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The QPainter class does low-level painting e.g. on widgets. More...
#include <qpainter.h>
Inherits Qt.
Inherited by QDirectPainter.
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:
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:
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.
See also clipRegion().
See also drawText().
Notice that all painter settings (setPen, setBrush etc.) are reset to default values when begin() is called.
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().
Returns the current background color.
See also setBackgroundColor() and QColor.
Returns the current background mode.
See also setBackgroundMode() and BGMode.
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.
Examples: aclock/aclock.cpp, application/application.cpp, desktop/desktop.cpp, hello/hello.cpp, picture/picture.cpp, t10/cannon.cpp, and xform/xform.cpp.
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().
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:
| Flag | Meaning |
|---|---|
| AlignAuto | aligns according to the language, usually left. |
| AlignLeft | aligns to the left border. |
| AlignRight | aligns to the right border. |
| AlignHCenter | aligns horizontally centered. |
| AlignTop | aligns to the top border. |
| AlignBottom | aligns to the bottom border. |
| AlignVCenter | aligns vertically centered. |
| AlignCenter | (== AlignHCenter | AlignVCenter). |
| SingleLine | ignores newline characters in the text. |
| ExpandTabs | expands tabs. |
| ShowPrefix | interprets "&x" as "x". |
| WordBreak | breaks the text to fit the rectangle. |
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.
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.
Returns the painter's current brush.
See also QPainter::setBrush().
Examples: themes/metal.cpp and themes/wood.cpp.
Returns the brush origin currently set.
See also setBrushOrigin().
See also setClipRegion(), setClipRect(), setClipping(), and QPainter::CoordinateMode.
Example: themes/wood.cpp.
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.
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().
Draws the arc that fits inside the rectangle r with start angle a and arc length 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().
Draws a chord that fits inside the rectangle r with start angle a and arc length alen.
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.
Control points after a[index + 3] are ignored. Nothing happens if there aren't enough control points.
Examples: drawdemo/drawdemo.cpp, picture/picture.cpp, and tictac/tictac.cpp.
Draws the ellipse that fits inside rectangle r.
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.
Draws the rectangle sr from the image at the given point.
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.
Draws the image i into the rectangle r. The image will be scaled to fit the rectangle if image and rectangle dimensions differ.
See also pen().
Examples: aclock/aclock.cpp, drawlines/connect.cpp, progress/progress.cpp, splitter/splitter.cpp, themes/metal.cpp, and themes/wood.cpp.
Draws a line from point p1 to point p2.
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.
This function does exactly the same as QPicture::play() when called with (x, y) = (0, 0).
Examples: picture/picture.cpp and xform/xform.cpp.
Use one of the other QPainter::drawPicture() functions with a (0, 0) offset instead.
Draws picture pic at point p.
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.
Draws a pie segment that fits inside the rectangle r with start angle a and arc length alen.
(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, qmag/qmag.cpp, showimg/showimg.cpp, t10/cannon.cpp, and xform/xform.cpp.
Draws the rectangle sr of pixmap pm with its origin at point p.
Draws the pixmap pm with its origin at point p.
Draws the pixmap pm into the rectangle r. The pixmap is scaled to fit the rectangle, if image and rectangle size disagree.
See also QPen.
Examples: desktop/desktop.cpp and drawlines/connect.cpp.
Draws the point p.
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.
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.
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.
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.
Draws the rectangle r.
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.
Examples: drawdemo/drawdemo.cpp and themes/wood.cpp.
Draws a rounded rectangle r, rounding to the x position xRnd and the y position yRnd on each corner.
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.
Note that the meaning of y is not the same for the two drawText() varieties. For overloads that take a simple x, y pair (or a point), the y value is the text's baseline; for overloads that take a rectangle, rect.y() is the top of the rectangle and the text is aligned within that rectangle in accordance with the alignment flags.
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.
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
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.
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Draws the text at the given point.
See also QPainter::TextDirection.
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
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.
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
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.
Draws at most len characters from str in the rectangle r.
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().
(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().
Draws a tiled pixmap, pm, inside rectangle r with its origin at point sp.
Draws a tiled pixmap, pm, inside rectangle r.
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().
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().
Draws rectangle r as a window focus rectangle.
Draws rectangle r as a window focus rectangle using background color bgColor.
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( 0, 0, 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.
Erases the area inside x, y, w, h. Equivalent to fillRect( x, y, w, h, backgroundColor() ).
