A collection of QPainter workarounds. More...

#include <qwt_painter.h>

Static Public Member Functions
static void	setPolylineSplitting (bool)
	Enable/disable line splitting for the raster paint engine.

static bool	polylineSplitting ()

static void	setRoundingAlignment (bool)
	Enable/disable coordinate rounding before painting.

static bool	roundingAlignment ()
	Check whether coordinates should be rounded, before they are painted to a paint engine that rounds to integer values.

static bool	roundingAlignment (const QPainter *)

static void	drawText (QPainter *, qreal x, qreal y, const QString &)
	Wrapper for QPainter::drawText()

static void	drawText (QPainter *, const QPointF &, const QString &)
	Wrapper for QPainter::drawText()

static void	drawText (QPainter *, qreal x, qreal y, qreal w, qreal h, int flags, const QString &)
	Wrapper for QPainter::drawText()

static void	drawText (QPainter *, const QRectF &, int flags, const QString &)
	Wrapper for QPainter::drawText()

static void	drawSimpleRichText (QPainter *, const QRectF &, int flags, const QTextDocument &)
	Draw a text document into a rectangle.

static void	drawRect (QPainter *, qreal x, qreal y, qreal w, qreal h)
	Wrapper for QPainter::drawRect()

static void	drawRect (QPainter *, const QRectF &rect)
	Wrapper for QPainter::drawRect()

static void	fillRect (QPainter *, const QRectF &, const QBrush &)
	Wrapper for QPainter::fillRect()

static void	drawEllipse (QPainter *, const QRectF &)
	Wrapper for QPainter::drawEllipse()

static void	drawPie (QPainter *, const QRectF &r, int a, int alen)
	Wrapper for QPainter::drawPie()

static void	drawLine (QPainter *, qreal x1, qreal y1, qreal x2, qreal y2)
	Wrapper for QPainter::drawLine()

static void	drawLine (QPainter *, const QPointF &p1, const QPointF &p2)
	Wrapper for QPainter::drawLine()

static void	drawLine (QPainter *, const QLineF &)
	Wrapper for QPainter::drawLine()

static void	drawPolygon (QPainter *, const QPolygonF &)
	Wrapper for QPainter::drawPolygon()

static void	drawPolyline (QPainter *, const QPolygonF &)
	Wrapper for QPainter::drawPolyline()

static void	drawPolyline (QPainter , const QPointF , int pointCount)
	Wrapper for QPainter::drawPolyline()

static void	drawPolygon (QPainter *, const QPolygon &)
	Wrapper for QPainter::drawPolygon()

static void	drawPolyline (QPainter *, const QPolygon &)
	Wrapper for QPainter::drawPolyline()

static void	drawPolyline (QPainter , const QPoint , int pointCount)
	Wrapper for QPainter::drawPolyline()

static void	drawPoint (QPainter *, const QPoint &)
	Wrapper for QPainter::drawPoint()

static void	drawPoints (QPainter *, const QPolygon &)
	Wrapper for QPainter::drawPoints()

static void	drawPoints (QPainter , const QPoint , int pointCount)
	Wrapper for QPainter::drawPoints()

static void	drawPoint (QPainter *, qreal x, qreal y)
	Wrapper for QPainter::drawPoint()

static void	drawPoint (QPainter *, const QPointF &)
	Wrapper for QPainter::drawPoint()

static void	drawPoints (QPainter *, const QPolygonF &)
	Wrapper for QPainter::drawPoints()

static void	drawPoints (QPainter , const QPointF , int pointCount)
	Wrapper for QPainter::drawPoints()

static void	drawPath (QPainter *, const QPainterPath &)
	Wrapper for QPainter::drawPath()

static void	drawImage (QPainter *, const QRectF &, const QImage &)
	Wrapper for QPainter::drawImage()

static void	drawPixmap (QPainter *, const QRectF &, const QPixmap &)
	Wrapper for QPainter::drawPixmap()

static void	drawRoundFrame (QPainter *, const QRectF &, const QPalette &, int lineWidth, int frameStyle)
	Draw a round frame.

static void	drawRoundedFrame (QPainter *, const QRectF &, qreal xRadius, qreal yRadius, const QPalette &, int lineWidth, int frameStyle)
	Draw a rectangular frame with rounded borders.

