Bug 1168527 - Add support to gfxContext for clip exporting. r=jrmuizel

--HG--
extra : rebase_source : 3747753f0285a9fe9803d851b234744603e2e0f4
extra : histedit_source : 73abebe3363945850bc42d17144cb0e90e184a7e

gfx/thebes/gfxContext.cpp

@@ -636,6 +636,40 @@ gfxContext::HasComplexClip() const
   return false;
 }
 
+bool
+gfxContext::ExportClip(ClipExporter& aExporter)
+{
+  unsigned int lastReset = 0;
+  for (int i = mStateStack.Length() - 1; i > 0; i--) {
+    if (mStateStack[i].clipWasReset) {
+      lastReset = i;
+      break;
+    }
+  }
+
+  for (unsigned int i = lastReset; i < mStateStack.Length(); i++) {
+    for (unsigned int c = 0; c < mStateStack[i].pushedClips.Length(); c++) {
+      AzureState::PushedClip &clip = mStateStack[i].pushedClips[c];
+      gfx::Matrix transform = clip.transform;
+      transform.PostTranslate(-GetDeviceOffset());
+
+      aExporter.BeginClip(transform);
+      if (clip.path) {
+        clip.path->StreamToSink(&aExporter);
+      } else {
+        aExporter.MoveTo(clip.rect.TopLeft());
+        aExporter.LineTo(clip.rect.TopRight());
+        aExporter.LineTo(clip.rect.BottomRight());
+        aExporter.LineTo(clip.rect.BottomLeft());
+        aExporter.Close();
+      }
+      aExporter.EndClip();
+    }
+  }
+
+  return true;
+}
+
 bool
 gfxContext::ClipContainsRect(const gfxRect& aRect)
 {

gfx/thebes/gfxContext.h

@@ -28,6 +28,8 @@ struct RectCornerRadii;
 }
 }
 
+class ClipExporter;
+
 /**
  * This is the main class for doing actual drawing. It is initialized using
  * a surface and can be drawn on. It manages various state information like
@@ -457,6 +459,11 @@ public:
      */
     bool ClipContainsRect(const gfxRect& aRect);
 
+     /**
+      * Exports the current clip using the provided exporter.
+      */
+    bool ExportClip(ClipExporter& aExporter);
+
     /**
      * Groups
      */
@@ -728,4 +735,12 @@ private:
   mozilla::gfx::Pattern *mPattern;
 };
 
+/* This interface should be implemented to handle exporting the clip from a context.
+ */
+class ClipExporter : public mozilla::gfx::PathSink {
+public:
+  virtual void BeginClip(const mozilla::gfx::Matrix& aMatrix) = 0;
+  virtual void EndClip() = 0;
+};
+
 #endif /* GFX_CONTEXT_H */