Question

以下JNA使用JNA 4.2.2崩溃 - 如果你运行它，同时最小化和最大化窗口，JVM退出以下。发生在Ubuntu 16.04上，但更常见于Redhat 6u2。

X error of failed request: BadWindow (invalid Window parameter)
Major opcode of failed request: 20 (X_GetProperty)
...

我猜测窗口ID在从XQueryTree返回时有效，但在调用XGetWMName之前变为无效。问题是这导致JVM退出，而不仅仅是我可以很好地处理的异常。我该如何避免这个问题？

public class X11WindowFinder {

    private X11 x11;

    public X11WindowFinder() {
        x11 = X11.INSTANCE;
    }

    public List<Window> find(Pattern title) {
        Display display = x11.XOpenDisplay(null);
        Window root = x11.XDefaultRootWindow(display);
        List<Window> windows = recurse(x11, display, root, title);
        x11.XCloseDisplay(display);
        return windows;
    }

    private synchronized List<Window> recurse(X11 x11, Display display, Window root, Pattern pattern) {
        List<Window> windows = new ArrayList<>(1);
        X11.WindowByReference windowRef = new X11.WindowByReference();
        X11.WindowByReference parentRef = new X11.WindowByReference();
        PointerByReference childrenRef = new PointerByReference();
        IntByReference childCountRef = new IntByReference();

        x11.XQueryTree(display, root, windowRef, parentRef, childrenRef, childCountRef);
        if (childrenRef.getValue() == null) {
            return Collections.emptyList();
        }


        long[] ids = {};

        if (Native.LONG_SIZE == Long.BYTES) {
            ids = childrenRef.getValue().getLongArray(0, childCountRef.getValue());
        } else if (Native.LONG_SIZE == Integer.BYTES) {
            int[] intIds = childrenRef.getValue().getIntArray(0, childCountRef.getValue());
            ids = new long[intIds.length];
            for (int i = 0; i < intIds.length; i++) {
                ids[i] = intIds[i];
            }
        }

        for (long id : ids) {
            Window child = new Window(id);
            X11.XTextProperty name = new X11.XTextProperty();
            x11.XGetWMName(display, child, name);
            String value = name.value;
            if (value != null) {
                System.out.println(String.format("Found window %s free %s", value, name));
            }
            if (value != null && pattern.matcher(value).matches()) {
                windows.add(child);
            }
            windows.addAll(recurse(x11, display, child, pattern));
        }
        return windows;
    }

    public static void main(String[] args) {
        X11WindowFinder finder = new X11WindowFinder();
        while (true) {
            finder.find(Pattern.compile(".*Firefox.*"));
        }
    }
}

Answer 1

看起来默认错误处理程序会导致退出，但可以覆盖。例如

x11.XSetErrorHandler(new XErrorHandler() {

    @Override
    public int apply(Display display, XErrorEvent errorEvent) {
        System.err.println("bad fish " + errorEvent);
        return 0;
    }
});

X11 JNA坏窗口（窗口参数无效）导致JVM退出

1 个答案: