bug#26816: mouse movement support for OS X

["Charles A. Roelli" <charles@aurox.ch>]

As far as I know, mouse movement by Emacs has never worked in OS X.

The following change to frame_set_mouse_pixel_position allows you to 
move the mouse from Lisp:

diff --git a/src/nsterm.m b/src/nsterm.m
index c22c5a7..e81b7ee 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -2322,14 +2322,14 @@ so some key presses (TAB) are swallowed by the 
system. */
  {
    NSTRACE ("frame_set_mouse_pixel_position");
    ns_raise_frame (f);
-#if 0
-  /* FIXME: this does not work, and what about GNUstep? */
+  /* FIXME: what about GNUstep? */
  #ifdef NS_IMPL_COCOA
    [FRAME_NS_VIEW (f) lockFocus];
-  PSsetmouse ((float)pix_x, (float)pix_y);
+  CGPoint mouse_pos = CGPointMake(f->left_pos + pix_x,
+                                  f->top_pos + pix_y);
+  CGWarpMouseCursorPosition (mouse_pos);
    [FRAME_NS_VIEW (f) unlockFocus];
  #endif
-#endif
  }

  static int

(test with (set-mouse-position (selected-frame) 0 0))

Still some things to fix:

With a portrait monitor to the left of the main monitor (the left 
monitor being in the negative x-coord. space), running the above test 
code on a single frame inside the left monitor leaves the mouse pointer 
about half a frame further down than the bottom-left corner of the 
frame.  The pointer should end up in the top-left corner.

Also, tested only in 10.6, but it should work in later versions.