Implement frame restacking under Android

* java/org/gnu/emacs/EmacsActivity.java (invalidateFocus1):
Synchronize with window.children for iteration through it.

* java/org/gnu/emacs/EmacsService.java (queryTree): Synchronize
with windowList for iteration through it.

* java/org/gnu/emacs/EmacsView.java (moveChildToBack): Correct
formatting mistake.
(moveAbove, moveBelow): New functions.

* java/org/gnu/emacs/EmacsWindow.java (destroyHandle, reparentTo)
(raise, lower): Remedy synchronization blunders.
(reconfigure): New function.

* src/android.c (android_init_emacs_window): Link with
`reconfigure'.
(android_reconfigure_wm_window): New wrapper function.

* src/androidfns.c (android_frame_restack): New function.
(Fandroid_frame_restack): Properly implement this function and
expunge outdated comment.

* src/androidgui.h (enum android_stack_mode)
(enum android_window_changes): New enumerators.

3 files changed, 93 insertions, 10 deletions

diff --git a/src/android.c b/src/android.c
index b9236075a1e..d1182698669 100644
--- a/src/android.c
+++ b/src/android.c
@@ -104,6 +104,7 @@ struct android_emacs_window
   jmethodID make_input_focus;
   jmethodID raise;
   jmethodID lower;
+  jmethodID reconfigure;
   jmethodID get_window_geometry;
   jmethodID translate_coordinates;
   jmethodID set_dont_accept_focus;
@@ -1755,6 +1756,7 @@ android_init_emacs_window (void)
   FIND_METHOD (make_input_focus, "makeInputFocus", "(J)V");
   FIND_METHOD (raise, "raise", "()V");
   FIND_METHOD (lower, "lower", "()V");
+  FIND_METHOD (reconfigure, "reconfigure", "(Lorg/gnu/emacs/EmacsWindow;I)V");
   FIND_METHOD (get_window_geometry, "getWindowGeometry",
                "()[I");
   FIND_METHOD (translate_coordinates, "translateCoordinates",
@@ -4963,6 +4965,37 @@ android_lower_window (android_window handle)
   android_exception_check ();
 }
 
+void
+android_reconfigure_wm_window (android_window handle,
+                               enum android_wc_value_mask value_mask,
+                               struct android_window_changes *values)
+{
+  jobject sibling, window;
+
+  window = android_resolve_handle (handle, ANDROID_HANDLE_WINDOW);
+
+  if (!(value_mask & ANDROID_CW_STACK_MODE))
+    return;
+
+  /* If value_mask & ANDROID_CW_SIBLING, place HANDLE above or below
+     values->sibling pursuant to values->stack_mode; else, reposition
+     it at the top or the bottom of its parent.  */
+
+  sibling = NULL;
+
+  if (value_mask & ANDROID_CW_SIBLING)
+    sibling = android_resolve_handle (values->sibling,
+                                      ANDROID_HANDLE_WINDOW);
+
+  (*android_java_env)->CallNonvirtualVoidMethod (android_java_env,
+                                                 window,
+                                                 window_class.class,
+                                                 window_class.reconfigure,
+                                                 sibling,
+                                                 (jint) values->stack_mode);
+  android_exception_check ();
+}
+
 int
 android_query_tree (android_window handle, android_window *root_return,
                     android_window *parent_return,
diff --git a/src/androidfns.c b/src/androidfns.c
index 3ee9f7634aa..772a4f51e78 100644
--- a/src/androidfns.c
+++ b/src/androidfns.c
@@ -1591,7 +1591,8 @@ and width values are in pixels.
 #endif
 }
 
-DEFUN ("android-frame-edges", Fandroid_frame_edges, Sandroid_frame_edges, 0, 2, 0,
+DEFUN ("android-frame-edges", Fandroid_frame_edges,
+       Sandroid_frame_edges, 0, 2, 0,
        doc: /* Return edge coordinates of FRAME.
 FRAME must be a live frame and defaults to the selected one.  The return
 value is a list of the form (LEFT, TOP, RIGHT, BOTTOM).  All values are
@@ -1693,6 +1694,28 @@ TERMINAL is a frame.  */)
 #endif
 }
 
