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Qt
Internal/Contributor docs for the Qt SDK. Note: These are NOT official API docs; those are found at https://doc.qt.io/
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\reentrant More...
#include <qtextlayout.h>
Classes | |
class | FormatRange |
\reentrant More... | |
Public Types | |
enum | GlyphRunRetrievalFlag : quint16 { RetrieveGlyphIndexes = 0x1 , RetrieveGlyphPositions = 0x2 , RetrieveStringIndexes = 0x4 , RetrieveString = 0x8 , DefaultRetrievalFlags = RetrieveGlyphIndexes | RetrieveGlyphPositions , RetrieveAll = 0xffff } |
enum | CursorMode { SkipCharacters , SkipWords } |
\value SkipCharacters \value SkipWords More... | |
Public Member Functions | |
QTextLayout () | |
Constructs an empty text layout. | |
QTextLayout (const QString &text) | |
Constructs a text layout to lay out the given text. | |
QTextLayout (const QString &text, const QFont &font, const QPaintDevice *paintdevice=nullptr) | |
QTextLayout (const QTextBlock &b) | |
~QTextLayout () | |
Destructs the layout. | |
void | setFont (const QFont &f) |
Sets the layout's font to the given font. | |
QFont | font () const |
Returns the current font that is used for the layout, or a default font if none is set. | |
void | setRawFont (const QRawFont &rawFont) |
void | setText (const QString &string) |
Sets the layout's text to the given string. | |
QString | text () const |
Returns the layout's text. | |
void | setTextOption (const QTextOption &option) |
Sets the text option structure that controls the layout process to the given option. | |
const QTextOption & | textOption () const |
Returns the current text option used to control the layout process. | |
void | setPreeditArea (int position, const QString &text) |
Sets the position and text of the area in the layout that is processed before editing occurs. | |
int | preeditAreaPosition () const |
Returns the position of the area in the text layout that will be processed before editing occurs. | |
QString | preeditAreaText () const |
Returns the text that is inserted in the layout before editing occurs. | |
void | setFormats (const QList< FormatRange > &overrides) |
QList< FormatRange > | formats () const |
void | clearFormats () |
void | setCacheEnabled (bool enable) |
Enables caching of the complete layout information if enable is true; otherwise disables layout caching. | |
bool | cacheEnabled () const |
Returns true if the complete layout information is cached; otherwise returns false . | |
void | setCursorMoveStyle (Qt::CursorMoveStyle style) |
Sets the visual cursor movement style to the given style. | |
Qt::CursorMoveStyle | cursorMoveStyle () const |
The cursor movement style of this QTextLayout. | |
void | beginLayout () |
Begins the layout process. | |
void | endLayout () |
Ends the layout process. | |
void | clearLayout () |
QTextLine | createLine () |
Returns a new text line to be laid out if there is text to be inserted into the layout; otherwise returns an invalid text line. | |
int | lineCount () const |
Returns the number of lines in this text layout. | |
QTextLine | lineAt (int i) const |
Returns the {i}-th line of text in this text layout. | |
QTextLine | lineForTextPosition (int pos) const |
Returns the line that contains the cursor position specified by pos. | |
bool | isValidCursorPosition (int pos) const |
Returns true if position pos is a valid cursor position. | |
int | nextCursorPosition (int oldPos, CursorMode mode=SkipCharacters) const |
Returns the next valid cursor position after oldPos that respects the given cursor mode. | |
int | previousCursorPosition (int oldPos, CursorMode mode=SkipCharacters) const |
Returns the first valid cursor position before oldPos that respects the given cursor mode. | |
int | leftCursorPosition (int oldPos) const |
Returns the cursor position to the left of oldPos, next to it. | |
int | rightCursorPosition (int oldPos) const |
Returns the cursor position to the right of oldPos, next to it. | |
void | draw (QPainter *p, const QPointF &pos, const QList< FormatRange > &selections=QList< FormatRange >(), const QRectF &clip=QRectF()) const |
Draws the whole layout on the painter p at the position specified by pos. | |
void | drawCursor (QPainter *p, const QPointF &pos, int cursorPosition) const |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Draws a text cursor with the current pen at the given position using the painter specified. | |
void | drawCursor (QPainter *p, const QPointF &pos, int cursorPosition, int width) const |
Draws a text cursor with the current pen and the specified width at the given position using the painter specified. | |
QPointF | position () const |
void | setPosition (const QPointF &p) |
Moves the text layout to point p. | |
QRectF | boundingRect () const |
The smallest rectangle that contains all the lines in the layout. | |
qreal | minimumWidth () const |
The minimum width the layout needs. | |
qreal | maximumWidth () const |
The maximum width the layout could expand to; this is essentially the width of the entire text. | |
QList< QGlyphRun > | glyphRuns (int from=-1, int length=-1, GlyphRunRetrievalFlags flags=DefaultRetrievalFlags) const |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. Returns the glyph indexes and positions for all glyphs corresponding to the length characters starting at the position from in this QTextLayout. | |
QTextEngine * | engine () const |
void | setFlags (int flags) |
Friends | |
class | QPainter |
class | QGraphicsSimpleTextItemPrivate |
class | QGraphicsSimpleTextItem |
void | qt_format_text (const QFont &font, const QRectF &_r, int tf, const QTextOption *opt, const QString &str, QRectF *brect, int tabstops, int *tabarray, int tabarraylen, QPainter *painter) |
\reentrant
The QTextLayout class is used to lay out and render text. \inmodule QtGui
It offers many features expected from a modern text layout engine, including Unicode compliant rendering, line breaking and handling of cursor positioning. It can also produce and render device independent layout, something that is important for WYSIWYG applications.
