QPainter Class Reference

Detailed Description

The painter provides highly optimized functions to do most of the drawing GUI programs require. QPainter can draw everything from simple lines to complex shapes like pies and chords. It can also draw aligned text and pixmaps. Normally, it draws in a "natural" coordinate system, but it can also do view and world transformation.

The typical use of a painter is:

• Construct a painter.
• Set a pen, a brush etc.
• Draw.
• Destroy the painter.

Mostly, all this is done inside a paint event. (In fact, 99% of all QPainter use is in a reimplementation of QWidget::paintEvent(), and the painter is heavily optimized for such use.) Here's one very simple example:

    void SimpleExampleWidget::paintEvent()
    {
        QPainter paint( this );
        paint.setPen( Qt::blue );
        paint.drawText( rect(), AlignCenter, "The Text" );
    }
    

Usage is simple, and there are many settings you can use:

• font() is the currently set font. If you set a font that isn't available, Qt finds a close match. In fact font() returns what you set using setFont() and fontInfo() returns the font actually being used (which may be the same).

• brush() is the currently set brush; the color or pattern that's used for filling e.g. circles.

• pen() is the currently set pen; the color or stipple that's used for drawing lines or boundaries.

• backgroundMode() is Opaque or Transparent, i.e. whether backgroundColor() is used or not.

• backgroundColor() only applies when backgroundMode() is Opaque and pen() is a stipple. In that case, it describes the color of the background pixels in the stipple.

• rasterOp() is how pixels drawn interact with the pixels already there.

• brushOrigin() is the origin of the tiled brushes, normally the origin of the window.

• viewport(), window(), worldMatrix() and many more make up the painter's coordinate transformation system. See The Coordinate System for an explanation of this, or see below for a very brief overview of the functions.

• clipping() is whether the painter clips at all. (The paint device clips, too.) If the painter clips, it clips to clipRegion().

• pos() is the current position, set by moveTo() and used by lineTo().

Note that some of these settings mirror settings in some paint devices, e.g. QWidget::font(). QPainter::begin() (or the QPainter constructor) copies these attributes from the paint device. Calling, for example, QWidget::setFont() doesn't take effect until the next time a painter begins painting on it.

save() saves all of these settings on an internal stack, restore() pops them back.

The core functionality of QPainter is drawing, and there are functions to draw most primitives: drawPoint(), drawPoints(), drawLine(), drawRect(), drawWinFocusRect(), drawRoundRect(), drawEllipse(), drawArc(), drawPie(), drawChord(), drawLineSegments(), drawPolyline(), drawPolygon(), drawConvexPolygon() and drawCubicBezier(). All of these functions take integer coordinates; there are no floating-point versions since we want drawing to be as fast as possible.

There are functions to draw pixmaps/images, namely drawPixmap(), drawImage() and drawTiledPixmap(). drawPixmap() and drawImage() produce the same result, except that drawPixmap() is faster on-screen and drawImage() faster and sometimes better on QPrinter and QPicture.

Text drawing is done using drawText(), and when you need fine-grained positioning, boundingRect() tells you where a given drawText() command would draw.

There is a drawPicture() function that draws the contents of an entire QPicture using this painter. drawPicture() is the only function that disregards all the painter's settings: the QPicture has its own settings.

Normally, the QPainter operates on the device's own coordinate system (usually pixels), but QPainter has good support for coordinate transformation. See The Coordinate System for a more general overview and a simple example.

The most common functions used are scale(), rotate(), translate() and shear(), all of which operate on the worldMatrix(). setWorldMatrix() can replace or add to the currently set worldMatrix().

setViewport() sets the rectangle on which QPainter operates. The default is the entire device, which is usually fine, except on printers. setWindow() sets the coordinate system, that is, the rectangle that maps to viewport(). What's drawn inside the window() ends up being inside the viewport(). The window's default is the same as the viewport, and if you don't use the transformations, they are optimized away, gaining another little bit of speed.

After all the coordinate transformation is done, QPainter can clip the drawing to an arbitrary rectangle or region. hasClipping() is TRUE if QPainter clips, and clipRegion() returns the clip region. You can set it using either setClipRegion() or setClipRect(). Note that the clipping can be slow. It's all system-dependent, but as a rule of thumb, you can assume that drawing speed is inversely proportional to the number of rectangles in the clip region.

After QPainter's clipping, the paint device may also clip. For example, most widgets clip away the pixels used by child widgets, and most printers clip away an area near the edges of the paper. This additional clipping is not reflected by the return value of clipRegion() or hasClipping().

QPainter also includes some less-used functions that are very useful on those occasions when they're needed.

isActive() indicates whether the painter is active. begin() (and the most usual constructor) makes it active. end() (and the destructor) deactivates it. If the painter is active, device() returns the paint device on which the painter paints.

Sometimes it is desirable to make someone else paint on an unusual QPaintDevice. QPainter supports a static function to do this, redirect(). We recommend not using it, but for some hacks it's perfect.

setTabStops() and setTabArray() can change where the tab stops are, but these are very seldomly used.

Warning: Note that QPainter does not attempt to work around coordinate limitations in the underlying window system. Some platforms may behave incorrectly with coordinates as small as +/-4000.

See also QPaintDevice, QWidget, QPixmap, QPrinter, QPicture, Application Walkthrough, Coordinate System Overview, Graphics Classes and Image Processing Classes.

Member Type Documentation

QPainter::CoordinateMode

• QPainter::CoordDevice
• QPainter::CoordPainter

See also clipRegion().

