorPathCache *) data;
#ifdef QT_OPENGL_CACHE_AS_VBOS
    Q_ASSERT(engine->type() == QPaintEngine::OpenGL2);
    static_cast<QOpenGL2PaintEngineEx *>(engine)->d_func()->unusedVBOSToClean << c->vbo;
    if (c->ibo)
        d->unusedIBOSToClean << c->ibo;
#else
    Q_UNUSED(engine);
    free(c->vertices);
    free(c->indices);
#endif
    delete c;
}
 
// Assumes everything is configured for the brush you want to use
void QOpenGL2PaintEngineExPrivate::fill(const QVectorPath& path)
{
    transferMode(BrushDrawingMode);
 
    if (snapToPixelGrid) {
        snapToPixelGrid = false;
        matrixDirty = true;
    }
 
    // Might need to call updateMatrix to re-calculate inverseScale
    if (matrixDirty) {
        updateMatrix();
        if (currentBrush.style() > Qt::SolidPattern)
            brushUniformsDirty = true;
    }
 
    const bool supportsElementIndexUint = funcs.hasOpenGLExtension(QOpenGLExtensions::ElementIndexUint);
 
    const QPointF* const points = reinterpret_cast<const QPointF*>(path.points());
 
    // Check to see if there's any hints
    if (path.shape() == QVectorPath::RectangleHint) {
        QOpenGLRect rect(points[0].x(), points[0].y(), points[2].x(), points[2].y());
        prepareForDraw(currentBrush.isOpaque());
        composite(rect);
    } else if (path.isConvex()) {
 
        if (path.isCacheable()) {
            QVectorPath::CacheEntry *data = path.lookupCacheData(q);
            QOpenGL2PEVectorPathCache *cache;
 
            bool updateCache = false;
 
            if (data) {
                cache = (QOpenGL2PEVectorPathCache *) data->data;
                // Check if scale factor is exceeded and regenerate if so...
                qreal scaleFactor = cache->iscale / inverseScale;
                if (scaleFactor < 0.5 || scaleFactor > 2.0) {
#ifdef QT_OPENGL_CACHE_AS_VBOS
                    glDeleteBuffers(1, &cache->vbo);
                    cache->vbo = 0;
                    Q_ASSERT(cache->ibo == 0);
#else
                    free(cache->vertices);
                    Q_ASSERT(cache->indices == nullptr);
#endif
                    updateCache = true;
                }
            } else {
                cache = new QOpenGL2PEVectorPathCache;
                data = const_cast<QVectorPath &>(path).addCacheData(q, cache, cleanupVectorPath);
                updateCache = true;
            }
 
            // Flatten the path at the current scale factor and fill it into the cache struct.
            if (updateCache) {
                vertexCoordinateArray.clear();
                vertexCoordinateArray.addPath(path, inverseScale, false);
                int vertexCount = vertexCoordinateArray.vertexCount();
                int floatSizeInBytes = vertexCount * 2 * sizeof(float);
                cache->vertexCount = vertexCount;
                cache->indexCount = 0;
                cache->primitiveType = GL_TRIANGLE_FAN;
                cache->iscale = inverseScale;
#ifdef QT_OPENGL_CACHE_AS_VBOS
                funcs.glGenBuffers(1, &cache->vbo);
                funcs.glBindBuffer(GL_ARRAY_BUFFER, cache->vbo);
                funcs.glBufferData(GL_ARRAY_BUFFER, floatSizeInBytes, vertexCoordinateArray.data(), GL_STATIC_DRAW);
                cache->ibo = 0;
#else
                cache->vertices = (float *) malloc(floatSizeInBytes);
                memcpy(cache->vertices, vertexCoordinateArray.data(), floatSizeInBytes);
                cache->indices = nullptr;
#endif
            }
 
            prepareForDraw(currentBrush.isOpaque());
#ifdef QT_OPENGL_CACHE_AS_VBOS
            funcs.glBindBuffer(GL_ARRAY_BUFFER, cache->vbo);
            uploadData(QT_VERTEX_COORD_ATTR, 0, cache->vertexCount);
            setVertexAttributePointer(QT_VERTEX_COORDS_ATTR, 0);
#else
            uploadData(QT_VERTEX_COORDS_ATTR, cache->vertices, cache->vertexCount * 2);
#endif
            funcs.glDrawArrays(cache->primitiveType, 0, cache->vertexCount);
 
        } else {
      //        printf(" - Marking path as cachable...\n");
            // Tag it for later so that if the same path is drawn twice, it is assumed to be static and thus cachable
            path.makeCacheable();
            vertexCoordinateArray.clear();
            vertexCoordinateArray.addPath(path, inverseScale, false);
            prepareForDraw(currentBrush.isOpaque());
            drawVertexArrays(vertexCoordinateArray, GL_TRIANGLE_FAN);
        }
 
    } else {
        bool useCache = path.isCacheable();
        if (useCache) {
            QRectF bbox = path.controlPointRect();
            // If the path doesn't fit within these limits, it is possible that the triangulation will fail.
            useCache &= (bbox.left() > -0x8000 * inverseScale)
                     && (bbox.right() < 0x8000 * inverseScale)
                     && (bbox.top() > -0x8000 * inverseScale)
                     && (bbox.bottom() < 0x8000 * inverseScale);
        }
 
        if (useCache) {
            QVectorPath::CacheEntry *data = path.lookupCacheData(q);
            QOpenGL2PEVectorPathCache *cache;
 
            bool updateCache = false;
 
            if (data) {
                cache = (QOpenGL2PEVectorPathCache *) data->data;
                // Check if scale factor is exceeded and regenerate if so...
                qreal scaleFactor = cache->iscale / inverseScale;
                if (scaleFactor < 0.5 || scaleFactor > 2.0) {
#ifdef QT_OPENGL_CACHE_AS_VBOS
                    glDeleteBuffers(1, &cache->vbo);
                    glDeleteBuffers(1, &cache->ibo);
#else
                    free(cache->vertices);
                    free(cache->indices);
#endif
                    updateCache = true;
                }
            } else {
                cache = new QOpenGL2PEVectorPathCache;
                data = const_cast<QVectorPath &>(path).addCacheData(q, cache, cleanupVectorPath);
                updateCache = true;
            }
 
            // Flatten the path at the current scale factor and fill it into the cache struct.
            if (updateCache) {
                QTriangleSet polys = qTriangulate(path, QTransform().scale(1 / inverseScale, 1 / inverseScale), 1, supportsElementIndexUint);
                cache->vertexCount = polys.vertices.size() / 2;
                cache->indexCount = polys.indices.size();
                cache->primitiveType = GL_TRIANGLES;
                cache->iscale = inverseScale;
                cache->indexType = polys.indices.type();
#ifdef QT_OPENGL_CACHE_AS_VBOS
                funcs.glGenBuffers(1, &cache->vbo);
                funcs.glGenBuffers(1, &cache->ibo);
                funcs.glBindBuffer(GL_ARRAY_BUFFER, cache->vbo);
                funcs.glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, cache->ibo);
 
                if (polys.indices.type() == QVertexIndexVector::UnsignedInt)
                    funcs.glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(quint32) * polys.indices.size(), polys.indices.data(), GL_STATIC_DRAW);
                else
                    funcs.glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(quint16) * polys.indices.size(), polys.indices.data(), GL_STATIC_DRAW);
 
                QVarLengthArray<float> vertices(polys.vertices.size());
                for (int i = 0; i < polys.vertices.size(); ++i)
                    vertices[i] = float(inverseScale * polys.vertices.at(i));
                funcs.glBufferData(GL_ARRAY_BUFFER, sizeof(float) * vertices.size(), vertices.data(), GL_STATIC_DRAW);
#else
                cache->vertices = (float *) malloc(sizeof(float) * polys.vertices.size());
                if (polys.indices.type() == QVertexIndexVector::UnsignedInt) {
                    cache->indices = (quint32 *) malloc(sizeof(quint32) * polys.indices.size());
                    memcpy(cache->indices, polys.indices.data(), sizeof(quint32) * polys.indices.size());
                } else {
                    cache->indices = (quint16 *) malloc(sizeof(quint16) * polys.indices.size());
                    memcpy(cache->indices, polys.indices.data(), sizeof(quint16) * polys.indices.size());
                }
                for (int i = 0; i < polys.vertices.size(); ++i)
                    cache->vertices[i] = float(inverseScale * polys.vertices.at(i));
#endif
            }
 
            prepareForDraw(currentBrush.isOpaque());
#ifdef QT_OPENGL_CACHE_AS_VBOS
            funcs.glBindBuffer(GL_ARRAY_BUFFER, cache->vbo);
            funcs.glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, cache->ibo);
            uploadData(QT_VERTEX_COORDS_ATTR, 0, cache->vertexCount);
            setVertexAttributePointer(QT_VERTEX_COORDS_ATTR, 0);
            if (cache->indexType == QVertexIndexVector::UnsignedInt)
                funcs.glDrawElements(cache->primitiveType, cache->indexCount, GL_UNSIGNED_INT, 0);
            else
                funcs.glDrawElements(cache->primitiveType, cache->indexCount, GL_UNSIGNED_SHORT, 0);
            funcs.glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
            funcs.glBindBuffer(GL_ARRAY_BUFFER, 0);
#else
            uploadData(QT_VERTEX_COORDS_ATTR, cache->vertices, cache->vertexCount * 2);
            const GLenum indexValueType = cache->indexType == QVertexIndexVector::UnsignedInt ? GL_UNSIGNED_INT : GL_UNSIGNED_SHORT;
            const bool useIndexVbo = uploadIndexData(cache->indices, indexValueType, cache->indexCount);
            funcs.glDrawElements(cache->primitiveType, cache->indexCount, indexValueType, useIndexVbo ? nullptr : cache->indices);
#endif
 
        } else {
      //        printf(" - Marking path as cachable...\n");
            // Tag it for later so that if the same path is drawn twice, it is assumed to be static and thus cachable
            path.makeCacheable();
 
            if (device->context()->format().stencilBufferSize() <= 0) {
                // If there is no stencil buffer, triangulate the path instead.
 