The class has a rather low level API and unless you intend to implement your own text rendering for some specialized widget, you probably won't need to use it directly.
QTextLayout can be used with both plain and rich text.
QTextLayout can be used to create a sequence of QTextLine instances with given widths and can position them independently on the screen. Once the layout is done, these lines can be drawn on a paint device.
The text to be laid out can be provided in the constructor or set with setText().
The layout can be seen as a sequence of QTextLine objects; use createLine() to create a QTextLine instance, and lineAt() or lineForTextPosition() to retrieve created lines.
Here is a code snippet that demonstrates the layout phase:
The text can then be rendered by calling the layout's draw() function:
It is also possible to draw each line individually, for instance to draw the last line that fits into a widget elided:
For a given position in the text you can find a valid cursor position with isValidCursorPosition(), nextCursorPosition(), and previousCursorPosition().
The QTextLayout itself can be positioned with setPosition(); it has a boundingRect(), and a minimumWidth() and a maximumWidth().
Definition at line 69 of file qtextlayout.h.
\value SkipCharacters \value SkipWords
Enumerator | |
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SkipCharacters | |
SkipWords |
Definition at line 137 of file qtextlayout.h.
GlyphRunRetrievalFlag specifies flags passed to the glyphRuns() functions to determine which properties of the layout are returned in the QGlyphRun objects. Since each property will consume memory and may require additional allocations, it is a good practice to only request the properties you will need to access later.
\value RetrieveGlyphIndexes Retrieves the indexes in the font which correspond to the glyphs. \value RetrieveGlyphPositions Retrieves the relative positions of the glyphs in the layout. \value RetrieveStringIndexes Retrieves the indexes in the original string that correspond to each of the glyphs. \value RetrieveString Retrieves the original source string from the layout. \value RetrieveAll Retrieves all available properties of the layout. \omitvalue DefaultRetrievalFlags
Enumerator | |
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RetrieveGlyphIndexes | |
RetrieveGlyphPositions | |
RetrieveStringIndexes | |
RetrieveString | |
DefaultRetrievalFlags | |
RetrieveAll |
Definition at line 72 of file qtextlayout.h.
QTextLayout::QTextLayout | ( | ) |
QTextLayout::QTextLayout | ( | const QString & | text | ) |
Constructs a text layout to lay out the given text.
Definition at line 326 of file qtextlayout.cpp.
QTextLayout::QTextLayout | ( | const QString & | text, |
const QFont & | font, | ||
const QPaintDevice * | paintdevice = nullptr ) |
Constructs a text layout to lay out the given text with the specified font.
All the metric and layout calculations will be done in terms of the paint device, paintdevice. If paintdevice is \nullptr the calculations will be done in screen metrics.
Definition at line 343 of file qtextlayout.cpp.
QTextLayout::QTextLayout | ( | const QTextBlock & | block | ) |
Constructs a text layout to lay out the given block.
Definition at line 353 of file qtextlayout.cpp.
QTextLayout::~QTextLayout | ( | ) |
Destructs the layout.
Definition at line 362 of file qtextlayout.cpp.
void QTextLayout::beginLayout | ( | ) |
Begins the layout process.
Definition at line 593 of file qtextlayout.cpp.
QRectF QTextLayout::boundingRect | ( | ) | const |
The smallest rectangle that contains all the lines in the layout.
Definition at line 876 of file qtextlayout.cpp.
bool QTextLayout::cacheEnabled | ( | ) | const |
Returns true
if the complete layout information is cached; otherwise returns false
.
Definition at line 556 of file qtextlayout.cpp.
void QTextLayout::clearFormats | ( | ) |
Clears the list of additional formats supported by the text layout.
