2 files changed, 78 insertions, 0 deletions

diff --git a/java/org/gnu/emacs/EmacsActivity.java b/java/org/gnu/emacs/EmacsActivity.java
index 439a8defa32..6970728998b 100644
--- a/java/org/gnu/emacs/EmacsActivity.java
+++ b/java/org/gnu/emacs/EmacsActivity.java
@@ -50,6 +50,11 @@ import android.view.WindowInsetsController;
 
 import android.widget.FrameLayout;
 
+import android.window.BackEvent;
+import android.window.OnBackAnimationCallback;
+import android.window.OnBackInvokedCallback;
+import android.window.OnBackInvokedDispatcher;
+
 public class EmacsActivity extends Activity
   implements EmacsWindowManager.WindowConsumer,
   ViewTreeObserver.OnGlobalLayoutListener
@@ -252,6 +257,59 @@ public class EmacsActivity extends Activity
     return window;
   }
 
+  private void
+  interceptBackGesture ()
+  {
+    OnBackInvokedDispatcher dispatcher;
+    int priority = OnBackInvokedDispatcher.PRIORITY_DEFAULT;
+    OnBackInvokedCallback callback;
+
+    dispatcher = getOnBackInvokedDispatcher ();
+    callback = new OnBackAnimationCallback () {
+        @Override
+        public void
+        onBackInvoked ()
+        {
+          View view = EmacsActivity.this.getCurrentFocus ();
+          EmacsWindow window;
+
+          if (view instanceof EmacsView)
+            {
+              window = ((EmacsView) view).window;
+              window.onBackInvoked ();
+            }
+        }
+
+        /* The three functions are overridden to prevent a misleading
+           back animation from being displayed, as Emacs intercepts all
+           back gestures and will not return to the home screen.  */
+
+        @Override
+        public void
+        onBackCancelled ()
+        {
+
+        }
+
+        @Override
+        public void
+        onBackProgressed (BackEvent gestureEvent)
+        {
+
+        }
+
+        @Override
+        public void
+        onBackStarted (BackEvent gestureEvent)
+        {
+
+        }
+    };
+    dispatcher.registerOnBackInvokedCallback (priority, callback);
+  }
+
+
+
   @Override
   public void
   onCreate (Bundle savedInstanceState)
@@ -286,6 +344,11 @@ public class EmacsActivity extends Activity
     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.VANILLA_ICE_CREAM)
       layout.setFitsSystemWindows (true);
 
+    /* Android 16 replaces KEYCODE_BACK with a callback registered at
+       the window level.  */
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.BAKLAVA)
+      interceptBackGesture ();
+
     /* Maybe start the Emacs service if necessary.  */
     EmacsService.startEmacsService (this);
 
diff --git a/java/org/gnu/emacs/EmacsWindow.java b/java/org/gnu/emacs/EmacsWindow.java
index 394b2c26414..fffa2cc5d49 100644
--- a/java/org/gnu/emacs/EmacsWindow.java
+++ b/java/org/gnu/emacs/EmacsWindow.java
@@ -58,6 +58,7 @@ import android.util.SparseArray;
 import android.util.Log;
 
 import android.os.Build;
+import android.os.SystemClock;
 
 /* This defines a window, which is a handle.  Windows represent a
    rectangular subset of the screen with their own contents.
@@ -890,6 +891,20 @@ public final class EmacsWindow extends EmacsHandleObject
     EmacsNative.sendWindowAction (this.handle, 0);
   }
 
+  /* Dispatch a back gesture invocation as a KeyPress event.  Lamentably
+     the platform does not appear to support reporting keyboard
+     modifiers with these events.  */
+
+  public void
+  onBackInvoked ()
+  {
+    long time = SystemClock.uptimeMillis ();
+    EmacsNative.sendKeyPress (this.handle, time, 0,
+                              KeyEvent.KEYCODE_BACK, 0);
+    EmacsNative.sendKeyRelease (this.handle, time, 0,
+                                KeyEvent.KEYCODE_BACK, 0);
+  }
+
 
 
   /* Mouse and touch event handling.