Enable customization of the quit key on Android

* doc/emacs/android.texi (Android Windowing):

* doc/emacs/input.texi (On-Screen Keyboards): Document various
tidbits related to the quit key.

* java/org/gnu/emacs/EmacsNative.java (getQuitKeycode): New
function.

* java/org/gnu/emacs/EmacsWindow.java (EmacsWindow): Rename
`lastVolumeButtonRelease' to `lastQuitKeyRelease'.
(onKeyUp): Treat value returned by getQuitKeycode as the quit
key rather than mandate KEYCODE_VOLUME_DOWN.

* src/android.c (getQuitKeycode): Implement new function.

* src/androidterm.c (syms_of_androidterm)
<android_quit_keycode>: New variable.

2 files changed, 11 insertions, 10 deletions

diff --git a/java/org/gnu/emacs/EmacsNative.java b/java/org/gnu/emacs/EmacsNative.java
index 9b3e60e1a84..acf9e4b204b 100644
--- a/java/org/gnu/emacs/EmacsNative.java
+++ b/java/org/gnu/emacs/EmacsNative.java
@@ -228,6 +228,10 @@ public final class EmacsNative
      be prevented from reaching the system input method.  */
   public static native boolean shouldForwardCtrlSpace ();
 
+  /* Return the keycode repeated activation of which should signal
+     quit.  */
+  public static native int getQuitKeycode ();
+
   /* Initialize the current thread, by blocking signals that do not
      interest it.  */
   public static native void setupSystemThread ();
diff --git a/java/org/gnu/emacs/EmacsWindow.java b/java/org/gnu/emacs/EmacsWindow.java
index 911e082144e..961292af527 100644
--- a/java/org/gnu/emacs/EmacsWindow.java
+++ b/java/org/gnu/emacs/EmacsWindow.java
@@ -136,10 +136,10 @@ public final class EmacsWindow extends EmacsHandleObject
      there is no such window manager.  */
   private WindowManager windowManager;
 
-  /* The time of the last KEYCODE_VOLUME_DOWN release.  This is used
-     to quit Emacs upon two rapid clicks of the volume down
-     button.  */
-  private long lastVolumeButtonRelease;
+  /* The time of the last release of the quit keycode, generally
+     KEYCODE_VOLUME_DOWN.  This is used to signal quit upon two rapid
+     presses of such key.  */
+  private long lastQuitKeyRelease;
 
   /* Linked list of character strings which were recently sent as
      events.  */
@@ -790,15 +790,12 @@ public final class EmacsWindow extends EmacsHandleObject
 
         if ((event.getFlags () & KeyEvent.FLAG_CANCELED) != 0)
           return;
-
-        EmacsNative.sendKeyPress (this.handle, event.getEventTime (),
-                                  state, keyCode, unicode_char);
       }
 
     EmacsNative.sendKeyRelease (this.handle, event.getEventTime (),
                                 state, keyCode, unicode_char);
 
-    if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN)
+    if (keyCode == EmacsNative.getQuitKeycode ())
       {
         /* Check if this volume down press should quit Emacs.
            Most Android devices have no physical keyboard, so it
@@ -806,10 +803,10 @@ public final class EmacsWindow extends EmacsHandleObject
 
         time = event.getEventTime ();
 
-        if (time - lastVolumeButtonRelease < 350)
+        if (time - lastQuitKeyRelease < 350)
           EmacsNative.quit ();
 
-        lastVolumeButtonRelease = time;
+        lastQuitKeyRelease = time;
       }
   }