                QRectF bbox = path.controlPointRect();
                // If the path doesn't fit within these limits, it is possible that the triangulation will fail.
                bool withinLimits = (bbox.left() > -0x8000 * inverseScale)
                                  && (bbox.right() < 0x8000 * inverseScale)
                                  && (bbox.top() > -0x8000 * inverseScale)
                                  && (bbox.bottom() < 0x8000 * inverseScale);
                if (withinLimits) {
                    QTriangleSet polys = qTriangulate(path, QTransform().scale(1 / inverseScale, 1 / inverseScale), 1, supportsElementIndexUint);
 
                    QVarLengthArray<float> vertices(polys.vertices.size());
                    for (int i = 0; i < polys.vertices.size(); ++i)
                        vertices[i] = float(inverseScale * polys.vertices.at(i));
 
                    prepareForDraw(currentBrush.isOpaque());
                    uploadData(QT_VERTEX_COORDS_ATTR, vertices.constData(), vertices.size());
                    const GLenum indexValueType = funcs.hasOpenGLExtension(QOpenGLExtensions::ElementIndexUint) ? GL_UNSIGNED_INT : GL_UNSIGNED_SHORT;
                    const bool useIndexVbo = uploadIndexData(polys.indices.data(), indexValueType, polys.indices.size());
                    funcs.glDrawElements(GL_TRIANGLES, polys.indices.size(), indexValueType, useIndexVbo ? nullptr : polys.indices.data());
                } else {
                    // We can't handle big, concave painter paths with OpenGL without stencil buffer.
                    qWarning("Painter path exceeds +/-32767 pixels.");
                }
                return;
            }
 
            // The path is too complicated & needs the stencil technique
            vertexCoordinateArray.clear();
            vertexCoordinateArray.addPath(path, inverseScale, false);
 
            fillStencilWithVertexArray(vertexCoordinateArray, path.hasWindingFill());
 
            funcs.glStencilMask(0xff);
            funcs.glStencilOp(GL_KEEP, GL_REPLACE, GL_REPLACE);
 
            if (q->state()->clipTestEnabled) {
                // Pass when high bit is set, replace stencil value with current clip
                funcs.glStencilFunc(GL_NOTEQUAL, q->state()->currentClip, GL_STENCIL_HIGH_BIT);
            } else if (path.hasWindingFill()) {
                // Pass when any bit is set, replace stencil value with 0
                funcs.glStencilFunc(GL_NOTEQUAL, 0, 0xff);
            } else {
                // Pass when high bit is set, replace stencil value with 0
                funcs.glStencilFunc(GL_NOTEQUAL, 0, GL_STENCIL_HIGH_BIT);
            }
            prepareForDraw(currentBrush.isOpaque());
 
            // Stencil the brush onto the dest buffer
            composite(vertexCoordinateArray.boundingRect());
            funcs.glStencilMask(0);
            updateClipScissorTest();
        }
    }
}
 
 
void QOpenGL2PaintEngineExPrivate::fillStencilWithVertexArray(const float *data,
                                                          int count,
                                                          int *stops,
                                                          int stopCount,
                                                          const QOpenGLRect &bounds,
                                                          StencilFillMode mode)
{
    Q_ASSERT(count || stops);
 
//     qDebug("QOpenGL2PaintEngineExPrivate::fillStencilWithVertexArray()");
    funcs.glStencilMask(0xff); // Enable stencil writes
 
    if (dirtyStencilRegion.intersects(currentScissorBounds)) {
        const QRegion clearRegion = dirtyStencilRegion.intersected(currentScissorBounds);
        funcs.glClearStencil(0); // Clear to zero
        for (const QRect &rect : clearRegion) {
#ifndef QT_GL_NO_SCISSOR_TEST
            setScissor(rect);
#endif
            funcs.glClear(GL_STENCIL_BUFFER_BIT);
        }
 
        dirtyStencilRegion -= currentScissorBounds;
 
#ifndef QT_GL_NO_SCISSOR_TEST
        updateClipScissorTest();
#endif
    }
 
    funcs.glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE); // Disable color writes
    useSimpleShader();
#ifndef QT_NO_DEBUG
    if (ctx->format().stencilBufferSize() <= 0)
        qWarning("OpenGL paint engine: attempted to use stencil test without requesting a stencil buffer.");
#endif
    funcs.glEnable(GL_STENCIL_TEST); // For some reason, this has to happen _after_ the simple shader is use()'d
 
    if (mode == WindingFillMode) {
        Q_ASSERT(stops && !count);
        if (q->state()->clipTestEnabled) {
            // Flatten clip values higher than current clip, and set high bit to match current clip
            funcs.glStencilFunc(GL_LEQUAL, GL_STENCIL_HIGH_BIT | q->state()->currentClip, ~GL_STENCIL_HIGH_BIT);
            funcs.glStencilOp(GL_KEEP, GL_REPLACE, GL_REPLACE);
            composite(bounds);
 
            funcs.glStencilFunc(GL_EQUAL, GL_STENCIL_HIGH_BIT, GL_STENCIL_HIGH_BIT);
        } else if (!stencilClean) {
            // Clear stencil buffer within bounding rect
            funcs.glStencilFunc(GL_ALWAYS, 0, 0xff);
            funcs.glStencilOp(GL_ZERO, GL_ZERO, GL_ZERO);
            composite(bounds);
        }
 
        // Inc. for front-facing triangle
        funcs.glStencilOpSeparate(GL_FRONT, GL_KEEP, GL_INCR_WRAP, GL_INCR_WRAP);
        // Dec. for back-facing "holes"
        funcs.glStencilOpSeparate(GL_BACK, GL_KEEP, GL_DECR_WRAP, GL_DECR_WRAP);
        funcs.glStencilMask(~GL_STENCIL_HIGH_BIT);
        drawVertexArrays(data, stops, stopCount, GL_TRIANGLE_FAN);
 
        if (q->state()->clipTestEnabled) {
            // Clear high bit of stencil outside of path
            funcs.glStencilFunc(GL_EQUAL, q->state()->currentClip, ~GL_STENCIL_HIGH_BIT);
            funcs.glStencilOp(GL_KEEP, GL_REPLACE, GL_REPLACE);
            funcs.glStencilMask(GL_STENCIL_HIGH_BIT);
            composite(bounds);
        }
    } else if (mode == OddEvenFillMode) {
        funcs.glStencilMask(GL_STENCIL_HIGH_BIT);
        funcs.glStencilOp(GL_KEEP, GL_KEEP, GL_INVERT); // Simply invert the stencil bit
        drawVertexArrays(data, stops, stopCount, GL_TRIANGLE_FAN);
 
    } else { // TriStripStrokeFillMode
        Q_ASSERT(count && !stops); // tristrips generated directly, so no vertexArray or stops
        funcs.glStencilMask(GL_STENCIL_HIGH_BIT);
#if 0
        funcs.glStencilOp(GL_KEEP, GL_KEEP, GL_INVERT); // Simply invert the stencil bit
        setVertexAttributePointer(QT_VERTEX_COORDS_ATTR, data);
        funcs.glDrawArrays(GL_TRIANGLE_STRIP, 0, count);
#else
 
        funcs.glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
        if (q->state()->clipTestEnabled) {
            funcs.glStencilFunc(GL_LEQUAL, q->state()->currentClip | GL_STENCIL_HIGH_BIT,
                                ~GL_STENCIL_HIGH_BIT);
        } else {
            funcs.glStencilFunc(GL_ALWAYS, GL_STENCIL_HIGH_BIT, 0xff);
        }
 
        uploadData(QT_VERTEX_COORDS_ATTR, data, count * 2);
        funcs.glDrawArrays(GL_TRIANGLE_STRIP, 0, count);
#endif
    }
 
    // Enable color writes & disable stencil writes
    funcs.glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
}
 
/*
    If the maximum value in the stencil buffer is GL_STENCIL_HIGH_BIT - 1,
    restore the stencil buffer to a pristine state.  The current clip region
    is set to 1, and the rest to 0.
*/
void QOpenGL2PaintEngineExPrivate::resetClipIfNeeded()
{
    if (maxClip != (GL_STENCIL_HIGH_BIT - 1))
        return;
 
    Q_Q(QOpenGL2PaintEngineEx);
 
    useSimpleShader();
    funcs.glEnable(GL_STENCIL_TEST);
    funcs.glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
 
    QRectF bounds = q->state()->matrix.inverted().mapRect(QRectF(0, 0, width, height));
    QOpenGLRect rect(bounds.left(), bounds.top(), bounds.right(), bounds.bottom());
 
    // Set high bit on clip region
    funcs.glStencilFunc(GL_LEQUAL, q->state()->currentClip, 0xff);
    funcs.glStencilOp(GL_KEEP, GL_INVERT, GL_INVERT);
    funcs.glStencilMask(GL_STENCIL_HIGH_BIT);
    composite(rect);
 
    // Reset clipping to 1 and everything else to zero
    funcs.glStencilFunc(GL_NOTEQUAL, 0x01, GL_STENCIL_HIGH_BIT);
    funcs.glStencilOp(GL_ZERO, GL_REPLACE, GL_REPLACE);
    funcs.glStencilMask(0xff);
    composite(rect);
 
    q->state()->currentClip = 1;
    q->state()->canRestoreClip = false;
 
    maxClip = 1;
 
    funcs.glStencilMask(0x0);
    funcs.glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
}
 
bool QOpenGL2PaintEngineExPrivate::prepareForCachedGlyphDraw(const QFontEngineGlyphCache &cache)
{
    Q_Q(QOpenGL2PaintEngineEx);
 
    Q_ASSERT(cache.transform().type() <= QTransform::TxScale);
 
    QTransform &transform = q->state()->matrix;
    transform.scale(1.0 / cache.transform().m11(), 1.0 / cache.transform().m22());
    bool ret = prepareForDraw(false);
    transform.scale(cache.transform().m11(), cache.transform().m22());
 
    return ret;
}
 
bool QOpenGL2PaintEngineExPrivate::prepareForDraw(bool srcPixelsAreOpaque)
{
    if (brushTextureDirty && (mode == TextDrawingMode || mode == BrushDrawingMode))
        updateBrushTexture();
 
    if (compositionModeDirty)
        updateCompositionMode();
 
    if (matrixDirty)
        updateMatrix();
 
    const bool stateHasOpacity = q->state()->opacity < 0.99f;
    if (q->state()->composition_mode == QPainter::CompositionMode_Source
        || (q->state()->composition_mode == QPainter::CompositionMode_SourceOver
            && srcPixelsAreOpaque && !stateHasOpacity))
    {
        funcs.glDisable(GL_BLEND);
    } else {
        funcs.glEnable(GL_BLEND);
    }
 
