In particular, this makes the asset shelf popup search highlight the
first asset when changing the search filter using text input. Pressing
Enter will activate this asset then. The feature is implemented
generally for grid and tree views, but only the asset shelf implements
filtering so far. Plus, it requires the
`UI_BUT2_FORCE_SEMI_MODAL_ACTIVE` behavior on the filter text button,
otherwise it captures all input. Only the popup version of the asset
shelf uses this currently. Moving the mouse makes the highlight jump
back to the brush under the cursor again. This is how search menus
behave too.
Part of the brush assets project, see blender/blender!123853. It's made
so it's possible to quickly spawn the brush asset shelf popup, input
text to search a brush and press Enter to activate it. Based on user
feedback this is an important workflow to support well.
More info about the changes in the pull request.
Pull Request: https://projects.blender.org/blender/blender/pulls/123853