QPainter Class Reference
The QPainter class paints on paint devices.
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#include <qpainter.h>
Inherits Qt.
List of all member functions.
Public Members
Static Public Members
voidÂ
redirect ( QPaintDevice * pdev, QPaintDevice * replacement )Â
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Related Functions
(Note that these are not member functions.)
- void qDrawPlainRect (QPainter * p, int x, int y, int w, int h, const QColor & c, int lineWidth, const QBrush * fill)
- void qDrawWinPanel (QPainter * p, int x, int y, int w, int h, const QColorGroup & g, bool sunken, const QBrush * fill)
- void qDrawShadeLine (QPainter * p, int x1, int y1, int x2, int y2, const QColorGroup & g, bool sunken, int lineWidth, int midLineWidth)
- void qDrawShadeRect (QPainter * p, int x, int y, int w, int h, const QColorGroup & g, bool sunken, int lineWidth, int midLineWidth, const QBrush * fill)
- void qDrawShadePanel (QPainter * p, int x, int y, int w, int h, const QColorGroup & g, bool sunken, int lineWidth, const QBrush * fill)
- void qDrawWinButton (QPainter * p, int x, int y, int w, int h, const QColorGroup & g, bool sunken, const QBrush * fill)
Detailed Description
The QPainter class paints on paint devices.
The painter provides efficient graphics rendering on any
QPaintDevice object. 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()).
Here's one very simple example:
void SimpleExampleWidget::paintEvent()
{
QPainter paint( this );
paint.setPen( Qt::blue );
paint.drawText( rect(), AlignCenter, "The Text" );
}
Simple. However, there are many settings you may use:
- font() is the currently set font. If you set a font that isn't
available, Qt finds a close match. In that case font() returns what
you set using setFont() and fontInfo() returns the font actually
being used.
- 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, ie. 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 data 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 a
paragraph below for a quick 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, changing
calling e.g. 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(), and
drawQuadBezier().
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() 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 walkthrough of 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 matrix().
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 draws 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 a little speed.
After all the coordinate transformation is done, QPainter can clip
the drawing to and 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 too will clip a bit.
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().
Finally, QPainter includes some little-used functions that are very
handy the few times you need them.
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 and Coordinate System Overview
Examples:
forever/forever.cpp
trivial/trivial.cpp
splitter/splitter.cpp
qtimage/qtimage.cpp
progress/progress.cpp
movies/main.cpp
picture/picture.cpp
xform/xform.cpp
menu/menu.cpp
drawlines/connect.cpp
qmag/qmag.cpp
desktop/desktop.cpp
scrollview/scrollview.cpp
grapher/grapher.cpp
drawdemo/drawdemo.cpp
Member Function Documentation
QPainter::QPainter ()
Constructs a painter.
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 )
Constructs a painter that begins painting the paint device pd
immediately.
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
}
See also begin() and end().
QPainter::QPainter ( const QPaintDevice * pd, const QWidget * copyAttributes )
Constructs a painter that begins painting the paint device pd
immediately, with the default arguments taken from copyAttributes.
See also begin().
QPainter::~QPainter ()
Destructs the painter.
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 )
Begins painting the paint device pd and returns TRUE if successful,
or FALSE if an error occurs.
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:
picture/picture.cpp
desktop/desktop.cpp
drawdemo/drawdemo.cpp
bool QPainter::begin ( const QPaintDevice * pd, const QWidget * copyAttributes )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
This version opens the painter on a paint device pd and sets the initial
pen, background color and font from copyAttributes. This is equivalent
with:
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 widgets's
font etc. This function does exactly that.
Example:
void MyWidget::paintEvent( QPaintEvent * )
{
QPixmap pm(size());
QPainter p;
p.begin(&pm, this);
// ... potential 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 tf, const QString & str, int len = -1, char ** internal=0 )
Returns the bounding rectangle of the aligned text that would be
printed with the corresponding drawText() function (the first len
characters from str). The drawing, and hence the bounding
rectangle, is constrained to the rectangle (x,y,w,h).
