From 4dd3275fd06857a9a36e60a63642fcc78c4082cb Mon Sep 17 00:00:00 2001
From: Matt Woodrow <mwoodrow@mozilla.com>
Date: Sun, 25 Jul 2021 08:31:25 +0000
Subject: [PATCH] Bug 1720986 - Reinstate clipping filters within SVG to the
 building rect. r=jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D120695
---
 gfx/layers/wr/WebRenderCommandBuilder.cpp    | 12 ++++++++++--
 layout/reftests/svg/filters/filter-giant.svg | 12 ++++++++++++
 layout/reftests/svg/filters/reftest.list     |  1 +
 3 files changed, 23 insertions(+), 2 deletions(-)
 create mode 100644 layout/reftests/svg/filters/filter-giant.svg

diff --git a/gfx/layers/wr/WebRenderCommandBuilder.cpp b/gfx/layers/wr/WebRenderCommandBuilder.cpp
index 666cf2c7cf44..a561e75c42d2 100644
--- a/gfx/layers/wr/WebRenderCommandBuilder.cpp
+++ b/gfx/layers/wr/WebRenderCommandBuilder.cpp
@@ -259,6 +259,12 @@ static bool IsContainerLayerItem(nsDisplayItem* aItem) {
 static bool DetectContainerLayerPropertiesBoundsChange(
     nsDisplayItem* aItem, BlobItemData* aData,
     nsDisplayItemGeometry& aGeometry) {
+  if (aItem->GetType() == DisplayItemType::TYPE_FILTER) {
+    // Filters get clipped to the BuildingRect since they can
+    // have huge bounds outside of the visible area.
+    aGeometry.mBounds = aGeometry.mBounds.Intersect(aItem->GetBuildingRect());
+  }
+
   return !aGeometry.mBounds.IsEqualEdges(aData->mGeometry->mBounds);
 }
 
@@ -1010,8 +1016,10 @@ void Grouper::PaintContainerItem(DIGroup* aGroup, nsDisplayItem* aItem,
       // outside the invalid rect.
       if (aDirty) {
         auto filterItem = static_cast<nsDisplayFilters*>(aItem);
-        filterItem->SetPaintRect(
-            filterItem->GetClippedBounds(mDisplayListBuilder));
+
+        nsRegion visible(aItem->GetClippedBounds(mDisplayListBuilder));
+        visible.And(visible, aItem->GetBuildingRect());
+        aItem->SetPaintRect(visible.GetBounds());
 
         filterItem->Paint(mDisplayListBuilder, aContext);
         TakeExternalSurfaces(aRecorder, aData->mExternalSurfaces, aRootManager,
diff --git a/layout/reftests/svg/filters/filter-giant.svg b/layout/reftests/svg/filters/filter-giant.svg
new file mode 100644
index 000000000000..e0a373a89218
--- /dev/null
+++ b/layout/reftests/svg/filters/filter-giant.svg
@@ -0,0 +1,12 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="100%" height="100%">
+<defs>
+<filter id="dropShadow" x="0" y="0" width="200%" height="200%">
+  <feOffset result="offOut" in="SourceAlpha" dx="1.5" dy="1.5"/>
+  <feGaussianBlur result="blurOut" in="offOut" stdDeviation="2"/>
+  <feBlend in="SourceGraphic" in2="blurOut" mode="normal"/>
+</filter>
+</defs>
+<g filter="url(#dropShadow)">
+  <rect x="-20000" y="-20000" width="40000" height="40000" fill="lime" />
+</g>
+</svg>
diff --git a/layout/reftests/svg/filters/reftest.list b/layout/reftests/svg/filters/reftest.list
index 24d60b81944b..ec699011034a 100644
--- a/layout/reftests/svg/filters/reftest.list
+++ b/layout/reftests/svg/filters/reftest.list
@@ -139,3 +139,4 @@ fuzzy(0-1,0-10000) == feTurbulence-zero-baseFreq-01.svg feTurbulence-zero-baseFr
 fails-if(!useDrawSnapshot&&webrender) == outside-sourcegraphic-2.svg outside-sourcegraphic-ref.svg
 fails-if(!useDrawSnapshot&&webrender) == outside-sourcegraphic-3.svg outside-sourcegraphic-ref.svg
 == nested-filter.html nested-filter-ref.html
+== filter-giant.svg pass.svg