Pass focus when KWin falls back to the desktop window on close/minimize (issue 136) - #195
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When the active window is closed or minimized, KWin activates another window before it emits `windowRemoved` or `minimizedChanged`. With KWin's default `SeparateScreenFocus=true`, its focus chain only considers windows whose frame intersects the screen. When all other windows are entirely off-screen (e.g. a full-width column with no gaps and margins), KWin finds no candidate and activates the desktop window instead. Karousel then saw the desktop window as the last focused client, so it skipped passing focus from the closed window, leaving no window focused. Treat a desktop window that got activated right after the closed/minimized window as a KWin fallback rather than a real focus change, and still pass focus to the neighboring window in that case. Tests: model KWin's pre-removal activation (including the desktop window fallback) in the mock workspace, and make MockQSignal match Qt by not delivering an emission to handlers connected during that emission.
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Fixes #136. Very likely also fixes #146 (same trigger: only one window visible, neighbors entirely off-screen).
Problem
With no gaps and margins, a full-width column's neighbors lie entirely off-screen. Closing (or minimizing) that column's window then leaves no window focused.
Cause
On Wayland, KWin activates another window before it emits
windowRemoved(Workspace::removeWaylandWindow→activateNextWindow) and beforeminimizedChanged(XdgToplevelWindow::doMinimize→activateNextWindow).Since Plasma 6,
SeparateScreenFocusdefaults totrue(kwin.kcfg). With it on,FocusChain::isUsableFocusCandidaterequiresWindow::isOnOutput, which isoutput->geometry().intersects(frameGeometry()). A neighbor that is entirely off-screen fails that check, so KWin finds no candidate and falls back to activating the desktop window (findDesktop).Karousel receives
windowActivated(desktopWindow)first, records it as the last focused client, and thenClientManager.removeClientsees the closed window is no longer the last focused client and downgradespassFocustoNone. Karousel's own neighbor-focus logic never runs. With a left/right margin the neighbor intersects the screen by a few pixels, KWin's chain accepts it, and everything works, which is why the bug only shows with zero margins.(Verified against the Plasma/6.7 sources:
activation.cpp,focuschain.cpp,window.cpp,xdgshellwindow.cpp,kwin.kcfg.)Fix
ClientManagernow remembers the previously focused client. If the last focused client is a desktop window and the client being removed/minimized is the one focused right before it, treat that as KWin's fallback rather than a real focus change and still pass focus. Karousel'sWindow.focus()goes throughWorkspace.activeWindow = …→activateWindow→requestFocus, which has no on-screen check, so focusing the off-screen neighbor succeeds and the resulting focus event scrolls it into view.desktopWindowis added to theKwinClientinterface (KWin scripting API:Q_PROPERTY(bool desktopWindow READ isDesktop CONSTANT)).Tests
MockWorkspace.removeWindowand the mockminimizedsetter now mimicWorkspace::activateNextWindow: only windows intersecting the screen are candidates, otherwise the desktop window gets activated (a desktop window is now always present in the mock workspace).passFocus.tscover close and minimize with zero gaps and full-width windows. Both fail on master (focus stays onDesktop) and pass with the fix.MockQSignal.fireno longer delivers an emission to handlers connected (or disconnected) during that emission, matching Qt. Without this, minimizing a tiled window in the mock ping-pongs betweenTiledandTiledMinimizedforever.make lintandmake test(51 tests) pass.