If len is negative (default value), the whole string is used.
The tf argument is
the bitwise OR of the following flags:
-
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 tabulators.
-
ShowPrefix interprets "&x" as "x" underlined.
-
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.
These flags are defined in qnamespace.h.
See also drawText(), fontMetrics(), QFontMetrics::boundingRect() and Qt::AlignmentFlags.
QRect QPainter::boundingRect ( const QRect & r, int tf, const QString &, int len = -1, char ** i=0 )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
const QBrush & QPainter::brush () const
Returns the current painter brush.
See also QPainter::setBrush().
const QPoint & QPainter::brushOrigin () const
Returns the brush origin currently set.
See also setBrushOrigin().
void QPainter::cleanup () [static]
Internal function that cleans up the painter.
const QRegion & QPainter::clipRegion () const
Returns the currently set clip region. Note that the clip region is
given in physical device coordinates and not subject to any
coordinate transformation.
See also setClipRegion(), setClipRect() and setClipping().
QPaintDevice * QPainter::device () const
Returns the paint device on which this painter is currently
painting, or null if the painter is not active.
See also QPaintDevice::paintingActive().
void QPainter::drawArc ( int x, int y, int w, int h, int a, int alen )
Draws an arc defined by the rectangle (x,y,w,h), the start
angle a and the arc length 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 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 )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawChord ( int x, int y, int w, int h, int a, int alen )
Draws a chord defined by the rectangle (x,y,w,h), the start
angle a and the 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 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 )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawEllipse ( int x, int y, int w, int h )
Draws an ellipse with center at (x+w/2,y+h/2) and size (w,h).
Examples:
picture/picture.cpp
drawdemo/drawdemo.cpp
void QPainter::drawEllipse ( const QRect & r )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawImage ( int x, int y, const QImage & image, int sx, int sy, int sw, int sh, int conversion_flags )
Draws at (x, y) the sw by sh area of pixels
from (sx, sy) in image, using conversion_flags if
the image needs to be converted to a pixmap.
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.
See also drawPixmap() and QPixmap::convertFromImage().
void QPainter::drawImage ( const QPoint &, const QImage & )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawImage ( const QPoint &, const QImage &, const QRect & sr )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawImage ( const QPoint &, const QImage &, const QRect & sr, int conversion_flags )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawImage ( const QPoint &, const QImage &, int conversion_flags )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawImage ( int x, int y, const QImage & image, int sx=0, int sy=0, int sw=-1, int sh=-1 )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawLine ( int x1, int y1, int x2, int y2 )
Draws a line from (x1,y2) to (x2,y2) and sets (x2,y2) to be
the new current pen position.
See also QPen.
Examples:
splitter/splitter.cpp
progress/progress.cpp
drawlines/connect.cpp
scrollview/scrollview.cpp
grapher/grapher.cpp
void QPainter::drawLine ( const QPoint & p1, const QPoint & p2 )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawLineSegments ( const QPointArray & a, int index=0, int nlines=-1 )
Draws nlines separate lines from points defined in a, starting
at a[index] (index defaults to 0). If nlines is -1 (the
defauls) all points until the end of the array are used
(i.e. (a.size()-index)/2 lines are drawn).
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 ( const QPicture & pic )
Replays the picture pic.
This function does exactly the same as QPicture::play().
Examples:
picture/picture.cpp
void QPainter::drawPie ( int x, int y, int w, int h, int a, int alen )
Draws a pie defined by the rectangle (x,y,w,h), the start
angle a and the arc length 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 clockwise direction.
Zero degrees is at the 3'o clock position.
See also drawArc() and drawChord().
Examples:
grapher/grapher.cpp
drawdemo/drawdemo.cpp
void QPainter::drawPie ( const QRect & r, int a, int alen )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawPixmap ( int x, int y, const QPixmap & pixmap, int sx=0, int sy=0, int sw=-1, int sh=-1 )
Draws a pixmap at (x,y) by copying a part of pixmap into the
paint device.
