master 207ee7f9880: Dismiss Android Back key events that are canceled

[Po Lu]

branch: master
commit 207ee7f9880c72920d4b323d7d6ed16544ba948b
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Dismiss Android Back key events that are canceled
    
    * java/org/gnu/emacs/EmacsWindow.java (onKeyDown): Disregard
    KEYCODE_BACK events.
    (onKeyUp): If the event is KEYCODE_BACK, deliver the disregarded
    key press event, unless FLAG_CANCELED is set.
---
 java/org/gnu/emacs/EmacsWindow.java | 37 +++++++++++++++++++++++++++++++------
 1 file changed, 31 insertions(+), 6 deletions(-)

diff --git a/java/org/gnu/emacs/EmacsWindow.java 
b/java/org/gnu/emacs/EmacsWindow.java
index 013f09cb756..7d161fdcf88 100644
--- a/java/org/gnu/emacs/EmacsWindow.java
+++ b/java/org/gnu/emacs/EmacsWindow.java
@@ -648,6 +648,21 @@ public final class EmacsWindow extends EmacsHandleObject
     long serial;
     String characters;
 
+    if (keyCode == KeyEvent.KEYCODE_BACK)
+      {
+       /* New Android systems display Back navigation buttons on a
+          row of virtual buttons at the bottom of the screen.  These
+          buttons function much as physical buttons do, in that key
+          down events are produced when a finger taps them, even if
+          the finger is not ultimately released after the OS's
+          gesture navigation is activated.
+
+          Deliver onKeyDown events in onKeyUp instead, so as not to
+          navigate backwards during gesture navigation.  */
+
+       return;
+      }
+
     state = eventModifiers (event);
 
     /* Ignore meta-state understood by Emacs for now, or key presses
@@ -677,7 +692,7 @@ public final class EmacsWindow extends EmacsHandleObject
   public void
   onKeyUp (int keyCode, KeyEvent event)
   {
-    int state, state_1;
+    int state, state_1, unicode_char;
     long time;
 
     /* Compute the event's modifier mask.  */
@@ -691,11 +706,21 @@ public final class EmacsWindow extends EmacsHandleObject
       = state & ~(KeyEvent.META_ALT_MASK | KeyEvent.META_CTRL_MASK
                  | KeyEvent.META_SYM_ON | KeyEvent.META_META_MASK);
 
-    EmacsNative.sendKeyRelease (this.handle,
-                               event.getEventTime (),
-                               state, keyCode,
-                               getEventUnicodeChar (event,
-                                                    state_1));
+    unicode_char = getEventUnicodeChar (event, state_1);
+
+    if (keyCode == KeyEvent.KEYCODE_BACK)
+      {
+       /* If the key press's been canceled, return immediately.  */
+
+       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)
       {