static void	drawFrame (QPainter *, const QRectF &rect, const QPalette &palette, QPalette::ColorRole foregroundRole, int lineWidth, int midLineWidth, int frameStyle)
	Draw a rectangular frame.

static void	drawFocusRect (QPainter , const QWidget )
	Draw a focus rectangle on a widget using its style.

static void	drawFocusRect (QPainter , const QWidget , const QRect &)
	Draw a focus rectangle on a widget using its style.

static void	drawColorBar (QPainter *, const QwtColorMap &, const QwtInterval &, const QwtScaleMap &, Qt::Orientation, const QRectF &)
	Draw a color bar into a rectangle.

static bool	isAligning (const QPainter *)
	Check if the painter is using a paint engine that aligns coordinates to integers.

static bool	isX11GraphicsSystem ()
	Check if the application is running with the X11 graphics system.

static void	fillPixmap (const QWidget *, QPixmap &, const QPoint &offset=QPoint())
	Fill a pixmap with the content of a widget.

static void	fillRegion (QPainter *painter, const QRegion &region)
	Fill a region by drawing all its rectangles.

static void	fillBackground (QPainter painter, QWidget widget, const QVector< QRectF > &fillRects)
	Fill specified rectangular areas of a widget with its parent's background.

static void	fillBackground (QPainter painter, QWidget canvas)
	Auto-detect and fill a widget's background.

static void	drawBackgound (QPainter , const QRectF &, const QWidget )
	Fill rect with the background of a widget.

static void	drawCanvasBackgound (QPainter painter, QWidget canvas)
	Draw a widget's canvas background.

static void	drawStyledBackground (QWidget w, QPainter painter)
	Ensure widget background is drawn correctly per current GUI style.

static QPixmap	backingStore (QWidget *, const QSize &)
	Create a pixmap that can be used as backing store.

static qreal	devicePixelRatio (const QPaintDevice *)
	Get pixel ratio for a paint device.

static qreal	effectivePenWidth (const QPen &)

static int	horizontalAdvance (const QFontMetrics &, const QString &)
	Distance appropriate for drawing a subsequent character after text.

static qreal	horizontalAdvance (const QFontMetricsF &, const QString &)
	Distance appropriate for drawing a subsequent character after text.

static int	horizontalAdvance (const QFontMetrics &, QChar)
	Distance appropriate for drawing a subsequent character after ch.

static qreal	horizontalAdvance (const QFontMetricsF &, QChar)
	Distance appropriate for drawing a subsequent character after ch.

static QFont	scaledFont (const QFont &, const QPaintDevice *=nullptr)
	Adjust the DPI value of font according to the DPI value of the paint device.

static QWidget *	findBackgroundWidget (QWidget *w)
	Find the top-level widget with a visible background.

Detailed Description

A collection of QPainter workarounds.

QwtPainter provides a set of static methods that wrap QPainter operations with workarounds for various Qt rendering issues. It handles device-specific clipping, coordinate rounding, and performance optimizations for different paint engines (raster, SVG, PDF, etc.).

Member Function Documentation

◆ backingStore()

QPixmap QwtPainter::backingStore	(	QWidget *	widget,
		const QSize &	size
	)

static

Create a pixmap that can be used as backing store.

Parameters

[in]	widget	Widget for which the backing store is intended
[in]	size	Size of the pixmap

Returns: Backing store pixmap

◆ devicePixelRatio()

qreal QwtPainter::devicePixelRatio ( const QPaintDevice * paintDevice )

static

Get pixel ratio for a paint device.

Parameters

[in] paintDevice Paint device

Returns: Pixel ratio

◆ drawBackgound()

void QwtPainter::drawBackgound	(	QPainter *	painter,
		const QRectF &	rect,
		const QWidget *	widget
	)

static

Fill rect with the background of a widget.

Parameters

[in]	painter	Painter
[in]	rect	Rectangle to be filled
[in]	widget	Widget

See also: QStyle::PE_Widget, QWidget::backgroundRole()

◆ drawCanvasBackgound()

void QwtPainter::drawCanvasBackgound	(	QPainter *	painter,
		QWidget *	canvas
	)

static

Draw a widget's canvas background.

Draws the background of a canvas widget supporting solid colors, gradients, and texture patterns. Handles custom border path clipping and optimized rendering for different brush types.