(x,y) specify the top-left point in the paint device that is to
be drawn onto. (sx,sy) specify the top-left point in pixmap
that is to be drawn (the default is (0,0). (sw,sh) specify the
size of the pixmap that is to be drawn (the default, (-1,-1), means
all the way to the right/bottom of the pixmap).
See also bitBlt() and QPixmap::setMask().
Examples:
qtimage/qtimage.cpp
movies/main.cpp
picture/picture.cpp
qmag/qmag.cpp
scrollview/scrollview.cpp
grapher/grapher.cpp
void QPainter::drawPixmap ( const QPoint & p, const QPixmap & pm )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
This version of the call draws the entire pixmap.
void QPainter::drawPixmap ( const QPoint & p, const QPixmap & pm, const QRect & sr )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawPoint ( int x, int y )
Draws/plots a single point at (x,y) using the current pen.
See also QPen.
Examples:
drawlines/connect.cpp
desktop/desktop.cpp
void QPainter::drawPoint ( const QPoint & p )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawPoints ( const QPointArray & a, int index=0, int npoints=-1 )
Draws/plots an array of points using the current pen.
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 is is zero or greater, npoints points are drawn.
void QPainter::drawPolygon ( const QPointArray & a, bool winding=FALSE, int index=0, int npoints=-1 )
Draws the polygon defined by the npoints points in a starting at
a[index]. (index defaults to 0.)
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:
picture/picture.cpp
desktop/desktop.cpp
void QPainter::drawPolyline ( const QPointArray & a, int index=0, int npoints=-1 )
Draws the polyline defined by the npoints points in a starting
at a[index]. (index defaults to 0.)
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.
void QPainter::drawQuadBezier ( const QPointArray & a, int index=0 )
Draws a cubic Bezier curve defined by the control points in a,
starting at a[index]. (index defaults to 0.)
Control points after a[index+3] are ignored. Nothing happens if
there aren't enough control points.
void QPainter::drawRect ( int x, int y, int w, int h )
Draws a rectangle with upper left corner at (x,y) and with
width w and height h.
See also QPen and drawRoundRect().
Examples:
forever/forever.cpp
trivial/trivial.cpp
picture/picture.cpp
grapher/grapher.cpp
drawdemo/drawdemo.cpp
void QPainter::drawRect ( const QRect & r )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawRoundRect ( int x, int y, int w, int h, int xRnd, int yRnd )
Draws a rectangle with round corners at (x,y), with width w
and height h.
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
void QPainter::drawRoundRect ( const QRect & r, int xRnd, int yRnd )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawRoundRect ( const QRect & )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
As the main version of the function, but with the roundness
arguments fixed at 25.
void QPainter::drawRoundRect ( int x, int y, int w, int h )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
As the main version of the function, but with the roundness
arguments fixed at 25.
void QPainter::drawText ( int x, int y, const QString & str, int len = -1 )
Draws at most len characters from str at position (x,y).
(x,y) is the base line position. Note that the meaning of
y is not the same for the two drawText() varieties.
Examples:
trivial/trivial.cpp
progress/progress.cpp
movies/main.cpp
picture/picture.cpp
menu/menu.cpp
desktop/desktop.cpp
scrollview/scrollview.cpp
grapher/grapher.cpp
drawdemo/drawdemo.cpp
void QPainter::drawText ( int x, int y, int w, int h, int tf, const QString & str, int len = -1, QRect * brect=0, char ** internal=0 )
Draws at most len characters from str in the rectangle (x,y,w,h).
Note that the meaning of y is not the same for the two drawText()
varieties.
This function draws formatted text. The tf text formatting is
really of type Qt::AlignmentFlags.
Horizontal alignment defaults to AlignLeft and vertical alignment
defaults to AlignTop.
brect (if non-null) is set to the actual bounding rectangle of
the output. internal is, yes, internal.
