Fixed bug 3410 - SDL_WINDOW_HIDDEN flag is inaccurate.

Jason Wyatt

After hiding the window, SDL_WINDOW_HIDDEN/SDL_WINDOW_SHOWN flags on a window are correctly updated. However on the next SDL_PumpEvents, they are set incorrectly.

This appears to be because X11_GetNetWMState does not check whether the _NET_WM_STATE property exists (it shouldn't on unmapped windows, see https://specifications.freedesktop.org/wm-spec/wm-spec-1.3.html#idm140130317598336). This results in an empty list of atoms for the state, which would imply that the window is not hidden.

(Seen on Fedora 24, Gnome)

--

Dan Ginsburg

More details on my proposed patch: I am on Kubuntu 16.04.2.  I ran into this same bug, but with Jason's patch I found that actualType != None was true so the SDL_WINDOW_HIDDEN would still not be set.  My fix instead is to explicitly check for whether the window is unmapped rather than relying on the returned values in XGetWindowProperty.

src/video/x11/SDL_x11window.c

@@ -225,6 +225,19 @@ X11_GetNetWMState(_THIS, Window xwindow)
         if (fullscreen == 1) {
             flags |= SDL_WINDOW_FULLSCREEN;
         }
+
+        /* If the window is unmapped, numItems will be zero and _NET_WM_STATE_HIDDEN
+         * will not be set. Do an additional check to see if the window is unmapped
+         * and mark it as SDL_WINDOW_HIDDEN if it is.
+         */
+        {
+            XWindowAttributes attr;
+            SDL_memset(&attr,0,sizeof(attr));
+            X11_XGetWindowAttributes(videodata->display, xwindow, &attr);
+            if (attr.map_state == IsUnmapped) {
+                flags |= SDL_WINDOW_HIDDEN;
+            }
+        }
         X11_XFree(propertyValue);
     }