Provided by: libqwt-doc_6.1.2-5_all 
NAME
QwtGraphic -
A paint device for scalable graphics.
SYNOPSIS
#include <qwt_graphic.h>
Inherits QwtNullPaintDevice.
Public Types
enum RenderHint { RenderPensUnscaled = 0x1 }
typedef QFlags< RenderHint > RenderHints
Render hints.
Public Member Functions
QwtGraphic ()
Constructor.
QwtGraphic (const QwtGraphic &)
Copy constructor.
virtual ~QwtGraphic ()
Destructor.
QwtGraphic & operator= (const QwtGraphic &)
Assignment operator.
void reset ()
Clear all stored commands.
bool isNull () const
bool isEmpty () const
void render (QPainter *) const
Replay all recorded painter commands.
void render (QPainter *, const QSizeF &, Qt::AspectRatioMode=Qt::IgnoreAspectRatio) const
Replay all recorded painter commands.
void render (QPainter *, const QRectF &, Qt::AspectRatioMode=Qt::IgnoreAspectRatio) const
Replay all recorded painter commands.
void render (QPainter *, const QPointF &, Qt::Alignment=Qt::AlignTop|Qt::AlignLeft) const
Replay all recorded painter commands.
QPixmap toPixmap () const
Convert the graphic to a QPixmap.
QPixmap toPixmap (const QSize &, Qt::AspectRatioMode=Qt::IgnoreAspectRatio) const
Convert the graphic to a QPixmap.
QImage toImage () const
Convert the graphic to a QImage.
QImage toImage (const QSize &, Qt::AspectRatioMode=Qt::IgnoreAspectRatio) const
Convert the graphic to a QImage.
QRectF scaledBoundingRect (double sx, double sy) const
Calculate the target rectangle for scaling the graphic.
QRectF boundingRect () const
QRectF controlPointRect () const
const QVector
< QwtPainterCommand > & commands () const "
void setCommands (QVector< QwtPainterCommand > &)
Append paint commands.
void setDefaultSize (const QSizeF &)
Set a default size.
QSizeF defaultSize () const
Default size.
void setRenderHint (RenderHint, bool on=true)
bool testRenderHint (RenderHint) const
Protected Member Functions
virtual QSize sizeMetrics () const
virtual void drawPath (const QPainterPath &)
virtual void drawPixmap (const QRectF &, const QPixmap &, const QRectF &)
Store a pixmap command in the command list.
virtual void drawImage (const QRectF &, const QImage &, const QRectF &,
Qt::ImageConversionFlags)
Store a image command in the command list.
virtual void updateState (const QPaintEngineState &state)
Store a state command in the command list.
Detailed Description
A paint device for scalable graphics.
QwtGraphic is the representation of a graphic that is tailored for scalability. Like
QPicture it will be initialized by QPainter operations and can be replayed later to any
target paint device.
While the usual image representations QImage and QPixmap are not scalable Qt offers two
paint devices, that might be candidates for representing a vector graphic:
• QPicture
Unfortunately QPicture had been forgotten, when Qt4 introduced floating point based
render engines. Its API is still on integers, what make it unusable for proper scaling.
• QSvgRenderer/QSvgGenerator
Unfortunately QSvgRenderer hides to much information about its nodes in internal APIs,
that are necessary for proper layout calculations. Also it is derived from QObject and
can't be copied like QImage/QPixmap.
QwtGraphic maps all scalable drawing primitives to a QPainterPath and stores them together
with the painter state changes ( pen, brush, transformation ... ) in a list of
QwtPaintCommands. For being a complete QPaintDevice it also stores pixmaps or images, what
is somehow against the idea of the class, because these objects can't be scaled without a
loss in quality.
The main issue about scaling a QwtGraphic object are the pens used for drawing the
outlines of the painter paths. While non cosmetic pens ( QPen::isCosmetic() ) are scaled
with the same ratio as the path, cosmetic pens have a fixed width. A graphic might have
paths with different pens - cosmetic and non-cosmetic.
QwtGraphic caches 2 different rectangles:
• control point rectangle
The control point rectangle is the bounding rectangle of all control point rectangles
of the painter paths, or the target rectangle of the pixmaps/images.
• bounding rectangle
The bounding rectangle extends the control point rectangle by what is needed for
rendering the outline with an unscaled pen.
