When the pointer enters the Qemu window it calls SDL_WM_GrabInput, which calls
XGrabPointer in a busyloop until it returns GrabSuccess. However if there's already
a pointer grab (screen is locked, a menu is open) then qemu will hang until the
grab can be taken.  In the specific case of a headless X server on an autobuilder, once
the screensaver has kicked in any qemu instance that appears underneath the
pointer will hang.

I'm not entirely sure why pointer grabs are required (the documentation
explicitly says it doesn't do grabs when using a tablet, which we are) so wrap
them in a conditional that can be set by the autobuilder environment, preserving
the current grabbing behaviour for everyone else.

Upstream-Status: Pending
Signed-off-by: Ross Burton <ross.burton@intel.com>

From 4b1988ecb01a178269ec0513a75f2ec620c7ef6a Mon Sep 17 00:00:00 2001
From: Ross Burton <ross.burton@intel.com>
Date: Wed, 18 Sep 2013 14:04:54 +0100
Subject: [PATCH] sdl.c: allow user to disable pointer grabs

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Eric Bénard <eric@eukrea.com>
---
 ui/sdl.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/ui/sdl.c b/ui/sdl.c
index 39a42d6..9b8abe5 100644
--- a/ui/sdl.c
+++ b/ui/sdl.c
@@ -59,6 +59,10 @@ static SDL_Cursor *guest_sprite = NULL;
 static SDL_PixelFormat host_format;
 static int scaling_active = 0;
 static Notifier mouse_mode_notifier;
+#ifndef True
+#define True 1
+#endif
+static doing_grabs = True;
 
 static void sdl_update(DisplayChangeListener *dcl,
                        int x, int y, int w, int h)
@@ -384,14 +388,16 @@ static void sdl_grab_start(void)
             SDL_WarpMouse(guest_x, guest_y);
     } else
         sdl_hide_cursor();
-    SDL_WM_GrabInput(SDL_GRAB_ON);
+    if (doing_grabs)
+      SDL_WM_GrabInput(SDL_GRAB_ON);
     gui_grab = 1;
     sdl_update_caption();
 }
 
 static void sdl_grab_end(void)
 {
-    SDL_WM_GrabInput(SDL_GRAB_OFF);
+    if (doing_grabs)
+      SDL_WM_GrabInput(SDL_GRAB_OFF);
     gui_grab = 0;
     sdl_show_cursor();
     sdl_update_caption();
@@ -909,6 +915,8 @@ void sdl_display_init(DisplayState *ds, int full_screen, int no_frame)
      * This requires SDL >= 1.2.14. */
     setenv("SDL_DISABLE_LOCK_KEYS", "1", 1);
 
+    doing_grabs = (getenv("QEMU_DONT_GRAB") == NULL);
+
     flags = SDL_INIT_VIDEO | SDL_INIT_NOPARACHUTE;
     if (SDL_Init (flags)) {
         fprintf(stderr, "Could not initialize SDL(%s) - exiting\n",
-- 
1.8.3.1