As well as takes text color transparency into account. That is, text
"shadow" now virtually casts shadow of however the text itself + outline
looks like. The result is blurred, and extra shadow color tint and
transparency is applied.
Performance testing: seems to be slightly faster than before in my tests.
Probably because the shadow "image" that is now blurred only contains
one byte per pixel (the transparency), instead of full uchar4 per pixel
(with only the "transparency" being blurred).
I have extended sequencer render tests to better cover various text
outline/shadow/box combinations.
Pull Request: https://projects.blender.org/blender/blender/pulls/125445
160f27330f