For bounded operators, we need a different approach then. We will probably have to override the pattern supplied by CreateBrushForPattern(aSource) to return transparent black....
Bug 1816775 Comment 12 Edit History
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For bounded operators, we need a different approach then. We will probably have to override the pattern supplied by CreateBrushForPattern(aSource) to return a clear pattern, and override the blend mode. Looks like this would be dest-out to be compatible with D2D layers and such, but here's a patch that might work (so long as IsOperatorBoundByMask is fixed): https://paste.mozilla.org/FzyWWxh9