Send non zero repaint delay due to animation.

[navneetankur]

Is your feature request related to a problem? Please describe.

There can be slight flickering when side panel is enabled on a button click. Where the size of side panel gets adjusted.

According to docs, this is unavoidable.

This is a fundamental shortcoming of immediate mode GUIs, and any attempt to resolve it comes with its own downsides.

One workaround is to store the size and use it the next frame. This produces a frame-delay for the correct layout, producing occasional flickering the first frame something shows up. egui does this for some things such as windows and grid layouts.

In my own application, I can avoid that flickering easily by running the layout code multiple times (without sending output to gpu) until repaint_delay returned by Egui is non zero.

But this results in animations not working, as while it's animating the repaint_delay is always zero.

Describe the solution you'd like

This can be resolved if repaint caused by animation use a (very very) small repaint delay instead of zero.
From a simple look it seems that we only need to change Context::animate_bool to use Context::request_repaint_after(_, Duration::from_micros(1)) instead of Context::request_repaint.

And even logically animation frames have some time delay between them, no animation actually displays at infinite fps and zero delay in real life anyways.

Describe alternatives you've considered

Some api which describes that layout is not completely done yet vs layout is done.