Parameters

[in]	painter	QPainter for drawing
[in]	canvas	Target widget to draw background on

Process:

Save painter state
Invoke borderPath() method via meta-object for clipping
Apply different strategies based on brush type:
- Texture: create pixmap, fillPixmap, draw
- Gradient: fill clip region or entire rect based on coordinate mode
- Plain: fill clip region directly
Restore painter state

Note: Uses Qt meta-object system to call borderPath() method. Canvas class needs Q_INVOKABLE QPainterPath borderPath(const QRect&) const;

Warning: If canvas lacks borderPath() method, uses default rect boundary

See also: fillPixmap(), fillRegion(), backgroundRole(), palette()

◆ drawColorBar()

void QwtPainter::drawColorBar	(	QPainter *	painter,
		const QwtColorMap &	colorMap,
		const QwtInterval &	interval,
		const QwtScaleMap &	scaleMap,
		Qt::Orientation	orientation,
		const QRectF &	rect
	)

static

Draw a color bar into a rectangle.

Paints to a pixmap first for scalable output in print documents.

Parameters

[in]	painter	Painter
[in]	colorMap	Color map
[in]	interval	Value range
[in]	scaleMap	Scale map
[in]	orientation	Orientation
[in]	rect	Target rectangle

◆ drawFrame()

void QwtPainter::drawFrame	(	QPainter *	painter,
		const QRectF &	rect,
		const QPalette &	palette,
		QPalette::ColorRole	foregroundRole,
		int	frameWidth,
		int	midLineWidth,
		int	frameStyle
	)

static

Draw a rectangular frame.

Parameters

[in]	painter	Painter
[in]	rect	Frame rectangle
[in]	palette	Palette
[in]	foregroundRole	Foreground role used for QFrame::Plain
[in]	frameWidth	Frame width
[in]	midLineWidth	Used for QFrame::Box
[in]	frameStyle	Bitwise OR'ed value of QFrame::Shape and QFrame::Shadow

◆ drawRoundedFrame()

void QwtPainter::drawRoundedFrame	(	QPainter *	painter,
		const QRectF &	rect,
		qreal	xRadius,
		qreal	yRadius,
		const QPalette &	palette,
		int	lineWidth,
		int	frameStyle
	)

static

Draw a rectangular frame with rounded borders.

Parameters

[in]	painter	Painter
[in]	rect	Frame rectangle
[in]	xRadius	X-radius of the ellipses defining the corners
[in]	yRadius	Y-radius of the ellipses defining the corners
[in]	palette	QPalette::WindowText for plain borders, QPalette::Dark and QPalette::Light for raised/sunken
[in]	lineWidth	Line width
[in]	frameStyle	Bitwise OR'ed value of QFrame::Shape and QFrame::Shadow

◆ drawRoundFrame()

void QwtPainter::drawRoundFrame	(	QPainter *	painter,
		const QRectF &	rect,
		const QPalette &	palette,
		int	lineWidth,
		int	frameStyle
	)

static

Draw a round frame.

Parameters

[in]	painter	Painter
[in]	rect	Frame rectangle
[in]	palette	QPalette::WindowText is used for plain borders, QPalette::Dark and QPalette::Light for raised/sunken borders
[in]	lineWidth	Line width
[in]	frameStyle	Bitwise OR'ed value of QFrame::Shape and QFrame::Shadow

◆ drawSimpleRichText()

void QwtPainter::drawSimpleRichText	(	QPainter *	painter,
		const QRectF &	rect,
		int	flags,
		const QTextDocument &	text
	)

static

Draw a text document into a rectangle.

Parameters

[in]	painter	Painter
[in]	rect	Target rectangle
[in]	flags	Alignments/Text flags, see QPainter::drawText()
[in]	text	Text document

◆ drawStyledBackground()

void QwtPainter::drawStyledBackground	(	QWidget *	w,
		QPainter *	painter
	)

static

Ensure widget background is drawn correctly per current GUI style.

Supports gradients, textures, rounded corners and other complex effects. Automatically adapts to system or application theme settings.

