From 3ad99c4674e670b73e7dcd8de3fa00b6dec4448f Mon Sep 17 00:00:00 2001
From: Eli Zaretskii <eliz@gnu.org>
Date: Sun, 27 Dec 2015 20:52:21 +0200
Subject: [PATCH] Avoid leaving "ghost" of mouse pointer on MS-Windows

* src/w32term.c (frame_set_mouse_pixel_position):
* src/w32fns.c (Fw32_mouse_absolute_pixel_position): Momentarily
disable "mouse trails" when moving the mouse pointer.  (Bug#22247)
* src/w32term.c (frame_set_mouse_pixel_position): Include
w32common.h.
---
 src/w32fns.c  | 11 +++++++++++
 src/w32term.c | 11 +++++++++++
 2 files changed, 22 insertions(+)

diff --git a/src/w32fns.c b/src/w32fns.c
index 4be322182ce..c1d9bff98ab 100644
--- a/src/w32fns.c
+++ b/src/w32fns.c
@@ -8093,11 +8093,22 @@ The coordinates X and Y are interpreted in pixels relative to a position
 (0, 0) of the selected frame's display.  */)
   (Lisp_Object x, Lisp_Object y)
 {
+  UINT trail_num = 0;
+  BOOL ret = false;
+
   CHECK_TYPE_RANGED_INTEGER (int, x);
   CHECK_TYPE_RANGED_INTEGER (int, y);
 
   block_input ();
+  /* When "mouse trails" are in effect, moving the mouse cursor
+     sometimes leaves behind an annoying "ghost" of the pointer.
+     Avoid that by momentarily switching off mouse trails.  */
+  if (os_subtype == OS_NT
+      && w32_major_version + w32_minor_version >= 6)
+    ret = SystemParametersInfo (SPI_GETMOUSETRAILS, 0, &trail_num, 0);
   SetCursorPos (XINT (x), XINT (y));
+  if (ret)
+    SystemParametersInfo (SPI_SETMOUSETRAILS, trail_num, NULL, 0);
   unblock_input ();
 
   return Qnil;
diff --git a/src/w32term.c b/src/w32term.c
index 0b8bef239f8..60d64f7fd0f 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -23,6 +23,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "lisp.h"
 #include "blockinput.h"
 #include "w32term.h"
+#include "w32common.h"	/* for OS version info */
 
 #include <ctype.h>
 #include <errno.h>
@@ -6237,6 +6238,8 @@ x_set_window_size (struct frame *f, bool change_gravity,
 void
 frame_set_mouse_pixel_position (struct frame *f, int pix_x, int pix_y)
 {
+  UINT trail_num = 0;
+  BOOL ret = false;
   RECT rect;
   POINT pt;
 
@@ -6247,7 +6250,15 @@ frame_set_mouse_pixel_position (struct frame *f, int pix_x, int pix_y)
   pt.y = rect.top + pix_y;
   ClientToScreen (FRAME_W32_WINDOW (f), &pt);
 
+  /* When "mouse trails" are in effect, moving the mouse cursor
+     sometimes leaves behind an annoying "ghost" of the pointer.
+     Avoid that by momentarily switching off mouse trails.  */
+  if (os_subtype == OS_NT
+      && w32_major_version + w32_minor_version >= 6)
+    ret = SystemParametersInfo (SPI_GETMOUSETRAILS, 0, &trail_num, 0);
   SetCursorPos (pt.x, pt.y);
+  if (ret)
+    SystemParametersInfo (SPI_SETMOUSETRAILS, trail_num, NULL, 0);
 
   unblock_input ();
 }
-- 
2.39.2