If you add a transparency or filter mask to a fill layer and then choose to flatten that layer, it will convert it to a regular paint layer instead of keeping it as a fill layer. This may affect other masks as well, but they didn't seem relevant to fill layers. STEPS TO REPRODUCE 1. Add a fill layer. 2. Add a mask to that layer. 3. Flatten that layer. OBSERVED RESULT It converts the fill layer to a paint layer. EXPECTED RESULT It should remain a fill layer after the flattening operation.
A Fill layer is a simple repeated copy of a single colour pixel or a Pattern chosen from the available patterns. If you apply a transparency or filter mask, the rendered result can't be represented by a Fill layer so the result after flattening has to be a paint layer.
Re-thinking this for the case of a transparency mask, an applied transparency mask could be 'applied' by multiplication onto the Fill layer's built in transparency mask.
This is already supported and covers the use case you are describing To add the transparency information to the fill mask: - right click on the mask - Split Alpha > Write as alpha Fill layer will remain as fill layer. Flatten layer is designed to "apply" a layer projection an make it a pixel layer.
(In reply to vanyossi from comment #3) > This is already supported and covers the use case you are describing > > To add the transparency information to the fill mask: > - right click on the mask > - Split Alpha > Write as alpha > > Fill layer will remain as fill layer. > > Flatten layer is designed to "apply" a layer projection an make it a pixel > layer. Ya, the write to alpha option is what I ended up finding as a solution, but -tiar- from the subreddit suggested I file it as a bug anyhow, since write to alpha was not at all intuitive in comparison to flattening the layer, took us a while to find that.