    QOpenGLEngineShaderManager::OpacityMode opacityMode;
    if (mode == ImageOpacityArrayDrawingMode) {
        opacityMode = QOpenGLEngineShaderManager::AttributeOpacity;
    } else {
        opacityMode = stateHasOpacity ? QOpenGLEngineShaderManager::UniformOpacity
                                      : QOpenGLEngineShaderManager::NoOpacity;
        if (stateHasOpacity && (mode != ImageDrawingMode && mode != ImageArrayDrawingMode)) {
            // Using a brush
            bool brushIsPattern = (currentBrush.style() >= Qt::Dense1Pattern) &&
                                  (currentBrush.style() <= Qt::DiagCrossPattern);
 
            if ((currentBrush.style() == Qt::SolidPattern) || brushIsPattern)
                opacityMode = QOpenGLEngineShaderManager::NoOpacity; // Global opacity handled by srcPixel shader
        }
    }
    shaderManager->setOpacityMode(opacityMode);
 
    bool changed = shaderManager->useCorrectShaderProg();
    // If the shader program needs changing, we change it and mark all uniforms as dirty
    if (changed) {
        // The shader program has changed so mark all uniforms as dirty:
        brushUniformsDirty = true;
        opacityUniformDirty = true;
        matrixUniformDirty = true;
    }
 
    if (brushUniformsDirty && (mode == TextDrawingMode || mode == BrushDrawingMode))
        updateBrushUniforms();
 
    if (opacityMode == QOpenGLEngineShaderManager::UniformOpacity && opacityUniformDirty) {
        shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::GlobalOpacity), (GLfloat)q->state()->opacity);
        opacityUniformDirty = false;
    }
 
    if (matrixUniformDirty && shaderManager->hasComplexGeometry()) {
        shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::Matrix),
                                                         pmvMatrix);
        matrixUniformDirty = false;
    }
 
    return changed;
}
 
void QOpenGL2PaintEngineExPrivate::composite(const QOpenGLRect& boundingRect)
{
    setCoords(staticVertexCoordinateArray, boundingRect);
 
    uploadData(QT_VERTEX_COORDS_ATTR, staticVertexCoordinateArray, 8);
    funcs.glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
}
 
// Draws the vertex array as a set of <vertexArrayStops.size()> triangle fans.
void QOpenGL2PaintEngineExPrivate::drawVertexArrays(const float *data, int *stops, int stopCount,
                                                GLenum primitive)
{
    // Now setup the pointer to the vertex array:
    uploadData(QT_VERTEX_COORDS_ATTR, data, stops[stopCount-1] * 2);
 
    int previousStop = 0;
    for (int i=0; i<stopCount; ++i) {
        int stop = stops[i];
 
        funcs.glDrawArrays(primitive, previousStop, stop - previousStop);
        previousStop = stop;
    }
}
 
/////////////////////////////////// Public Methods //////////////////////////////////////////
 
QOpenGL2PaintEngineEx::QOpenGL2PaintEngineEx()
    : QPaintEngineEx(*(new QOpenGL2PaintEngineExPrivate(this)))
{
    gccaps &= ~QPaintEngine::RasterOpModes;
}
 
QOpenGL2PaintEngineEx::~QOpenGL2PaintEngineEx()
{
}
 
void QOpenGL2PaintEngineEx::fill(const QVectorPath &path, const QBrush &brush)
{
    Q_D(QOpenGL2PaintEngineEx);
 
    if (qbrush_style(brush) == Qt::NoBrush)
        return;
    ensureActive();
    d->setBrush(brush);
    d->fill(path);
}
 
Q_GUI_EXPORT extern bool qt_scaleForTransform(const QTransform &transform, qreal *scale); // qtransform.cpp
 
 
void QOpenGL2PaintEngineEx::stroke(const QVectorPath &path, const QPen &pen)
{
    Q_D(QOpenGL2PaintEngineEx);
 
    const QBrush &penBrush = qpen_brush(pen);
    if (qpen_style(pen) == Qt::NoPen || qbrush_style(penBrush) == Qt::NoBrush)
        return;
 
    QOpenGL2PaintEngineState *s = state();
    if (pen.isCosmetic() && !qt_scaleForTransform(s->transform(), nullptr)) {
        // QTriangulatingStroker class is not meant to support cosmetically sheared strokes.
        QPaintEngineEx::stroke(path, pen);
        return;
    }
 
    ensureActive();
    d->setBrush(penBrush);
    d->stroke(path, pen);
}
 
void QOpenGL2PaintEngineExPrivate::stroke(const QVectorPath &path, const QPen &pen)
{
    const QOpenGL2PaintEngineState *s = q->state();
    if (snapToPixelGrid) {
        snapToPixelGrid = false;
        matrixDirty = true;
    }
 
    const Qt::PenStyle penStyle = qpen_style(pen);
    const QBrush &penBrush = qpen_brush(pen);
    const bool opaque = penBrush.isOpaque() && s->opacity > 0.99;
 
    transferMode(BrushDrawingMode);
 
    // updateMatrix() is responsible for setting the inverse scale on
    // the strokers, so we need to call it here and not wait for
    // prepareForDraw() down below.
    updateMatrix();
 
    QRectF clip = q->state()->matrix.inverted().mapRect(q->state()->clipEnabled
                                                        ? q->state()->rectangleClip
                                                        : QRectF(0, 0, width, height));
 
    if (penStyle == Qt::SolidLine) {
        stroker.process(path, pen, clip, s->renderHints);
 
    } else { // Some sort of dash
        dasher.process(path, pen, clip, s->renderHints);
 
        QVectorPath dashStroke(dasher.points(),
                               dasher.elementCount(),
                               dasher.elementTypes());
        stroker.process(dashStroke, pen, clip, s->renderHints);
    }
 
    if (!stroker.vertexCount())
        return;
 
    if (opaque) {
        prepareForDraw(opaque);
 
        uploadData(QT_VERTEX_COORDS_ATTR, stroker.vertices(), stroker.vertexCount());
        funcs.glDrawArrays(GL_TRIANGLE_STRIP, 0, stroker.vertexCount() / 2);
    } else {
        qreal width = qpen_widthf(pen) / 2;
        if (width == 0)
            width = 0.5;
        qreal extra = pen.joinStyle() == Qt::MiterJoin
                      ? qMax(pen.miterLimit() * width, width)
                      : width;
 
        if (pen.isCosmetic())
            extra = extra * inverseScale;
 
        QRectF bounds = path.controlPointRect().adjusted(-extra, -extra, extra, extra);
 
        fillStencilWithVertexArray(stroker.vertices(), stroker.vertexCount() / 2,
                                      nullptr, 0, bounds, QOpenGL2PaintEngineExPrivate::TriStripStrokeFillMode);
 
        funcs.glStencilOp(GL_KEEP, GL_REPLACE, GL_REPLACE);
 
        // Pass when any bit is set, replace stencil value with 0
        funcs.glStencilFunc(GL_NOTEQUAL, 0, GL_STENCIL_HIGH_BIT);
        prepareForDraw(false);
 
        // Stencil the brush onto the dest buffer
        composite(bounds);
 
        funcs.glStencilMask(0);
 
        updateClipScissorTest();
    }
}
 
void QOpenGL2PaintEngineEx::penChanged() { }
void QOpenGL2PaintEngineEx::brushChanged() { }
 
void QOpenGL2PaintEngineEx::brushOriginChanged()
{
    Q_D(QOpenGL2PaintEngineEx);
    d->brushUniformsDirty = true;
}
 
void QOpenGL2PaintEngineEx::opacityChanged()
{
//    qDebug("QOpenGL2PaintEngineEx::opacityChanged()");
    Q_D(QOpenGL2PaintEngineEx);
    state()->opacityChanged = true;
 
    Q_ASSERT(d->shaderManager);
    d->brushUniformsDirty = true;
    d->opacityUniformDirty = true;
}
 
void QOpenGL2PaintEngineEx::compositionModeChanged()
{
//     qDebug("QOpenGL2PaintEngineEx::compositionModeChanged()");
    Q_D(QOpenGL2PaintEngineEx);
    state()->compositionModeChanged = true;
    d->compositionModeDirty = true;
}
 
void QOpenGL2PaintEngineEx::renderHintsChanged()
{
    state()->renderHintsChanged = true;
 
#if !QT_CONFIG(opengles2)
    if (!QOpenGLContext::currentContext()->isOpenGLES()) {
        Q_D(QOpenGL2PaintEngineEx);
        if (state()->renderHints & QPainter::Antialiasing)
            d->funcs.glEnable(GL_MULTISAMPLE);
        else
            d->funcs.glDisable(GL_MULTISAMPLE);
    }
#endif // !QT_CONFIG(opengles2)
 
    Q_D(QOpenGL2PaintEngineEx);
 
    // This is a somewhat sneaky way of conceptually making the next call to
    // updateTexture() use FoceUpdate for the TextureUpdateMode. We need this
    // as new render hints may require updating the filter mode.
    d->lastTextureUsed = GLuint(-1);
 
    d->brushTextureDirty = true;
    d->brushUniformsDirty = true;
}
 
void QOpenGL2PaintEngineEx::transformChanged()
{
    Q_D(QOpenGL2PaintEngineEx);
    d->matrixDirty = true;
    state()->matrixChanged = true;
}
 
 
static const QRectF scaleRect(const QRectF &r, qreal sx, qreal sy)
{
    return QRectF(r.x() * sx, r.y() * sy, r.width() * sx, r.height() * sy);
}
 
void QOpenGL2PaintEngineEx::drawPixmap(const QRectF& dest, const QPixmap & pixmap, const QRectF & src)
{
    Q_D(QOpenGL2PaintEngineEx);
    QOpenGLContext *ctx = d->ctx;
 
