Bug 360316 - Avoid group opacity when possible. r=jwatt, sr=roc

layout/svg/base/src/nsSVGGeometryFrame.cpp

@@ -333,6 +333,15 @@ SetupCairoColor(cairo_t *aCtx, nscolor aRGB, float aOpacity)
                         aOpacity);
 }
 
+float
+nsSVGGeometryFrame::MaybeOptimizeOpacity(float aOpacity)
+{
+  if (nsSVGUtils::CanOptimizeOpacity(this)) {
+    aOpacity *= GetStyleDisplay()->mOpacity;
+  }
+  return aOpacity;
+}
+
 nsresult
 nsSVGGeometryFrame::SetupCairoFill(gfxContext *aContext,
                                    void **aClosure)
@@ -345,21 +354,19 @@ nsSVGGeometryFrame::SetupCairoFill(gfxContext *aContext,
   else
     cairo_set_fill_rule(ctx, CAIRO_FILL_RULE_WINDING);
 
+  float opacity = MaybeOptimizeOpacity(GetStyleSVG()->mFillOpacity);
+
   if (GetStateBits() & NS_STATE_SVG_FILL_PSERVER) {
     nsSVGPaintServerFrame *ps = NS_STATIC_CAST(nsSVGPaintServerFrame*,
                                                GetProperty(nsGkAtoms::fill));
-    return ps->SetupPaintServer(ctx, this,
-                                GetStyleSVG()->mFillOpacity,
-                                aClosure);
+    return ps->SetupPaintServer(ctx, this, opacity, aClosure);
   } else if (GetStyleSVG()->mFill.mType == eStyleSVGPaintType_Server) {
     // should have a paint server but something has gone wrong configuring it.
-    SetupCairoColor(ctx,
-                    sInvalidPaintColour,
-                    GetStyleSVG()->mFillOpacity);
+    SetupCairoColor(ctx, sInvalidPaintColour, opacity);
   } else
     SetupCairoColor(ctx,
                     GetStyleSVG()->mFill.mPaint.mColor,
-                    GetStyleSVG()->mFillOpacity);
+                    opacity);
 
   return NS_OK;
 }
@@ -428,16 +435,16 @@ nsSVGGeometryFrame::SetupCairoStroke(gfxContext *aContext,
 
   SetupCairoStrokeHitGeometry(aCtx);
 
+  float opacity = MaybeOptimizeOpacity(GetStyleSVG()->mStrokeOpacity);
+
   if (GetStateBits() & NS_STATE_SVG_STROKE_PSERVER) {
     nsSVGPaintServerFrame *ps = NS_STATIC_CAST(nsSVGPaintServerFrame*,
                                                GetProperty(nsGkAtoms::stroke));
-    return ps->SetupPaintServer(aCtx, this,
-                                GetStyleSVG()->mStrokeOpacity,
-                                aClosure);
+    return ps->SetupPaintServer(aCtx, this, opacity, aClosure);
   } else
     SetupCairoColor(aCtx,
                     GetStyleSVG()->mStroke.mPaint.mColor,
-                    GetStyleSVG()->mStrokeOpacity);
+                    opacity);
 
   return NS_OK;
 }

layout/svg/base/src/nsSVGGeometryFrame.h

@@ -115,6 +115,14 @@ private:
   nsresult GetStrokeDashArray(double **arr, PRUint32 *count);
   float GetStrokeDashoffset();
   void RemovePaintServerProperties();
+
+  // Returns opacity that should be used in rendering this primitive.
+  // In the general case the return value is just the passed opacity.
+  // If we can avoid the expense of a specified group opacity, we
+  // multiply the passed opacity by the value of the 'opacity'
+  // property, and elsewhere pretend the 'opacity' property has a
+  // value of 1.
+  float MaybeOptimizeOpacity(float aOpacity);
 };
 
 #endif // __NS_SVGGEOMETRYFRAME_H__

layout/svg/base/src/nsSVGImageFrame.cpp

@@ -291,8 +291,15 @@ nsSVGImageFrame::PaintSVG(nsSVGRenderState *aContext, nsRect *aDirtyRect)
       nsSVGUtils::SetClipRect(gfx, ctm, x, y, width, height);
     }
 
-    nsSVGUtils::CompositeSurfaceMatrix(gfx, thebesSurface, fini,
-                                       mStyleContext->GetStyleDisplay()->mOpacity);
+    // fill-opacity doesn't affect <image>, so if we're allowed to
+    // optimize group opacity, the opacity used for compositing the
+    // image into the current canvas is just the group opacity.
+    float opacity = 1.0f;
+    if (nsSVGUtils::CanOptimizeOpacity(this)) {
+      opacity = GetStyleDisplay()->mOpacity;
+    }
+
+    nsSVGUtils::CompositeSurfaceMatrix(gfx, thebesSurface, fini, opacity);
 
     if (GetStyleDisplay()->IsScrollableOverflow())
       gfx->Restore();

layout/svg/base/src/nsSVGUtils.cpp

@@ -626,6 +626,8 @@ nsSVGUtils::PaintChildWithEffects(nsSVGRenderState *aContext,
     return;
 
   float opacity = aFrame->GetStyleDisplay()->mOpacity;
+  if (opacity == 0.0f)
+    return;
 
   /* Properties are added lazily and may have been removed by a restyle,
      so make sure all applicable ones are set again. */
@@ -658,6 +660,9 @@ nsSVGUtils::PaintChildWithEffects(nsSVGRenderState *aContext,
    * + Merge opacity and masking if both used together.
    */
 
+  if (opacity != 1.0 && nsSVGUtils::CanOptimizeOpacity(aFrame))
+    opacity = 1.0;
+
   gfxContext *gfx = aContext->GetGfxContext();
   cairo_t *ctx = nsnull;
 
@@ -1039,6 +1044,22 @@ nsSVGUtils::SetClipRect(gfxContext *aContext,
   aContext->SetMatrix(oldMatrix);
 }
 
+PRBool
+nsSVGUtils::CanOptimizeOpacity(nsIFrame *aFrame)
+{
+  if (!(aFrame->GetStateBits() & NS_STATE_SVG_FILTERED)) {
+    nsIAtom *type = aFrame->GetType();
+    if (type == nsGkAtoms::svgImageFrame)
+      return PR_TRUE;
+    if (type == nsGkAtoms::svgPathGeometryFrame) {
+      nsSVGGeometryFrame *geom = NS_STATIC_CAST(nsSVGGeometryFrame*, aFrame);
+      if (!(geom->HasFill() && geom->HasStroke()))
+        return PR_TRUE;
+    }
+  }
+  return PR_FALSE;
+}
+
 // ----------------------------------------------------------------------
 
 nsSVGRenderState::nsSVGRenderState(nsIRenderingContext *aContext) :

layout/svg/base/src/nsSVGUtils.h

@@ -323,6 +323,14 @@ public:
                           nsIDOMSVGMatrix *aCTM, float aX, float aY,
                           float aWidth, float aHeight);
 
+  /* Using group opacity instead of fill or stroke opacity on a
+   * geometry object seems to be a common authoring mistake.  If we're
+   * not applying filters and not both stroking and filling, we can
+   * generate the same result without going through the overhead of a
+   * push/pop group. */
+  static PRBool
+  CanOptimizeOpacity(nsIFrame *aFrame);
+
 private:
   /* Computational (nil) surfaces */
   static cairo_surface_t *mCairoComputationalSurface;