Bug 600909: Optimize DrawPath for working with D2D surfaces. r=vlad a=blocking-betaN

content/canvas/src/nsCanvasRenderingContext2D.cpp

@@ -1960,13 +1960,25 @@ nsCanvasRenderingContext2D::ShadowFinalize(gfxAlphaBoxBlur& blur)
 nsresult
 nsCanvasRenderingContext2D::DrawPath(Style style, gfxRect *dirtyRect)
 {
-    /*
-     * Need an intermediate surface when:
-     * - globalAlpha != 1 and gradients/patterns are used (need to paint_with_alpha)
-     * - certain operators are used
-     */
-    PRBool doUseIntermediateSurface = NeedToUseIntermediateSurface() ||
-                                      NeedIntermediateSurfaceToHandleGlobalAlpha(style);
+    PRBool doUseIntermediateSurface = PR_FALSE;
+    
+    if (mSurface->GetType() == gfxASurface::SurfaceTypeD2D) {
+      if (style == STYLE_FILL) {
+        // D2D does all operators correctly even if transparent areas of SOURCE
+        // affect dest. We need to use an intermediate surface for STROKE because
+        // we can't clip to the actual stroke shape easily, but prefer a geometric
+        // clip over an intermediate surface for a FILL.
+        doUseIntermediateSurface = NeedIntermediateSurfaceToHandleGlobalAlpha(style);
+      }
+    } else {
+      /*
+       * Need an intermediate surface when:
+       * - globalAlpha != 1 and gradients/patterns are used (need to paint_with_alpha)
+       * - certain operators are used
+       */
+      doUseIntermediateSurface = NeedToUseIntermediateSurface() ||
+                                 NeedIntermediateSurfaceToHandleGlobalAlpha(style);
+    }
 
     PRBool doDrawShadow = NeedToDrawShadow();
 
@@ -2018,14 +2030,31 @@ nsCanvasRenderingContext2D::DrawPath(Style style, gfxRect *dirtyRect)
         mThebes->NewPath();
         mThebes->AppendPath(path);
 
-        // don't want operators to be applied twice
-        mThebes->SetOperator(gfxContext::OPERATOR_SOURCE);
+        // don't want operators to be applied twice,
+        if (mSurface->GetType() != gfxASurface::SurfaceTypeD2D) {
+            mThebes->SetOperator(gfxContext::OPERATOR_SOURCE);
+        } else {
+            // In the case of D2D OPERATOR_OVER is much faster. So we can just
+            // use that since it's the same as SOURCE for a transparent
+            // destinations. It would be nice if cairo backends could make this
+            // optimization internally but I see no very good way of doing this.
+            mThebes->SetOperator(gfxContext::OPERATOR_OVER);
+        }
     }
 
     ApplyStyle(style);
-    if (style == STYLE_FILL)
-        mThebes->Fill();
-    else
+
+    if (style == STYLE_FILL) {
+        if (!doUseIntermediateSurface &&
+            CurrentState().globalAlpha != 1.0 &&
+            !CurrentState().StyleIsColor(style))
+        {
+            mThebes->Clip();
+            mThebes->Paint(CurrentState().globalAlpha);
+        } else {
+            mThebes->Fill();
+        }
+    } else
         mThebes->Stroke();
 
     // XXX do some more work to calculate the extents of shadows