Replacement for the old appbar drawer which used QtQuick's "Drawer" item and caused scrolling problems due to interference with its drag up and down open and close gesture. This doesn't have a way to drag it open and closed as of writing but it's a lot less janky. Still need to reimplement the "tap outside the popup to close" thing and improve keyboard focus so it goes through the appbar drawer items (I was thinking it could auto-expand the appbar drawer when tabbing to the appbar drawer expand button but that would be too annoying maybe); I think the focus can be shown by highlighting the focused item with a rectangle outline of the user's accent color (I saw somewhere that Qt has a way to tell how something gained focus, whether by keyboard or mouse click or touchscreen tap and I want to use that but I lost it, maybe it's a QtWidgets thing).
Something I need to figure out is how to have the new appbar not overlay the app's page if the app doesn't want it to.
TODO:
- fix the back button icon being in the wrong spot when expanded
- make the appbar drawer's parent the appbar for each of the apps that use it.
- clean up appbar and appbar-related comments that talk about the old drawer item to not be confusing
- add the MouseArea that allows closing the appbar drawer by tapping or clicking outside it
- try to get keyboard focus working with the drawer
- if I can figure it out, get some sort of a drag-to-open gesture on the left and right sides
- replace the Back button text with an icon like the ellipsis button so it can be aligned at the top
- scroll the flickable in the drawer to the top when opening it
See also: #540.