Definition at line 530 of file qtextlayout.cpp.
void QTextLayout::clearLayout | ( | ) |
Clears the line information in the layout. After having called this function, lineCount() returns 0.
Definition at line 638 of file qtextlayout.cpp.
QTextLine QTextLayout::createLine | ( | ) |
Returns a new text line to be laid out if there is text to be inserted into the layout; otherwise returns an invalid text line.
The text layout creates a new line object that starts after the last line in the layout, or at the beginning if the layout is empty. The layout maintains an internal cursor, and each line is filled with text from the cursor position onwards when the QTextLine::setLineWidth() function is called.
Once QTextLine::setLineWidth() is called, a new line can be created and filled with text. Repeating this process will lay out the whole block of text contained in the QTextLayout. If there is no text left to be inserted into the layout, the QTextLine returned will not be valid (isValid() will return false).
Definition at line 783 of file qtextlayout.cpp.
Qt::CursorMoveStyle QTextLayout::cursorMoveStyle | ( | ) | const |
The cursor movement style of this QTextLayout.
The default is Qt::LogicalMoveStyle.
Definition at line 580 of file qtextlayout.cpp.
void QTextLayout::draw | ( | QPainter * | p, |
const QPointF & | pos, | ||
const QList< FormatRange > & | selections = QList<FormatRange>(), | ||
const QRectF & | clip = QRectF() ) const |
Draws the whole layout on the painter p at the position specified by pos.
The rendered layout includes the given selections and is clipped within the rectangle specified by clip.
Definition at line 1087 of file qtextlayout.cpp.
void QTextLayout::drawCursor | ( | QPainter * | painter, |
const QPointF & | position, | ||
int | cursorPosition ) const |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Draws a text cursor with the current pen at the given position using the painter specified.
The corresponding position within the text is specified by cursorPosition.
Definition at line 1271 of file qtextlayout.cpp.
void QTextLayout::drawCursor | ( | QPainter * | painter, |
const QPointF & | position, | ||
int | cursorPosition, | ||
int | width ) const |
Draws a text cursor with the current pen and the specified width at the given position using the painter specified.
The corresponding position within the text is specified by cursorPosition.
Definition at line 1283 of file qtextlayout.cpp.
void QTextLayout::endLayout | ( | ) |
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Returns the text engine used to render the text layout.
Definition at line 173 of file qtextlayout.h.
QFont QTextLayout::font | ( | ) | const |
Returns the current font that is used for the layout, or a default font if none is set.
Definition at line 405 of file qtextlayout.cpp.
QList< QTextLayout::FormatRange > QTextLayout::formats | ( | ) | const |
Returns the list of additional formats supported by the text layout.
Definition at line 518 of file qtextlayout.cpp.
QList< QGlyphRun > QTextLayout::glyphRuns | ( | int | from = -1, |
int | length = -1, | ||
GlyphRunRetrievalFlags | flags = DefaultRetrievalFlags ) const |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. Returns the glyph indexes and positions for all glyphs corresponding to the length characters starting at the position from in this QTextLayout.
This is an expensive function, and should not be called in a time sensitive context.
If from is less than zero, then the glyph run will begin at the first character in the layout. If length is less than zero, it will span the entire string from the start position.
The retrievalFlags specifies which properties of the QGlyphRun will be retrieved from the layout. To minimize allocations and memory consumption, this should be set to include only the properties that you need to access later.
Definition at line 1033 of file qtextlayout.cpp.
bool QTextLayout::isValidCursorPosition | ( | int | pos | ) | const |
Returns true
if position pos is a valid cursor position.
In a Unicode context some positions in the text are not valid cursor positions, because the position is inside a Unicode surrogate or a grapheme cluster.
A grapheme cluster is a sequence of two or more Unicode characters that form one indivisible entity on the screen. For example the latin character ‘\unicode{0xC4}’ can be represented in Unicode by two characters, ‘A’ (0x41), and the combining diaeresis (0x308). A text cursor can only validly be positioned before or after these two characters, never between them since that wouldn't make sense. In indic languages every syllable forms a grapheme cluster.
Definition at line 759 of file qtextlayout.cpp.
int QTextLayout::leftCursorPosition | ( | int | oldPos | ) | const |
Returns the cursor position to the left of oldPos, next to it.
It's dependent on the visual position of characters, after bi-directional reordering.
Definition at line 737 of file qtextlayout.cpp.
QTextLine QTextLayout::lineAt | ( | int | i | ) | const |
Returns the {i}-th line of text in this text layout.
Definition at line 834 of file qtextlayout.cpp.
int QTextLayout::lineCount | ( | ) | const |
Returns the number of lines in this text layout.
Definition at line 824 of file qtextlayout.cpp.
