LINUX X11剪贴板/clipboard访问C代码范例

参考博客:https://blog.csdn.net/quantum7/article/details/103079567

真奇怪啊。关于LINUX剪贴板的C代码，网上完全找不到。找到的都是一些SHELL命令。

经过千辛万苦，自己理解，终于找到一个代码范例。

https://github.com/exebook/x11clipboard
https://stackoverflow.com/questions/27378318/c-get-string-from-clipboard-on-linux

为了方便他人，提供代码如下（初步测试表明，图片取不到数据）：

标准情况：

// gcc -o xclipget xclipget.c -lX11
#include <stdio.h>
#include <limits.h>
#include <X11/Xlib.h>

Bool PrintSelection(Display *display, Window window, const char *bufname, const char *fmtname)
{
  char *result;
  unsigned long ressize, restail;
  int resbits;
  Atom bufid = XInternAtom(display, bufname, False),
       fmtid = XInternAtom(display, fmtname, False),
       propid = XInternAtom(display, "XSEL_DATA", False),
       incrid = XInternAtom(display, "INCR", False);
  XEvent event;

  XConvertSelection(display, bufid, fmtid, propid, window, CurrentTime);
  do {
    XNextEvent(display, &event);
  } while (event.type != SelectionNotify || event.xselection.selection != bufid);

  if (event.xselection.property)
  {
    XGetWindowProperty(display, window, propid, 0, LONG_MAX/4, False, AnyPropertyType,
      &fmtid, &resbits, &ressize, &restail, (unsigned char**)&result);

    if (fmtid == incrid)
      printf("Buffer is too large and INCR reading is not implemented yet.\n");
    else
      printf("%.*s", (int)ressize, result);

    XFree(result);
    return True;
  }
  else // request failed, e.g. owner can't convert to the target format
    return False;
}

int main()
{
  Display *display = XOpenDisplay(NULL);
  unsigned long color = BlackPixel(display, DefaultScreen(display));
  Window window = XCreateSimpleWindow(display, DefaultRootWindow(display), 0,0, 1,1, 0, color, color);
  Bool result = PrintSelection(display, window, "CLIPBOARD", "UTF8_STRING") ||
                PrintSelection(display, window, "CLIPBOARD", "STRING");
  XDestroyWindow(display, window);
  XCloseDisplay(display);
  return !result;
}

超大内存情况

// gcc -o xclipget xclipget.c -lX11
#include <stdio.h>
#include <limits.h>
#include <X11/Xlib.h>

Bool PrintSelection(Display *display, Window window, const char *bufname, const char *fmtname)
{
  char *result;
  unsigned long ressize, restail;
  int resbits;
  Atom bufid = XInternAtom(display, bufname, False),
       fmtid = XInternAtom(display, fmtname, False),
       propid = XInternAtom(display, "XSEL_DATA", False),
       incrid = XInternAtom(display, "INCR", False);
  XEvent event;

  XSelectInput (display, window, PropertyChangeMask);
  XConvertSelection(display, bufid, fmtid, propid, window, CurrentTime);
  do {
    XNextEvent(display, &event);
  } while (event.type != SelectionNotify || event.xselection.selection != bufid);

  if (event.xselection.property)
  {
    XGetWindowProperty(display, window, propid, 0, LONG_MAX/4, True, AnyPropertyType,
      &fmtid, &resbits, &ressize, &restail, (unsigned char**)&result);
    if (fmtid != incrid)
      printf("%.*s", (int)ressize, result);
    XFree(result);

    if (fmtid == incrid)
      do {
        do {
          XNextEvent(display, &event);
        } while (event.type != PropertyNotify || event.xproperty.atom != propid || event.xproperty.state != PropertyNewValue);

        XGetWindowProperty(display, window, propid, 0, LONG_MAX/4, True, AnyPropertyType,
          &fmtid, &resbits, &ressize, &restail, (unsigned char**)&result);
        printf("%.*s", (int)ressize, result);
        XFree(result);
      } while (ressize > 0);

    return True;
  }
  else // request failed, e.g. owner can't convert to the target format
    return False;
}

int main()
{
  Display *display = XOpenDisplay(NULL);
  unsigned long color = BlackPixel(display, DefaultScreen(display));
  Window window = XCreateSimpleWindow(display, DefaultRootWindow(display), 0,0, 1,1, 0, color, color);
  Bool result = PrintSelection(display, window, "CLIPBOARD", "UTF8_STRING") ||
                PrintSelection(display, window, "CLIPBOARD", "STRING");
  XDestroyWindow(display, window);
  XCloseDisplay(display);
  return !result;
}

