X11复制仅返回GDK_SELECTION，CLIPBOARD选择

这通常发生在使用Linux系统时，因为系统默认使用X11窗口系统。要解决这个问题，您需要使用X11 API来访问CLIPBOARD选择。以下是一个示例：

#include <X11/Xlib.h>
#include <X11/Xatom.h>

int main() {
    Display *display = XOpenDisplay(NULL);
    Window window = XCreateSimpleWindow(display, DefaultRootWindow(display), 0, 0, 1, 1, 0, 0, 0);
    XSelectInput(display, window, SelectionNotify);
    XSetSelectionOwner(display, XA_PRIMARY, window, CurrentTime);
    Atom clipboard = XInternAtom(display, "CLIPBOARD", False);
    XSetSelectionOwner(display, clipboard, window, CurrentTime);
    XFlush(display);
    XEvent event;
    while (true) {
        XNextEvent(display, &event);
        switch (event.type) {
            case SelectionRequest: {
                XSelectionRequestEvent *request = &(event.xselectionrequest);
                if (request->selection == clipboard) {
                    XChangeProperty(display,
                                    request->requestor,
                                    request->property,
                                    request->target,
                                    8,
                                    PropModeReplace,
                                    (unsigned char*) "Hello World",
                                    11);
                    XEvent sendEvent;
                    sendEvent.xselection.type = SelectionNotify;
                    sendEvent.xselection.display = request->display;
                    sendEvent.xselection.requestor = request->requestor;
                    sendEvent.xselection.selection = request->selection;
                    sendEvent.xselection.target = request->target;
                    sendEvent.xselection.property = request->property;
                    sendEvent.xselection.time = request->time;
                    XSendEvent(request->display, request->requestor, False, NoEventMask, &sendEvent);
                }
                break;
            }
            case SelectionClear:
                XCloseDisplay(display);
                return 0;
            default:
                break;
        }
    }
}

此示例程序使用X11 API来创建一个窗口并将其设置为CLIPBOARD的拥有者。它接受来自其他应用程序的粘贴请求，并将