QPainter::TextDirection

• QPainter::Auto
• QPainter::RTL - right to left
• QPainter::LTR - left to right

See also drawText().

Member Function Documentation

QPainter::QPainter ()

Notice that all painter settings (setPen, setBrush etc.) are reset to default values when begin() is called.

See also begin() and end().

QPainter::QPainter ( const QPaintDevice * pd, bool unclipped = FALSE )

This constructor is convenient for short-lived painters, e.g. in a paint event and should be used only once. The constructor calls begin() for you and the QPainter destructor automatically calls end().

Here's an example using begin() and end():

        void MyWidget::paintEvent( QPaintEvent * )
        {
            QPainter p;
            p.begin( this );
            p.drawLine( ... );  // drawing code
            p.end();
        }
    

The same example using this constructor:

        void MyWidget::paintEvent( QPaintEvent * )
        {
            QPainter p( this );
            p.drawLine( ... );  // drawing code
        }
    

Since the constructor cannot provide feedback when the initialization of the painter failed you should rather use begin() and end() to paint on external devices, e.g. printers.

See also begin() and end().

QPainter::QPainter ( const QPaintDevice * pd, const QWidget * copyAttributes, bool unclipped = FALSE )

See also begin().

QPainter::~QPainter ()

const QColor & QPainter::backgroundColor () const

Returns the current background color.

See also setBackgroundColor() and QColor.

BGMode QPainter::backgroundMode () const

Returns the current background mode.

See also setBackgroundMode() and BGMode.

bool QPainter::begin ( const QPaintDevice * pd, bool unclipped = FALSE )

The errors that can occur are serious problems, such as these:

        p->begin( 0 ); // impossible - paint device cannot be 0

        QPixmap pm( 0, 0 );
        p->begin( pm ); // impossible - pm.isNull();

        p->begin( myWidget );
        p2->begin( myWidget ); // impossible - only one painter at a time
    

Note that most of the time, you can use one of the constructors instead of begin(), and that end() is automatically done at destruction.

Warning: A paint device can only be painted by one painter at a time.

See also end() and flush().

Examples: aclock/aclock.cpp, application/application.cpp, desktop/desktop.cpp, hello/hello.cpp, picture/picture.cpp, t10/cannon.cpp and xform/xform.cpp.

bool QPainter::begin ( const QPaintDevice * pd, const QWidget * copyAttributes, bool unclipped = FALSE )

This version opens the painter on a paint device pd and sets the initial pen, background color and font from copyAttributes, painting over the paint device's children when unclipped is TRUE. This is equivalent to:

        QPainter p;
        p.begin( pd );
        p.setPen( copyAttributes->foregroundColor() );
        p.setBackgroundColor( copyAttributes->backgroundColor() );
        p.setFont( copyAttributes->font() );
    

This begin function is convenient for double buffering. When you draw in a pixmap instead of directly in a widget (to later bitBlt the pixmap into the widget) you will need to set the widget's font etc. This function does exactly that.

Example:

        void MyWidget::paintEvent( QPaintEvent * )
        {
            QPixmap pm(size());
            QPainter p;
            p.begin(&pm, this);
            // ... potentially flickering paint operation ...
            p.end();
            bitBlt(this, 0, 0, &pm);
        }
    

See also end().

QRect QPainter::boundingRect ( int x, int y, int w, int h, int flags, const QString &, int len = -1, QTextParag ** intern = 0 )

Returns the bounding rectangle of the aligned text that would be printed with the corresponding drawText() function using the first len characters of the string if len is > -1, or the whole of the string if len is -1. The drawing, and hence the bounding rectangle, is constrained to the rectangle that begins at point (x, y) with width w and hight h.

The flags argument is the bitwise OR of the following flags:

Horizontal alignment defaults to AlignLeft and vertical alignment defaults to AlignTop.

If several of the horizontal or several of the vertical alignment flags are set, the resulting alignment is undefined.

The intern parameter should not be used.

See also Qt::TextFlags.

QRect QPainter::boundingRect ( const QRect & r, int flags, const QString & str, int len = -1, QTextParag ** internal = 0 )

Returns the bounding rectangle of the aligned text that would be printed with the corresponding drawText() function using the first len characters from str if len is > -1, or the whole of str if len is -1. The drawing, and hence the bounding rectangle, is constrained to the rectangle r.

The internal parameter should not be used.

See also drawText(), fontMetrics(), QFontMetrics::boundingRect() and Qt::TextFlags.

const QBrush & QPainter::brush () const

Returns the painter's current brush.

See also QPainter::setBrush().

Examples: themes/metal.cpp and themes/wood.cpp.

const QPoint & QPainter::brushOrigin () const

Returns the brush origin currently set.

See also setBrushOrigin().

QRegion QPainter::clipRegion ( CoordinateMode m = CoordDevice ) const

See also setClipRegion(), setClipRect(), setClipping() and QPainter::CoordinateMode.

Example: themes/wood.cpp.

QPaintDevice * QPainter::device () const

Returns the paint device on which this painter is currently painting, or 0 if the painter is not active.

See also QPaintDevice::paintingActive().

Examples: helpviewer/helpwindow.cpp and listboxcombo/listboxcombo.cpp.

void QPainter::drawArc ( int x, int y, int w, int h, int a, int alen )

The angles a and alen are 1/16th of a degree, i.e. a full circle equals 5760 (16*360). Positive values of a and alen mean counter-clockwise while negative values mean the clockwise direction. Zero degrees is at the 3 o'clock position.

