Bug 876157 - Avoid expensive nsSVGGradientFrame::GetGradientTransform calls when gradients paint only a single color. r=roc

layout/svg/nsSVGGradientFrame.cpp

@@ -174,18 +174,9 @@ nsSVGGradientFrame::GetGradientTransform(nsIFrame *aSource,
   gfxMatrix bboxMatrix;
 
   uint16_t gradientUnits = GetGradientUnits();
-  if (gradientUnits == SVG_UNIT_TYPE_USERSPACEONUSE) {
-    // If this gradient is applied to text, our caller
-    // will be the glyph, which is not a container, so we
-    // need to get the parent
-    if (aSource->GetContent()->IsNodeOfType(nsINode::eTEXT))
-      mSource = aSource->GetParent();
-    else
-      mSource = aSource;
-  } else {
-    NS_ASSERTION(
-      gradientUnits == SVG_UNIT_TYPE_OBJECTBOUNDINGBOX,
-      "Unknown gradientUnits type");
+  if (gradientUnits != SVG_UNIT_TYPE_USERSPACEONUSE) {
+    NS_ASSERTION(gradientUnits == SVG_UNIT_TYPE_OBJECTBOUNDINGBOX,
+                 "Unknown gradientUnits type");
     // objectBoundingBox is the default anyway
 
     gfxRect bbox =
@@ -242,11 +233,16 @@ nsSVGGradientFrame::GetPaintServerPattern(nsIFrame *aSource,
                                           float aGraphicOpacity,
                                           const gfxRect *aOverrideBounds)
 {
-  // Get the transform list (if there is one)
-  gfxMatrix patternMatrix = GetGradientTransform(aSource, aOverrideBounds);
-
-  if (patternMatrix.IsSingular())
-    return nullptr;
+  uint16_t gradientUnits = GetGradientUnits();
+  MOZ_ASSERT(gradientUnits == SVG_UNIT_TYPE_OBJECTBOUNDINGBOX ||
+             gradientUnits == SVG_UNIT_TYPE_USERSPACEONUSE);
+  if (gradientUnits == SVG_UNIT_TYPE_USERSPACEONUSE) {
+    // Set mSource for this consumer.
+    // If this gradient is applied to text, our caller will be the glyph, which
+    // is not an element, so we need to get the parent
+    mSource = aSource->GetContent()->IsNodeOfType(nsINode::eTEXT) ?
+                aSource->GetParent() : aSource;
+  }
 
   uint32_t nStops = GetStopCount();
 
@@ -272,6 +268,15 @@ nsSVGGradientFrame::GetPaintServerPattern(nsIFrame *aSource,
     return pattern.forget();
   }
 
+  // Get the transform list (if there is one). We do this after the returns
+  // above since this call can be expensive when "gradientUnits" is set to
+  // "objectBoundingBox" (since that requiring a GetBBox() call).
+  gfxMatrix patternMatrix = GetGradientTransform(aSource, aOverrideBounds);
+
+  if (patternMatrix.IsSingular()) {
+    return nullptr;
+  }
+
   // revert the vector effect transform so that the gradient appears unchanged
   if (aFillOrStroke == &nsStyleSVG::mStroke) {
     patternMatrix.Multiply(nsSVGUtils::GetStrokeTransform(aSource).Invert());