java-native-access/jna · error · IllegalStateException

Attempting to retrieve VisualID from a null Visual

Error message

Attempting to retrieve VisualID from a null Visual

What it means

X11.Visual wraps a native Xlib Visual pointer; getVisualID() reads the VisualID field at offset POINTER_SIZE. If the underlying pointer is null there is no native Visual to read, so an IllegalStateException is thrown. toString() calls getVisualID(), so even printing a null Visual triggers it.

Source

Thrown at contrib/platform/src/com/sun/jna/platform/unix/X11.java:274

        private static final long serialVersionUID = 1L;
        public static final Pixmap None = null;
        public Pixmap() { }
        public Pixmap(long id) { super(id); }
        @Override
        public Object fromNative(Object nativeValue, FromNativeContext context) {
            if (isNone(nativeValue))
                return None;
            return new Pixmap(((Number)nativeValue).longValue());
        }
    }
    // TODO: define structure
    class Display extends PointerType { }
    // TODO: define structure
    class Visual extends PointerType {
        public VisualID getVisualID() {
            if (getPointer() != null)
                return new VisualID(getPointer().getNativeLong(Native.POINTER_SIZE).longValue());
            throw new IllegalStateException("Attempting to retrieve VisualID from a null Visual");
        }
        @Override
        public String toString() {
            return "Visual: VisualID=0x" + Long.toHexString(getVisualID().longValue());
        }
    }
    // TODO: define structure
    class Screen extends PointerType { }
    // TODO: define structure
    class GC extends PointerType { }
    // TODO: define structure
    class XImage extends PointerType { }

    /**
     * The XQueryExtension function determines if the named extension is present.
     * @param display Specifies the connection to the X server.
     * @param name Specifies the extension name.
     * @param major_opcode_return Returns the major opcode.

View on GitHub (pinned to d036ad9781)

Solutions

1. Check getPointer() != null before calling getVisualID() or toString()
2. Ensure the Visual was obtained from a successful X11 call and not a NULL return
3. Catch IllegalStateException in logging paths and print a placeholder

Example fix

// before
System.out.println("visual=" + visual);
// after
System.out.println("visual=" + (visual.getPointer() != null ? visual : "<null visual>"));

if (visual == null || visual.getPointer() == null) {
    return; // no native Visual to inspect
}

boolean hasNativeVisual(X11.Visual v) { return v != null && v.getPointer() != null; }

try { id = visual.getVisualID(); } catch (IllegalStateException e) { id = null; }

When it happens

Trigger: Calling toString() (or getVisualID()) on a Visual object constructed without a valid native pointer, e.g. Visual obtained from an API that returned NULL or a default-constructed Visual.

Common situations: Debug/logging code that stringifies Visual objects received from XGetVisualInfo or window attributes where the visual pointer was NULL; uninitialized Visual instances.

Related errors

• Can't open X Display
• Can't open X Display
• X Display is null
• Cannot get window manager info properties. (_NET_SUPPORTING_
• Cannot get client list properties (_NET_CLIENT_LIST or _WIN_

AI-assisted analysis of java-native-access/jna@d036ad9781 (2026-09-12). Data as JSON: /api/errors/ff921e076b098f0f. Report an issue: GitHub.