QDirectPainter Class Reference

Detailed Description

Only available in Qt/Embedded.

When the hardware is known and well defined, as is often the case with software for embedded devices, it may be useful to manipulate the underlying video hardware directly. In order to do this in a way that is co-operative with other applications, you must lock the video hardware for exclusive use for a small time while you write to it, and you must know the clipping region which is allocated to a widget.

QDirectPainter provides this functionality.

In the simplest case, you make a QDirectPainter on a widget and then, observing the clip region, perform some platform-specific operation. For example:

        void MyWidget::updatePlatformGraphics()
        {
            QDirectPainter dp( this );
            for ( int i = 0; i < dp.numRects; i++ ) {
                const QRect& clip = dp.rect(i);
                ... // platform specific operation
            }
        }
    

The platform-specific code has access to the display, but should only modify graphics in the rectangles specified by numRects() and rect(). Note that these rectangles are relative to the entire display.

The offset() function returns the position of the widget relative to the entire display, allowing you to offset platform-specific operations appropriately. The xOffset() and yOffset() functions merely return the component values of offset().

For simple frame-buffer hardware, the frameBuffer(), lineStep(), and depth() functions provide basic access, though some hardware configurations are insufficiently specified by such simple parameters.

Note that while a QDirectPainter exists, the entire Qt/Embedded window system is locked from use by other applications. Always construct the QDirectPainter as an auto (stack) variable, and be very careful to write robust and stable code within its scope.

See also Graphics Classes.

Member Function Documentation

QDirectPainter::QDirectPainter ( const QWidget * w )

QDirectPainter::~QDirectPainter ()

int QDirectPainter::depth () const

uchar * QDirectPainter::frameBuffer ()

int QDirectPainter::height () const

int QDirectPainter::lineStep ()

int QDirectPainter::numRects () const

See also rect() and region().

QPoint QDirectPainter::offset () const

const QRect & QDirectPainter::rect ( int i ) const

See also region().

QRegion QDirectPainter::region () const

See also numRects() and rect().

void QDirectPainter::setAreaChanged ( const QRect & r )

QSize QDirectPainter::size () const

See also width() and height().

int QDirectPainter::transformOrientation ()

int QDirectPainter::width () const

int QDirectPainter::xOffset () const

int QDirectPainter::yOffset () const

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