Bug 1543482 - Extract a helper to identify clip paths WR can handle without masks. r=mattwoodrow

Differential Revision: https://phabricator.services.mozilla.com/D27454

--HG--
extra : moz-landing-system : lando

layout/painting/nsDisplayList.cpp

@@ -9532,19 +9532,12 @@ static Maybe<wr::WrClipId> CreateSimpleClipRegion(
   nsIFrame* frame = aDisplayItem.Frame();
   auto* style = frame->StyleSVGReset();
   MOZ_ASSERT(style->HasClipPath() || style->HasMask());
-  if (style->HasMask()) {
+  if (!nsSVGIntegrationUtils::UsingSimpleClipPathForFrame(frame)) {
     return Nothing();
   }
 
   const auto& clipPath = style->mClipPath;
-  if (clipPath.GetType() != StyleShapeSourceType::Shape) {
-    return Nothing();
-  }
-
   const auto& shape = clipPath.BasicShape();
-  if (shape.GetShapeType() == StyleBasicShapeType::Polygon) {
-    return Nothing();
-  }
 
   auto appUnitsPerDevPixel = frame->PresContext()->AppUnitsPerDevPixel();
   const nsRect refBox =
@@ -9602,8 +9595,8 @@ static Maybe<wr::WrClipId> CreateSimpleClipRegion(
       // Please don't add more exceptions, try to find a way to define the clip
       // without using a mask image.
       //
-      // And if you _really really_ need to add an exception, add it to where
-      // the polygon check is.
+      // And if you _really really_ need to add an exception, add it to
+      // nsSVGIntegrationUtils::UsingSimpleClipPathForFrame
       MOZ_ASSERT_UNREACHABLE("Unhandled shape id?");
       return Nothing();
   }

layout/svg/nsSVGIntegrationUtils.cpp

@@ -169,6 +169,22 @@ bool nsSVGIntegrationUtils::UsingMaskOrClipPathForFrame(
   return style->HasClipPath() || style->HasMask();
 }
 
+bool nsSVGIntegrationUtils::UsingSimpleClipPathForFrame(
+    const nsIFrame* aFrame) {
+  const nsStyleSVGReset* style = aFrame->StyleSVGReset();
+  if (!style->HasClipPath() || style->HasMask()) {
+    return false;
+  }
+
+  const auto& clipPath = style->mClipPath;
+  if (clipPath.GetType() != StyleShapeSourceType::Shape) {
+    return false;
+  }
+
+  const auto& shape = clipPath.BasicShape();
+  return (shape.GetShapeType() != StyleBasicShapeType::Polygon);
+}
+
 nsPoint nsSVGIntegrationUtils::GetOffsetToBoundingBox(nsIFrame* aFrame) {
   if ((aFrame->GetStateBits() & NS_FRAME_SVG_LAYOUT)) {
     // Do NOT call GetAllInFlowRectsUnion for SVG - it will get the

layout/svg/nsSVGIntegrationUtils.h

@@ -68,6 +68,12 @@ class nsSVGIntegrationUtils final {
    */
   static bool UsingMaskOrClipPathForFrame(const nsIFrame* aFrame);
 
+  /**
+   * Returns true if the element has a clippath that is simple enough to
+   * be represented without a mask in WebRender.
+   */
+  static bool UsingSimpleClipPathForFrame(const nsIFrame* aFrame);
+
   /**
    * Returns the size of the union of the border-box rects of all of
    * aNonSVGFrame's continuations.