Only pause rendering if the Android activity is stopped

[grorp]

Depends on minetest/irrlicht#269.

Since #14058, rendering is paused on Android when the app is paused. However, it is also paused when the app is merely "unfocused" (e.g. a text input dialog is open). This is a problem because:

• The app might still be partially visible when it is "unfocused".

• It seems to result in bugs with text input: Android: Add selection dialog (drop down/combo box) #13814 (review). I have no idea why since the paused rendering shouldn't affect event handling, but this PR seems to fix the issue.

To do

This PR is a Ready for Review.

How to test

Verify that rendering still happens while the text input dialog is open.

Verify that the issue described in #13814 (review) is fixed.

[grorp]

I think this is still wrong. Apparently we shouldn't pause rendering when the activity is paused (onPause), but when the activity is stopped (onStop).

However, as mentioned in the section about onResume(), a Paused activity might still be fully visible if the app is in multi-window mode. Consider using onStop() instead of onPause() to fully release or adjust UI-related resources and operations to better support multi-window mode.
https://developer.android.com/guide/components/activities/activity-lifecycle#onpause

A GLSurfaceView must be notified when to pause and resume rendering. GLSurfaceView clients are required to call onPause() when the activity stops and onResume() when the activity starts. These calls allow GLSurfaceView to pause and resume the rendering thread, and also allow GLSurfaceView to release and recreate the OpenGL display.
https://developer.android.com/reference/android/opengl/GLSurfaceView#activity-life-cycle (emphasis mine)

So you're supposed to map Activity::onStop to GLSurfaceView::onPause and Activity::onStart to GLSurfaceView::onResume, if I understand this correctly. I'm not sure whether Irrlicht actually uses GLSurfaceView, but it's probably a good reference anyway.

This PR can stay as is, but I'll prepare another PR to Irrlicht.

[grorp]

This PR is now ready for review.

Pausing rendering in onStop instead of onPause has, in addition to being correct, another big benefit: If you now press "Share debug log" on the "About" tab, the clouds continue moving behind the dialog 😎

the_cool_video.mp4

Out of curiosity, I tested this with 5.8.0 from Google Play. The clouds don't continue moving there, although 5.8.0 doesn't have any "pause rendering" code 🤔

... and I tested again with a CI build of 5.8.0 (https://github.com/minetest/minetest/actions/runs/7090139065). The clouds do continue moving there. Maybe the Google Play build was made with an outdated Irrlicht version (before minetest/irrlicht#255)? I sometimes had to delete deps.zip and the deps folder manually to get it to update. @rubenwardy