Bug 1777411 - Improve error messages when cloning ImageBitmap. r=gfx-reviewers,lsalzman

Differential Revision: https://phabricator.services.mozilla.com/D150697

dom/base/StructuredCloneHolder.cpp

@@ -1059,15 +1059,13 @@ bool StructuredCloneHolder::CustomWriteHandler(
   {
     ImageBitmap* imageBitmap = nullptr;
     if (NS_SUCCEEDED(UNWRAP_OBJECT(ImageBitmap, &obj, imageBitmap))) {
-      if (imageBitmap->IsWriteOnly()) {
-        return false;
-      }
-
       SameProcessScopeRequired(aSameProcessScopeRequired);
 
       if (CloneScope() == StructuredCloneScope::SameProcess) {
-        return ImageBitmap::WriteStructuredClone(aWriter, GetSurfaces(),
+        ErrorResult rv;
-                                                 imageBitmap);
+        ImageBitmap::WriteStructuredClone(aWriter, GetSurfaces(), imageBitmap,
+                                          rv);
+        return !rv.MaybeSetPendingException(aCx);
       }
       return false;
     }

dom/canvas/ImageBitmap.cpp

@@ -1734,16 +1734,20 @@ JSObject* ImageBitmap::ReadStructuredClone(
 }
 
 /*static*/
-bool ImageBitmap::WriteStructuredClone(
+void ImageBitmap::WriteStructuredClone(
     JSStructuredCloneWriter* aWriter,
     nsTArray<RefPtr<DataSourceSurface>>& aClonedSurfaces,
-    ImageBitmap* aImageBitmap) {
+    ImageBitmap* aImageBitmap, ErrorResult& aRv) {
   MOZ_ASSERT(aWriter);
   MOZ_ASSERT(aImageBitmap);
 
+  if (aImageBitmap->IsWriteOnly()) {
+    return aRv.ThrowDataCloneError("Cannot clone ImageBitmap, is write-only");
+  }
+
   if (!aImageBitmap->mData) {
     // A closed image cannot be cloned.
-    return false;
+    return aRv.ThrowDataCloneError("Cannot clone ImageBitmap, is closed");
   }
 
   const uint32_t picRectX = BitwiseCast<uint32_t>(aImageBitmap->mPictureRect.x);
@@ -1762,17 +1766,18 @@ bool ImageBitmap::WriteStructuredClone(
       NS_WARN_IF(!JS_WriteUint32Pair(aWriter, picRectWidth, picRectHeight)) ||
       NS_WARN_IF(
           !JS_WriteUint32Pair(aWriter, alphaType, aImageBitmap->mWriteOnly))) {
-    return false;
+    return aRv.ThrowDataCloneError(
+        "Cannot clone ImageBitmap, failed to write params");
   }
 
   RefPtr<SourceSurface> surface = aImageBitmap->mData->GetAsSourceSurface();
   if (NS_WARN_IF(!surface)) {
-    return false;
+    return aRv.ThrowDataCloneError("Cannot clone ImageBitmap, no surface");
   }
 
   RefPtr<DataSourceSurface> snapshot = surface->GetDataSurface();
   if (NS_WARN_IF(!snapshot)) {
-    return false;
+    return aRv.ThrowDataCloneError("Cannot clone ImageBitmap, no data surface");
   }
 
   RefPtr<DataSourceSurface> dstDataSurface;
@@ -1782,18 +1787,18 @@ bool ImageBitmap::WriteStructuredClone(
     // directly, using ScopedMap to get stride.
     DataSourceSurface::ScopedMap map(snapshot, DataSourceSurface::READ);
     if (NS_WARN_IF(!map.IsMapped())) {
-      return false;
+      return aRv.ThrowDataCloneError(
+          "Cannot clone ImageBitmap, cannot map surface");
     }
 
     dstDataSurface = Factory::CreateDataSourceSurfaceWithStride(
         snapshot->GetSize(), snapshot->GetFormat(), map.GetStride(), true);
   }
   if (NS_WARN_IF(!dstDataSurface)) {
-    return false;
+    return aRv.ThrowDataCloneError("Cannot clone ImageBitmap, out of memory");
   }
   Factory::CopyDataSourceSurface(snapshot, dstDataSurface);
   aClonedSurfaces.AppendElement(dstDataSurface);
-  return true;
 }
 
 size_t ImageBitmap::GetAllocatedSize() const {

dom/canvas/ImageBitmap.h

@@ -130,10 +130,10 @@ class ImageBitmap final : public nsISupports, public nsWrapperCache {
       const nsTArray<RefPtr<gfx::DataSourceSurface>>& aClonedSurfaces,
       uint32_t aIndex);
 
-  static bool WriteStructuredClone(
+  static void WriteStructuredClone(
       JSStructuredCloneWriter* aWriter,
       nsTArray<RefPtr<gfx::DataSourceSurface>>& aClonedSurfaces,
-      ImageBitmap* aImageBitmap);
+      ImageBitmap* aImageBitmap, ErrorResult& aRv);
 
   friend CreateImageBitmapFromBlob;
   friend CreateImageBitmapFromBlobTask;