Bug 1746356 - Null-check the result of CreateSimilarDrawTarget. r=gfx-reviewers,lsalzman

Differential Revision: https://phabricator.services.mozilla.com/D148512

gfx/2d/DrawTargetOffset.cpp

@@ -208,5 +208,19 @@ void DrawTargetOffset::PopLayer() {
   SetPermitSubpixelAA(mDrawTarget->GetPermitSubpixelAA());
 }
 
+RefPtr<DrawTarget> DrawTargetOffset::CreateClippedDrawTarget(
+    const Rect& aBounds, SurfaceFormat aFormat) {
+  RefPtr<DrawTarget> result;
+  RefPtr<DrawTarget> dt =
+      mDrawTarget->CreateClippedDrawTarget(aBounds, aFormat);
+  if (dt) {
+    result = gfx::Factory::CreateOffsetDrawTarget(dt, mOrigin);
+    if (result) {
+      result->SetTransform(mTransform);
+    }
+  }
+  return result;
+}
+
 }  // namespace gfx
 }  // namespace mozilla

gfx/2d/DrawTargetOffset.h

@@ -164,14 +164,7 @@ class DrawTargetOffset : public DrawTarget {
     return mDrawTarget->CanCreateSimilarDrawTarget(aSize, aFormat);
   }
   virtual RefPtr<DrawTarget> CreateClippedDrawTarget(
-      const Rect& aBounds, SurfaceFormat aFormat) override {
-    RefPtr<DrawTarget> dt =
-        mDrawTarget->CreateClippedDrawTarget(aBounds, aFormat);
-    RefPtr<DrawTarget> result =
-        gfx::Factory::CreateOffsetDrawTarget(dt, mOrigin);
-    result->SetTransform(mTransform);
-    return result;
-  }
+      const Rect& aBounds, SurfaceFormat aFormat) override;
 
   virtual already_AddRefed<PathBuilder> CreatePathBuilder(
       FillRule aFillRule = FillRule::FILL_WINDING) const override {

gfx/2d/DrawTargetSkia.cpp

@@ -1596,9 +1596,13 @@ RefPtr<DrawTarget> DrawTargetSkia::CreateClippedDrawTarget(
   if (mCanvas->getDeviceClipBounds(&clipBounds)) {
     RefPtr<DrawTarget> dt = CreateSimilarDrawTarget(
         IntSize(clipBounds.width(), clipBounds.height()), aFormat);
-    result = gfx::Factory::CreateOffsetDrawTarget(
-        dt, IntPoint(clipBounds.x(), clipBounds.y()));
-    result->SetTransform(mTransform);
+    if (dt) {
+      result = gfx::Factory::CreateOffsetDrawTarget(
+          dt, IntPoint(clipBounds.x(), clipBounds.y()));
+      if (result) {
+        result->SetTransform(mTransform);
+      }
+    }
   } else {
     // Everything is clipped but we still want some kind of surface
     result = CreateSimilarDrawTarget(IntSize(1, 1), aFormat);