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# svgalibpaintengine.cpp Example File
qws/svgalib/svgalibpaintengine.cpp

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     ** Alternatively, this file may be used under the terms of the GNU
     ** General Public License version 3.0 as published by the Free Software
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     #include "svgalibpaintengine.h"

     #include <QColor>
     #include <vga.h>
     #include <vgagl.h>

     SvgalibPaintEngine::SvgalibPaintEngine()
     {
     }

     SvgalibPaintEngine::~SvgalibPaintEngine()
     {
     }

     bool SvgalibPaintEngine::begin(QPaintDevice *dev)
     {
         device = dev;
         pen = Qt::NoPen;
         simplePen = true;
         brush = Qt::NoBrush;
         simpleBrush = true;
         matrix = QMatrix();
         simpleMatrix = true;
         setClip(QRect(0, 0, device->width(), device->height()));
         opaque = true;
         aliased = true;
         sourceOver = true;

         return QRasterPaintEngine::begin(dev);
     }

     bool SvgalibPaintEngine::end()
     {
         gl_setclippingwindow(0, 0, device->width() - 1, device->height() - 1);
         return QRasterPaintEngine::end();
     }

     void SvgalibPaintEngine::updateState(const QPaintEngineState &state)
     {
         QPaintEngine::DirtyFlags flags = state.state();

         if (flags & DirtyTransform) {
             matrix = state.matrix();
             simpleMatrix = (matrix.m12() == 0 && matrix.m21() == 0);
         }

         if (flags & DirtyPen) {
             pen = state.pen();
             simplePen = (pen.width() == 0 || pen.widthF() <= 1)
                         && (pen.style() == Qt::NoPen || pen.style() == Qt::SolidLine)
                         && (pen.color().alpha() == 255);
         }

         if (flags & DirtyBrush) {
             brush = state.brush();
             simpleBrush = (brush.style() == Qt::SolidPattern
                            || brush.style() == Qt::NoBrush)
                           && (brush.color().alpha() == 255);
         }

         if (flags & DirtyClipRegion)
             setClip(state.clipRegion());

         if (flags & DirtyClipEnabled) {
             clipEnabled = state.isClipEnabled();
             updateClip();
         }

         if (flags & DirtyClipPath) {
             setClip(QRegion());
             simpleClip = false;
         }

         if (flags & DirtyCompositionMode) {
             const QPainter::CompositionMode m = state.compositionMode();
             sourceOver = (m == QPainter::CompositionMode_SourceOver);
         }

         if (flags & DirtyOpacity)
             opaque = (state.opacity() == 256);

         if (flags & DirtyHints)
             aliased = !(state.renderHints() & QPainter::Antialiasing);

         QRasterPaintEngine::updateState(state);
     }

     void SvgalibPaintEngine::setClip(const QRegion &region)
     {
         if (region.isEmpty())
             clip = QRect(0, 0, device->width(), device->height());
         else
             clip = matrix.map(region) & QRect(0, 0, device->width(), device->height());
         clipEnabled = true;
         updateClip();
     }

     void SvgalibPaintEngine::updateClip()
     {
         QRegion clipRegion = QRect(0, 0, device->width(), device->height());

         if (!systemClip().isEmpty())
             clipRegion &= systemClip();
         if (clipEnabled)
             clipRegion &= clip;

         simpleClip = (clipRegion.rects().size() <= 1);

         const QRect r = clipRegion.boundingRect();
         gl_setclippingwindow(r.left(), r.top(),
                              r.x() + r.width(),
                              r.y() + r.height());
     }

     void SvgalibPaintEngine::drawRects(const QRect *rects, int rectCount)
     {
         const bool canAccelerate = simplePen && simpleBrush && simpleMatrix
                                    && simpleClip && opaque && aliased
                                    && sourceOver;
         if (!canAccelerate) {
             QRasterPaintEngine::drawRects(rects, rectCount);
             return;
         }

         for (int i = 0; i < rectCount; ++i) {
             const QRect r = matrix.mapRect(rects[i]);
             if (brush != Qt::NoBrush) {
                 gl_fillbox(r.left(), r.top(), r.width(), r.height(),
                            brush.color().rgba());
             }
             if (pen != Qt::NoPen) {
                 const int c = pen.color().rgba();
                 gl_hline(r.left(), r.top(), r.right(), c);
                 gl_hline(r.left(), r.bottom(), r.right(), c);
                 gl_line(r.left(), r.top(), r.left(), r.bottom(), c);
                 gl_line(r.right(), r.top(), r.right(), r.bottom(), c);
             }
         }
     }