Example:

        QPainter p( myWidget );
        p.drawArc( 10,10, 70,100, 100*16, 160*16 ); // draws a "(" arc
    

See also drawPie() and drawChord().

void QPainter::drawArc ( const QRect & r, int a, int alen )

Draws the arc that fits inside the rectangle r with start angle a and arc length alen.

void QPainter::drawChord ( int x, int y, int w, int h, int a, int alen )

The chord is filled with the current brush().

The angles a and alen are 1/16th of a degree, i.e. a full circle equals 5760 (16*360). Positive values of a and alen mean counter-clockwise while negative values mean the clockwise direction. Zero degrees is at the 3 o'clock position.

See also drawArc() and drawPie().

void QPainter::drawChord ( const QRect & r, int a, int alen )

Draws a chord that fits inside the rectangle r with start angle a and arc length alen.

void QPainter::drawConvexPolygon ( const QPointArray & pa, int index = 0, int npoints = -1 )

If the supplied polygon is not convex, the results are undefined.

On some platforms (e.g. X Window), this is faster than drawPolygon().

Example: aclock/aclock.cpp.

void QPainter::drawCubicBezier ( const QPointArray & a, int index = 0 )

Control points after a[index + 3] are ignored. Nothing happens if there aren't enough control points.

void QPainter::drawEllipse ( int x, int y, int w, int h )

Examples: drawdemo/drawdemo.cpp, picture/picture.cpp and tictac/tictac.cpp.

void QPainter::drawEllipse ( const QRect & r )

Draws the ellipse that fits inside rectangle r.

void QPainter::drawImage ( int x, int y, const QImage & image, int sx = 0, int sy = 0, int sw = -1, int sh = -1, int conversionFlags = 0 )

This function may convert image to a pixmap and then draw it, if device() is a QPixmap or a QWidget, or else draw it directly, if device() is a QPrinter or QPicture.

Currently alpha masks of the image are ignored when painting on a QPrinter.

See also drawPixmap() and QPixmap::convertFromImage().

Example: canvas/canvas.cpp.

void QPainter::drawImage ( const QPoint &, const QImage &, const QRect & sr, int conversionFlags = 0 )

Draws the rectangle sr from the image at the given point.

void QPainter::drawImage ( const QPoint & p, const QImage & i, int conversion_flags = 0 )

Draws the image i at point p.

If the image needs to be modified to fit in a lower-resolution result (e.g. converting from 32-bit to 8-bit), use the conversion_flags to specify how you'd prefer this to happen.

See also Qt::ImageConversionFlags.

void QPainter::drawImage ( const QRect & r, const QImage & i )

Draws the image i into the rectangle r. The image will be scaled to fit the rectangle if image and rectangle dimensions differ.

void QPainter::drawLine ( int x1, int y1, int x2, int y2 )

See also pen().

Examples: aclock/aclock.cpp, drawlines/connect.cpp, progress/progress.cpp, splitter/splitter.cpp, themes/metal.cpp and themes/wood.cpp.

void QPainter::drawLine ( const QPoint & p1, const QPoint & p2 )

Draws a line from point p1 to point p2.

void QPainter::drawLineSegments ( const QPointArray & a, int index = 0, int nlines = -1 )

Draws the 1st line from a[index] to a[index+1]. Draws the 2nd line from a[index+2] to a[index+3] etc.

See also drawPolyline(), drawPolygon() and QPen.

void QPainter::drawPicture ( int x, int y, const QPicture & pic )

This function does exactly the same as QPicture::play() when called with (x, y) = (0, 0).

Examples: picture/picture.cpp and xform/xform.cpp.

void QPainter::drawPicture ( const QPicture & pic )

Use one of the other QPainter::drawPicture() functions with a (0, 0) offset instead.

void QPainter::drawPicture ( const QPoint & p, const QPicture & pic )

Draws picture pic at point p.

void QPainter::drawPie ( int x, int y, int w, int h, int a, int alen )

The pie is filled with the current brush().

The angles a and alen are 1/16th of a degree, i.e. a full circle equals 5760 (16*360). Positive values of a and alen mean counter-clockwise while negative values mean the clockwise direction. Zero degrees is at the 3 o'clock position.

See also drawArc() and drawChord().

Examples: drawdemo/drawdemo.cpp, grapher/grapher.cpp, t10/cannon.cpp and t9/cannon.cpp.

void QPainter::drawPie ( const QRect & r, int a, int alen )

Draws a pie segment that fits inside the rectangle r with start angle a and arc length alen.

void QPainter::drawPixmap ( int x, int y, const QPixmap & pixmap, int sx = 0, int sy = 0, int sw = -1, int sh = -1 )

(x, y) specifies the top-left point in the paint device that is to be drawn onto. (sx, sy) specifies the top-left point in pixmap that is to be drawn. The default is (0, 0).

(sw, sh) specifies the size of the pixmap that is to be drawn. The default, (-1, -1), means all the way to the bottom right of the pixmap.

Currently the mask of the pixmap or it's alpha channel are ignored when painting on a QPrinter.

See also bitBlt() and QPixmap::setMask().

Examples: grapher/grapher.cpp, picture/picture.cpp, qdir/qdir.cpp, qtimage/qtimage.cpp, showimg/showimg.cpp, t10/cannon.cpp and xform/xform.cpp.

void QPainter::drawPixmap ( const QPoint & p, const QPixmap & pm, const QRect & sr )

Draws the rectangle sr of pixmap pm with its origin at point p.

void QPainter::drawPixmap ( const QPoint & p, const QPixmap & pm )

Draws the pixmap pm with its origin at point p.

void QPainter::drawPixmap ( const QRect & r, const QPixmap & pm )

Draws the pixmap pm into the rectangle r. The pixmap is scaled to fit the rectangle, if image and rectangle size disagree.

void QPainter::drawPoint ( int x, int y )

See also QPen.