Parameters

[in]	w	Widget to draw background for
[in]	painter	QPainter for drawing

◆ effectivePenWidth()

qreal QwtPainter::effectivePenWidth ( const QPen & pen )

inlinestatic

Returns: pen.widthF() expanded to at least 1.0

Parameters

pen Pen

◆ fillBackground() [1/2]

void QwtPainter::fillBackground	(	QPainter *	painter,
		QWidget *	canvas
	)

static

Auto-detect and fill a widget's background.

Detects background areas based on widget style properties and applies appropriate fill strategy. Supports styled backgrounds and rounded borders.

Parameters

[in]	painter	QPainter for drawing
[in]	canvas	Target widget needing background fill

Logic:

If WA_StyledBackground is enabled: use stylesheet recorder to detect areas, use clipRects if opaque, otherwise use entire widget rect
If borderRadius property is set: calculate four corner rect areas
Call fillBackground() for actual filling

Note: Entry point for background filling, auto-selects appropriate strategy

See also: fillBackground(), QwtStyleSheetRecorder

◆ fillBackground() [2/2]

void QwtPainter::fillBackground	(	QPainter *	painter,
		QWidget *	widget,
		const QVector< QRectF > &	fillRects
	)

static

Fill specified rectangular areas of a widget with its parent's background.

This function handles background filling optimization for transparent or semi-transparent widgets.

Parameters

[in]	painter	QPainter for drawing
[in]	widget	Target widget needing background fill
[in]	fillRects	List of rectangular areas to fill

Process:

Return if fillRects is empty
Determine clip region from painter or widget's content rect
Find background widget that can fill unfilled areas
For each fill rect: check intersection, create pixmap, fill, draw

Note: Typically used for rounded borders or partial background filling

See also: fillPixmap(), findBackgroundWidget()

◆ fillPixmap()

void QwtPainter::fillPixmap	(	const QWidget *	widget,
		QPixmap &	pixmap,
		const QPoint &	offset = `QPoint()`
	)

static

Fill a pixmap with the content of a widget.

In Qt >= 5.0 QPixmap::fill() is a nop, in Qt 4.x it is buggy for backgrounds with gradients. Thus fillPixmap() offers an alternative.

Parameters

[in]	widget	Widget
[out]	pixmap	Pixmap to be filled
[in]	offset	Offset

See also: QPixmap::fill()

◆ fillRegion()

void QwtPainter::fillRegion	(	QPainter *	painter,
		const QRegion &	region
	)

static

Fill a region by drawing all its rectangles.

Parameters

[in]	painter	Painter
[in]	region	Region to fill

◆ findBackgroundWidget()

QWidget * QwtPainter::findBackgroundWidget ( QWidget * w )

static

Find the top-level widget with a visible background.

Recursively traverses up the widget hierarchy to find the first widget with an opaque background. Used to optimize drawing operations by avoiding unnecessary background painting on transparent widgets.

Parameters

[in] w Starting widget to check

Returns: First widget with visible background, or root widget if none found

Logic:

If widget has no parent (root widget), return it
If autoFillBackground is enabled and background is opaque, return it
If WA_StyledBackground is set, test by actual drawing, return if visible
Otherwise, recursively check parent widget

Note: Used for drawing optimization to determine where to start background drawing

See also: autoFillBackground(), backgroundRole(), testAttribute()

◆ horizontalAdvance() [1/4]

int QwtPainter::horizontalAdvance	(	const QFontMetrics &	fontMetrics,
		const QString &	text
	)

static

Distance appropriate for drawing a subsequent character after text.

Parameters

[in]	fontMetrics	Font metrics
[in]	text	Text

Returns: Horizontal advance in pixels

◆ horizontalAdvance() [2/4]

int QwtPainter::horizontalAdvance	(	const QFontMetrics &	fontMetrics,
		QChar	ch
	)

static

Distance appropriate for drawing a subsequent character after ch.

Parameters

[in]	fontMetrics	Font metrics
[in]	ch	Character

Returns: Horizontal advance in pixels

◆ horizontalAdvance() [3/4]

qreal QwtPainter::horizontalAdvance	(	const QFontMetricsF &	fontMetrics,
		const QString &	text
	)

static

Distance appropriate for drawing a subsequent character after text.

Parameters

[in]	fontMetrics	Font metrics
[in]	text	Text

Returns: Horizontal advance in pixels

◆ horizontalAdvance() [4/4]

qreal QwtPainter::horizontalAdvance	(	const QFontMetricsF &	fontMetrics,
		QChar	ch
	)

static

Distance appropriate for drawing a subsequent character after ch.