Because the offset for drawing the outline depends on the shape of the painter path ( the
peak of a triangle is different than the flat side ) scaling with a fixed aspect ratio
always needs to be calculated from the control point rectangle.
See Also:
QwtPainterCommand
Member Typedef Documentation
typedef QFlags<RenderHint> QwtGraphic::RenderHints
Render hints. The default setting is to disable all hints
Member Enumeration Documentation
enum QwtGraphic::RenderHint
Hint how to render a graphic
See Also:
setRenderHint(), testRenderHint()
Enumerator
RenderPensUnscaled
When rendering a QwtGraphic a specific scaling between the controlPointRect() and
the coordinates of the target rectangle is set up internally in render().
When RenderPensUnscaled is set this specific scaling is applied for the control points
only, but not for the pens. All other painter transformations ( set up by application code
) are supposed to work like usual.
See Also:
render();
Constructor & Destructor Documentation
QwtGraphic::QwtGraphic ()
Constructor. Initializes a null graphic
See Also:
isNull()
QwtGraphic::QwtGraphic (const QwtGraphic &other)
Copy constructor.
Parameters:
other Source
See Also:
operator=()
Member Function Documentation
QRectF QwtGraphic::boundingRect () const
The bounding rectangle is the controlPointRect() extended by the areas needed for
rendering the outlines with unscaled pens.
Returns:
Bounding rectangle of the graphic
See Also:
controlPointRect(), scaledBoundingRect()
const QVector< QwtPainterCommand > & QwtGraphic::commands () const
Returns:
List of recorded paint commands
See Also:
setCommands()
QRectF QwtGraphic::controlPointRect () const
The control point rectangle is the bounding rectangle of all control points of the paths
and the target rectangles of the images/pixmaps.
Returns:
Control point rectangle
See Also:
boundingRect(), scaledBoundingRect()
QSizeF QwtGraphic::defaultSize () const
Default size. When a non empty size has been assigned by setDefaultSize() this size will
be returned. Otherwise the default size is the size of the bounding rectangle.
The default size is used in all methods rendering the graphic, where no size is explicitly
specified.
Returns:
Default size
See Also:
setDefaultSize(), boundingRect()
void QwtGraphic::drawImage (const QRectF &rect, const QImage &image, const QRectF &subRect,
Qt::ImageConversionFlagsflags) [protected], [virtual]
Store a image command in the command list.
Parameters:
rect traget rectangle
image Image to be painted
subRect Reactangle of the pixmap to be painted
flags Image conversion flags
See Also:
QPaintEngine::drawImage()
Reimplemented from QwtNullPaintDevice.
void QwtGraphic::drawPath (const QPainterPath &path) [protected], [virtual]
Store a path command in the command list
Parameters:
path Painter path
See Also:
QPaintEngine::drawPath()
Reimplemented from QwtNullPaintDevice.
void QwtGraphic::drawPixmap (const QRectF &rect, const QPixmap &pixmap, const QRectF &subRect)
[protected], [virtual]
Store a pixmap command in the command list.
Parameters:
rect target rectangle
pixmap Pixmap to be painted
subRect Reactangle of the pixmap to be painted
See Also:
QPaintEngine::drawPixmap()
Reimplemented from QwtNullPaintDevice.
bool QwtGraphic::isEmpty () const
Returns:
True, when the bounding rectangle is empty
See Also:
boundingRect(), isNull()
bool QwtGraphic::isNull () const
Returns:
True, when no painter commands have been stored
See Also:
isEmpty(), commands()
QwtGraphic & QwtGraphic::operator= (const QwtGraphic &other)
Assignment operator.
Parameters:
other Source
Returns:
A reference of this object
void QwtGraphic::render (QPainter *painter) const
Replay all recorded painter commands.
Parameters:
painter Qt painter
void QwtGraphic::render (QPainter *painter, const QSizeF &size,
Qt::AspectRatioModeaspectRatioMode = Qt::IgnoreAspectRatio) const
Replay all recorded painter commands. The graphic is scaled to fit into the rectangle of
the given size starting at ( 0, 0 ).
