QOpenGLPaintDevice Class▲
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Header: QOpenGLPaintDevice
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Since: Qt 5.0
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CMake:
find_package(Qt6 REQUIRED COMPONENTS OpenGL)
target_link_libraries(mytarget PRIVATE Qt6::OpenGL)
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qmake: QT += opengl
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Inherits: QPaintDevice
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Group: QOpenGLPaintDevice is part of painting-3D
Detailed Description▲
The QOpenGLPaintDevice uses the current QOpenGL context to render QPainter draw commands. The context is captured upon construction. It requires support for OpenGL (ES) 2.0 or higher.
Performance▲
The QOpenGLPaintDevice is almost always hardware accelerated and has the potential of being much faster than software rasterization. However, it is more sensitive to state changes, and therefore requires the drawing commands to be carefully ordered to achieve optimal performance.
Antialiasing and Quality▲
Antialiasing in the OpenGL paint engine is done using multisampling. Most hardware require significantly more memory to do multisampling and the resulting quality is not on par with the quality of the software paint engine. The OpenGL paint engine's strength lies in its performance, not its visual rendering quality.
State Changes▲
When painting to a QOpenGLPaintDevice using QPainter, the state of the current OpenGL context will be altered by the paint engine to reflect its needs. Applications should not rely upon the OpenGL state being reset to its original conditions, particularly the current shader program, OpenGL viewport, texture units, and drawing modes.
Mixing QPainter and OpenGL▲
When intermixing QPainter and OpenGL, it is important to notify QPainter that the OpenGL state may have been cluttered so it can restore its internal state. This is achieved by calling QPainter::beginNativePainting() before starting the OpenGL rendering and calling QPainter::endNativePainting() after finishing.
See Also▲
See also OpenGL Window Example
Member Function Documentation▲
QOpenGLPaintDevice::QOpenGLPaintDevice()▲
Constructs a QOpenGLPaintDevice.
The QOpenGLPaintDevice is only valid for the current context.
See Also▲
See also QOpenGLContext::currentContext()
[explicit] QOpenGLPaintDevice::QOpenGLPaintDevice(const QSize &size)▲
Constructs a QOpenGLPaintDevice with the given size.
The QOpenGLPaintDevice is only valid for the current context.
See Also▲
See also QOpenGLContext::currentContext()
QOpenGLPaintDevice::QOpenGLPaintDevice(int width, int height)▲
Constructs a QOpenGLPaintDevice with the given width and height.
The QOpenGLPaintDevice is only valid for the current context.
See Also▲
See also QOpenGLContext::currentContext()
[virtual] QOpenGLPaintDevice::~QOpenGLPaintDevice()▲
Destroys the QOpenGLPaintDevice.
QOpenGLContext *QOpenGLPaintDevice::context() const▲
Returns the OpenGL context associated with the paint device.
qreal QOpenGLPaintDevice::dotsPerMeterX() const▲
qreal QOpenGLPaintDevice::dotsPerMeterY() const▲
[virtual] void QOpenGLPaintDevice::ensureActiveTarget()▲
This virtual method is provided as a callback to allow re-binding a target frame buffer object or context when different QOpenGLPaintDevice instances are issuing draw calls alternately.
beginNativePainting() will also trigger this method.
The default implementation does nothing.
[override virtual protected] int QOpenGLPaintDevice::metric(QPaintDevice::PaintDeviceMetric metric) const▲
[override virtual] QPaintEngine *QOpenGLPaintDevice::paintEngine() const▲
Reimplements: QPaintDevice::paintEngine() const.
bool QOpenGLPaintDevice::paintFlipped() const▲
void QOpenGLPaintDevice::setDevicePixelRatio(qreal devicePixelRatio)▲
Sets the device pixel ratio for the paint device to devicePixelRatio.
void QOpenGLPaintDevice::setDotsPerMeterX(qreal dpmx)▲
void QOpenGLPaintDevice::setDotsPerMeterY(qreal dpmy)▲
void QOpenGLPaintDevice::setPaintFlipped(bool flipped)▲
Sets whether painting should be flipped around the Y-axis or not to flipped.
See Also▲
See also paintFlipped()