fix(android): keep the toolbar out of the status and navigation bars (Issue #50)

NativeActivity draws the whole window, also below the system bars, so the
top toolbar button lay under the status bar and taps there went to
Android (no other notebook could be opened). InkActivity now reports the
system bar and cutout insets; the app shrinks egui's screen rect to the
free area and adds the side insets to the page centering. The page itself
still scrolls below the bars.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packaging/android/java/eu/pansi/inknotes/InkActivity.java

@@ -5,11 +5,13 @@ import android.content.Context;
 import android.content.Intent;
 import android.database.Cursor;
 import android.net.Uri;
+import android.os.Build;
 import android.os.Bundle;
 import android.provider.OpenableColumns;
 import android.text.InputType;
 import android.view.View;
 import android.view.ViewGroup;
+import android.view.WindowInsets;
 import android.view.inputmethod.BaseInputConnection;
 import android.view.inputmethod.EditorInfo;
 import android.view.inputmethod.InputConnection;
@@ -29,6 +31,9 @@ import java.io.OutputStream;
  *   An invisible view with its own input connection passes committed text to Rust.
  * - Picking files: the system file dialog (ACTION_OPEN_DOCUMENT); the chosen file is copied to
  *   the cache folder, as Rust can only open files by path.
+ * - System bars: NativeActivity draws the whole window, also below the status and navigation
+ *   bars and display cutouts. Their sizes go to Rust, which keeps its buttons out of them
+ *   (Issue #50).
  *
  * Rust calls showKeyboard and pickFile through JNI and receives the native* calls
  * (src/android_bridge.rs).
@@ -49,6 +54,9 @@ public class InkActivity extends NativeActivity {
     /** Path of the copied file, or null if nothing was chosen or copying failed. */
     static native void nativeFilePicked(String path);
 
+    /** Window edges covered by system bars or cutouts, in pixels. */
+    static native void nativeSetInsets(int left, int top, int right, int bottom);
+
     private TextSink textSink;
 
     @Override
@@ -56,6 +64,26 @@ public class InkActivity extends NativeActivity {
         super.onCreate(savedInstanceState);
         textSink = new TextSink(this);
         addContentView(textSink, new ViewGroup.LayoutParams(1, 1));
+        View decor = getWindow().getDecorView();
+        decor.setOnApplyWindowInsetsListener((view, insets) -> {
+            reportInsets(insets);
+            return view.onApplyWindowInsets(insets);
+        });
+        decor.requestApplyInsets();
+    }
+
+    @SuppressWarnings("deprecation")
+    private static void reportInsets(WindowInsets insets) {
+        if (Build.VERSION.SDK_INT >= 30) {
+            android.graphics.Insets bars = insets.getInsets(
+                    WindowInsets.Type.systemBars() | WindowInsets.Type.displayCutout());
+            nativeSetInsets(bars.left, bars.top, bars.right, bars.bottom);
+        } else {
+            // Before Android 11 the system window insets include the bars (and since
+            // Android 9 the cutout)
+            nativeSetInsets(insets.getSystemWindowInsetLeft(), insets.getSystemWindowInsetTop(),
+                    insets.getSystemWindowInsetRight(), insets.getSystemWindowInsetBottom());
+        }
     }
 
     /** Shows or hides the soft keyboard; called from Rust on any thread. */