Added some FIXMEs.

src/events/SDL_mouse.c

@@ -246,6 +246,7 @@ SDL_PrivateSendMouseMotion(SDL_Window * window, SDL_MouseID mouseID, int relativ
         mouse->y += yrel;
     }
 
+    /* !!! FIXME: shouldn't this be (window) instead of (mouse->focus)? */
     SDL_GetWindowSize(mouse->focus, &x_max, &y_max);
     --x_max;
     --y_max;

src/video/SDL_video.c

@@ -2216,6 +2216,8 @@ SDL_OnWindowFocusLost(SDL_Window * window)
     }
 }
 
+/* !!! FIXME: is this different than SDL_GetKeyboardFocus()?
+   !!! FIXME:  Also, SDL_GetKeyboardFocus() is O(1), this isn't. */
 SDL_Window *
 SDL_GetFocusWindow(void)
 {