Examples: desktop/desktop.cpp and drawlines/connect.cpp.

void QPainter::drawPoint ( const QPoint & p )

Draws the point p.

void QPainter::drawPoints ( const QPointArray & a, int index = 0, int npoints = -1 )

If index is non-zero (the default is zero) only points from index are drawn. If npoints is negative (the default) the rest of the points from index are drawn. If npoints is zero or greater, npoints points are drawn.

void QPainter::drawPolygon ( const QPointArray & a, bool winding = FALSE, int index = 0, int npoints = -1 )

If npoints is -1 (the default) all points until the end of the array are used (i.e. a.size()-index line segments define the polygon).

The first point is always connected to the last point.

The polygon is filled with the current brush(). If winding is TRUE, the polygon is filled using the winding fill algorithm. If winding is FALSE, the polygon is filled using the even-odd (alternative) fill algorithm.

See also drawLineSegments(), drawPolyline() and QPen.

Examples: desktop/desktop.cpp and picture/picture.cpp.

void QPainter::drawPolyline ( const QPointArray & a, int index = 0, int npoints = -1 )

If npoints is -1 (the default) all points until the end of the array are used (i.e. a.size()-index-1 line segments are drawn).

See also drawLineSegments(), drawPolygon() and QPen.

Examples: scribble/scribble.cpp and themes/metal.cpp.

void QPainter::drawRect ( int x, int y, int w, int h )

See also QPen and drawRoundRect().

Examples: drawdemo/drawdemo.cpp, picture/picture.cpp, t10/cannon.cpp, t11/cannon.cpp, t9/cannon.cpp, tooltip/tooltip.cpp and trivial/trivial.cpp.

void QPainter::drawRect ( const QRect & r )

Draws the rectangle r.

void QPainter::drawRoundRect ( int x, int y, int w, int h, int xRnd = 25, int yRnd = 25 )

The xRnd and yRnd arguments specify how rounded the corners should be. 0 is angled corners, 99 is maximum roundedness.

The width and height include all of the drawn lines.

See also drawRect() and QPen.

Examples: drawdemo/drawdemo.cpp and themes/wood.cpp.

void QPainter::drawRoundRect ( const QRect & r, int xRnd = 25, int yRnd = 25 )

Draws a rounded rectangle r, rounding to the x position xRnd and the y position yRnd on each corner.

void QPainter::drawText ( const QPoint & p, const QString &, int pos, int len, TextDirection dir = Auto )

Draws the text from position pos, at point p. If len is -1 the entire string is drawn, otherwise just the first len characters. The text's direction is specified by dir.

See also QPainter::TextDirection.

Examples: desktop/desktop.cpp, drawdemo/drawdemo.cpp, grapher/grapher.cpp, picture/picture.cpp, progress/progress.cpp, t8/cannon.cpp and trivial/trivial.cpp.

void QPainter::drawText ( int x, int y, const QString &, int len = -1, TextDirection dir = Auto )

Draws the given text at position x, y. If len is -1 (the default) all the text is drawn, otherwise the first len characters are drawn. The text's direction is given by dir.

See also QPainter::TextDirection.

void QPainter::drawText ( const QPoint &, const QString &, int len = -1, TextDirection dir = Auto )

Draws the text at the given point.

See also QPainter::TextDirection.

void QPainter::drawText ( int x, int y, const QString &, int pos, int len, TextDirection dir = Auto )

Draws the text from position pos, at point (x, y). If len is -1 the entire string is drawn, otherwise just the first len characters. The text's direction is specified by dir.

void QPainter::drawText ( int x, int y, int w, int h, int flags, const QString &, int len = -1, QRect * br = 0, QTextParag ** internal = 0 )

Draws the given text within the rectangle starting at x, y, with width w and height h. If len is -1 (the default) all the text is drawn, otherwise the first len characters are drawn. The text's flags that are given in the flags parameter are Qt::AlignmentFlags and Qt::TextFlags OR'd together. br (if not null) is set to the actual bounding rectangle of the output. The internal parameter is for internal use only.

void QPainter::drawText ( const QRect & r, int tf, const QString & str, int len = -1, QRect * brect = 0, QTextParag ** internal = 0 )

Draws at most len characters from str in the rectangle r.

Note that the meaning of r.y() is not the same for the two drawText() varieties.

This function draws formatted text. The tf text format is really of type Qt::AlignmentFlags and Qt::TextFlags OR'd together.

Horizontal alignment defaults to AlignAuto and vertical alignment defaults to AlignTop.

brect (if not null) is set to the actual bounding rectangle of the output. internal is, yes, internal.

See also boundingRect().

void QPainter::drawTiledPixmap ( int x, int y, int w, int h, const QPixmap & pixmap, int sx = 0, int sy = 0 )

(x, y) specifies the top-left point in the paint device that is to be drawn onto; with the width and height given by w and h. (sx, sy) specifies the top-left point in pixmap that is to be drawn. The default is (0, 0).

Calling drawTiledPixmap() is similar to calling drawPixmap() several times to fill (tile) an area with a pixmap, but is potentially much more efficient depending on the underlying window system.