    // Draw pixmaps that are really images as images since drawImage has
    // better handling of non-default image formats.
    if (pixmap.paintEngine()->type() == QPaintEngine::Raster && !pixmap.isQBitmap())
        return drawImage(dest, pixmap.toImage(), src);
 
    int max_texture_size = ctx->d_func()->maxTextureSize();
    if (pixmap.width() > max_texture_size || pixmap.height() > max_texture_size) {
        QPixmap scaled = pixmap.scaled(max_texture_size, max_texture_size, Qt::KeepAspectRatio);
 
        const qreal sx = scaled.width() / qreal(pixmap.width());
        const qreal sy = scaled.height() / qreal(pixmap.height());
 
        drawPixmap(dest, scaled, scaleRect(src, sx, sy));
        return;
    }
 
    ensureActive();
    d->transferMode(ImageDrawingMode);
 
    GLenum filterMode = state()->renderHints & QPainter::SmoothPixmapTransform ? GL_LINEAR : GL_NEAREST;
    d->updateTexture(QT_IMAGE_TEXTURE_UNIT, pixmap, GL_CLAMP_TO_EDGE, filterMode);
 
    bool isBitmap = pixmap.isQBitmap();
    bool isOpaque = !isBitmap && !pixmap.hasAlpha();
 
    d->shaderManager->setSrcPixelType(isBitmap ? QOpenGLEngineShaderManager::PatternSrc : QOpenGLEngineShaderManager::ImageSrc);
 
    QOpenGLRect srcRect(src.left(), src.top(), src.right(), src.bottom());
    d->drawTexture(dest, srcRect, pixmap.size(), isOpaque, isBitmap);
}
 
void QOpenGL2PaintEngineEx::drawImage(const QRectF& dest, const QImage& image, const QRectF& src,
                        Qt::ImageConversionFlags)
{
    Q_D(QOpenGL2PaintEngineEx);
    QOpenGLContext *ctx = d->ctx;
 
    int max_texture_size = ctx->d_func()->maxTextureSize();
    if (image.width() > max_texture_size || image.height() > max_texture_size) {
        QImage scaled = image.scaled(max_texture_size, max_texture_size, Qt::KeepAspectRatio);
 
        const qreal sx = scaled.width() / qreal(image.width());
        const qreal sy = scaled.height() / qreal(image.height());
 
        drawImage(dest, scaled, scaleRect(src, sx, sy));
        return;
    }
 
    ensureActive();
    d->transferMode(ImageDrawingMode);
 
    QOpenGLTextureUploader::BindOptions bindOption = QOpenGLTextureUploader::PremultipliedAlphaBindOption;
    // Use specialized bind for formats we have specialized shaders for.
    switch (image.format()) {
    case QImage::Format_RGBA8888:
    case QImage::Format_ARGB32:
    case QImage::Format_RGBA64:
    case QImage::Format_RGBA16FPx4:
    case QImage::Format_RGBA32FPx4:
        d->shaderManager->setSrcPixelType(QOpenGLEngineShaderManager::NonPremultipliedImageSrc);
        bindOption = { };
        break;
    case QImage::Format_Alpha8:
        if (ctx->functions()->hasOpenGLFeature(QOpenGLFunctions::TextureRGFormats)) {
            d->shaderManager->setSrcPixelType(QOpenGLEngineShaderManager::AlphaImageSrc);
            bindOption = QOpenGLTextureUploader::UseRedForAlphaAndLuminanceBindOption;
        } else
            d->shaderManager->setSrcPixelType(QOpenGLEngineShaderManager::ImageSrc);
        break;
    case QImage::Format_Grayscale8:
    case QImage::Format_Grayscale16:
        if (ctx->functions()->hasOpenGLFeature(QOpenGLFunctions::TextureRGFormats)) {
            d->shaderManager->setSrcPixelType(QOpenGLEngineShaderManager::GrayscaleImageSrc);
            bindOption = QOpenGLTextureUploader::UseRedForAlphaAndLuminanceBindOption;
        } else
            d->shaderManager->setSrcPixelType(QOpenGLEngineShaderManager::ImageSrc);
        break;
    default:
        d->shaderManager->setSrcPixelType(QOpenGLEngineShaderManager::ImageSrc);
        break;
    }
 
    ImageWithBindOptions imageWithOptions = { image, bindOption };
    GLenum filterMode = state()->renderHints & QPainter::SmoothPixmapTransform ? GL_LINEAR : GL_NEAREST;
    d->updateTexture(QT_IMAGE_TEXTURE_UNIT, imageWithOptions, GL_CLAMP_TO_EDGE, filterMode);
 
    d->drawTexture(dest, src, image.size(), !image.hasAlphaChannel());
}
 
void QOpenGL2PaintEngineEx::drawStaticTextItem(QStaticTextItem *textItem)
{
    Q_D(QOpenGL2PaintEngineEx);
 
    ensureActive();
 
    QPainterState *s = state();
 
    QFontEngine *fontEngine = textItem->fontEngine();
    if (shouldDrawCachedGlyphs(fontEngine, s->matrix)) {
        QFontEngine::GlyphFormat glyphFormat = fontEngine->glyphFormat != QFontEngine::Format_None
                                                ? fontEngine->glyphFormat : d->glyphCacheFormat;
        if (glyphFormat == QFontEngine::Format_A32) {
            if (d->device->context()->format().alphaBufferSize() > 0 || s->matrix.type() > QTransform::TxTranslate
                || (s->composition_mode != QPainter::CompositionMode_Source
                && s->composition_mode != QPainter::CompositionMode_SourceOver))
            {
                glyphFormat = QFontEngine::Format_A8;
            }
        }
 
        d->drawCachedGlyphs(glyphFormat, textItem);
    } else {
        QPaintEngineEx::drawStaticTextItem(textItem);
    }
}
 
bool QOpenGL2PaintEngineEx::drawTexture(const QRectF &dest, GLuint textureId, const QSize &size, const QRectF &src)
{
    Q_D(QOpenGL2PaintEngineEx);
    if (!d->shaderManager)
        return false;
 
    ensureActive();
    d->transferMode(ImageDrawingMode);
 
    GLenum filterMode = state()->renderHints & QPainter::SmoothPixmapTransform ? GL_LINEAR : GL_NEAREST;
    d->updateTexture(QT_IMAGE_TEXTURE_UNIT, textureId, GL_CLAMP_TO_EDGE, filterMode);
 
    d->shaderManager->setSrcPixelType(QOpenGLEngineShaderManager::ImageSrc);
 
    QOpenGLRect srcRect(src.left(), src.bottom(), src.right(), src.top());
    d->drawTexture(dest, srcRect, size, false);
 
    return true;
}
 
void QOpenGL2PaintEngineEx::drawTextItem(const QPointF &p, const QTextItem &textItem)
{
    Q_D(QOpenGL2PaintEngineEx);
 
    ensureActive();
    QOpenGL2PaintEngineState *s = state();
 
    const QTextItemInt &ti = static_cast<const QTextItemInt &>(textItem);
 
    QTransform::TransformationType txtype = s->matrix.type();
 
    QFontEngine::GlyphFormat glyphFormat = ti.fontEngine->glyphFormat != QFontEngine::Format_None
                                                ? ti.fontEngine->glyphFormat : d->glyphCacheFormat;
 
    if (glyphFormat == QFontEngine::Format_A32) {
        if (d->device->context()->format().alphaBufferSize() > 0 || txtype > QTransform::TxTranslate
            || (state()->composition_mode != QPainter::CompositionMode_Source
            && state()->composition_mode != QPainter::CompositionMode_SourceOver))
        {
            glyphFormat = QFontEngine::Format_A8;
        }
    }
 
    if (shouldDrawCachedGlyphs(ti.fontEngine, s->matrix)) {
        QVarLengthArray<QFixedPoint> positions;
        QVarLengthArray<glyph_t> glyphs;
        QTransform matrix = QTransform::fromTranslate(p.x(), p.y());
        ti.fontEngine->getGlyphPositions(ti.glyphs, matrix, ti.flags, glyphs, positions);
 
        {
            QStaticTextItem staticTextItem;
            staticTextItem.setFontEngine(ti.fontEngine);
            staticTextItem.glyphs = glyphs.data();
            staticTextItem.numGlyphs = glyphs.size();
            staticTextItem.glyphPositions = positions.data();
 
            d->drawCachedGlyphs(glyphFormat, &staticTextItem);
        }
        return;
    }
 
    QPaintEngineEx::drawTextItem(p, ti);
}
 
namespace {
 
    class QOpenGLStaticTextUserData: public QStaticTextUserData
    {
    public:
        QOpenGLStaticTextUserData()
            : QStaticTextUserData(OpenGLUserData), cacheSize(0, 0), cacheSerialNumber(0)
        {
        }
 
        ~QOpenGLStaticTextUserData()
        {
        }
 
        QSize cacheSize;
        QOpenGL2PEXVertexArray vertexCoordinateArray;
        QOpenGL2PEXVertexArray textureCoordinateArray;
        QFontEngine::GlyphFormat glyphFormat;
        int cacheSerialNumber;
    };
 
}
 
 
// #define QT_OPENGL_DRAWCACHEDGLYPHS_INDEX_ARRAY_VBO
 
bool QOpenGL2PaintEngineEx::shouldDrawCachedGlyphs(QFontEngine *fontEngine, const QTransform &t) const
{
    // The paint engine does not support projected cached glyph drawing
    if (t.type() == QTransform::TxProject)
        return false;
 
