I ran into this with the following code // with a D2D DrawTarget dt which format is A8 RefPtr<SourceSurface> snapshot = dt->Snapshot(); // snapshot is A8 RefPtr<DataSourceSurface> dataSurface = snapshot->GetDataSurface(); // BGRA Visual studio tells me that the types of the objects are: dt: D2DDrawTarget snapshot: SourceSurfaceD2DDrawTarget dataSurface: DataSourceSurfaceD2DDrawTarget I don't know if we can assume that GetDataSurface returns something with the same format, or if it is okay to return a surface BGRA from an A8 one, but in my own selfish use case it triggers very slow code paths.

This seems like a nice invariant to have. If there aren't technical reasons to need different formats, then we should definitely do this.