Bug 1477366 - Only support SVG filters with a single input with WebRender. r=mstange

Differential Revision: https://phabricator.services.mozilla.com/D17088

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

layout/painting/nsDisplayList.cpp

@@ -9347,12 +9347,13 @@ bool nsDisplayFilters::CreateWebRenderCSSFilters(
   return true;
 }
 
-bool nsDisplayFilters::CanCreateWebRenderCommands(nsDisplayListBuilder* aBuilder) {
+bool nsDisplayFilters::CanCreateWebRenderCommands(
+    nsDisplayListBuilder* aBuilder) {
   nsTArray<mozilla::wr::FilterOp> wrFilters;
   Maybe<nsRect> filterClip;
   if (!CreateWebRenderCSSFilters(wrFilters) &&
-      !nsSVGIntegrationUtils::BuildWebRenderFilters(
-          mFrame, wrFilters, filterClip)) {
+      !nsSVGIntegrationUtils::BuildWebRenderFilters(mFrame, wrFilters,
+                                                    filterClip)) {
     return false;
   }
   return true;

layout/svg/nsFilterInstance.cpp

@@ -130,8 +130,26 @@ bool nsFilterInstance::BuildWebRenderFilters(nsIFrame* aFilteredFrame,
   // case.
   // We can lift this restriction once we have added support for primitive
   // subregions to WebRender's filters.
+  for (uint32_t i = 0; i < instance.mFilterDescription.mPrimitives.Length();
+       i++) {
+    const auto& primitive = instance.mFilterDescription.mPrimitives[i];
+
+    // WebRender only supports filters with one input.
+    if (primitive.NumberOfInputs() != 1) {
+      return false;
+    }
+    // The first primitive must have the source graphic as the input, all
+    // other primitives must have the prior primitive as the input, otherwise
+    // it's not supported by WebRender.
+    if (i == 0) {
+      if (primitive.InputPrimitiveIndex(0) !=
+          FilterPrimitiveDescription::kPrimitiveIndexSourceGraphic) {
+        return false;
+      }
+    } else if (primitive.InputPrimitiveIndex(0) != int32_t(i - 1)) {
+      return false;
+    }
 
-  for (const auto& primitive : instance.mFilterDescription.mPrimitives) {
     bool primIsSrgb = primitive.OutputColorSpace() == gfx::ColorSpace::SRGB;
     if (srgb && !primIsSrgb) {
       aWrFilters.AppendElement(wr::FilterOp::SrgbToLinear());