Parameters:
painter Qt painter
size Size for the scaled graphic
aspectRatioMode Mode how to scale - See Qt::AspectRatioMode
void QwtGraphic::render (QPainter *painter, const QRectF &rect,
Qt::AspectRatioModeaspectRatioMode = Qt::IgnoreAspectRatio) const
Replay all recorded painter commands. The graphic is scaled to fit into the given
rectangle
Parameters:
painter Qt painter
rect Rectangle for the scaled graphic
aspectRatioMode Mode how to scale - See Qt::AspectRatioMode
void QwtGraphic::render (QPainter *painter, const QPointF &pos, Qt::Alignmentalignment =
Qt::AlignTop | Qt::AlignLeft) const
Replay all recorded painter commands. The graphic is scaled to the defaultSize() and
aligned to a position.
Parameters:
painter Qt painter
pos Reference point, where to render
alignment Flags how to align the target rectangle to pos.
void QwtGraphic::reset ()
Clear all stored commands.
See Also:
isNull()
QRectF QwtGraphic::scaledBoundingRect (doublesx, doublesy) const
Calculate the target rectangle for scaling the graphic.
Parameters:
sx Horizontal scaling factor
sy Vertical scaling factor
Note:
In case of paths that are painted with a cosmetic pen ( see QPen::isCosmetic() ) the
target rectangle is different to multiplying the bounding rectangle.
Returns:
Scaled bounding rectangle
See Also:
boundingRect(), controlPointRect()
void QwtGraphic::setCommands (QVector< QwtPainterCommand > &commands)
Append paint commands.
Parameters:
commands Paint commands
See Also:
commands()
void QwtGraphic::setDefaultSize (const QSizeF &size)
Set a default size. The default size is used in all methods rendering the graphic, where
no size is explicitly specified. Assigning an empty size means, that the default size will
be calculated from the bounding rectangle.
The default setting is an empty size.
Parameters:
size Default size
See Also:
defaultSize(), boundingRect()
void QwtGraphic::setRenderHint (RenderHinthint, boolon = true)
Toggle an render hint
Parameters:
hint Render hint
on true/false
See Also:
testRenderHint(), RenderHint
QSize QwtGraphic::sizeMetrics () const [protected], [virtual]
Returns:
Ceiled defaultSize()
Implements QwtNullPaintDevice.
bool QwtGraphic::testRenderHint (RenderHinthint) const
Test a render hint
Parameters:
hint Render hint
Returns:
true/false
See Also:
setRenderHint(), RenderHint
QImage QwtGraphic::toImage () const
Convert the graphic to a QImage. All pixels of the image get initialized by 0 (
transparent ) before the graphic is scaled and rendered on it.
The format of the image is QImage::Format_ARGB32_Premultiplied.
The size of the image is the default size ( ceiled to integers ) of the graphic.
Returns:
The graphic as image in default size
See Also:
defaultSize(), toPixmap(), render()
QImage QwtGraphic::toImage (const QSize &size, Qt::AspectRatioModeaspectRatioMode =
Qt::IgnoreAspectRatio) const
Convert the graphic to a QImage. All pixels of the image get initialized by 0 (
transparent ) before the graphic is scaled and rendered on it.
The format of the image is QImage::Format_ARGB32_Premultiplied.
Parameters:
size Size of the image
aspectRatioMode Aspect ratio how to scale the graphic
Returns:
The graphic as image
See Also:
toPixmap(), render()
QPixmap QwtGraphic::toPixmap () const
Convert the graphic to a QPixmap. All pixels of the pixmap get initialized by
Qt::transparent before the graphic is scaled and rendered on it.
The size of the pixmap is the default size ( ceiled to integers ) of the graphic.
Returns:
The graphic as pixmap in default size
See Also:
defaultSize(), toImage(), render()
QPixmap QwtGraphic::toPixmap (const QSize &size, Qt::AspectRatioModeaspectRatioMode =
Qt::IgnoreAspectRatio) const
Convert the graphic to a QPixmap. All pixels of the pixmap get initialized by
Qt::transparent before the graphic is scaled and rendered on it.
Parameters:
size Size of the image
aspectRatioMode Aspect ratio how to scale the graphic
Returns:
The graphic as pixmap
See Also:
toImage(), render()
void QwtGraphic::updateState (const QPaintEngineState &state) [protected], [virtual]
Store a state command in the command list.
Parameters:
state State to be stored
See Also:
QPaintEngine::updateState()
Reimplemented from QwtNullPaintDevice.
Author
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