Closes #27159 (closed), #27160 (closed).
If layer is not active, the source item seems to get realized both in an offscreen window, and in the assigned window. This may be fine for items that can be batched good, but in our case there are many batches.
Before:
- Batch count 2X (X main window + X offscreen).
- Blending is enabled only in the transparent areas.
- Effect sits on top of input.
After:
- Batch count X + 1 (X offscreen + 1 for the alpha texture in main window).
- Blending is enabled in the whole area.
- Effect sits on top of what's behind of the input.