Allow switching between FS and desktop FS.

This should fix bug #2057 (https://bugzilla.libsdl.org/show_bug.cgi?id=2057)

src/video/SDL_sysvideo.h

@@ -79,6 +79,7 @@ struct SDL_Window
     int min_w, min_h;
     int max_w, max_h;
     Uint32 flags;
+    Uint32 last_fullscreen_flags;
 
     /* Stored position and size for windowed mode */
     SDL_Rect windowed;

src/video/SDL_video.c

@@ -115,6 +115,7 @@ static SDL_VideoDevice *_this = NULL;
         return retval; \
     }
 
+#define FULLSCREEN_MASK ( SDL_WINDOW_FULLSCREEN_DESKTOP | SDL_WINDOW_FULLSCREEN )
 
 #ifdef __MACOSX__
 /* Support for Mac OS X fullscreen spaces */
@@ -1096,6 +1097,7 @@ SDL_UpdateFullscreenMode(SDL_Window * window, SDL_bool fullscreen)
 
 #ifdef __MACOSX__
     if (Cocoa_SetWindowFullscreenSpace(window, fullscreen)) {
+        window->last_fullscreen_flags = window->flags;
         return;
     }
 #endif
@@ -1112,7 +1114,9 @@ SDL_UpdateFullscreenMode(SDL_Window * window, SDL_bool fullscreen)
 
     /* See if anything needs to be done now */
     if ((display->fullscreen_window == window) == fullscreen) {
-        return;
+        if ((window->last_fullscreen_flags & FULLSCREEN_MASK) == (window->flags & FULLSCREEN_MASK)) {
+            return;
+        }
     }
 
     /* See if there are any fullscreen windows */
@@ -1157,6 +1161,8 @@ SDL_UpdateFullscreenMode(SDL_Window * window, SDL_bool fullscreen)
                 }
 
                 SDL_RestoreMousePosition(other);
+
+                window->last_fullscreen_flags = window->flags;
                 return;
             }
         }
@@ -1175,6 +1181,8 @@ SDL_UpdateFullscreenMode(SDL_Window * window, SDL_bool fullscreen)
 
     /* Restore the cursor position */
     SDL_RestoreMousePosition(window);
+
+    window->last_fullscreen_flags = window->flags;
 }
 
 #define CREATE_FLAGS \
@@ -1277,6 +1285,7 @@ SDL_CreateWindow(const char *title, int x, int y, int w, int h, Uint32 flags)
         }
     }
     window->flags = ((flags & CREATE_FLAGS) | SDL_WINDOW_HIDDEN);
+    window->last_fullscreen_flags = window->flags;
     window->brightness = 1.0f;
     window->next = _this->windows;
 
@@ -1318,6 +1327,7 @@ SDL_CreateWindowFrom(const void *data)
     window->magic = &_this->window_magic;
     window->id = _this->next_object_id++;
     window->flags = SDL_WINDOW_FOREIGN;
+    window->last_fullscreen_flags = window->flags;
     window->brightness = 1.0f;
     window->next = _this->windows;
     if (_this->windows) {
@@ -1378,6 +1388,7 @@ SDL_RecreateWindow(SDL_Window * window, Uint32 flags)
     window->title = NULL;
     window->icon = NULL;
     window->flags = ((flags & CREATE_FLAGS) | SDL_WINDOW_HIDDEN);
+    window->last_fullscreen_flags = window->flags;
 
     if (_this->CreateWindow && !(flags & SDL_WINDOW_FOREIGN)) {
         if (_this->CreateWindow(_this, window) < 0) {
@@ -1857,7 +1868,6 @@ SDL_RestoreWindow(SDL_Window * window)
     }
 }
 
-#define FULLSCREEN_MASK ( SDL_WINDOW_FULLSCREEN_DESKTOP | SDL_WINDOW_FULLSCREEN )
 int
 SDL_SetWindowFullscreen(SDL_Window * window, Uint32 flags)
 {