Parameters

[in]	fontMetrics	Font metrics
[in]	ch	Character

Returns: Horizontal advance in pixels

◆ isAligning()

bool QwtPainter::isAligning ( const QPainter * painter )

static

Check if the painter is using a paint engine that aligns coordinates to integers.

Today these are all paint engines except QPaintEngine::Pdf and QPaintEngine::SVG. If we have an integer-based paint engine, it is also checked whether the painter has a transformation matrix that rotates or scales.

Parameters

[in] painter Painter to check

Returns: True when the painter is aligning

See also: setRoundingAlignment()

◆ isX11GraphicsSystem()

bool QwtPainter::isX11GraphicsSystem ( )

static

Check if the application is running with the X11 graphics system.

The X11 graphics system has special capabilities for incremental painting. With Qt 5.10+, X11 paint engine can be enabled via QT_XCB_NATIVE_PAINTING=1.

Returns: True when the graphics system is X11

◆ polylineSplitting()

bool QwtPainter::polylineSplitting ( )

inlinestatic

Returns: True, when line splitting for the raster paint engine is enabled.

See also: setPolylineSplitting()

◆ roundingAlignment() [1/2]

bool QwtPainter::roundingAlignment ( )

inlinestatic

Check whether coordinates should be rounded, before they are painted to a paint engine that rounds to integer values.

For other paint engines ( PDF, SVG ), this flag has no effect.

Returns: True, when rounding is enabled

See also: setRoundingAlignment(), isAligning()

◆ roundingAlignment() [2/2]

bool QwtPainter::roundingAlignment ( const QPainter * painter )

inlinestatic

Returns: roundingAlignment() && isAligning(painter);

Parameters

painter Painter

◆ scaledFont()

QFont QwtPainter::scaledFont	(	const QFont &	font,
		const QPaintDevice *	paintDevice = `nullptr`
	)

static

Adjust the DPI value of font according to the DPI value of the paint device.

Parameters

[in]	font	Unscaled font
[in]	paintDevice	Paint device providing a DPI value. If null, primary screen DPI is used

Returns: Font adjusted to the DPI value of the paint device

◆ setPolylineSplitting()

void QwtPainter::setPolylineSplitting ( bool enable )

static

Enable/disable line splitting for the raster paint engine.

In some Qt versions, the raster paint engine paints polylines much faster when split into smaller chunks. Also works around a bug for short lines in many Qt versions (Qt 4.8+).

Parameters

[in] enable Enable/disable splitting

See also: polylineSplitting()

◆ setRoundingAlignment()

void QwtPainter::setRoundingAlignment ( bool enable )

static

Enable/disable coordinate rounding before painting.

Coordinates are rounded before being painted to a paint engine that floors to integer values. For other paint engines (PDF, SVG), this flag has no effect. QwtPainter stores this flag only; the rounding itself is done in the painting code.

Parameters

[in] enable Enable/disable rounding

See also: roundingAlignment(), isAligning()

The documentation for this class was generated from the following files:

/home/runner/work/QWT/QWT/src/plot/qwt_painter.h
/home/runner/work/QWT/QWT/src/plot/qwt_painter.cpp

Static Public Member Functions

Detailed Description

Member Function Documentation

◆ backingStore()

◆ devicePixelRatio()

◆ drawBackgound()

◆ drawCanvasBackgound()

◆ drawColorBar()

◆ drawFrame()

◆ drawRoundedFrame()

◆ drawRoundFrame()

◆ drawSimpleRichText()

◆ drawStyledBackground()

◆ effectivePenWidth()

◆ fillBackground() [1/2]

◆ fillBackground() [2/2]

◆ fillPixmap()

◆ fillRegion()

◆ findBackgroundWidget()

◆ horizontalAdvance() [1/4]

◆ horizontalAdvance() [2/4]

◆ horizontalAdvance() [3/4]

◆ horizontalAdvance() [4/4]

◆ isAligning()

◆ isX11GraphicsSystem()

◆ polylineSplitting()

◆ roundingAlignment() [1/2]

◆ roundingAlignment() [2/2]

◆ scaledFont()

◆ setPolylineSplitting()

◆ setRoundingAlignment()