QwtGraphic - A paint device for scalable graphics.
NAME SYNOPSIS Public Types Public Member Functions Protected Member Functions Detailed Description Member Typedef Documentation typedef QFlags<CommandType > QwtGraphic::CommandTypes typedef QFlags<RenderHint > QwtGraphic::RenderHints Member Enumeration Documentation enum QwtGraphic::CommandType enum QwtGraphic::RenderHint Constructor & Destructor Documentation QwtGraphic::QwtGraphic () QwtGraphic::QwtGraphic (const QwtGraphic & other) QwtGraphic::˜QwtGraphic () [virtual] Member Function Documentation QRectF QwtGraphic::boundingRect () const const QVector< QwtPainterCommand > & QwtGraphic::commands () const QwtGraphic::CommandTypes QwtGraphic::commandTypes () const QRectF QwtGraphic::controlPointRect () const QSizeF QwtGraphic::defaultSize () const void QwtGraphic::drawImage (const QRectF & rect, const QImage & image,const QRectF & subRect, Qt::ImageConversionFlags flags) [override],[protected], [virtual] void QwtGraphic::drawPath (const QPainterPath & path) [override],[protected], [virtual] void QwtGraphic::drawPixmap (const QRectF & rect, const QPixmap & pixmap,const QRectF & subRect) [override], [protected], [virtual] qreal QwtGraphic::heightForWidth (qreal width) const bool QwtGraphic::isEmpty () const bool QwtGraphic::isNull () const QwtGraphic & QwtGraphic::operator= (const QwtGraphic & other) void QwtGraphic::render (QPainter * painter) const void QwtGraphic::render (QPainter * painter, const QPointF & pos,Qt::Alignment alignment = Qt::AlignTop | Qt::AlignLeft) const void QwtGraphic::render (QPainter * painter, const QRectF & rect,Qt::AspectRatioMode aspectRatioMode = Qt::IgnoreAspectRatio) const void QwtGraphic::render (QPainter * painter, const QSizeF & size,Qt::AspectRatioMode aspectRatioMode = Qt::IgnoreAspectRatio) const QwtGraphic::RenderHints QwtGraphic::renderHints () const void QwtGraphic::reset () QRectF QwtGraphic::scaledBoundingRect (qreal sx, qreal sy) const void QwtGraphic::setCommands (const QVector< QwtPainterCommand > &commands) void QwtGraphic::setDefaultSize (const QSizeF & size) void QwtGraphic::setRenderHint (RenderHint hint, bool on = true) QSize QwtGraphic::sizeMetrics () const [override], [protected], [virtual] bool QwtGraphic::testRenderHint (RenderHint hint) const QImage QwtGraphic::toImage (const QSize & size, Qt::AspectRatioModeaspectRatioMode = Qt::IgnoreAspectRatio, qreal devicePixelRatio = 0.0)const QImage QwtGraphic::toImage (qreal devicePixelRatio = 0.0) const QPixmap QwtGraphic::toPixmap (const QSize & size, Qt::AspectRatioModeaspectRatioMode = Qt::IgnoreAspectRatio, qreal devicePixelRatio = 0.0)const QPixmap QwtGraphic::toPixmap (qreal devicePixelRatio = 0.0) const void QwtGraphic::updateState (const QPaintEngineState & state) [override],[protected], [virtual] qreal QwtGraphic::widthForHeight (qreal height) const AuthorNAME
QwtGraphic − A paint device for scalable graphics.
SYNOPSIS
#include <qwt_graphic.h>
Inherits QwtNullPaintDevice.
Public Types
enum
RenderHint { RenderPensUnscaled = 0x1 }
enum CommandType { VectorData = 1 << 0,
RasterData = 1 << 1, Transformation = 1
<< 2 }
typedef QFlags< RenderHint > RenderHints
typedef QFlags< CommandType >
CommandTypes
Public Types inherited from QwtNullPaintDevice
enum Mode {
NormalMode, PolygonPathMode, PathMode }
Render mode.