Examples: listboxcombo/listboxcombo.cpp and showimg/showimg.cpp.
Erases the area inside the rectangle r.
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.
Fills the rectangle r using brush brush.
The flush may update the whole device if the platform does not support flushing to a specified region.
See also CoordinateMode.
Flushes any buffered drawing operations.
Returns the currently set painter font.
Example: fileiconview/qfileiconview.cpp.
See also fontMetrics() and isActive().
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.
Returns the platform-dependent handle used for drawing. Using this function is not portable.
Returns TRUE if clipping has been set; otherwise returns FALSE.
See also setClipping().
Example: themes/wood.cpp.
Returns TRUE if view transformation is enabled; otherwise returns FALSE.
See also setViewXForm() and xForm().
Returns TRUE if world transformation is enabled; otherwise returns FALSE.
See also setWorldXForm().
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.
Use drawLine() instead.
Draws a line from the current pen position to (x, y) and sets (x, y) to be the new current pen position.
See also QPen, moveTo(), drawLine(), and pos().
Draws a line to the point p.
Sets the current pen position to (x, y)
Moves to the point p.
Returns the painter's current pen.
See also setPen().
Examples: progress/progress.cpp and themes/wood.cpp.
Returns the current position of the pen.
See also moveTo().
Returns the current raster operation.
See also setRasterOp() and RasterOp.
In general, you'll probably find calling QPixmap::grabWidget() or QPixmap::grabWindow() is an easier solution.
See also worldMatrix(), viewport(), and window().
See also save().
Example: aclock/aclock.cpp.
We recommend using restore() instead.
See also translate(), scale(), shear(), resetXForm(), setWorldMatrix(), and xForm().
Examples: aclock/aclock.cpp, t10/cannon.cpp, and t9/cannon.cpp.
See also restore().
Example: aclock/aclock.cpp.
We recommend using save() instead.
See also translate(), shear(), rotate(), resetXForm(), setWorldMatrix(), and xForm().
Example: xform/xform.cpp.
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.
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.
Examples: aclock/aclock.cpp, drawdemo/drawdemo.cpp, picture/picture.cpp, t10/cannon.cpp, t9/cannon.cpp, themes/wood.cpp, and tooltip/tooltip.cpp.
Sets the painter's brush to brush.
The brush defines how shapes are filled.
See also brush().
Sets the painter's brush to have style SolidPattern and the specified color.
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().
Sets the brush origin to point p.
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, showimg/showimg.cpp, splitter/splitter.cpp, and trivial/trivial.cpp.
Sets the clip region to the rectangle r and enables clipping. The clip mode is set to m.
See also CoordinateMode.
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.
See also hasClipping(), setClipRect(), and setClipRegion().
Example: themes/wood.cpp.
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.
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.
Sets the painter's pen to have style style, width 0 and black color.
Sets the painter's pen to have style SolidLine, width 0 and the specified color.
See also rasterOp() and Qt::RasterOp.
If both a tab array and a tab top size is set, the tab array wins.
See also tabArray(), setTabStops(), drawText(), and fontMetrics().
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().
See also hasViewXForm(), setWindow(), setViewport(), setWorldMatrix(), setWorldXForm(), and xForm().
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.
Sets the painter's viewport to rectangle r.
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.
Sets the painter's window to rectangle r.
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:
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.
See also setWorldMatrix(), setWindow(), setViewport(), setViewXForm(), and xForm().
See also translate(), scale(), rotate(), resetXForm(), setWorldMatrix(), and xForm().
Returns the currently set tab stop array.
See also setTabArray().
Returns the tab stop setting.
See also setTabStops().
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.
See also setViewport() and setViewXForm().
Example: aclock/aclock.cpp.
See also setWindow() and setViewXForm().
See also setWorldMatrix().
See also xFormDev() and QWMatrix::map().
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().
Returns the point array av transformed from model coordinates to device coordinates.
See also xFormDev() and QWMatrix::map().
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().
If world transformation is enabled and rotation or shearing is used, then the bounding rectangle is returned.
See also xForm() and QWMatrix::map().
Returns the point pd transformed from device coordinates to model coordinates.
See also xForm() and QWMatrix::map().
Returns the point array ad transformed from device coordinates to model coordinates.
See also xForm() and QWMatrix::map().
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().
#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().
#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().
#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().
#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().
#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().
#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 © 1995-2003 Trolltech. All Rights Reserved.
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