See also drawPixmap().

void QPainter::drawTiledPixmap ( const QRect & r, const QPixmap & pm, const QPoint & sp )

Draws a tiled pixmap, pm, inside rectangle r with its origin at point sp.

void QPainter::drawTiledPixmap ( const QRect & r, const QPixmap & pm )

Draws a tiled pixmap, pm, inside rectangle r.

void QPainter::drawWinFocusRect ( int x, int y, int w, int h, const QColor & bgColor )

This function draws a stippled rectangle (XOR is not used) that is used to indicate keyboard focus (when the QApplication::style() is WindowStyle).

The pen color used to draw the rectangle is either white or black depending on the color of bgColor (see QColor::gray()).

Warning: This function draws nothing if the coordinate system has been rotated or sheared.

See also drawRect() and QApplication::style().

void QPainter::drawWinFocusRect ( int x, int y, int w, int h )

Draws a Windows focus rectangle with upper left corner at (x, y) and with width w and height h.

This function draws a stippled XOR rectangle that is used to indicate keyboard focus (when QApplication::style() is WindowStyle).

Warning: This function draws nothing if the coordinate system has been rotated or sheared.

See also drawRect() and QApplication::style().

void QPainter::drawWinFocusRect ( const QRect & r )

Draws rectangle r as a window focus rectangle.

void QPainter::drawWinFocusRect ( const QRect & r, const QColor & bgColor )

Draws rectangle r as a window focus rectangle using background color bgColor.

bool QPainter::end ()

Note that while you mostly don't need to call end(), the destructor will do it, there is at least one common case when it is needed, namely double buffering.

        QPainter p( myPixmap, this )
        // ...
        p.end(); // stops drawing on myPixmap
        p.begin( this );
        p.drawPixmap( myPixmap );
    

Since you can't draw a QPixmap while it is being painted, it is necessary to close the active painter.

See also begin() and isActive().

Examples: aclock/aclock.cpp, application/application.cpp, desktop/desktop.cpp, hello/hello.cpp, picture/picture.cpp, t10/cannon.cpp and xform/xform.cpp.

void QPainter::eraseRect ( int x, int y, int w, int h )

Erases the area inside x, y, w, h. Equivalent to fillRect( x, y, w, h, backgroundColor() ).

Examples: listboxcombo/listboxcombo.cpp and showimg/showimg.cpp.

void QPainter::eraseRect ( const QRect & r )

Erases the area inside the rectangle r.

void QPainter::fillRect ( int x, int y, int w, int h, const QBrush & brush )

You can specify a QColor as brush, since there is a QBrush constructor that takes a QColor argument and creates a solid pattern brush.

See also drawRect().

Examples: listboxcombo/listboxcombo.cpp, progress/progress.cpp, qdir/qdir.cpp, qfd/fontdisplayer.cpp, themes/metal.cpp and themes/wood.cpp.

void QPainter::fillRect ( const QRect & r, const QBrush & brush )

Fills the rectangle r using brush brush.

void QPainter::flush ( const QRegion & region, CoordinateMode cm = CoordDevice )

The flush may update the whole device if the platform does not support flushing to a specified region.

See also CoordinateMode.

void QPainter::flush ()

Flushes any buffered drawing operations.

const QFont & QPainter::font () const

Returns the currently set painter font.

See also setFont() and QFont.

Example: fileiconview/qfileiconview.cpp.

QFontInfo QPainter::fontInfo () const

See also fontMetrics() and isActive().

QFontMetrics QPainter::fontMetrics () const

See also fontInfo() and isActive().

Examples: action/application.cpp, application/application.cpp, desktop/desktop.cpp, drawdemo/drawdemo.cpp, helpviewer/helpwindow.cpp, mdi/application.cpp and qwerty/qwerty.cpp.

HDC QPainter::handle () const

Returns the platform-dependent handle used for drawing. Using this function is not portable.

bool QPainter::hasClipping () const

Returns TRUE if clipping has been set; otherwise returns FALSE.

See also setClipping().

Example: themes/wood.cpp.

bool QPainter::hasViewXForm () const

Returns TRUE if view transformation is enabled; otherwise returns FALSE.

See also setViewXForm() and xForm().

bool QPainter::hasWorldXForm () const

Returns TRUE if world transformation is enabled; otherwise returns FALSE.

See also setWorldXForm().

bool QPainter::isActive () const

Returns TRUE if the painter is active painting, i.e. begin() has been called and end() has not yet been called; otherwise returns FALSE.

See also QPaintDevice::paintingActive().

Example: desktop/desktop.cpp.

void QPainter::lineTo ( int x, int y )

See also QPen, moveTo(), drawLine() and pos().

void QPainter::lineTo ( const QPoint & p )

Draws a line to the point p.

void QPainter::moveTo ( int x, int y )

See also lineTo() and pos().

void QPainter::moveTo ( const QPoint & p )

Moves to the point p.

const QPen & QPainter::pen () const

Returns the painter's current pen.

See also setPen().

Examples: progress/progress.cpp and themes/wood.cpp.

QPoint QPainter::pos () const

See also moveTo().

RasterOp QPainter::rasterOp () const

Returns the current raster operation.

See also setRasterOp() and RasterOp.

void QPainter::redirect ( QPaintDevice * pdev, QPaintDevice * replacement ) [static]

In general, you'll probably find calling QPixmap::grabWidget() or QPixmap::grabWindow() is an easier solution.

void QPainter::resetXForm ()

See also worldMatrix(), viewport() and window().

void QPainter::restore ()

See also save().

Example: aclock/aclock.cpp.

void QPainter::restoreWorldMatrix ()

We recommend using restore() instead.

void QPainter::rotate ( double a )

See also translate(), scale(), shear(), resetXForm(), setWorldMatrix() and xForm().

