d3d8/tests: Work around focus-follows-mouse test failures.

dlls/d3d8/tests/device.c

@@ -2888,7 +2888,11 @@ static void test_wndproc(void)
     hr = reset_device(device, &device_desc);
     ok(SUCCEEDED(hr), "Failed to reset device, hr %#x.\n", hr);
 
-    ShowWindow(device_window, SW_HIDE);
+    /* Remove the WS_VISIBLE flag to test hidden windows. This is enough to trigger d3d's hidden
+     * window codepath, but does not actually hide the window without a SetWindowPos(SWP_FRAMECHANGED)
+     * call. This way we avoid focus changes and random failures on focus follows mouse WMs. */
+    device_style = GetWindowLongA(device_window, GWL_STYLE);
+    SetWindowLongA(device_window, GWL_STYLE, device_style & ~WS_VISIBLE);
     flush_events();
 
     expect_messages = focus_loss_messages_hidden;