See also boundingRect().
void QPainter::drawText ( const QPoint & p, const QString &, int len = -1 )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawText ( const QRect & r, int tf, const QString &, int len = -1, QRect * br=0, char ** i=0 )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawTiledPixmap ( int x, int y, int w, int h, const QPixmap & pixmap, int sx=0, int sy=0 )
Draws a tiled pixmap in the specified rectangle.
(x,y) specify the top-left point in the paint device that is to
be drawn onto. (sx,sy) specify 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 )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawTiledPixmap ( const QRect & r, const QPixmap & pm, const QPoint & sp )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
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 ( int x, int y, int w, int h, const QColor & bgColor )
Draws a Windows focus rectangle with upper left corner at (x,y) and with
width w and height h using a pen color that contrasts with 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 ( const QRect & r )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::drawWinFocusRect ( const QRect & r, const QColor & bgColor )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
bool QPainter::end ()
Ends painting. Any resources used while painting are released.
Note that while you mostly don't need to call end(), the destructor
will do it, there is at least one common case, 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:
picture/picture.cpp
desktop/desktop.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() )
void QPainter::eraseRect ( const QRect & r )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::fillRect ( int x, int y, int w, int h, const QBrush & brush )
Fills the rectangle (x,y,w,h) with the 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:
progress/progress.cpp
scrollview/scrollview.cpp
void QPainter::fillRect ( const QRect & r, const QBrush & brush )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::flush ()
Flushes any buffered drawing operations.
const QFont & QPainter::font () const
Returns the currently set painter font.
See also setFont() and QFont.
QFontInfo QPainter::fontInfo () const
Returns the font info for the painter, if the painter is active. It
is not possible to obtain font information for an inactive painter,
so the return value is undefined if the painter is not active.
See also fontMetrics() and isActive().
QFontMetrics QPainter::fontMetrics () const
Returns the font metrics for the painter, if the painter is active.
It is not possible to obtain metrics for an inactive painter, so the
return value is undefined if the painter is not active.
See also fontInfo() and isActive().
Examples:
movies/main.cpp
desktop/desktop.cpp
scrollview/scrollview.cpp
drawdemo/drawdemo.cpp
bool QPainter::hasClipping () const
Returns TRUE if clipping has been set, otherwise FALSE.
See also setClipping().
bool QPainter::hasViewXForm () const
Returns TRUE if view transformation is enabled, otherwise FALSE.
See also setViewXForm() and xForm().
bool QPainter::hasWorldXForm () const
Returns TRUE if world transformation is enabled, otherwise FALSE.
See also setWorldXForm().
void QPainter::initialize () [static]
Internal function that initializes the painter.
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.
See also QPaintDevice::paintingActive().
Examples:
desktop/desktop.cpp
void QPainter::lineTo ( int x, int y )
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().
void QPainter::lineTo ( const QPoint & p )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::moveTo ( int x, int y )
Sets the current pen position to (x,y)
See also lineTo() and pos().
void QPainter::moveTo ( const QPoint & p )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
const QPen & QPainter::pen () const
Returns the current pen for the painter.
See also setPen().
Examples:
progress/progress.cpp
QPoint QPainter::pos () const
Returns the current position of the pen.
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]
Redirects all paint command for a paint device pdev to another
paint device replacement, unless replacement is 0. If replacement is 0, the redirection for pdev is removed.
Mostly, you can get better results with less work by calling
QPixmap::grabWidget() or QPixmap::grapWindow().
void QPainter::resetXForm ()
Resets any transformations that were made using translate(), scale(),
shear(), rotate(), setWorldMatrix(), setViewport() and setWindow()
See also worldMatrix(), viewport() and window().
void QPainter::restore ()
Restores the current painter state (pops a saved state off the stack).
See also save().
void QPainter::restoreWorldMatrix ()
This function is obsolete. It is provided to keep old source working, and will probably be removed in a future version of Qt. We strongly advise against using it in new code.
We recommend using save() instead.
void QPainter::rotate ( double a )
Rotates the coordinate system a degrees.
