Implement DisplayServer::screen_get_usable_rect() for Android

[Klowner]

Fixes #20044 for me! Instead of showing letterboxes on the side, the full display is used, and OS.get_window_safe_area() should return a rectangle which excludes a device's cutout shapes.

It looks like lots of the methods for handling the cutout areas were updated in Android API 30, but hopefully this will work well enough for now.

[pouleyKetchoupp]

I haven't tested, but the code looks fine apart from the little detail I've pointed out.

Another thing that needs to be addressed is DisplayCutout is min API level 28 and the current minimum is 21.
https://developer.android.com/reference/android/view/DisplayCutout

Is there any way we could disable this code if API < 28? I don't know if Java allows something like that.

Otherwise, we need to decide if it's ok to raise the minimum API level to 28 for 4.0.

[akien-mga]

Otherwise, we need to decide if it's ok to raise the minimum API level to 28 for 4.0.

I'd say not OK, that excludes way too many users (40% of the market according to https://gs.statcounter.com/android-version-market-share/mobile/worldwide).

[Klowner]

Eep! Thank you for bringing attention to the minimum API version, @pouleyKetchoupp.

I think there's a mechanism for checking the device's supported API version? (I haven't done much android development)

Since older devices probably don't have cutouts anyway, would returning the full screen rectangle on devices with API <28 be a sufficient work around?

Thanks for the feedback!

[pouleyKetchoupp]

@Klowner Yes I think full screen rectangle would be fine as a fallback if you can figure out how to support both API versions.

[Klowner]

There we go, all squashed down 👍

[pouleyKetchoupp]

Looks good to me. I've tested the fallback case and it works fine. I don't have a device with recent enough API to test the cutout itself.

[akien-mga]

Thanks!

[Xioor]

Could I cherry pick this in 3.x.x or would it be incompatible? Do I have to use 4.0 for this feature?

[akien-mga]

This has already been merged in the 3.x branch and is included in 3.3-stable: #43140