After upgrading from xfwm4 4.13.1 to 4.13.2, Qt's QWindow::lower() function no longer works for maximized windows. Under the hood, QWindow::lower() calls XCB_CONFIG_WINDOW_STACK_MODE with XCB_STACK_MODE_BELOW [1]. Apparently this request is now ignored by xfwm4 when the target window is maximized. git bisect says "3751c2c716714f84dd3d527b60f3543e96fac54e is the first bad commit". Steps to reproduce: 1. git clone https://gitlab.com/yan12125/test-lower 2. cmake . 3. make 4. ./test_lower 5. Hit the "Run lower()" button and check if the window is lowered 6. Maximized the window and repeat step 5. This time the window is _not_ lowered. Environment: Arch Linux, Qt 5.12.4 [1] https://github.com/qt/qtbase/blob/5.12.4/src/plugins/platforms/xcb/qxcbwindow.cpp#L1378
Olivier Fourdan referenced this bugreport in commit d8435e5e462f8e1acd2d7a5d085dab9b851ebe8f Revert "events: ignore client configure requests when maxized" https://git.xfce.org/xfce/xfwm4/commit?id=d8435e5e462f8e1acd2d7a5d085dab9b851ebe8f