Commit 89b6209313cc65260f88a28ea99ec0df6dd807fc
2021-04-01T14:17:53
Fix race condition that can lead to ENTER/LEAVE window events never firing On windows, when toggling the state of RelativeMode rapidly, there is a high chance that SDL_WINDOWEVENT_ENTER / SDL_WINDOWEVENT_LEAVE events will stop firing indefinitely. This aims to resolve that shortcoming by ensuring mouse focus state is correctly updated via WM_MOUSELEAVE events arriving via the windows event hook.
diff --git a/src/video/windows/SDL_windowsevents.c b/src/video/windows/SDL_windowsevents.c
index 4f914aa..0fbe012 100644
--- a/src/video/windows/SDL_windowsevents.c
+++ b/src/video/windows/SDL_windowsevents.c
@@ -783,8 +783,16 @@ WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
}
}
}
- SDL_SetMouseFocus(NULL);
}
+
+ /* When WM_MOUSELEAVE is fired we can be assured that the cursor has left the window.
+ Regardless of relative mode, it is important that mouse focus is reset as there is a potential
+ race condition when in the process of leaving/entering relative mode, resulting in focus never
+ being lost. This then causes a cascading failure where SDL_WINDOWEVENT_ENTER / SDL_WINDOWEVENT_LEAVE
+ can stop firing permanently, due to the focus being in the wrong state and TrackMouseEvent never
+ resubscribing. */
+ SDL_SetMouseFocus(NULL);
+
returnCode = 0;
break;
#endif /* WM_MOUSELEAVE */