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

1 files changed, 17 insertions, 8 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
index 7213474..2cea8d6 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
@@ -77,8 +77,15 @@ public:
     QOpenGL2PaintEngineState();
     ~QOpenGL2PaintEngineState();
 
-    QRegion clipRegion;
-    bool hasClipping;
+    bool needsDepthBufferClear;
+    qreal depthBufferClearValue;
+
+    bool depthTestEnabled;
+    bool scissorTestEnabled;
+    qreal currentDepth;
+    qreal maxDepth;
+
+    bool canRestoreClip;
 };
 
 
@@ -116,7 +123,6 @@ public:
 
     Type type() const { return OpenGL; }
 
-    // State stuff is just for clipping and ripped off from QGLPaintEngine
     void setState(QPainterState *s);
     QPainterState *createState(QPainterState *orig) const;
     inline QOpenGL2PaintEngineState *state() {
@@ -125,7 +131,6 @@ public:
     inline const QOpenGL2PaintEngineState *state() const {
         return static_cast<const QOpenGL2PaintEngineState *>(QPaintEngineEx::state());
     }
-    void updateClipRegion(const QRegion &clipRegion, Qt::ClipOperation op);
     virtual void sync();
 
 private:
@@ -180,9 +185,10 @@ public:
     QGLDrawable drawable;
     int width, height;
     QGLContext *ctx;
-
     EngineMode mode;
 
+    mutable QOpenGL2PaintEngineState *last_created_state;
+
     // Dirty flags
     bool matrixDirty; // Implies matrix uniforms are also dirty
     bool compositionModeDirty;
@@ -190,7 +196,9 @@ public:
     bool brushUniformsDirty;
     bool simpleShaderMatrixUniformDirty;
     bool shaderMatrixUniformDirty;
-    bool stencilBuferDirty;
+    bool stencilBufferDirty;
+    bool depthUniformDirty;
+    bool simpleShaderDepthUniformDirty;
 
     const QBrush*    currentBrush; // May not be the state's brush!
 
@@ -206,8 +214,9 @@ public:
 
     QGLEngineShaderManager* shaderManager;
 
-    // Clipping & state stuff stolen from QOpenGLPaintEngine:
-    void updateDepthClip();
+    void writeClip(const QVectorPath &path, float depth);
+    void updateDepthScissorTest();
+    void regenerateDepthClip();
     void systemStateChanged();
     uint use_system_clip : 1;
 };