sdl: Dynamically grab input in absolute mouse mode

Not grabbing the input means that special keys like ALT+TAB are still
handled by the host. Improve the usability by grabbing input once the
mouse is inside the guest screen, provided the SDL window has the input
focus. Release it again when the mouse is moved to any border. Also grab
the input when we gain the input focus and the mouse is within the
screen limits.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

ui/sdl.c

@@ -490,15 +490,12 @@ static void sdl_mouse_mode_change(Notifier *notify, void *data)
 {
     if (kbd_mouse_is_absolute()) {
         if (!absolute_enabled) {
-            sdl_hide_cursor();
-            if (gui_grab) {
-                sdl_grab_end();
-            }
+            sdl_grab_start();
             absolute_enabled = 1;
         }
     } else if (absolute_enabled) {
-	sdl_show_cursor();
-	absolute_enabled = 0;
+        sdl_grab_end();
+        absolute_enabled = 0;
     }
 }
 
@@ -572,6 +569,19 @@ static void toggle_full_screen(DisplayState *ds)
     vga_hw_update();
 }
 
+static void absolute_mouse_grab(void)
+{
+    int mouse_x, mouse_y;
+
+    if (SDL_GetAppState() & SDL_APPINPUTFOCUS) {
+        SDL_GetMouseState(&mouse_x, &mouse_y);
+        if (mouse_x > 0 && mouse_x < real_screen->w - 1 &&
+            mouse_y > 0 && mouse_y < real_screen->h - 1) {
+            sdl_grab_start();
+        }
+    }
+}
+
 static void sdl_refresh(DisplayState *ds)
 {
     SDL_Event ev1, *ev = &ev1;
@@ -638,6 +648,7 @@ static void sdl_refresh(DisplayState *ds)
                             }
                         } else if (absolute_enabled) {
                             sdl_hide_cursor();
+                            absolute_mouse_grab();
                         }
                         break;
                     default:
@@ -724,6 +735,22 @@ static void sdl_refresh(DisplayState *ds)
             }
             break;
         case SDL_MOUSEMOTION:
+            if (is_graphic_console() &&
+                (kbd_mouse_is_absolute() || absolute_enabled)) {
+                int max_x = real_screen->w - 1;
+                int max_y = real_screen->h - 1;
+
+                if (gui_grab &&
+                    (ev->motion.x == 0 || ev->motion.y == 0 ||
+                     ev->motion.x == max_x || ev->motion.y == max_y)) {
+                    sdl_grab_end();
+                }
+                if (!gui_grab && SDL_GetAppState() & SDL_APPINPUTFOCUS &&
+                    (ev->motion.x > 0 && ev->motion.x < max_x &&
+                     ev->motion.y > 0 && ev->motion.y < max_y)) {
+                    sdl_grab_start();
+                }
+            }
             if (gui_grab || kbd_mouse_is_absolute() ||
                 absolute_enabled) {
                 sdl_send_mouse_event(ev->motion.xrel, ev->motion.yrel, 0,
@@ -764,6 +791,10 @@ static void sdl_refresh(DisplayState *ds)
                 !ev->active.gain && !gui_fullscreen) {
                 sdl_grab_end();
             }
+            if (!gui_grab && ev->active.gain && is_graphic_console() &&
+                (kbd_mouse_is_absolute() || absolute_enabled)) {
+                absolute_mouse_grab();
+            }
             if (ev->active.state & SDL_APPACTIVE) {
                 if (ev->active.gain) {
                     /* Back to default interval */