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
CommandTypes commandTypes () 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 QPointF &,
Qt::Alignment=Qt::AlignTop|Qt::AlignLeft) const
Replay all recorded painter commands.
void render (QPainter *, const QRectF &,
Qt::AspectRatioMode=Qt::IgnoreAspectRatio) const
Replay all recorded painter commands.
QPixmap toPixmap (qreal devicePixelRatio=0.0) const
Convert the graphic to a QPixmap.
QPixmap toPixmap (const QSize &,
Qt::AspectRatioMode=Qt::IgnoreAspectRatio, qreal
devicePixelRatio=0.0) const
Convert the graphic to a QPixmap.
QImage toImage (qreal devicePixelRatio=0.0) const
Convert the graphic to a QImage.
QImage toImage (const QSize &,
Qt::AspectRatioMode=Qt::IgnoreAspectRatio, qreal
devicePixelRatio=0.0) const
Convert the graphic to a QImage.
QRectF scaledBoundingRect (qreal sx, qreal sy) const
Calculate the target rectangle for scaling the graphic.
QRectF boundingRect () const
QRectF controlPointRect () const
const QVector< QwtPainterCommand > &
commands () const
void setCommands (const QVector<
QwtPainterCommand > &)
Append paint commands.
void setDefaultSize (const QSizeF &)
Set a default size.
QSizeF defaultSize () const
Default size.
qreal heightForWidth (qreal width) const
qreal widthForHeight (qreal height) const
void setRenderHint (RenderHint, bool on=true)
bool testRenderHint (RenderHint) const
RenderHints renderHints () const
Public Member Functions inherited from QwtNullPaintDevice
QwtNullPaintDevice ()
Constructor.
virtual ˜QwtNullPaintDevice ()
Destructor.
void setMode (Mode)
Mode mode () const
virtual QPaintEngine * paintEngine () const override
See QPaintDevice::paintEngine()
virtual int metric (PaintDeviceMetric) const override
virtual void drawRects (const QRect *, int)
See QPaintEngine::drawRects()
virtual void drawRects (const QRectF *, int)
See QPaintEngine::drawRects()
virtual void drawLines (const QLine *, int)
See QPaintEngine::drawLines()
virtual void drawLines (const QLineF *, int)
See QPaintEngine::drawLines()
virtual void drawEllipse (const QRectF &)
See QPaintEngine::drawEllipse()
virtual void drawEllipse (const QRect &)
See QPaintEngine::drawEllipse()
virtual void drawPoints (const QPointF *, int)
See QPaintEngine::drawPoints()
virtual void drawPoints (const QPoint *, int)
See QPaintEngine::drawPoints()
virtual void drawPolygon (const QPointF *, int,
QPaintEngine::PolygonDrawMode)
See QPaintEngine::drawPolygon()
virtual void drawPolygon (const QPoint *, int,
QPaintEngine::PolygonDrawMode)
See QPaintEngine::drawPolygon()
virtual void drawTextItem (const QPointF &, const
QTextItem &)
See QPaintEngine::drawTextItem()
virtual void drawTiledPixmap (const QRectF &,
const QPixmap &, const QPointF &)
See QPaintEngine::drawTiledPixmap()
Protected Member Functions
virtual QSize
sizeMetrics () const override
virtual void drawPath (const QPainterPath &)
override
virtual void drawPixmap (const QRectF &, const
QPixmap &, const QRectF &) override
Store a pixmap command in the command list.
virtual void drawImage (const QRectF &, const
QImage &, const QRectF &, Qt::ImageConversionFlags)
override
Store a image command in the command list.
virtual void updateState (const QPaintEngineState
&) override
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
Definition at line 75 of file qwt_graphic.h.
Member Typedef Documentation
typedef QFlags<CommandType > QwtGraphic::CommandTypes
An ORed combination of CommandType values.