g++ -lX11

copy

#include <string.h> // strlen
#include <X11/Xlib.h>

Display * display;
Window window;
Atom targets_atom, text_atom, UTF8, XA_ATOM = 4, XA_STRING = 31;

static void XCopy(Atom selection, unsigned char * text, int size) {
    XEvent event;
    Window owner;
    XSetSelectionOwner (display, selection, window, 0);
    if (XGetSelectionOwner (display, selection) != window) return;
    while (1) {
        XNextEvent (display, &event);
        switch (event.type) {
            case SelectionRequest:
            if (event.xselectionrequest.selection != selection) break;
            XSelectionRequestEvent * xsr = &event.xselectionrequest;
            XSelectionEvent ev = {0};
            int R = 0;
            ev.type = SelectionNotify, ev.display = xsr->display, ev.requestor = xsr->requestor,
            ev.selection = xsr->selection, ev.time = xsr->time, ev.target = xsr->target, ev.property = xsr->property;
            if (ev.target == targets_atom) R = XChangeProperty (ev.display, ev.requestor, ev.property, XA_ATOM, 32,
                    PropModeReplace, (unsigned char*)&UTF8, 1);
            else if (ev.target == XA_STRING || ev.target == text_atom) 
                R = XChangeProperty(ev.display, ev.requestor, ev.property, XA_STRING, 8, PropModeReplace, text, size);
            else if (ev.target == UTF8)
                R = XChangeProperty(ev.display, ev.requestor, ev.property, UTF8, 8, PropModeReplace, text, size);
            else ev.property = None;
            if ((R & 2) == 0) XSendEvent (display, ev.requestor, 0, 0, (XEvent *)&ev);
            break;
            case SelectionClear:
            return;
        }
    }
}

int main(int argc, char *argv[]) {
    display = XOpenDisplay(0);
    int N = DefaultScreen(display);
    window = XCreateSimpleWindow(display, RootWindow(display, N), 0, 0, 1, 1, 0,
        BlackPixel(display, N), WhitePixel(display, N));    
    targets_atom = XInternAtom(display, "TARGETS", 0);
    text_atom = XInternAtom(display, "TEXT", 0);
    UTF8 = XInternAtom(display, "UTF8_STRING", 1);
    if (UTF8 == None) UTF8 = XA_STRING;
    Atom selection = XInternAtom(display, "CLIPBOARD", 0);
    XCopy(selection, (unsigned char*) argv[1], strlen(argv[1]));
}

paste

#include <stdio.h> // printf
#include <string.h> // strndup
#include <X11/Xlib.h>
int XA_STRING = 31;

static Display * display;
static Window window;
static Atom UTF8; 

char * XPasteType(Atom atom) {
    XEvent event;
    int format;
    unsigned long N, size;
    char * data, * s = 0;
    Atom target,
        CLIPBOARD = XInternAtom(display, "CLIPBOARD", 0),
        XSEL_DATA = XInternAtom(display, "XSEL_DATA", 0);
    XConvertSelection(display, CLIPBOARD, atom, XSEL_DATA, window, CurrentTime);
    XSync(display, 0);
    XNextEvent(display, &event);

    switch(event.type) {
        case SelectionNotify:
        if(event.xselection.selection != CLIPBOARD) break;
        if(event.xselection.property) {
            XGetWindowProperty(event.xselection.display, event.xselection.requestor,
                event.xselection.property, 0L,(~0L), 0, AnyPropertyType, &target,
                &format, &size, &N,(unsigned char**)&data);
            if(target == UTF8 || target == XA_STRING) {
                s = strndup(data, size);
                XFree(data);
            }
            XDeleteProperty(event.xselection.display, event.xselection.requestor, event.xselection.property);
        }
    }
  return s;
}

char *XPaste() {
    char * c = 0;
    UTF8 = XInternAtom(display, "UTF8_STRING", True);
    if(UTF8 != None) c = XPasteType(UTF8);
    if(!c) c = XPasteType(XA_STRING);
    return c;
}

int main(int argc, char *argv[]) {
    display = XOpenDisplay(0);
    int N = DefaultScreen(display);
    window = XCreateSimpleWindow(display, RootWindow(display, N), 0, 0, 1, 1, 0,
        BlackPixel(display, N), WhitePixel(display, N)
    );  
    printf("%s\n", XPaste());
}