src_gui_graphicsview_qgraphicsscene.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
#include <QtWidgets>
#include <QPrinter>
 
void examples()
{
    {
        //! [0]
        QGraphicsScene scene;
        scene.addText("Hello, world!");
 
        QGraphicsView view(&scene);
        view.show();
        //! [0]
    }
 
    {
        QGraphicsItem *someItem;
 
        //! [1]
        QGraphicsScene scene;
        scene.addItem(someItem);
        //...
        QPrinter printer(QPrinter::HighResolution);
        printer.setPageSize(QPageSize::A4);
 
        QPainter painter(&printer);
        scene.render(&painter);
        //! [1]
    }
 
    {
        int depth;
        auto sceneRect = []() {return QRectF(); };
 
        //! [2]
        QSizeF segmentSize = sceneRect().size() / pow(2, depth - 1);
        //! [2]
    }
 
    {
        //! [3]
        QGraphicsScene scene;
        QGraphicsView view(&scene);
        view.show();
 
        // a blue background
        scene.setBackgroundBrush(Qt::blue);
 
        // a gradient background
        QRadialGradient gradient(0, 0, 10);
        gradient.setSpread(QGradient::RepeatSpread);
        scene.setBackgroundBrush(gradient);
        //! [3]
    }
 
    {
        //! [4]
        QGraphicsScene scene;
        QGraphicsView view(&scene);
        view.show();
 
        // a white semi-transparent foreground
        scene.setForegroundBrush(QColor(255, 255, 255, 127));
 
        // a grid foreground
        scene.setForegroundBrush(QBrush(Qt::lightGray, Qt::CrossPattern));
        //! [4]
    }
}
 
class TileScene : public QGraphicsScene
{
 public:
    TileScene(int numTilesH, int numTilesV, int tileWidth, int tileHeight, QObject *parent = nullptr);
 
    QRectF rectForTile(int x, int y) const;
    void setTile(int x, int y, const QPixmap &pixmap);
 
 protected:
    void drawBackground(QPainter *painter, const QRectF &exposed) override;
 
 private:
    int numTilesH;
    int numTilesV;
    int tileWidth;
    int tileHeight;
    QVector<QVector<QPixmap>> tiles;
};
 
//! [5]
QRectF TileScene::rectForTile(int x, int y) const
{
    // Return the rectangle for the tile at position (x, y).
    return QRectF(x * tileWidth, y * tileHeight, tileWidth, tileHeight);
}
 
void TileScene::setTile(int x, int y, const QPixmap &pixmap)
{
    // Sets or replaces the tile at position (x, y) with pixmap.
    if (x >= 0 && x < numTilesH && y >= 0 && y < numTilesV) {
        tiles[y][x] = pixmap;
        invalidate(rectForTile(x, y), BackgroundLayer);
    }
}
 
void TileScene::drawBackground(QPainter *painter, const QRectF &exposed)
{
    // Draws all tiles that intersect the exposed area.
    for (int y = 0; y < numTilesV; ++y) {
        for (int x = 0; x < numTilesH; ++x) {
            QRectF rect = rectForTile(x, y);
            if (exposed.intersects(rect))
                painter->drawPixmap(rect.topLeft(), tiles[y][x]);
        }
    }
}
//! [5]