See also translate(), scale(), shear(), resetXForm(), setWorldMatrix() and xForm().
void QPainter::save ()
Saves the current painter state (pushes the state onto a stack). A
save() must be followed by a corresponding restore(). end() unwinds
the stack().
See also restore().
void QPainter::saveWorldMatrix ()
This function is obsolete. It is provided to keep old source working, and will probably be removed in a future version of Qt. We strongly advise against using it in new code.
We recommend using save() instead.
void QPainter::scale ( double sx, double sy )
Scales the coordinate system by (sx,sy).
See also translate(), shear(), rotate(), resetXForm(), setWorldMatrix() and xForm().
void QPainter::setBackgroundColor ( const QColor & c )
Sets the background color of the painter to 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 )
Sets the background mode of the painter to m, which must be one
of TransparentMode (the default) and OpaqueMode.
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().
Examples:
picture/picture.cpp
void QPainter::setBrush ( BrushStyle style )
Sets a new painter brush with black color and the specified style.
See also brush() and QBrush.
void QPainter::setBrush ( const QBrush & brush )
Sets a new painter brush.
The brush defines how to fill shapes.
See also brush().
void QPainter::setBrush ( const QColor & color )
Sets a new painter brush with the style SolidPattern and the specified
color.
See also brush() and QBrush.
Examples:
forever/forever.cpp
picture/picture.cpp
desktop/desktop.cpp
grapher/grapher.cpp
drawdemo/drawdemo.cpp
void QPainter::setBrushOrigin ( int x, int y )
Sets the brush origin to (x,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 )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::setClipRect ( int x, int y, int w, int h )
Sets the clip region to the the rectangle (x,y,w,h) and enables clipping.
Note that the clip region is given in physical device coordinates and
not subject to any coordinate
transformation.
See also setClipRegion(), clipRegion() and setClipping().
Examples:
trivial/trivial.cpp
splitter/splitter.cpp
qtimage/qtimage.cpp
progress/progress.cpp
grapher/grapher.cpp
void QPainter::setClipRect ( const QRect & r )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
If the rectangle is invalid, the rectangle will be normalized() before the clipping region is set. This semantics will change in Qt-3
and an invalid rectangle will clip the painter to an empty rectangle.
See also QRect::isValid() and QRect::normalize().
void QPainter::setClipRegion ( const QRegion & rgn )
Sets the clip region to rgn and enables clipping.
Note that the clip region is given in physical device coordinates and
not subject to any coordinate
transformation.
See also setClipRect(), clipRegion() and setClipping().
void QPainter::setClipping ( bool enable )
Enables clipping if enable is TRUE, or disables clipping if enable
is FALSE.
See also hasClipping(), setClipRect() and setClipRegion().
void QPainter::setFont ( const QFont & font )
Sets a new painter 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:
movies/main.cpp
picture/picture.cpp
menu/menu.cpp
scrollview/scrollview.cpp
grapher/grapher.cpp
drawdemo/drawdemo.cpp
void QPainter::setPen ( PenStyle style )
Sets a new painter pen with style style, width 0 and black color.
See also pen() and QPen.
Examples:
forever/forever.cpp
progress/progress.cpp
movies/main.cpp
drawlines/connect.cpp
desktop/desktop.cpp
scrollview/scrollview.cpp
grapher/grapher.cpp
drawdemo/drawdemo.cpp
void QPainter::setPen ( const QColor & color )
Sets a new painter pen with style SolidLine, width 0 and the specified
color.
See also pen() and QPen.
void QPainter::setPen ( const QPen & pen )
Sets a new painter pen.
The pen defines how to draw lines and outlines, and it also defines
the text color.
See also pen().
void QPainter::setRasterOp ( RasterOp r )
Sets the raster operation to r. The default is CopyROP.
See also rasterOp().
void QPainter::setTabArray ( int * ta )
Sets the tab stop array to ta. This puts tab stops at ta[0],
ta[1] and so on. The array is null-terminated.
