Graphics rendering with NativeActivity, how to get screen margins, ie safe area?

[rnikander]

I'm trying to develop an Android app with NativeActivity. I've got some stuff rendering on screen, but it takes up the entire screen and draws in the same area as the clock, battery, and other icons at the top, and in the area of the system "back", "home", and "menu" buttons at the bottom of the screen.

I'm searching everywhere and can't find any documentation on how to get something like a "screen margin" or "safe area insets" so you know where you can draw if you want to not draw on top of those elements? How do you do this? Or, where should I ask this question, if not here?

I'm actually using Rust, not C/C++, but the ndk crate I think is just wrapping this ndk. (?)

[DanAlbert]

AWINDOW_FLAG_LAYOUT_INSET_DECOR, passed to ANativeActivity_setWindowFlags.

If that's not sufficient, the answer is probably to use the Java API via JNI. Not all Java APIs have native equivalents, and most UI stuff is not available to native code except via JNI.

[rnikander]

Thanks. The docs for that flag sound promising: "By also including this flag, the window manager will report the inset rectangle needed [...]" But... how does it "report the rectangle"? 🤔

[DanAlbert]

I don't know. I've never actually done anything like this before, I just grepped the NDK headers for "inset". It looks like setWindowFlags() just calls into Java: https://developer.android.com/reference/android/view/Window#setFlags(int,%20int). You can probably trace the behavior through the Java docs.