This prevents a window from getting reactivated when calling `SetWindowPos` inside the WM_ACTIVATE handler. For now I only was able to reproduce this by triggering a change in the active window from X11 with an alt-tab or by clicking another window, I was not able to write a wine test for this. This test program works for reproducing it. ```c #include <windows.h> LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) { if (uMsg == WM_ACTIVATE) { SetWindowPos(hwnd, 0, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE); } done: return DefWindowProc(hwnd, uMsg, wParam, lParam); } int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR pCmdLine, int nCmdShow) { HWND hwnd; const char CLASS_NAME[] = "class"; WNDCLASSA wc = {}; wc.lpfnWndProc = WindowProc; wc.hInstance = hInstance; wc.lpszClassName = CLASS_NAME; RegisterClass(&wc); hwnd = CreateWindowEx(0, CLASS_NAME, "test", 0, 4, 4, 1024, 768, NULL, NULL, hInstance, NULL); ShowWindow(hwnd, SW_SHOW); MSG msg; while (TRUE) { GetMessage(&msg, NULL, 0, 0); TranslateMessage(&msg); DispatchMessage(&msg); } } ``` -- https://gitlab.winehq.org/wine/wine/-/merge_requests/9398