Examples: aclock/aclock.cpp, t10/cannon.cpp and t9/cannon.cpp.

void QPainter::save ()

See also restore().

Example: aclock/aclock.cpp.

void QPainter::saveWorldMatrix ()

We recommend using save() instead.

void QPainter::scale ( double sx, double sy )

See also translate(), shear(), rotate(), resetXForm(), setWorldMatrix() and xForm().

Example: xform/xform.cpp.

void QPainter::setBackgroundColor ( const QColor & c )

The background color is the color that is filled in when drawing opaque text, stippled lines and bitmaps. The background color has no effect in transparent background mode (which is the default).

See also backgroundColor(), setBackgroundMode() and BackgroundMode.

void QPainter::setBackgroundMode ( BGMode m )

Transparent mode draws stippled lines and text without setting the background pixels. Opaque mode fills these space with the current background color.

Note that in order to draw a bitmap or pixmap transparently, you must use QPixmap::setMask().

See also backgroundMode() and setBackgroundColor().

Example: picture/picture.cpp.

void QPainter::setBrush ( BrushStyle style )

See also brush() and QBrush.

Examples: aclock/aclock.cpp, drawdemo/drawdemo.cpp, picture/picture.cpp, t10/cannon.cpp, t9/cannon.cpp, themes/wood.cpp and tooltip/tooltip.cpp.

void QPainter::setBrush ( const QBrush & brush )

Sets the painter's brush to brush.

The brush defines how shapes are filled.

See also brush().

void QPainter::setBrush ( const QColor & color )

Sets the painter's brush to have style SolidPattern and the specified color.

See also brush() and QBrush.

void QPainter::setBrushOrigin ( int x, int y )

The brush origin specifies the (0, 0) coordinate of the painter's brush. This setting only applies to pattern brushes and pixmap brushes.

See also brushOrigin().

void QPainter::setBrushOrigin ( const QPoint & p )

Sets the brush origin to point p.

void QPainter::setClipRect ( int x, int y, int w, int h, CoordinateMode m = CoordDevice )

Sets the clip region to the rectangle x, y, w, h and enables clipping. The clip mode is set to m.

Note that the clip region is given in physical device coordinates and not subject to any coordinate transformation if m is equal to CoordDevice (the default). If m equals CoordPainter the returned region is in model coordinates.

See also setClipRegion(), clipRegion(), setClipping() and QPainter::CoordinateMode.

Examples: grapher/grapher.cpp, progress/progress.cpp, qtimage/qtimage.cpp, showimg/showimg.cpp, splitter/splitter.cpp and trivial/trivial.cpp.

void QPainter::setClipRect ( const QRect & r, CoordinateMode m = CoordDevice )

Sets the clip region to the rectangle r and enables clipping. The clip mode is set to m.

See also CoordinateMode.

void QPainter::setClipRegion ( const QRegion & rgn, CoordinateMode m = CoordDevice )

Note that the clip region is given in physical device coordinates and not subject to any coordinate transformation.

See also setClipRect(), clipRegion(), setClipping() and CoordinateMode.

Examples: qfd/fontdisplayer.cpp and themes/wood.cpp.

void QPainter::setClipping ( bool enable )

See also hasClipping(), setClipRect() and setClipRegion().

Example: themes/wood.cpp.

void QPainter::setFont ( const QFont & font )

This font is used by subsequent drawText() functions. The text color is the same as the pen color.

See also font() and drawText().

Examples: application/application.cpp, drawdemo/drawdemo.cpp, grapher/grapher.cpp, hello/hello.cpp, picture/picture.cpp, t13/cannon.cpp and xform/xform.cpp.

void QPainter::setPen ( const QPen & pen )

The pen defines how to draw lines and outlines, and it also defines the text color.

See also pen().

Examples: desktop/desktop.cpp, drawdemo/drawdemo.cpp, progress/progress.cpp, t10/cannon.cpp, t9/cannon.cpp, themes/metal.cpp and themes/wood.cpp.

void QPainter::setPen ( PenStyle style )

Sets the painter's pen to have style style, width 0 and black color.

See also pen() and QPen.

void QPainter::setPen ( const QColor & color )

Sets the painter's pen to have style SolidLine, width 0 and the specified color.

See also pen() and QPen.

void QPainter::setRasterOp ( RasterOp r )

See also rasterOp() and Qt::RasterOp.

void QPainter::setTabArray ( int * ta )

If both a tab array and a tab top size is set, the tab array wins.

See also tabArray(), setTabStops(), drawText() and fontMetrics().

void QPainter::setTabStops ( int ts )

Tab stops are used when drawing formatted text with ExpandTabs set. This fixed tab stop value is used only if no tab array is set (which is the default case).

See also tabStops(), setTabArray(), drawText() and fontMetrics().

void QPainter::setViewXForm ( bool enable )

See also hasViewXForm(), setWindow(), setViewport(), setWorldMatrix(), setWorldXForm() and xForm().

void QPainter::setViewport ( int x, int y, int w, int h )

The viewport rectangle is part of the view transformation. The viewport specifies the device coordinate system and is specified by the x, y, w width and h height parameters. Its sister, the window(), specifies the logical coordinate system.

The default viewport rectangle is the same as the device's rectangle. See the Coordinate System Overview for an overview of coordinate transformation.

See also viewport(), setWindow(), setViewXForm(), setWorldMatrix(), setWorldXForm() and xForm().