+#ifndef ANDROID_STUBIFY
+
+static void
+android_frame_restack (struct frame *f1, struct frame *f2,
+                       bool above_flag)
+{
+  android_window window1;
+  struct android_window_changes wc;
+  unsigned long mask;
+
+  window1 = FRAME_ANDROID_WINDOW (f1);
+  wc.sibling = FRAME_ANDROID_WINDOW (f2);
+  wc.stack_mode = above_flag ? ANDROID_ABOVE : ANDROID_BELOW;
+  mask = ANDROID_CW_SIBLING | ANDROID_CW_STACK_MODE;
+
+  block_input ();
+  android_reconfigure_wm_window (window1, mask, &wc);
+  unblock_input ();
+}
+
+#endif /* !ANDROID_STUBIFY */
+
 DEFUN ("android-frame-restack", Fandroid_frame_restack,
        Sandroid_frame_restack, 2, 3, 0,
        doc: /* Restack FRAME1 below FRAME2.
@@ -1709,19 +1732,25 @@ that of FRAME2.  Hence the position of FRAME2 in its display's Z
 \(stacking) order relative to all other frames excluding FRAME1 remains
 unaltered.
 
-The Android system refuses to restack windows, so this does not
-work.  */)
-  (Lisp_Object frame1, Lisp_Object frame2, Lisp_Object frame3)
+Android does not facilitate restacking top-level windows managed by
+its own window manager; nor is it possible to restack frames that are
+children of different parents.  Consequently, this function only
+functions when FRAME1 and FRAME2 are both child frames subordinate to
+the same parent frame.  */)
+  (Lisp_Object frame1, Lisp_Object frame2, Lisp_Object above)
 {
 #ifdef ANDROID_STUBIFY
   error ("Android cross-compilation stub called!");
   return Qnil;
-#else
-  /* This is not supported on Android because of limitations in the
-     platform that prevent ViewGroups from restacking
-     SurfaceViews.  */
-  return Qnil;
-#endif
+#else /* !ANDROID_STUBIFY */
+  struct frame *f1 = decode_live_frame (frame1);
+  struct frame *f2 = decode_live_frame (frame2);
+
+  if (!(FRAME_ANDROID_WINDOW (f1) && FRAME_ANDROID_WINDOW (f2)))
+    error ("Cannot restack frames");
+  android_frame_restack (f1, f2, !NILP (above));
+  return Qt;
+#endif /* ANDROID_STUBIFY */
 }
 
 DEFUN ("android-mouse-absolute-pixel-position",
diff --git a/src/androidgui.h b/src/androidgui.h
index 936706b092e..b58c39a5276 100644
--- a/src/androidgui.h
+++ b/src/androidgui.h
@@ -564,6 +564,24 @@ enum android_ic_mode
     ANDROID_IC_MODE_TEXT   = 2,
   };
 
+enum android_stack_mode
+  {
+    ANDROID_ABOVE = 0,
+    ANDROID_BELOW = 1,
+  };
+
+enum android_wc_value_mask
+  {
+    ANDROID_CW_SIBLING    = 0,
+    ANDROID_CW_STACK_MODE = 1,
+  };
+
+struct android_window_changes
+{
+  android_window sibling;
+  enum android_stack_mode stack_mode;
+};
+
 extern int android_pending (void);
 extern void android_next_event (union android_event *);
 extern bool android_check_if_event (union android_event *,
@@ -643,6 +661,9 @@ extern void android_bell (void);
 extern void android_set_input_focus (android_window, unsigned long);
 extern void android_raise_window (android_window);
 extern void android_lower_window (android_window);
+extern void android_reconfigure_wm_window (android_window,
+                                           enum android_wc_value_mask,
+                                           struct android_window_changes *);
 extern int android_query_tree (android_window, android_window *,
                                android_window *, android_window **,
                                unsigned int *);