    // The font engine might not support filling the glyph cache
    // with the given transform applied, in which case we need to
    // fall back to the QPainterPath code-path.
    if (!fontEngine->supportsTransformation(t)) {
        // Except that drawing paths is slow, so for scales between
        // 0.5 and 2.0 we leave the glyph cache untransformed and deal
        // with the transform ourselves when painting, resulting in
        // drawing 1x cached glyphs with a smooth-scale.
        float det = t.determinant();
        if (det >= 0.25f && det <= 4.f) {
            // Assuming the baseclass still agrees
            return QPaintEngineEx::shouldDrawCachedGlyphs(fontEngine, t);
        }
 
        return false; // Fall back to path-drawing
    }
 
    return QPaintEngineEx::shouldDrawCachedGlyphs(fontEngine, t);
}
 
 
// MSVC 19.28 does show spurious warning "C4723: potential divide by 0" for the code
// that divides by QOpenGLTextureGlyphCache::height() in release builds.
// Anyhow, the code path in this method is only executed
// if height() != 0. Therefore disable the warning.
QT_WARNING_PUSH
QT_WARNING_DISABLE_MSVC(4723)
 
void QOpenGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngine::GlyphFormat glyphFormat,
                                                QStaticTextItem *staticTextItem)
{
    Q_Q(QOpenGL2PaintEngineEx);
 
    QOpenGL2PaintEngineState *s = q->state();
 
    void *cacheKey = ctx; // use context, not the shareGroup() -> the GL glyph cache uses FBOs which may not be shareable
    bool recreateVertexArrays = false;
 
    QTransform glyphCacheTransform;
    QFontEngine *fe = staticTextItem->fontEngine();
    if (fe->supportsTransformation(s->matrix)) {
        // The font-engine supports rendering glyphs with the current transform, so we
        // build a glyph-cache with the scale pre-applied, so that the cache contains
        // glyphs with the appropriate resolution in the case of retina displays.
        glyphCacheTransform = s->matrix.type() < QTransform::TxRotate ?
            QTransform::fromScale(qAbs(s->matrix.m11()), qAbs(s->matrix.m22())) :
            QTransform::fromScale(
                QVector2D(s->matrix.m11(), s->matrix.m12()).length(),
                QVector2D(s->matrix.m21(), s->matrix.m22()).length());
    }
 
    QOpenGLTextureGlyphCache *cache =
            (QOpenGLTextureGlyphCache *) fe->glyphCache(cacheKey, glyphFormat, glyphCacheTransform);
    if (!cache || cache->glyphFormat() != glyphFormat || cache->contextGroup() == nullptr) {
        cache = new QOpenGLTextureGlyphCache(glyphFormat, glyphCacheTransform);
        fe->setGlyphCache(cacheKey, cache);
        recreateVertexArrays = true;
    }
 
    if (staticTextItem->userDataNeedsUpdate) {
        recreateVertexArrays = true;
    } else if (staticTextItem->userData() == nullptr) {
        recreateVertexArrays = true;
    } else if (staticTextItem->userData()->type != QStaticTextUserData::OpenGLUserData) {
        recreateVertexArrays = true;
    } else {
        QOpenGLStaticTextUserData *userData = static_cast<QOpenGLStaticTextUserData *>(staticTextItem->userData());
        if (userData->glyphFormat != glyphFormat) {
            recreateVertexArrays = true;
        } else if (userData->cacheSerialNumber != cache->serialNumber()) {
            recreateVertexArrays = true;
        }
    }
 
    // We only need to update the cache with new glyphs if we are actually going to recreate the vertex arrays.
    // If the cache size has changed, we do need to regenerate the vertices, but we don't need to repopulate the
    // cache so this text is performed before we test if the cache size has changed.
    if (recreateVertexArrays) {
        cache->setPaintEnginePrivate(this);
        if (!cache->populate(fe, staticTextItem->numGlyphs,
                             staticTextItem->glyphs, staticTextItem->glyphPositions,
                             s->renderHints)) {
            // No space for glyphs in cache. We need to reset it and try again.
            cache->clear();
            cache->populate(fe, staticTextItem->numGlyphs,
                            staticTextItem->glyphs, staticTextItem->glyphPositions,
                            s->renderHints);
        }
 
        if (cache->hasPendingGlyphs()) {
            // Filling in the glyphs binds and sets parameters, so we need to
            // ensure that the glyph cache doesn't mess with whatever unit
            // is currently active. Note that the glyph cache internally
            // uses the image texture unit for blitting to the cache, while
            // we switch between image and mask units when drawing.
            static const GLenum glypchCacheTextureUnit = QT_IMAGE_TEXTURE_UNIT;
            activateTextureUnit(glypchCacheTextureUnit);
 
            cache->fillInPendingGlyphs();
 
            // We assume the cache can be trusted on which texture was bound
            lastTextureUsed = cache->texture();
 
            // But since the brush and image texture units are possibly shared
            // we may have to re-bind brush textures after filling in the cache.
            brushTextureDirty = (QT_BRUSH_TEXTURE_UNIT == glypchCacheTextureUnit);
        }
        cache->setPaintEnginePrivate(nullptr);
    }
 
    if (cache->width() == 0 || cache->height() == 0)
        return;
 
    if (glyphFormat == QFontEngine::Format_ARGB)
        transferMode(ImageArrayDrawingMode);
    else
        transferMode(TextDrawingMode);
 
    int margin = fe->glyphMargin(glyphFormat);
 
    GLfloat dx = 1.0 / cache->width();
    GLfloat dy = 1.0 / cache->height();
 
    // Use global arrays by default
    QOpenGL2PEXVertexArray *vertexCoordinates = &vertexCoordinateArray;
    QOpenGL2PEXVertexArray *textureCoordinates = &textureCoordinateArray;
 
    if (staticTextItem->useBackendOptimizations) {
        QOpenGLStaticTextUserData *userData = nullptr;
 
        if (staticTextItem->userData() == nullptr
            || staticTextItem->userData()->type != QStaticTextUserData::OpenGLUserData) {
 
            userData = new QOpenGLStaticTextUserData();
            staticTextItem->setUserData(userData);
 
        } else {
            userData = static_cast<QOpenGLStaticTextUserData*>(staticTextItem->userData());
        }
 
        userData->glyphFormat = glyphFormat;
        userData->cacheSerialNumber = cache->serialNumber();
 
        // Use cache if backend optimizations is turned on
        vertexCoordinates = &userData->vertexCoordinateArray;
        textureCoordinates = &userData->textureCoordinateArray;
 
        QSize size(cache->width(), cache->height());
        if (userData->cacheSize != size) {
            recreateVertexArrays = true;
            userData->cacheSize = size;
        }
    }
 
    if (recreateVertexArrays) {
        vertexCoordinates->clear();
        textureCoordinates->clear();
 
        bool supportsSubPixelPositions = fe->supportsSubPixelPositions();
        bool verticalSubPixelPositions = fe->supportsVerticalSubPixelPositions()
                && (s->renderHints & QPainter::VerticalSubpixelPositioning) != 0;
        for (int i=0; i<staticTextItem->numGlyphs; ++i) {
            QFixedPoint subPixelPosition;
            if (supportsSubPixelPositions) {
                subPixelPosition = fe->subPixelPositionFor(staticTextItem->glyphPositions[i]);
                if (!verticalSubPixelPositions)
                    subPixelPosition.y = 0;
            }
 
            QTextureGlyphCache::GlyphAndSubPixelPosition glyph(staticTextItem->glyphs[i], subPixelPosition);
 
            const QTextureGlyphCache::Coord &c = cache->coords[glyph];
            if (c.isNull())
                continue;
 
            int x = qFloor(staticTextItem->glyphPositions[i].x.toReal() * cache->transform().m11()) + c.baseLineX - margin;
            int y = verticalSubPixelPositions
                    ? qRound(staticTextItem->glyphPositions[i].y.toReal() * cache->transform().m22())
                    : qFloor(staticTextItem->glyphPositions[i].y.toReal() * cache->transform().m22());
            y -= c.baseLineY + margin;
 
            vertexCoordinates->addQuad(QRectF(x, y, c.w, c.h));
            textureCoordinates->addQuad(QRectF(c.x*dx, c.y*dy, c.w * dx, c.h * dy));
        }
 
        staticTextItem->userDataNeedsUpdate = false;
    }
 
    int numGlyphs = vertexCoordinates->vertexCount() / 4;
    if (numGlyphs == 0)
        return;
 
    if (elementIndices.size() < numGlyphs*6) {
        Q_ASSERT(elementIndices.size() % 6 == 0);
        int j = elementIndices.size() / 6 * 4;
        while (j < numGlyphs*4) {
            elementIndices.append(j + 0);
            elementIndices.append(j + 0);
            elementIndices.append(j + 1);
            elementIndices.append(j + 2);
            elementIndices.append(j + 3);
            elementIndices.append(j + 3);
 
            j += 4;
        }
 
#if defined(QT_OPENGL_DRAWCACHEDGLYPHS_INDEX_ARRAY_VBO)
        if (elementIndicesVBOId == 0)
            funcs.glGenBuffers(1, &elementIndicesVBOId);
 
        funcs.glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementIndicesVBOId);
        funcs.glBufferData(GL_ELEMENT_ARRAY_BUFFER, elementIndices.size() * sizeof(GLushort),
                           elementIndices.constData(), GL_STATIC_DRAW);
#endif
    } else {
#if defined(QT_OPENGL_DRAWCACHEDGLYPHS_INDEX_ARRAY_VBO)
        funcs.glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementIndicesVBOId);
#endif
    }
 
    if (glyphFormat != QFontEngine::Format_ARGB || recreateVertexArrays) {
        uploadData(QT_VERTEX_COORDS_ATTR, (GLfloat*)vertexCoordinates->data(), vertexCoordinates->vertexCount() * 2);
        uploadData(QT_TEXTURE_COORDS_ATTR, (GLfloat*)textureCoordinates->data(), textureCoordinates->vertexCount() * 2);
    }
 
    if (!snapToPixelGrid) {
        snapToPixelGrid = true;
        matrixDirty = true;
    }
 
    QBrush pensBrush = q->state()->pen.brush();
    setBrush(pensBrush);
 
    if (glyphFormat == QFontEngine::Format_A32) {
 
        // Subpixel antialiasing without gamma correction
 
        QPainter::CompositionMode compMode = q->state()->composition_mode;
        Q_ASSERT(compMode == QPainter::CompositionMode_Source
            || compMode == QPainter::CompositionMode_SourceOver);
 
        shaderManager->setMaskType(QOpenGLEngineShaderManager::SubPixelMaskPass1);
 
        if (pensBrush.style() == Qt::SolidPattern) {
            // Solid patterns can get away with only one pass.
            QColor c = pensBrush.color();
            qreal oldOpacity = q->state()->opacity;
            if (compMode == QPainter::CompositionMode_Source) {
                c = qt_premultiplyColor(c, q->state()->opacity);
                q->state()->opacity = 1;
                opacityUniformDirty = true;
            }
 
            compositionModeDirty = false; // I can handle this myself, thank you very much
            prepareForCachedGlyphDraw(*cache);
 