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 )
Set the tab stop width to ts, ie. locates tab stops at ts, 2*ts,
3*ts and so on.
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 )
Enables view transformations if enable is TRUE, or disables
view transformations if enable is FALSE.
See also hasViewXForm(), setWindow(), setViewport(), setWorldMatrix(), setWorldXForm() and xForm().
void QPainter::setViewport ( int x, int y, int w, int h )
Sets the viewport rectangle view transformation for the painter and
enables view transformation.
The viewport rectangle is part of the view transformation. The
viewport specifies the device coordinate system. 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().
void QPainter::setViewport ( const QRect & r )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::setWindow ( int x, int y, int w, int h )
Sets the window rectangle view transformation for the painter and
enables view transformation.
The window rectangle is part of the view transformation. The window
specifies the logical coordinate system. 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:
drawdemo/drawdemo.cpp
void QPainter::setWindow ( const QRect & r )
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
void QPainter::setWorldMatrix ( const QWMatrix & m, bool combine=FALSE )
Sets the world transformation matrix to m and enables world
transformation.
If combine is TRUE, then m is combined with the current
transformation matrix, otherwise m replaces the current
transformation matrix.
If m 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
void QPainter::setWorldXForm ( bool enable )
Enables world transformations if enable is TRUE, or disables
world transformations if enable is FALSE. The world
transformation matrix is not changed.
See also setWorldMatrix(), setWindow(), setViewport(), setViewXForm() and xForm().
void QPainter::shear ( double sh, double sv )
Shears the coordinate system (sh,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 )
Translates the coordinate system by (dx,dy).
For example, the following code draws a single vertical line 20 pixels high.
void MyWidget::paintEvent()
{
QPainter paint( this );
paint.drawLine(10,0,10,20);
paint.translate(100.0,100.0);
paint.drawLine(-90,-80,-90,-70);
}
See also scale(), shear(), rotate(), resetXForm(), setWorldMatrix() and xForm().
QRect QPainter::viewport () const
Returns the viewport rectangle.
See also setViewport() and setViewXForm().
QRect QPainter::window () const
Returns the window rectangle.
See also setWindow() and setViewXForm().
const QWMatrix & QPainter::worldMatrix () const
Returns the world transformation matrix.
See also setWorldMatrix().
QPoint QPainter::xForm ( const QPoint & pv ) const
Returns the point pv transformed from model coordinates to device
coordinates.
See also xFormDev() and QWMatrix::map().
QPointArray QPainter::xForm ( const QPointArray & av ) const
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
Returns the 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
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
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::xForm ( const QRect & rv ) const
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
Returns the 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().
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().
QRect QPainter::xFormDev ( const QRect & rd ) const
Returns the rectangle rd transformed from device coordinates to model
coordinates.
If world transformation is enabled and rotation or shearing is used,
then the bounding rectangle is returned.
See also xForm() and QWMatrix::map().
QPointArray QPainter::xFormDev ( const QPointArray & ad, int index, int npoints ) const
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
Returns the 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 a plain rectangle given 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 interior is filled with the fill brush unless fill
is null.
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::drawRect().
void qDrawWinPanel (QPainter * p, int x, int y, int w, int h, const QColorGroup & g, bool sunken, const QBrush * fill)
#include <qdrawutil.h>
Draws a Windows-style panel given 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 interior is filled with the fill brush unless fill is
null.
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::drawPanel().
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::drawSeparator().
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 a shaded rectangle/box given 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 interior is filled with the fill brush unless fill
is null.
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::drawRect() and QStyle::drawRectStrong().
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 a shaded panel given 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 interior is filled with the fill brush unless fill is
null.
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::drawPanel().
void qDrawWinButton (QPainter * p, int x, int y, int w, int h, const QColorGroup & g, bool sunken, const QBrush * fill)
#include <qdrawutil.h>
Draws a Windows-style button given 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 interior is filled with the *fill brush unless fill is
null.
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::drawButton().
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