QTextLine QTextLayout::lineForTextPosition | ( | int | pos | ) | const |
Returns the line that contains the cursor position specified by pos.
Definition at line 844 of file qtextlayout.cpp.
qreal QTextLayout::maximumWidth | ( | ) | const |
The maximum width the layout could expand to; this is essentially the width of the entire text.
Definition at line 920 of file qtextlayout.cpp.
qreal QTextLayout::minimumWidth | ( | ) | const |
The minimum width the layout needs.
This is the width of the layout's smallest non-breakable substring.
Definition at line 906 of file qtextlayout.cpp.
int QTextLayout::nextCursorPosition | ( | int | oldPos, |
CursorMode | mode = SkipCharacters ) const |
Returns the next valid cursor position after oldPos that respects the given cursor mode.
Returns value of oldPos, if oldPos is not a valid cursor position.
Definition at line 650 of file qtextlayout.cpp.
QPointF QTextLayout::position | ( | ) | const |
The global position of the layout. This is independent of the bounding rectangle and of the layout process.
Definition at line 858 of file qtextlayout.cpp.
int QTextLayout::preeditAreaPosition | ( | ) | const |
Returns the position of the area in the text layout that will be processed before editing occurs.
Definition at line 480 of file qtextlayout.cpp.
QString QTextLayout::preeditAreaText | ( | ) | const |
Returns the text that is inserted in the layout before editing occurs.
Definition at line 490 of file qtextlayout.cpp.
int QTextLayout::previousCursorPosition | ( | int | oldPos, |
CursorMode | mode = SkipCharacters ) const |
Returns the first valid cursor position before oldPos that respects the given cursor mode.
Returns value of oldPos, if oldPos is not a valid cursor position.
Definition at line 686 of file qtextlayout.cpp.
int QTextLayout::rightCursorPosition | ( | int | oldPos | ) | const |
Returns the cursor position to the right of oldPos, next to it.
It's dependent on the visual position of characters, after bi-directional reordering.
Definition at line 723 of file qtextlayout.cpp.
void QTextLayout::setCacheEnabled | ( | bool | enable | ) |
Enables caching of the complete layout information if enable is true; otherwise disables layout caching.
Usually QTextLayout throws most of the layouting information away after a call to endLayout() to reduce memory consumption. If you however want to draw the laid out text directly afterwards enabling caching might speed up drawing significantly.
Definition at line 545 of file qtextlayout.cpp.
void QTextLayout::setCursorMoveStyle | ( | Qt::CursorMoveStyle | style | ) |
Sets the visual cursor movement style to the given style.
If the QTextLayout is backed by a document, you can ignore this and use the option in QTextDocument, this option is for widgets like QLineEdit or custom widgets without a QTextDocument. Default value is Qt::LogicalMoveStyle.
Definition at line 569 of file qtextlayout.cpp.
void QTextLayout::setFlags | ( | int | flags | ) |
Definition at line 929 of file qtextlayout.cpp.
Sets the layout's font to the given font.
The layout is invalidated and must be laid out again.
Definition at line 390 of file qtextlayout.cpp.
void QTextLayout::setFormats | ( | const QList< FormatRange > & | formats | ) |
Sets the additional formats supported by the text layout to formats. The formats are applied with preedit area text in place.
Definition at line 503 of file qtextlayout.cpp.
Moves the text layout to point p.
Definition at line 868 of file qtextlayout.cpp.
Sets the position and text of the area in the layout that is processed before editing occurs.
The layout is invalidated and must be laid out again.
Definition at line 464 of file qtextlayout.cpp.
Sets a raw font, to be used with QTextLayout::glyphRuns. Note that this only supports the needs of WebKit. Use of this function with e.g. QTextLayout::draw will result in undefined behaviour.
Definition at line 376 of file qtextlayout.cpp.
Sets the layout's text to the given string.
The layout is invalidated and must be laid out again.
Notice that when using this QTextLayout as part of a QTextDocument this method will have no effect.
Definition at line 419 of file qtextlayout.cpp.
void QTextLayout::setTextOption | ( | const QTextOption & | option | ) |
Sets the text option structure that controls the layout process to the given option.
Definition at line 442 of file qtextlayout.cpp.
QString QTextLayout::text | ( | ) | const |
const QTextOption & QTextLayout::textOption | ( | ) | const |
Returns the current text option used to control the layout process.
Definition at line 452 of file qtextlayout.cpp.
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Definition at line 181 of file qtextlayout.h.
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Definition at line 180 of file qtextlayout.h.
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Definition at line 179 of file qtextlayout.h.
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Definition at line 7128 of file qpainter.cpp.
References QPainter::QTextEngine.