Comment 1 for bug 1688743

I've started to look at the source for this, and it appears that perhaps the bug is actually that the paint bucket tool is not honoring the blend settings under the hood.

PaintBucketTool does not use UserBlendOps.NormalBlendOp.ApplyStatic to combine with the existing color, so just overwrites what is there using ColorBgra.ToPremultipliedAlpha.

I guess what really needs to happen is the addition of a new 'OverwriteBlendOp' and the exposure of the blendop being used in the gui, in a similar way to Paint.net