Definition at line 117 of file qwt_graphic.h.
typedef QFlags<RenderHint > QwtGraphic::RenderHints
An ORed combination of RenderHint values.
Definition at line 99 of file qwt_graphic.h.
Member Enumeration Documentation
enum QwtGraphic::CommandType
Indicator if the graphic contains a specific type of painter command
See also
CommandTypes, commandTypes();
Enumerator
VectorData
The graphic contains scalable vector data.
RasterData
The graphic contains raster data ( QPixmap or QImage )
Transformation
The graphic contains transformations beyond simple translations.
Definition at line 105 of file qwt_graphic.h.
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();
Definition at line 82 of file qwt_graphic.h.
Constructor & Destructor Documentation
QwtGraphic::QwtGraphic ()
Constructor. Initializes a null graphic
See also
isNull()
Definition at line 355 of file qwt_graphic.cpp.
QwtGraphic::QwtGraphic (const QwtGraphic & other)
Copy constructor.
Parameters
other Source
See also
operator=()
Definition at line 367 of file qwt_graphic.cpp.
QwtGraphic::˜QwtGraphic () [virtual]
Destructor.
Definition at line 374 of file qwt_graphic.cpp.
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()
Definition at line 477 of file qwt_graphic.cpp.
const QVector< QwtPainterCommand > & QwtGraphic::commands () const
Returns
List of recorded paint commands
See also
setCommands()
Definition at line 1131 of file qwt_graphic.cpp.
QwtGraphic::CommandTypes QwtGraphic::commandTypes () const
Returns
Types of painter commands being used
Definition at line 430 of file qwt_graphic.cpp.
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()
Definition at line 493 of file qwt_graphic.cpp.
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()
Definition at line 574 of file qwt_graphic.cpp.
void QwtGraphic::drawImage (const QRectF & rect, const QImage & image,const QRectF & subRect, Qt::ImageConversionFlags flags) [override],[protected], [virtual]
Store a image command in the command list.
Parameters
rect target 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.
Definition at line 1059 of file qwt_graphic.cpp.
void QwtGraphic::drawPath (const QPainterPath & path) [override],[protected], [virtual]
Store a path command in the command list
Parameters
path Painter path
See also
QPaintEngine::drawPath()
Reimplemented from QwtNullPaintDevice.
Definition at line 995 of file qwt_graphic.cpp.
void QwtGraphic::drawPixmap (const QRectF & rect, const QPixmap & pixmap,const QRectF & subRect) [override], [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.
Definition at line 1034 of file qwt_graphic.cpp.
qreal QwtGraphic::heightForWidth (qreal width) const
Find the height for a given width
The height is calculated using the aspect ratio of defaultSize().
Parameters
width Width
Returns
Calculated height
See also
defaultSize()
Definition at line 592 of file qwt_graphic.cpp.
bool QwtGraphic::isEmpty () const
Returns
True, when the bounding rectangle is empty
See also
boundingRect(), isNull()
Definition at line 422 of file qwt_graphic.cpp.
bool QwtGraphic::isNull () const
Returns
True, when no painter commands have been stored
See also
isEmpty(), commands()
Definition at line 413 of file qwt_graphic.cpp.
QwtGraphic & QwtGraphic::operator= (const QwtGraphic & other)
Assignment operator.
Parameters
other Source
Returns
A reference of this object
Definition at line 385 of file qwt_graphic.cpp.
void QwtGraphic::render (QPainter * painter) const
Replay all recorded painter commands.
Parameters
painter Qt painter
Definition at line 624 of file qwt_graphic.cpp.
void QwtGraphic::render (QPainter * painter, const QPointF & pos,Qt::Alignment alignment = 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.
Definition at line 762 of file qwt_graphic.cpp.
void QwtGraphic::render (QPainter * painter, const QRectF & rect,Qt::AspectRatioMode aspectRatioMode = 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
Definition at line 676 of file qwt_graphic.cpp.
void QwtGraphic::render (QPainter * painter, const QSizeF & size,Qt::AspectRatioMode aspectRatioMode = 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
Definition at line 660 of file qwt_graphic.cpp.
