{"record":{"id":"fa29df54e932b9fa","repo":"java-native-access/jna","slug":"cannot-get-window-manager-info-properties-net-supporting-wm","errorCode":null,"errorMessage":"Cannot get window manager info properties. (_NET_SUPPORTING_WM_CHECK or _WIN_SUPPORTING_WM_CHECK)","messagePattern":"Cannot get window manager info properties\\. \\(_NET_SUPPORTING_WM_CHECK or _WIN_SUPPORTING_WM_CHECK\\)","errorType":"exception","errorClass":"X11Exception","httpStatus":null,"severity":"error","filePath":"contrib/x11/src/jnacontrib/x11/api/X.java","lineNumber":169,"sourceCode":"            return atom;\n        }\n\n        /**\n         * Returns the window manager information as an window.\n         *\n         * @return window manager information as an window\n         * @throws X11Exception thrown if X11 window errors occurred\n         */\n        public Window getWindowManagerInfo() throws X11Exception {\n            Window rootWindow = getRootWindow();\n\n            try {\n                return rootWindow.getWindowProperty(X11.XA_WINDOW, \"_NET_SUPPORTING_WM_CHECK\");\n            } catch (X11Exception e) {\n                try {\n                    return rootWindow.getWindowProperty(X11.XA_CARDINAL, \"_WIN_SUPPORTING_WM_CHECK\");\n                } catch (X11Exception e1) {\n                    throw new X11Exception(\"Cannot get window manager info properties. (_NET_SUPPORTING_WM_CHECK or _WIN_SUPPORTING_WM_CHECK)\");\n                }\n            }\n        }\n\n        /**\n         * Returns the root window.\n         *\n         * @return root window\n         */\n        public Window getRootWindow() {\n            return new Window(this, x11.XDefaultRootWindow(x11Display));\n        }\n\n        /**\n         * Returns the current active window.\n         *\n         * @return current active window\n         * @throws X11Exception thrown if X11 window errors occurred","sourceCodeStart":151,"sourceCodeEnd":187,"githubUrl":"https://github.com/java-native-access/jna/blob/d036ad9781adad4b66693e8fa7098e4ac665e0a3/contrib/x11/src/jnacontrib/x11/api/X.java#L151-L187","documentation":"X.getWindowManagerInfo() tries to read the _NET_SUPPORTING_WM_CHECK root-window property (EWMH), falling back to _WIN_SUPPORTING_WM_CHECK. If both property reads raise X11Exception, it throws X11Exception 'Cannot get window manager info properties...'. This means no EWMH-compatible window-manager info could be retrieved from the root window.","triggerScenarios":"Calling getWindowManagerInfo on a system where the window manager does not set _NET_SUPPORTING_WM_CHECK or _WIN_SUPPORTING_WM_CHECK on the root window, or when reading the property fails (wrong type/atom, no WM running).","commonSituations":"Bare X server with no window manager (Xvfb sessions), minimal tiling WMs without EWMH support, or Wayland sessions where the X root-window properties don't exist.","solutions":["Verify a window manager is running and EWMH-compliant (most modern WMs set _NET_SUPPORTING_WM_CHECK).","Use xprop -root | grep SUPPORTING to confirm the property exists before calling the API.","In headless/test setups, run a lightweight EWMH WM (e.g. openbox, mutter, i3) alongside Xvfb.","Catch X11Exception and degrade: proceed without WM info instead of failing the whole operation."],"exampleFix":"// before\nX.Window wmInfo = x.getWindowManagerInfo();\n// after\ntry {\n    X.Window wmInfo = x.getWindowManagerInfo();\n} catch (X11Exception e) {\n    LOG.warn(\"No EWMH window manager detected, skipping WM info\");\n}","handlingStrategy":"try-catch","validationCode":"// shell probe before calling the API\n// xprop -root _NET_SUPPORTING_WM_CHECK  (non-empty => supported)","typeGuard":null,"tryCatchPattern":"try {\n    info = x.getWindowManagerInfo();\n} catch (X11Exception e) {\n    info = null; // no EWMH WM present; continue without WM info\n}","preventionTips":["Ensure an EWMH-compliant window manager is running on the display.","Probe with xprop -root during environment setup/CI.","Delay calls until after WM startup.","Design APIs to tolerate missing WM properties."],"tags":["x11","window-manager","ewmh","linux"],"backgroundTag":"resource-not-found","analyzedSha":"d036ad9781adad4b66693e8fa7098e4ac665e0a3","analyzedAt":"2026-09-12T06:50:59.239Z","contentChangedAt":"2026-09-12T06:50:59.239Z","schemaVersion":2},"datasetVersion":"2026-09-14T05:17:10.506Z"}