            // prepareForCachedGlyphDraw() have set the opacity on the current shader, so the opacity state can now be reset.
            if (compMode == QPainter::CompositionMode_Source) {
                q->state()->opacity = oldOpacity;
                opacityUniformDirty = true;
            }
 
            funcs.glEnable(GL_BLEND);
            funcs.glBlendFunc(GL_CONSTANT_COLOR, GL_ONE_MINUS_SRC_COLOR);
            funcs.glBlendColor(c.redF(), c.greenF(), c.blueF(), c.alphaF());
        } else {
            // Other brush styles need two passes.
 
            qreal oldOpacity = q->state()->opacity;
            if (compMode == QPainter::CompositionMode_Source) {
                q->state()->opacity = 1;
                opacityUniformDirty = true;
                pensBrush = Qt::white;
                setBrush(pensBrush);
            }
 
            compositionModeDirty = false; // I can handle this myself, thank you very much
            prepareForCachedGlyphDraw(*cache);
            funcs.glEnable(GL_BLEND);
            funcs.glBlendFunc(GL_ZERO, GL_ONE_MINUS_SRC_COLOR);
 
            updateTexture(QT_MASK_TEXTURE_UNIT, cache->texture(), GL_REPEAT, GL_NEAREST, ForceUpdate);
 
#if defined(QT_OPENGL_DRAWCACHEDGLYPHS_INDEX_ARRAY_VBO)
            funcs.glDrawElements(GL_TRIANGLE_STRIP, 6 * numGlyphs, GL_UNSIGNED_SHORT, 0);
#else
            const bool useIndexVbo = uploadIndexData(elementIndices.data(), GL_UNSIGNED_SHORT, 6 * numGlyphs);
            funcs.glDrawElements(GL_TRIANGLE_STRIP, 6 * numGlyphs, GL_UNSIGNED_SHORT, useIndexVbo ? nullptr : elementIndices.data());
#endif
 
            shaderManager->setMaskType(QOpenGLEngineShaderManager::SubPixelMaskPass2);
 
            if (compMode == QPainter::CompositionMode_Source) {
                q->state()->opacity = oldOpacity;
                opacityUniformDirty = true;
                pensBrush = q->state()->pen.brush();
                setBrush(pensBrush);
            }
 
            compositionModeDirty = false;
            prepareForCachedGlyphDraw(*cache);
            funcs.glEnable(GL_BLEND);
            funcs.glBlendFunc(GL_ONE, GL_ONE);
        }
        compositionModeDirty = true;
    } else if (glyphFormat == QFontEngine::Format_ARGB) {
        currentBrush = noBrush;
        shaderManager->setSrcPixelType(QOpenGLEngineShaderManager::ImageSrc);
        if (prepareForCachedGlyphDraw(*cache))
            shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::ImageTexture), QT_IMAGE_TEXTURE_UNIT);
    } else {
        // Grayscale/mono glyphs
 
        shaderManager->setMaskType(QOpenGLEngineShaderManager::PixelMask);
        prepareForCachedGlyphDraw(*cache);
    }
 
    GLenum textureUnit = QT_MASK_TEXTURE_UNIT;
    if (glyphFormat == QFontEngine::Format_ARGB)
        textureUnit = QT_IMAGE_TEXTURE_UNIT;
 
    QOpenGLTextureGlyphCache::FilterMode filterMode = (s->matrix.type() > QTransform::TxTranslate) ?
        QOpenGLTextureGlyphCache::Linear : QOpenGLTextureGlyphCache::Nearest;
 
    GLenum glFilterMode = filterMode == QOpenGLTextureGlyphCache::Linear ? GL_LINEAR : GL_NEAREST;
 
    TextureUpdateMode updateMode = UpdateIfNeeded;
    if (cache->filterMode() != filterMode) {
        updateMode = ForceUpdate;
        cache->setFilterMode(filterMode);
    }
 
    updateTexture(textureUnit, cache->texture(), GL_REPEAT, glFilterMode, updateMode);
 
#if defined(QT_OPENGL_DRAWCACHEDGLYPHS_INDEX_ARRAY_VBO)
    funcs.glDrawElements(GL_TRIANGLE_STRIP, 6 * numGlyphs, GL_UNSIGNED_SHORT, 0);
    funcs.glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
#else
    const bool useIndexVbo = uploadIndexData(elementIndices.data(), GL_UNSIGNED_SHORT, 6 * numGlyphs);
    funcs.glDrawElements(GL_TRIANGLE_STRIP, 6 * numGlyphs, GL_UNSIGNED_SHORT, useIndexVbo ? nullptr : elementIndices.data());
#endif
}
 
QT_WARNING_POP
 
void QOpenGL2PaintEngineEx::drawPixmapFragments(const QPainter::PixmapFragment *fragments, int fragmentCount, const QPixmap &pixmap,
                                            QPainter::PixmapFragmentHints hints)
{
    Q_D(QOpenGL2PaintEngineEx);
    // Use fallback for extended composition modes.
    if (state()->composition_mode > QPainter::CompositionMode_Plus) {
        QPaintEngineEx::drawPixmapFragments(fragments, fragmentCount, pixmap, hints);
        return;
    }
 
    ensureActive();
    int max_texture_size = d->ctx->d_func()->maxTextureSize();
    if (pixmap.width() > max_texture_size || pixmap.height() > max_texture_size) {
        QPixmap scaled = pixmap.scaled(max_texture_size, max_texture_size, Qt::KeepAspectRatio);
        d->drawPixmapFragments(fragments, fragmentCount, scaled, hints);
    } else {
        d->drawPixmapFragments(fragments, fragmentCount, pixmap, hints);
    }
}
 
 
void QOpenGL2PaintEngineExPrivate::drawPixmapFragments(const QPainter::PixmapFragment *fragments,
                                                   int fragmentCount, const QPixmap &pixmap,
                                                   QPainter::PixmapFragmentHints hints)
{
    GLfloat dx = 1.0f / pixmap.size().width();
    GLfloat dy = 1.0f / pixmap.size().height();
 
    vertexCoordinateArray.clear();
    textureCoordinateArray.clear();
    opacityArray.reset();
 
    if (snapToPixelGrid) {
        snapToPixelGrid = false;
        matrixDirty = true;
    }
 
    bool allOpaque = true;
 
    for (int i = 0; i < fragmentCount; ++i) {
        qreal s = 0;
        qreal c = 1;
        if (fragments[i].rotation != 0) {
            s = qFastSin(qDegreesToRadians(fragments[i].rotation));
            c = qFastCos(qDegreesToRadians(fragments[i].rotation));
        }
 
        qreal right = 0.5 * fragments[i].scaleX * fragments[i].width;
        qreal bottom = 0.5 * fragments[i].scaleY * fragments[i].height;
        QOpenGLPoint bottomRight(right * c - bottom * s, right * s + bottom * c);
        QOpenGLPoint bottomLeft(-right * c - bottom * s, -right * s + bottom * c);
 
        vertexCoordinateArray.addVertex(bottomRight.x + fragments[i].x, bottomRight.y + fragments[i].y);
        vertexCoordinateArray.addVertex(-bottomLeft.x + fragments[i].x, -bottomLeft.y + fragments[i].y);
        vertexCoordinateArray.addVertex(-bottomRight.x + fragments[i].x, -bottomRight.y + fragments[i].y);
        vertexCoordinateArray.addVertex(-bottomRight.x + fragments[i].x, -bottomRight.y + fragments[i].y);
        vertexCoordinateArray.addVertex(bottomLeft.x + fragments[i].x, bottomLeft.y + fragments[i].y);
        vertexCoordinateArray.addVertex(bottomRight.x + fragments[i].x, bottomRight.y + fragments[i].y);
 
        QOpenGLRect src(fragments[i].sourceLeft * dx, fragments[i].sourceTop * dy,
                    (fragments[i].sourceLeft + fragments[i].width) * dx,
                    (fragments[i].sourceTop + fragments[i].height) * dy);
 
        textureCoordinateArray.addVertex(src.right, src.bottom);
        textureCoordinateArray.addVertex(src.right, src.top);
        textureCoordinateArray.addVertex(src.left, src.top);
        textureCoordinateArray.addVertex(src.left, src.top);
        textureCoordinateArray.addVertex(src.left, src.bottom);
        textureCoordinateArray.addVertex(src.right, src.bottom);
 
        qreal opacity = fragments[i].opacity * q->state()->opacity;
        opacityArray << opacity << opacity << opacity << opacity << opacity << opacity;
        allOpaque &= (opacity >= 0.99f);
    }
 
    transferMode(ImageOpacityArrayDrawingMode);
 
    uploadData(QT_VERTEX_COORDS_ATTR, (GLfloat*)vertexCoordinateArray.data(), vertexCoordinateArray.vertexCount() * 2);
    uploadData(QT_TEXTURE_COORDS_ATTR, (GLfloat*)textureCoordinateArray.data(), textureCoordinateArray.vertexCount() * 2);
    uploadData(QT_OPACITY_ATTR, (GLfloat*)opacityArray.data(), opacityArray.size());
 
    GLenum filterMode = q->state()->renderHints & QPainter::SmoothPixmapTransform ? GL_LINEAR : GL_NEAREST;
    updateTexture(QT_IMAGE_TEXTURE_UNIT, pixmap, GL_CLAMP_TO_EDGE, filterMode);
 
    bool isBitmap = pixmap.isQBitmap();
    bool isOpaque = !isBitmap && (!pixmap.hasAlpha() || (hints & QPainter::OpaqueHint)) && allOpaque;
 
