Added clipping to the dashed stroke processor in the GL2 engine.

Without clipping, the stroker could consume a huge amount of
memory when scaling up cosmetic, dashed strokes. I also made
QDashStroker clip more aggressively.

Task-number: QTBUG-7832
Reviewed-by: Samuel
(cherry picked from commit ee6c26115959f46621f5a45f3fbe4a49989fd095)

3 files changed, 12 insertions, 7 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index fb06e0e..2b27506 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -1048,16 +1048,20 @@ void QGL2PaintEngineExPrivate::stroke(const QVectorPath &path, const QPen &pen)
     // prepareForDraw() down below.
     updateMatrix();
 
+    QRectF clip = q->state()->matrix.inverted().mapRect(q->state()->clipEnabled
+                                                        ? q->state()->rectangleClip
+                                                        : QRectF(0, 0, width, height));
+
     if (penStyle == Qt::SolidLine) {
-        stroker.process(path, pen);
+        stroker.process(path, pen, clip);
 
     } else { // Some sort of dash
-        dasher.process(path, pen);
+        dasher.process(path, pen, clip);
 
         QVectorPath dashStroke(dasher.points(),
                                dasher.elementCount(),
                                dasher.elementTypes());
-        stroker.process(dashStroke, pen);
+        stroker.process(dashStroke, pen, clip);
     }
 
     if (opaque) {
diff --git a/src/opengl/gl2paintengineex/qtriangulatingstroker.cpp b/src/opengl/gl2paintengineex/qtriangulatingstroker.cpp
index e992c1a..8f1273d 100644
--- a/src/opengl/gl2paintengineex/qtriangulatingstroker.cpp
+++ b/src/opengl/gl2paintengineex/qtriangulatingstroker.cpp
@@ -73,7 +73,7 @@ void QTriangulatingStroker::endCapOrJoinClosed(const qreal *start, const qreal *
 }
 
 
-void QTriangulatingStroker::process(const QVectorPath &path, const QPen &pen)
+void QTriangulatingStroker::process(const QVectorPath &path, const QPen &pen, const QRectF &)
 {
     const qreal *pts = path.points();
     const QPainterPath::ElementType *types = path.elements();
@@ -488,7 +488,7 @@ QDashedStrokeProcessor::QDashedStrokeProcessor()
     m_dash_stroker.setCubicToHook(qdashprocessor_cubicTo);
 }
 
-void QDashedStrokeProcessor::process(const QVectorPath &path, const QPen &pen)
+void QDashedStrokeProcessor::process(const QVectorPath &path, const QPen &pen, const QRectF &clip)
 {
 
     const qreal *pts = path.points();
@@ -505,6 +505,7 @@ void QDashedStrokeProcessor::process(const QVectorPath &path, const QPen &pen)
     m_dash_stroker.setDashPattern(pen.dashPattern());
     m_dash_stroker.setStrokeWidth(pen.isCosmetic() ? width * m_inv_scale : width);
     m_dash_stroker.setMiterLimit(pen.miterLimit());
+    m_dash_stroker.setClipRect(clip);
     qreal curvyness = sqrt(width) * m_inv_scale / 8;
 
     if (count < 2)
diff --git a/src/opengl/gl2paintengineex/qtriangulatingstroker_p.h b/src/opengl/gl2paintengineex/qtriangulatingstroker_p.h
index 0c2e7df..b8f4b0c 100644
--- a/src/opengl/gl2paintengineex/qtriangulatingstroker_p.h
+++ b/src/opengl/gl2paintengineex/qtriangulatingstroker_p.h
@@ -54,7 +54,7 @@ QT_BEGIN_NAMESPACE
 class QTriangulatingStroker
 {
 public:
-    void process(const QVectorPath &path, const QPen &pen);
+    void process(const QVectorPath &path, const QPen &pen, const QRectF &clip);
 
     inline int vertexCount() const { return m_vertices.size(); }
     inline const float *vertices() const { return m_vertices.data(); }
@@ -96,7 +96,7 @@ class QDashedStrokeProcessor
 public:
     QDashedStrokeProcessor();
 
-    void process(const QVectorPath &path, const QPen &pen);
+    void process(const QVectorPath &path, const QPen &pen, const QRectF &clip);
 
     inline void addElement(QPainterPath::ElementType type, qreal x, qreal y) {
         m_points.add(x);