java-native-access/jna · error · X11Exception

Cannot get desktop names properties (_NET_DESKTOP_NAMES or _

Error message

Cannot get desktop names properties (_NET_DESKTOP_NAMES or _WIN_WORKSPACE_NAMES)

What it means

X.getDesktops() reads desktop name lists from the root window: first the EWMH UTF8 property _NET_DESKTOP_NAMES, falling back to _WIN_WORKSPACE_NAMES. If both list-property reads throw X11Exception, this combined X11Exception is thrown, meaning desktop names cannot be resolved. Note the error is also reachable later: getDesktopCount() may succeed but produce a count larger than desktopNames.length, causing an ArrayIndexOutOfBoundsException when building Desktop objects.

Source

Thrown at contrib/x11/src/jnacontrib/x11/api/X.java:280

            return cur_desktop;
        }

        /**
         * Returns the available desktops.
         *
         * @return available desktops
         * @throws X11Exception thrown if X11 window errors occurred
         */
        public Desktop[] getDesktops() throws X11Exception {
            Window root = getRootWindow();
            String[] desktopNames;
            try {
                desktopNames = root.getUtf8ListProperty(getAtom("UTF8_STRING"), "_NET_DESKTOP_NAMES");
            } catch (X11Exception e) {
                try {
                    desktopNames = root.getStringListProperty(X11.XA_STRING, "_WIN_WORKSPACE_NAMES");
                } catch (X11Exception e1) {
                    throw new X11Exception("Cannot get desktop names properties (_NET_DESKTOP_NAMES or _WIN_WORKSPACE_NAMES)");
                }
            }

            Desktop[] desktops = new Desktop[getDesktopCount()];
            for (int i = 0; i < desktops.length; i++) {
                desktops[i] = new Desktop(this, i, desktopNames[i]);
            }

            return desktops;
        }

        /**
         * Switches to the given desktop.
         *
         * @param nr desktop number
         * @throws X11Exception thrown if X11 window errors occurred
         */
        public void switchDesktop(int nr) throws X11Exception {

View on GitHub (pinned to d036ad9781)

Solutions

Run a WM that publishes _NET_DESKTOP_NAMES (GNOME/KDE/XFCE)
Check xprop -root _NET_DESKTOP_NAMES returns data
Catch X11Exception and synthesize default names ("Desktop 1", "Desktop 2", ...) based on getDesktopCount()
Guard desktopNames[i] against index >= length and use an empty placeholder name

Example fix

// before
Desktop[] desktops = x.getDesktops();
// after
Desktop[] desktops;
try {
    desktops = x.getDesktops();
} catch (X11Exception e) {
    desktops = new Desktop[0]; // or generate default names
}

Defensive patterns

Strategy: fallback

Validate before calling

Process p = Runtime.getRuntime().exec(new String[]{"xprop","-root","_NET_DESKTOP_NAMES"});
boolean namesAvailable = p.waitFor() == 0;

Try / catch

try {
    desktops = x.getDesktops();
} catch (X11Exception e) {
    // synthesize defaults
    int n = 1;
    try { n = x.getDesktopCount(); } catch (X11Exception ignored) {}
    desktops = new Desktop[n == 0 ? 1 : n];
}

Prevention

Use a WM that publishes _NET_DESKTOP_NAMES
Guard name-list length against desktop count when building UI
Catch X11Exception and generate placeholder names
Avoid combining count and name reads in one non-failing path

When it happens

Trigger: Calling X.getDesktops() when neither _NET_DESKTOP_NAMES nor _WIN_WORKSPACE_NAMES is set on the root window; also when desktop count > number of names, indexing desktopNames[i] out of bounds.

Common situations: Minimal WMs that set the count atom but no name atoms, bare Xvfb, mismatch between _NET_NUMBER_OF_DESKTOPS and the name list length after a WM restart.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

AI-assisted analysis of java-native-access/jna@d036ad9781 (2026-09-12). Data as JSON: /api/errors/d3d6463d754670ea. Report an issue: GitHub.