    // Setup for texture drawing
    currentBrush = noBrush;
    shaderManager->setSrcPixelType(isBitmap ? QOpenGLEngineShaderManager::PatternSrc
                                            : QOpenGLEngineShaderManager::ImageSrc);
    if (prepareForDraw(isOpaque))
        shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::ImageTexture), QT_IMAGE_TEXTURE_UNIT);
 
    if (isBitmap) {
        QColor col = qt_premultiplyColor(q->state()->pen.color(), (GLfloat)q->state()->opacity);
        shaderManager->currentProgram()->setUniformValue(location(QOpenGLEngineShaderManager::PatternColor), col);
    }
 
    funcs.glDrawArrays(GL_TRIANGLES, 0, 6 * fragmentCount);
}
 
bool QOpenGL2PaintEngineEx::begin(QPaintDevice *pdev)
{
    Q_D(QOpenGL2PaintEngineEx);
 
    Q_ASSERT(pdev->devType() == QInternal::OpenGL);
    d->device = static_cast<QOpenGLPaintDevice*>(pdev);
 
    if (!d->device)
        return false;
 
    d->device->ensureActiveTarget();
 
    if (d->device->context() != QOpenGLContext::currentContext() || !d->device->context()) {
        qWarning("QPainter::begin(): QOpenGLPaintDevice's context needs to be current");
        return false;
    }
 
    if (d->ctx != QOpenGLContext::currentContext()
            || (d->ctx && QOpenGLContext::currentContext() && d->ctx->format() != QOpenGLContext::currentContext()->format())) {
        d->vertexBuffer.destroy();
        d->texCoordBuffer.destroy();
        d->opacityBuffer.destroy();
        d->indexBuffer.destroy();
        d->vao.destroy();
    }
 
    d->ctx = QOpenGLContext::currentContext();
    d->ctx->d_func()->active_engine = this;
 
    QOpenGLPaintDevicePrivate::get(d->device)->beginPaint();
 
    d->funcs.initializeOpenGLFunctions();
 
    // Generate a new Vertex Array Object if we don't have one already.  We can
    // only hit the VAO-based path when using a core profile context.  This is
    // because while non-core contexts can support VAOs via extensions, legacy
    // components like the QtOpenGL module do not know about VAOs. There are
    // still tests for QGL-QOpenGL paint engine interoperability, so keep the
    // status quo for now, and avoid introducing a VAO in non-core contexts.
    const bool needsVAO = d->ctx->format().profile() == QSurfaceFormat::CoreProfile
        && d->ctx->format().version() >= std::pair(3, 2);
    if (needsVAO && !d->vao.isCreated()) {
        bool created = d->vao.create();
 
        // If we managed to create it then we have a profile that supports VAOs
        if (created)
            d->vao.bind();
    }
 
    // Generate a new Vertex Buffer Object if we don't have one already
    if (!d->vertexBuffer.isCreated()) {
        d->vertexBuffer.create();
        // Set its usage to StreamDraw, we will use this buffer only a few times before refilling it
        d->vertexBuffer.setUsagePattern(QOpenGLBuffer::StreamDraw);
    }
    if (!d->texCoordBuffer.isCreated()) {
        d->texCoordBuffer.create();
        d->texCoordBuffer.setUsagePattern(QOpenGLBuffer::StreamDraw);
    }
    if (!d->opacityBuffer.isCreated()) {
        d->opacityBuffer.create();
        d->opacityBuffer.setUsagePattern(QOpenGLBuffer::StreamDraw);
    }
    if (!d->indexBuffer.isCreated()) {
        d->indexBuffer.create();
        d->indexBuffer.setUsagePattern(QOpenGLBuffer::StreamDraw);
    }
 
    for (int i = 0; i < QT_GL_VERTEX_ARRAY_TRACKED_COUNT; ++i)
        d->vertexAttributeArraysEnabledState[i] = false;
 
    const QSize sz = d->device->size();
    d->width = sz.width();
    d->height = sz.height();
    d->mode = BrushDrawingMode;
    d->brushTextureDirty = true;
    d->brushUniformsDirty = true;
    d->matrixUniformDirty = true;
    d->matrixDirty = true;
    d->compositionModeDirty = true;
    d->opacityUniformDirty = true;
    d->needsSync = true;
    d->useSystemClip = !systemClip().isEmpty();
    d->currentBrush = QBrush();
 
    d->dirtyStencilRegion = QRect(0, 0, d->width, d->height);
    d->stencilClean = true;
 
    d->shaderManager = new QOpenGLEngineShaderManager(d->ctx);
 
    d->funcs.glDisable(GL_STENCIL_TEST);
    d->funcs.glDisable(GL_DEPTH_TEST);
    d->funcs.glDisable(GL_SCISSOR_TEST);
 
    d->glyphCacheFormat = QFontEngine::Format_A8;
 
#if !QT_CONFIG(opengles2)
    if (!QOpenGLContext::currentContext()->isOpenGLES()) {
        d->funcs.glDisable(GL_MULTISAMPLE);
        d->glyphCacheFormat = QFontEngine::Format_A32;
        d->multisamplingAlwaysEnabled = false;
    } else
#endif // !QT_CONFIG(opengles2)
    {
        // OpenGL ES can't switch MSAA off, so if the gl paint device is
        // multisampled, it's always multisampled.
        d->multisamplingAlwaysEnabled = d->device->context()->format().samples() > 1;
    }
 
    return true;
}
 
bool QOpenGL2PaintEngineEx::end()
{
    Q_D(QOpenGL2PaintEngineEx);
 
    QOpenGLPaintDevicePrivate::get(d->device)->endPaint();
 
    QOpenGLContext *ctx = d->ctx;
    d->funcs.glUseProgram(0);
    d->transferMode(BrushDrawingMode);
 
    ctx->d_func()->active_engine = nullptr;
 
    d->resetGLState();
 
    delete d->shaderManager;
    d->shaderManager = nullptr;
    d->currentBrush = QBrush();
 
#ifdef QT_OPENGL_CACHE_AS_VBOS
    if (!d->unusedVBOSToClean.isEmpty()) {
        glDeleteBuffers(d->unusedVBOSToClean.size(), d->unusedVBOSToClean.constData());
        d->unusedVBOSToClean.clear();
    }
    if (!d->unusedIBOSToClean.isEmpty()) {
        glDeleteBuffers(d->unusedIBOSToClean.size(), d->unusedIBOSToClean.constData());
        d->unusedIBOSToClean.clear();
    }
#endif
 
    return false;
}
 
void QOpenGL2PaintEngineEx::ensureActive()
{
    Q_D(QOpenGL2PaintEngineEx);
    QOpenGLContext *ctx = d->ctx;
 
    if (d->vao.isCreated())
        d->vao.bind();
 
    if (isActive() && ctx->d_func()->active_engine != this) {
        ctx->d_func()->active_engine = this;
        d->needsSync = true;
    }
 
    if (d->needsSync) {
        d->device->ensureActiveTarget();
 
        d->transferMode(BrushDrawingMode);
        d->funcs.glViewport(0, 0, d->width, d->height);
        d->needsSync = false;
        d->shaderManager->setDirty();
        d->syncGlState();
        for (int i = 0; i < 3; ++i)
            d->vertexAttribPointers[i] = (GLfloat*)-1; // Assume the pointers are clobbered
        setState(state());
    }
}
 
void QOpenGL2PaintEngineExPrivate::updateClipScissorTest()
{
    Q_Q(QOpenGL2PaintEngineEx);
    if (q->state()->clipTestEnabled) {
#ifndef QT_NO_DEBUG
        if (ctx->format().stencilBufferSize() <= 0)
            qWarning("OpenGL paint engine: attempted to use stencil test for clipping without requesting a stencil buffer.");
#endif
        funcs.glEnable(GL_STENCIL_TEST);
        funcs.glStencilFunc(GL_LEQUAL, q->state()->currentClip, ~GL_STENCIL_HIGH_BIT);
    } else {
        funcs.glDisable(GL_STENCIL_TEST);
        funcs.glStencilFunc(GL_ALWAYS, 0, 0xff);
    }
 
#ifdef QT_GL_NO_SCISSOR_TEST
    currentScissorBounds = QRect(0, 0, width, height);
#else
    QRect bounds = q->state()->rectangleClip;
    if (!q->state()->clipEnabled) {
        if (useSystemClip)
            bounds = systemClip.boundingRect();
        else
            bounds = QRect(0, 0, width, height);
    } else {
        if (useSystemClip)
            bounds = bounds.intersected(systemClip.boundingRect());
        else
            bounds = bounds.intersected(QRect(0, 0, width, height));
    }
 
    currentScissorBounds = bounds;
 
    if (bounds == QRect(0, 0, width, height)) {
        funcs.glDisable(GL_SCISSOR_TEST);
    } else {
        funcs.glEnable(GL_SCISSOR_TEST);
        setScissor(bounds);
    }
#endif
}
 
void QOpenGL2PaintEngineExPrivate::setScissor(const QRect &rect)
{
    const int left = rect.left();
    const int width = rect.width();
    int bottom = height - (rect.top() + rect.height());
    if (device->paintFlipped()) {
        bottom = rect.top();
    }
    const int height = rect.height();
 
    funcs.glScissor(left, bottom, width, height);
}
 
void QOpenGL2PaintEngineEx::clipEnabledChanged()
{
    Q_D(QOpenGL2PaintEngineEx);
 
    state()->clipChanged = true;
 
    if (painter()->hasClipping())
        d->regenerateClip();
    else
        d->systemStateChanged();
}
 
void QOpenGL2PaintEngineExPrivate::clearClip(uint value)
{
    dirtyStencilRegion -= currentScissorBounds;
 
    funcs.glStencilMask(0xff);
    funcs.glClearStencil(value);
    funcs.glClear(GL_STENCIL_BUFFER_BIT);
    funcs.glStencilMask(0x0);
 
    q->state()->needsClipBufferClear = false;
}
 
void QOpenGL2PaintEngineExPrivate::writeClip(const QVectorPath &path, uint value)
{
    transferMode(BrushDrawingMode);
 
    if (snapToPixelGrid) {
        snapToPixelGrid = false;
        matrixDirty = true;
    }
 
    if (matrixDirty)
        updateMatrix();
 
    stencilClean = false;
 
