AppChooser portal: Overhaul UI
This commit introduces a series of inter-related changes that combine together to overhaul and modernize the UI, and make it more visually and functionally consistent with other KDE UIs.
Here are the individual changes:
- Merge the top two pieces of text into one, and use it as the the dialog's title
- Move the search field and "show all apps" button to the top, since they're both scope selectors
- Make the search field filter all visible items in the view, not just non-preferred apps
- Mark the default app using bold text, not a background highlight that can mislead you into thinking it has keyboard focus (but it does not)
- When grid delegates are hovered, show a normal-style highlight effect rather than changing the cursor shape
- Move the "find more apps" message to the bottom to support a normal top-to-bottom flow: first you choose your scope (or not), then you look for the app, then if you don't find one, you can use Discover to search for more
- Add a placeholder message when the view is empty, either because no relevant apps are installed or because no apps matched the user's search text
| Before | After | |
|---|---|---|
| Default view |  |
 |
| All apps view |  |
 |
| "Nothing found in a search" view |  |
 |