Fix two mouse drag and drop issues (Bug#28620, Bug#36269)

Allow 'mouse-drag-and-drop-region' to move/copy text from one
frame to another (Bug#28620).  Prevent mouse avoidance mode from
interfering with 'mouse-drag-and-drop-region' (Bug#36269).

* lisp/avoid.el (mouse-avoidance-ignore-p): Suspend avoidance
when 'track-mouse' equals 'dropping'.
* lisp/mouse.el (mouse-drag-and-drop-region): Set
'track-mouse' to 'dropping'.  Continue reading events also
when switching frames.
* src/keyboard.c (Finternal_track_mouse): Rename from
Ftrack_mouse.
(some_mouse_moved): Return NULL also when mouse is not tracked.
(show_help_echo, readable_events, kbd_buffer_get_event): Don't
check whether mouse is tracked, some_mouse_moved does it now.
(track_mouse): Rename variable from do_mouse_tracking.  Adjust
all users.  In doc-string explain meanings of special values
'dragging' and 'dropping'.
* src/nsterm.m (ns_mouse_position): During drag and drop
consider last mouse frame only when there is no currently
focused frame.
* src/w32fns.c (w32_wnd_proc): Don't set mouse capture during a
drag and drop operation.
* src/w32term.c (w32_mouse_position): Track frame under mouse
during mouse drag and drop.
(mouse_or_wdesc_frame): New function.
(w32_read_socket): Call mouse_or_wdesc_frame on mouse events.
* src/xdisp.c (define_frame_cursor1): Don't change mouse cursor
shape during mouse drag and drop.
(syms_of_xdisp): New symbol Qdropping.
* src/xterm.c (XTmouse_position): Allow mouse drag and drop move
to another frame
(mouse_or_wdesc_frame): New function.
(handle_one_xevent): Use mouse_or_wdesc_frame for mouse events.

1 files changed, 10 insertions, 5 deletions

diff --git a/src/w32fns.c b/src/w32fns.c
index acd9c80528a..a2a88b25881 100644
--- a/src/w32fns.c
+++ b/src/w32fns.c
@@ -4586,7 +4586,8 @@ w32_wnd_proc (HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
 	if (button_state & this)
 	  return 0;
 
-	if (button_state == 0)
+	/* Don't capture mouse when dropping.  */
+	if (button_state == 0 && !EQ (track_mouse, Qdropping))
 	  SetCapture (hwnd);
 
 	button_state |= this;
@@ -4707,8 +4708,11 @@ w32_wnd_proc (HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
 
 	if (parse_button (msg, HIWORD (wParam), &button, &up))
 	  {
-	    if (up) ReleaseCapture ();
-	    else SetCapture (hwnd);
+	    if (up)
+	      ReleaseCapture ();
+	    /* Don't capture mouse when dropping.  */
+	    else if (!EQ (track_mouse, Qdropping))
+	      SetCapture (hwnd);
 	    button = (button == 0) ? LMOUSE :
 	      ((button == 1) ? MMOUSE  : RMOUSE);
 	    if (up)
@@ -5351,8 +5355,9 @@ w32_wnd_proc (HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
 	else if (button_state & RMOUSE)
 	  flags |= TPM_RIGHTBUTTON;
 
-	/* Remember we did a SetCapture on the initial mouse down event,
-	   so for safety, we make sure the capture is canceled now.  */
+	/* We may have done a SetCapture on the initial mouse down
+	   event, so for safety, make sure the capture is canceled
+	   now.  */
 	ReleaseCapture ();
 	button_state = 0;