    const bool singlePass = !path.hasWindingFill()
        && (((q->state()->currentClip == maxClip - 1) && q->state()->clipTestEnabled)
            || q->state()->needsClipBufferClear);
    const uint referenceClipValue = q->state()->needsClipBufferClear ? 1 : q->state()->currentClip;
 
    if (q->state()->needsClipBufferClear)
        clearClip(1);
 
    if (path.isEmpty()) {
        funcs.glEnable(GL_STENCIL_TEST);
        funcs.glStencilFunc(GL_LEQUAL, value, ~GL_STENCIL_HIGH_BIT);
        return;
    }
 
    if (q->state()->clipTestEnabled)
        funcs.glStencilFunc(GL_LEQUAL, q->state()->currentClip, ~GL_STENCIL_HIGH_BIT);
    else
        funcs.glStencilFunc(GL_ALWAYS, 0, 0xff);
 
    vertexCoordinateArray.clear();
    vertexCoordinateArray.addPath(path, inverseScale, false);
 
    if (!singlePass)
        fillStencilWithVertexArray(vertexCoordinateArray, path.hasWindingFill());
 
    funcs.glColorMask(false, false, false, false);
    funcs.glEnable(GL_STENCIL_TEST);
    useSimpleShader();
 
    if (singlePass) {
        // Under these conditions we can set the new stencil value in a single
        // pass, by using the current value and the "new value" as the toggles
 
        funcs.glStencilFunc(GL_LEQUAL, referenceClipValue, ~GL_STENCIL_HIGH_BIT);
        funcs.glStencilOp(GL_KEEP, GL_INVERT, GL_INVERT);
        funcs.glStencilMask(value ^ referenceClipValue);
 
        drawVertexArrays(vertexCoordinateArray, GL_TRIANGLE_FAN);
    } else {
        funcs.glStencilOp(GL_KEEP, GL_REPLACE, GL_REPLACE);
        funcs.glStencilMask(0xff);
 
        if (!q->state()->clipTestEnabled && path.hasWindingFill()) {
            // Pass when any clip bit is set, set high bit
            funcs.glStencilFunc(GL_NOTEQUAL, GL_STENCIL_HIGH_BIT, ~GL_STENCIL_HIGH_BIT);
            composite(vertexCoordinateArray.boundingRect());
        }
 
        // Pass when high bit is set, replace stencil value with new clip value
        funcs.glStencilFunc(GL_NOTEQUAL, value, GL_STENCIL_HIGH_BIT);
 
        composite(vertexCoordinateArray.boundingRect());
    }
 
    funcs.glStencilFunc(GL_LEQUAL, value, ~GL_STENCIL_HIGH_BIT);
    funcs.glStencilMask(0);
 
    funcs.glColorMask(true, true, true, true);
}
 
void QOpenGL2PaintEngineEx::clip(const QVectorPath &path, Qt::ClipOperation op)
{
//     qDebug("QOpenGL2PaintEngineEx::clip()");
    Q_D(QOpenGL2PaintEngineEx);
 
    state()->clipChanged = true;
 
    ensureActive();
 
    if (op == Qt::ReplaceClip) {
        op = Qt::IntersectClip;
        if (d->hasClipOperations()) {
            d->systemStateChanged();
            state()->canRestoreClip = false;
        }
    }
 
#ifndef QT_GL_NO_SCISSOR_TEST
    if (!path.isEmpty() && op == Qt::IntersectClip && (path.shape() == QVectorPath::RectangleHint)) {
        const QPointF* const points = reinterpret_cast<const QPointF*>(path.points());
        QRectF rect(points[0], points[2]);
 
        if (state()->matrix.type() <= QTransform::TxScale
            || (state()->matrix.type() == QTransform::TxRotate
                && qFuzzyIsNull(state()->matrix.m11())
                && qFuzzyIsNull(state()->matrix.m22())))
        {
            state()->rectangleClip &= qt_mapFillRect(rect, state()->matrix);
            d->updateClipScissorTest();
            return;
        }
    }
#endif
 
    const QRect pathRect = state()->matrix.mapRect(path.controlPointRect()).toAlignedRect();
 
    switch (op) {
    case Qt::NoClip:
        if (d->useSystemClip) {
            state()->clipTestEnabled = true;
            state()->currentClip = 1;
        } else {
            state()->clipTestEnabled = false;
        }
        state()->rectangleClip = QRect(0, 0, d->width, d->height);
        state()->canRestoreClip = false;
        d->updateClipScissorTest();
        break;
    case Qt::IntersectClip:
        state()->rectangleClip = state()->rectangleClip.intersected(pathRect);
        d->updateClipScissorTest();
        d->resetClipIfNeeded();
        ++d->maxClip;
        d->writeClip(path, d->maxClip);
        state()->currentClip = d->maxClip;
        state()->clipTestEnabled = true;
        break;
    default:
        break;
    }
}
 
void QOpenGL2PaintEngineExPrivate::regenerateClip()
{
    systemStateChanged();
    replayClipOperations();
}
 
void QOpenGL2PaintEngineExPrivate::systemStateChanged()
{
    Q_Q(QOpenGL2PaintEngineEx);
 
    q->state()->clipChanged = true;
 
    if (systemClip.isEmpty()) {
        useSystemClip = false;
    } else {
        if (q->paintDevice()->devType() == QInternal::Widget && currentClipDevice) {
            //QWidgetPrivate *widgetPrivate = qt_widget_private(static_cast<QWidget *>(currentClipDevice)->window());
            //useSystemClip = widgetPrivate->extra && widgetPrivate->extra->inRenderWithPainter;
            useSystemClip = true;
        } else {
            useSystemClip = true;
        }
    }
 
    q->state()->clipTestEnabled = false;
    q->state()->needsClipBufferClear = true;
 
    q->state()->currentClip = 1;
    maxClip = 1;
 
    q->state()->rectangleClip = useSystemClip ? systemClip.boundingRect() : QRect(0, 0, width, height);
    updateClipScissorTest();
 
    if (systemClip.rectCount() == 1) {
        if (systemClip.boundingRect() == QRect(0, 0, width, height))
            useSystemClip = false;
#ifndef QT_GL_NO_SCISSOR_TEST
        // scissoring takes care of the system clip
        return;
#endif
    }
 
    if (useSystemClip) {
        clearClip(0);
 
        QPainterPath path;
        path.addRegion(systemClip);
 
        q->state()->currentClip = 0;
        writeClip(qtVectorPathForPath(q->state()->matrix.inverted().map(path)), 1);
        q->state()->currentClip = 1;
        q->state()->clipTestEnabled = true;
    }
}
 
void QOpenGL2PaintEngineEx::setState(QPainterState *new_state)
{
    //     qDebug("QOpenGL2PaintEngineEx::setState()");
 
    Q_D(QOpenGL2PaintEngineEx);
 
    QOpenGL2PaintEngineState *s = static_cast<QOpenGL2PaintEngineState *>(new_state);
    QOpenGL2PaintEngineState *old_state = state();
 
    QPaintEngineEx::setState(s);
 
    if (s->isNew) {
        // Newly created state object.  The call to setState()
        // will either be followed by a call to begin(), or we are
        // setting the state as part of a save().
        s->isNew = false;
        return;
    }
 
    // Setting the state as part of a restore().
 
    if (old_state == s || old_state->renderHintsChanged)
        renderHintsChanged();
 
    if (old_state == s || old_state->matrixChanged)
        d->matrixDirty = true;
 
    if (old_state == s || old_state->compositionModeChanged)
        d->compositionModeDirty = true;
 
    if (old_state == s || old_state->opacityChanged)
        d->opacityUniformDirty = true;
 
    if (old_state == s || old_state->clipChanged) {
        if (old_state && old_state != s && old_state->canRestoreClip) {
            d->updateClipScissorTest();
            d->funcs.glDepthFunc(GL_LEQUAL);
        } else {
            d->regenerateClip();
        }
    }
}
 
QPainterState *QOpenGL2PaintEngineEx::createState(QPainterState *orig) const
{
    if (orig)
        const_cast<QOpenGL2PaintEngineEx *>(this)->ensureActive();
 
    QOpenGL2PaintEngineState *s;
    if (!orig)
        s = new QOpenGL2PaintEngineState();
    else
        s = new QOpenGL2PaintEngineState(*static_cast<QOpenGL2PaintEngineState *>(orig));
 
    s->matrixChanged = false;
    s->compositionModeChanged = false;
    s->opacityChanged = false;
    s->renderHintsChanged = false;
    s->clipChanged = false;
 
    return s;
}
 
QOpenGL2PaintEngineState::QOpenGL2PaintEngineState(const QOpenGL2PaintEngineState &other)
    : QPainterState(other)
{
    isNew = true;
    needsClipBufferClear = other.needsClipBufferClear;
    clipTestEnabled = other.clipTestEnabled;
    currentClip = other.currentClip;
    canRestoreClip = other.canRestoreClip;
    rectangleClip = other.rectangleClip;
}
 
QOpenGL2PaintEngineState::QOpenGL2PaintEngineState()
{
    isNew = true;
    needsClipBufferClear = true;
    clipTestEnabled = false;
    canRestoreClip = true;
}
 
QOpenGL2PaintEngineState::~QOpenGL2PaintEngineState()
{
}
 
void QOpenGL2PaintEngineExPrivate::setVertexAttribArrayEnabled(int arrayIndex, bool enabled)
{
    Q_ASSERT(arrayIndex < QT_GL_VERTEX_ARRAY_TRACKED_COUNT);
 
    if (vertexAttributeArraysEnabledState[arrayIndex] && !enabled)
        funcs.glDisableVertexAttribArray(arrayIndex);
 
    if (!vertexAttributeArraysEnabledState[arrayIndex] && enabled)
        funcs.glEnableVertexAttribArray(arrayIndex);
 
    vertexAttributeArraysEnabledState[arrayIndex] = enabled;
}
 
void QOpenGL2PaintEngineExPrivate::syncGlState()
{
    for (int i = 0; i < QT_GL_VERTEX_ARRAY_TRACKED_COUNT; ++i) {
        if (vertexAttributeArraysEnabledState[i])
            funcs.glEnableVertexAttribArray(i);
        else
            funcs.glDisableVertexAttribArray(i);
    }
}
 
 
QT_END_NAMESPACE