Improved clipping in GL2 paint engine.

Use the stencil method to draw clip paths and regions to the Z-buffer
instead of using glClear / glScissor. Using different depth values for
the various clip parts also makes restore() very cheap when only
IntersectClip is used.

As an additional bonus this patch gives antialiased clip in the GL 2
paint engine.

Task-number: 254658
Reviewed-by: Trond

3 files changed, 97 insertions, 16 deletions

diff --git a/src/gui/painting/qpaintengineex.cpp b/src/gui/painting/qpaintengineex.cpp
index 28f9220..3cf5ff9 100644
--- a/src/gui/painting/qpaintengineex.cpp
+++ b/src/gui/painting/qpaintengineex.cpp
@@ -138,6 +138,76 @@ QPaintEngineExPrivate::~QPaintEngineExPrivate()
 }
 
 
+void QPaintEngineExPrivate::replayClipOperations()
+{
+    Q_Q(QPaintEngineEx);
+
+    QPainter *p = q->painter();
+    if (!p || !p->d_ptr)
+        return;
+
+    QPainterPrivate *pp = p->d_ptr;
+    QList<QPainterClipInfo> clipInfo = pp->state->clipInfo;
+
+    QTransform transform = q->state()->matrix;
+
+    QTransform redirection;
+    redirection.translate(-q->state()->redirection_offset.x(), -q->state()->redirection_offset.y());
+
+    for (int i = 0; i <  clipInfo.size(); ++i) {
+        const QPainterClipInfo &info = clipInfo.at(i);
+
+        QTransform combined = info.matrix * redirection;
+
+        if (combined != q->state()->matrix) {
+            q->state()->matrix = combined;
+            q->transformChanged();
+        }
+
+        switch (info.clipType) {
+        case QPainterClipInfo::RegionClip:
+            q->clip(info.region, info.operation);
+            break;
+        case QPainterClipInfo::PathClip:
+            q->clip(info.path, info.operation);
+            break;
+        case QPainterClipInfo::RectClip:
+            q->clip(info.rect, info.operation);
+            break;
+        case QPainterClipInfo::RectFClip: {
+            qreal right = info.rectf.x() + info.rectf.width();
+            qreal bottom = info.rectf.y() + info.rectf.height();
+            qreal pts[] = { info.rectf.x(), info.rectf.y(),
+                            right, info.rectf.y(),
+                            right, bottom,
+                            info.rectf.x(), bottom };
+            QVectorPath vp(pts, 4, 0, QVectorPath::RectangleHint);
+            q->clip(vp, info.operation);
+            break;
+            }
+        }
+    }
+
+    if (transform != q->state()->matrix) {
+        q->state()->matrix = transform;
+        q->transformChanged();
+    }
+}
+
+
+bool QPaintEngineExPrivate::hasClipOperations() const
+{
+    Q_Q(const QPaintEngineEx);
+
+    QPainter *p = q->painter();
+    if (!p || !p->d_ptr)
+        return false;
+
+    QPainterPrivate *pp = p->d_ptr;
+    QList<QPainterClipInfo> clipInfo = pp->state->clipInfo;
+
+    return !clipInfo.isEmpty();
+}
 
 /*******************************************************************************
  *
@@ -244,13 +314,18 @@ static void qpaintengineex_cubicTo(qreal c1x, qreal c1y, qreal c2x, qreal c2y, q
     ((StrokeHandler *) data)->types.add(QPainterPath::CurveToDataElement);
 }
 
+QPaintEngineEx::QPaintEngineEx()
+    : QPaintEngine(*new QPaintEngineExPrivate, AllFeatures)
+{
+    extended = true;
+}
+
 QPaintEngineEx::QPaintEngineEx(QPaintEngineExPrivate &data)
     : QPaintEngine(data, AllFeatures)
 {
     extended = true;
 }
 
-
 QPainterState *QPaintEngineEx::createState(QPainterState *orig) const
 {
     if (!orig)
@@ -483,6 +558,9 @@ void QPaintEngineEx::clip(const QRect &r, Qt::ClipOperation op)
 
 void QPaintEngineEx::clip(const QRegion &region, Qt::ClipOperation op)
 {
+    if (region.numRects() == 1)
+        clip(region.boundingRect(), op);
+
     QVector<QRect> rects = region.rects();
     if (rects.size() <= 32) {
         qreal pts[2*32*4];
diff --git a/src/gui/painting/qpaintengineex_p.h b/src/gui/painting/qpaintengineex_p.h
index 1c55242..3f64260 100644
--- a/src/gui/painting/qpaintengineex_p.h
+++ b/src/gui/painting/qpaintengineex_p.h
@@ -139,27 +139,13 @@ public:
 QDebug Q_GUI_EXPORT &operator<<(QDebug &, const QVectorPath &path);
 #endif
 
-class Q_GUI_EXPORT QPaintEngineExPrivate : public QPaintEnginePrivate
-{
-public:
-    QPaintEngineExPrivate();
-    ~QPaintEngineExPrivate();
-
-    QStroker stroker;
-    QDashStroker dasher;
-    StrokeHandler *strokeHandler;
-    QStrokerOps *activeStroker;
-    QPen strokerPen;
-};
-
 class QPixmapFilter;
 
 class Q_GUI_EXPORT QPaintEngineEx : public QPaintEngine
 {
     Q_DECLARE_PRIVATE(QPaintEngineEx)
 public:
-    inline QPaintEngineEx()
-        : QPaintEngine(*new QPaintEngineExPrivate, AllFeatures) { extended = true; }
+    QPaintEngineEx();
 
     virtual QPainterState *createState(QPainterState *orig) const;
 
@@ -224,6 +210,22 @@ protected:
     QPaintEngineEx(QPaintEngineExPrivate &data);
 };
 
+class Q_GUI_EXPORT QPaintEngineExPrivate : public QPaintEnginePrivate
+{
+    Q_DECLARE_PUBLIC(QPaintEngineEx)
+public:
+    QPaintEngineExPrivate();
+    ~QPaintEngineExPrivate();
+
+    void replayClipOperations();
+    bool hasClipOperations() const;
+
+    QStroker stroker;
+    QDashStroker dasher;
+    StrokeHandler *strokeHandler;
+    QStrokerOps *activeStroker;
+    QPen strokerPen;
+};
 
 inline uint QVectorPath::polygonFlags(QPaintEngine::PolygonDrawMode mode) {
     switch (mode) {
diff --git a/src/gui/painting/qpainter.h b/src/gui/painting/qpainter.h
index f3df7a3..78cd713 100644
--- a/src/gui/painting/qpainter.h
+++ b/src/gui/painting/qpainter.h
@@ -507,6 +507,7 @@ private:
     friend class QFontEngineXLFD;
     friend class QWSManager;
     friend class QPaintEngine;
+    friend class QPaintEngineExPrivate;
     friend class QOpenGLPaintEngine;
     friend class QX11PaintEngine;
     friend class QX11PaintEnginePrivate;