QwtGraphic::RenderHints QwtGraphic::renderHints () const
Returns
Render hints
Definition at line 464 of file qwt_graphic.cpp.
void QwtGraphic::reset ()
Clear all stored commands.
See also
isNull()
Definition at line 397 of file qwt_graphic.cpp.
QRectF QwtGraphic::scaledBoundingRect (qreal sx, qreal sy) 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()
Definition at line 514 of file qwt_graphic.cpp.
void QwtGraphic::setCommands (const QVector< QwtPainterCommand > &commands)
Append paint commands.
Parameters
commands Paint commands
See also
commands()
Definition at line 1142 of file qwt_graphic.cpp.
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()
Definition at line 553 of file qwt_graphic.cpp.
void QwtGraphic::setRenderHint (RenderHint hint, bool on = true)
Toggle an render hint
Parameters
hint Render hint
on true/false
See also
testRenderHint(), RenderHint
Definition at line 443 of file qwt_graphic.cpp.
QSize QwtGraphic::sizeMetrics () const [override], [protected], [virtual]
Returns
Ceiled defaultSize()
Implements QwtNullPaintDevice.
Definition at line 533 of file qwt_graphic.cpp.
bool QwtGraphic::testRenderHint (RenderHint hint) const
Test a render hint
Parameters
hint Render hint
Returns
true/false
See also
setRenderHint(), RenderHint
Definition at line 458 of file qwt_graphic.cpp.
QImage QwtGraphic::toImage (const QSize & size, Qt::AspectRatioModeaspectRatioMode = Qt::IgnoreAspectRatio, qreal devicePixelRatio = 0.0)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 (
will be multiplied by the devicePixelRatio )
aspectRatioMode Aspect ratio how to scale the graphic
devicePixelRatio Device pixel ratio for the image. If
devicePixelRatio <= 0.0 the pixmap is initialized with
the system default.
Returns
The graphic as image
See also
toPixmap(), render()
Definition at line 907 of file qwt_graphic.cpp.
QImage QwtGraphic::toImage (qreal devicePixelRatio = 0.0) 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 multiplied by the devicePixelRatio.
Parameters
devicePixelRatio Device pixel ratio for the image. If devicePixelRatio <= 0.0 the pixmap is initialized with the system default.
Returns
The graphic as image in default size
See also
defaultSize(), toPixmap(), render()
Definition at line 953 of file qwt_graphic.cpp.
QPixmap QwtGraphic::toPixmap (const QSize & size, Qt::AspectRatioModeaspectRatioMode = Qt::IgnoreAspectRatio, qreal devicePixelRatio = 0.0)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
devicePixelRatio Device pixel ratio for the pixmap. If
devicePixelRatio <= 0.0 the pixmap is initialized with
the system default.
Returns
The graphic as pixmap
See also
toImage(), render()
Definition at line 863 of file qwt_graphic.cpp.
QPixmap QwtGraphic::toPixmap (qreal devicePixelRatio = 0.0) 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.
Parameters
devicePixelRatio Device pixel ratio for the pixmap. If devicePixelRatio <= 0.0 the pixmap is initialized with the system default.
Returns
The graphic as pixmap in default size
See also
defaultSize(), toImage(), render()
Definition at line 812 of file qwt_graphic.cpp.
void QwtGraphic::updateState (const QPaintEngineState & state) [override],[protected], [virtual]
Store a state command in the command list.
Parameters
state State to be stored
See also
QPaintEngine::updateState()
Reimplemented from QwtNullPaintDevice.
Definition at line 1081 of file qwt_graphic.cpp.
qreal QwtGraphic::widthForHeight (qreal height) const
Find the width for a given height
The width is calculated using the aspect ratio of defaultSize().
Parameters
height Height
Returns
Calculated width
See also
defaultSize()
Definition at line 611 of file qwt_graphic.cpp.
Author
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