Example: aclock/aclock.cpp.

void QPainter::setViewport ( const QRect & r )

Sets the painter's viewport to rectangle r.

void QPainter::setWindow ( int x, int y, int w, int h )

The window rectangle is part of the view transformation. The window specifies the logical coordinate system and is specified by the x, y, w width and h height parameters. Its sister, the viewport(), specifies the device coordinate system.

The default window rectangle is the same as the device's rectangle. See the Coordinate System Overview for an overview of coordinate transformation.

See also window(), setViewport(), setViewXForm(), setWorldMatrix() and setWorldXForm().

Examples: aclock/aclock.cpp and drawdemo/drawdemo.cpp.

void QPainter::setWindow ( const QRect & r )

Sets the painter's window to rectangle r.

void QPainter::setWorldMatrix ( const QWMatrix & m, bool combine = FALSE )

If combine is TRUE, then m is combined with the current transformation matrix, otherwise m replaces the current transformation matrix.

If m is the identity matrix and combine is FALSE, this function calls setWorldXForm(FALSE). (The identity matrix is the matrix where QWMatrix::m11() and QWMatrix::m22() are 1.0 and the rest are 0.0.)

World transformations are applied after the view transformations (i.e. window and viewport).

The following functions can transform the coordinate system without using a QWMatrix:

• translate()
• scale()
• shear()
• rotate()

They operate on the painter's worldMatrix() and are implemented like this:

        void QPainter::rotate( double a )
        {
            QWMatrix m;
            m.rotate( a );
            setWorldMatrix( m, TRUE );
        }
    

Note that you should always use combine when you are drawing into a QPicture. Otherwise it may not be possible to replay the picture with additional transformations. Using translate(), scale(), etc., is safe.

For a brief overview of coordinate transformation, see the Coordinate System Overview.

See also worldMatrix(), setWorldXForm(), setWindow(), setViewport(), setViewXForm(), xForm() and QWMatrix.

Examples: drawdemo/drawdemo.cpp and xform/xform.cpp.

void QPainter::setWorldXForm ( bool enable )

See also setWorldMatrix(), setWindow(), setViewport(), setViewXForm() and xForm().

void QPainter::shear ( double sh, double sv )

See also translate(), scale(), rotate(), resetXForm(), setWorldMatrix() and xForm().

int * QPainter::tabArray () const

Returns the currently set tab stop array.

See also setTabArray().

int QPainter::tabStops () const

Returns the tab stop setting.

See also setTabStops().

void QPainter::translate ( double dx, double dy )

For example, the following code draws the same point twice:

        void MyWidget::paintEvent()
        {
            QPainter paint( this );

            paint.drawPoint( 0, 0 );

            paint.translate( 100.0, 40.0 );
            paint.drawPoint( -100, -40 );
        }
    

See also scale(), shear(), rotate(), resetXForm(), setWorldMatrix() and xForm().

Examples: helpviewer/helpwindow.cpp, t10/cannon.cpp, t9/cannon.cpp, themes/metal.cpp, themes/wood.cpp and xform/xform.cpp.

QRect QPainter::viewport () const

See also setViewport() and setViewXForm().

Example: aclock/aclock.cpp.

QRect QPainter::window () const

See also setWindow() and setViewXForm().

const QWMatrix & QPainter::worldMatrix () const

See also setWorldMatrix().

QPoint QPainter::xForm ( const QPoint & pv ) const

See also xFormDev() and QWMatrix::map().

QRect QPainter::xForm ( const QRect & rv ) const

Returns the rectangle rv transformed from model coordinates to device coordinates.

If world transformation is enabled and rotation or shearing has been specified, then the bounding rectangle is returned.

See also xFormDev() and QWMatrix::map().

QPointArray QPainter::xForm ( const QPointArray & av ) const

Returns the point array av transformed from model coordinates to device coordinates.

See also xFormDev() and QWMatrix::map().

QPointArray QPainter::xForm ( const QPointArray & av, int index, int npoints ) const

Returns the point array av transformed from model coordinates to device coordinates. The index is the first point in the array and npoints denotes the number of points to be transformed. If npoints is negative, all points from av[index] until the last point in the array are transformed.

The returned point array consists of the number of points that were transformed.

Example:

        QPointArray a(10);
        QPointArray b;
        b = painter.xForm(a, 2, 4);  // b.size() == 4
        b = painter.xForm(a, 2, -1); // b.size() == 8
    

See also xFormDev() and QWMatrix::map().

QRect QPainter::xFormDev ( const QRect & rd ) const

If world transformation is enabled and rotation or shearing is used, then the bounding rectangle is returned.

See also xForm() and QWMatrix::map().

QPoint QPainter::xFormDev ( const QPoint & pd ) const

Returns the point pd transformed from device coordinates to model coordinates.

See also xForm() and QWMatrix::map().

QPointArray QPainter::xFormDev ( const QPointArray & ad ) const

Returns the point array ad transformed from device coordinates to model coordinates.

See also xForm() and QWMatrix::map().

QPointArray QPainter::xFormDev ( const QPointArray & ad, int index, int npoints ) const

Returns the point array ad transformed from device coordinates to model coordinates. The index is the first point in the array and npoints denotes the number of points to be transformed. If npoints is negative, all points from ad[index] until the last point in the array are transformed.

The returned point array consists of the number of points that were transformed.

Example:

        QPointArray a(10);
        QPointArray b;
        b = painter.xFormDev(a, 1, 3);  // b.size() == 3
        b = painter.xFormDev(a, 1, -1); // b.size() == 9
    

See also xForm() and QWMatrix::map().

