Icons can have contrasting outlines, but currently this can only happen
for some icons and when the theme setting "Icon Border" is greater than
zero. This change shows them in the same situations but also allows
them to be shown when needed. For special situations like having an
icon overlay on an icon, or for the icons in the corners of File
Browser preview items, etc. In a nutshell this allows UI_icon_draw_ex
to honor its outline argument, rather than ignoring it unless the theme
setting was also set.
Pull Request: https://projects.blender.org/blender/blender/pulls/123863
9ae237d0b4