On device rotation, the current TabBar content view area exhibits different rendering behaviour from system TabBar

[boscojwho]

This issue is part of an investigation into some rendering issues in various top-level views in each tab vertical (e.g. FeedView).

• Issues include: Shifting scroll positions, unnecessary re-renders, performance issues.

Describe the bug In system TabBar (TabView) setup, content area progressively rotates to new viewport dimensions, and arrives at new dimensions the moment rotation ends.

In the current TabBar setup, on device rotation, content area (ZStack) doesn't update to fit new viewport dimensions until after system finishes rotation.

• Furthermore, this behaviour becomes more evident if Low Power Mode is enabled, suggesting that there is could be an "extra computational work being done" aspect to this behaviour.

Compare behaviour via these videos

Mlem TabBar

https://github.com/mlemgroup/mlem/assets/2549615/64517892-73ac-46fb-8ac2-a308499d35d7

System TabBar (TabView)

https://github.com/mlemgroup/mlem/assets/2549615/d68f7f8a-a5fe-4ab5-a7c5-f4166f3d649a