Related Functions

void qDrawPlainRect ( QPainter * p, int x, int y, int w, int h, const QColor & c, int lineWidth, const QBrush * fill )

#include <qdrawutil.h>

Draws the plain rectangle specified by (x, y, w, h) using the painter p.

The color argument c specifies the line color.

The lineWidth argument specifies the line width.

The rectangle's interior is filled with the fill brush unless fill is 0.

If you want to use a QFrame widget instead, you can make it display a plain rectangle, for example QFrame::setFrameStyle( QFrame::Box | QFrame::Plain ).

Warning: This function does not look at QWidget::style() or QApplication::style(). Use the drawing functions in QStyle to make widgets that follow the current GUI style.

See also qDrawShadeRect() and QStyle::drawPrimitive().

void qDrawShadeLine ( QPainter * p, int x1, int y1, int x2, int y2, const QColorGroup & g, bool sunken, int lineWidth, int midLineWidth )

#include <qdrawutil.h>

Draws a horizontal (y1 == y2) or vertical (x1 == x2) shaded line using the painter p.

Nothing is drawn if y1 != y2 and x1 != x2 (i.e. the line is neither horizontal nor vertical).

The color group argument g specifies the shading colors (light, dark and middle colors).

The line appears sunken if sunken is TRUE, or raised if sunken is FALSE.

The lineWidth argument specifies the line width for each of the lines. It is not the total line width.

The midLineWidth argument specifies the width of a middle line drawn in the QColorGroup::mid() color.

If you want to use a QFrame widget instead, you can make it display a shaded line, for example QFrame::setFrameStyle( QFrame::HLine | QFrame::Sunken ).

Warning: This function does not look at QWidget::style() or QApplication::style(). Use the drawing functions in QStyle to make widgets that follow the current GUI style.

See also qDrawShadeRect(), qDrawShadePanel() and QStyle::drawPrimitive().

void qDrawShadePanel ( QPainter * p, int x, int y, int w, int h, const QColorGroup & g, bool sunken, int lineWidth, const QBrush * fill )

#include <qdrawutil.h>

Draws the shaded panel specified by (x, y, w, h) using the painter p.

The color group argument g specifies the shading colors (light, dark and middle colors).

The panel appears sunken if sunken is TRUE, or raised if sunken is FALSE.

The lineWidth argument specifies the line width.

The panel's interior is filled with the fill brush unless fill is 0.

If you want to use a QFrame widget instead, you can make it display a shaded panel, for example QFrame::setFrameStyle( QFrame::Panel | QFrame::Sunken ).

Warning: This function does not look at QWidget::style() or QApplication::style(). Use the drawing functions in QStyle to make widgets that follow the current GUI style.

See also qDrawWinPanel(), qDrawShadeLine(), qDrawShadeRect() and QStyle::drawPrimitive().

void qDrawShadeRect ( QPainter * p, int x, int y, int w, int h, const QColorGroup & g, bool sunken, int lineWidth, int midLineWidth, const QBrush * fill )

#include <qdrawutil.h>

Draws the shaded rectangle specified by (x, y, w, h) using the painter p.

The color group argument g specifies the shading colors (light, dark and middle colors).

The rectangle appears sunken if sunken is TRUE, or raised if sunken is FALSE.

The lineWidth argument specifies the line width for each of the lines. It is not the total line width.

The midLineWidth argument specifies the width of a middle line drawn in the QColorGroup::mid() color.

The rectangle's interior is filled with the fill brush unless fill is 0.

If you want to use a QFrame widget instead, you can make it display a shaded rectangle, for example QFrame::setFrameStyle( QFrame::Box | QFrame::Raised ).

Warning: This function does not look at QWidget::style() or QApplication::style(). Use the drawing functions in QStyle to make widgets that follow the current GUI style.

See also qDrawShadeLine(), qDrawShadePanel(), qDrawPlainRect(), QStyle::drawItem(), QStyle::drawControl() and QStyle::drawComplexControl().

void qDrawWinButton ( QPainter * p, int x, int y, int w, int h, const QColorGroup & g, bool sunken, const QBrush * fill )

#include <qdrawutil.h>

Draws the Windows-style button specified by (x, y, w, h) using the painter p.

The color group argument g specifies the shading colors (light, dark and middle colors).

The button appears sunken if sunken is TRUE, or raised if sunken is FALSE.

The line width is 2 pixels.

The button's interior is filled with the *fill brush unless fill is 0.

Warning: This function does not look at QWidget::style() or QApplication::style(). Use the drawing functions in QStyle to make widgets that follow the current GUI style.

See also qDrawWinPanel() and QStyle::drawControl().

void qDrawWinPanel ( QPainter * p, int x, int y, int w, int h, const QColorGroup & g, bool sunken, const QBrush * fill )

#include <qdrawutil.h>

Draws the Windows-style panel specified by (x, y, w, h) using the painter p.

The color group argument g specifies the shading colors.

The panel appears sunken if sunken is TRUE, or raised if sunken is FALSE.

The line width is 2 pixels.

The button's interior is filled with the fill brush unless fill is 0.

If you want to use a QFrame widget instead, you can make it display a shaded panel, for example QFrame::setFrameStyle( QFrame::WinPanel | QFrame::Raised ).

Warning: This function does not look at QWidget::style() or QApplication::style(). Use the drawing functions in QStyle to make widgets that follow the current GUI style.

See also qDrawShadePanel(), qDrawWinButton() and QStyle::drawPrimitive().

This file is part of the Qt toolkit. Copyright © 1995-2002 Trolltech. All Rights Reserved.