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Xlib：为什么我必须关闭显示才能映射和取消映射窗口？

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Xlib：为什么我必须关闭显示才能映射和取消映射窗口？ 
// ...
int main(int argc, char *argv[]) {
  int rev;
  Window win;
  Display *dis = XOpenDisplay(NULL);

  XGetInputFocus(dis, &win, &rev);

  XUnmapWindow(dis, win);
  XCloseDisplay(dis);

  // ...

  dis = XOpenDisplay(NULL);
  XMapWindow(dis, win);
  XCloseDisplay(dis);

  return 0;
}

请注意，在取消映射窗口之前，我必须关闭显示，因此，我必须在映射之前重新初始化它以使程序正常工作。
这里发生了什么？

解决方案：

// ...
int main(int argc, char *argv[]) {
  int rev;
  Window win;
  Display *dis = XOpenDisplay(NULL);

  XGetInputFocus(dis, &win, &rev);

  XUnmapWindow(dis, win);
  XFlush(dis); // The fix

  //...

  XMapWindow(dis, win);
  XCloseDisplay(dis);

  return 0;
}

答案1

您不需要在 XUnmapWindow 之后调用 XCloseDisplay。如果这不起作用，您的程序中一定有其他错误可能会扰乱某些变量？

这是我快速尝试过的一个例子。它取消映射和映射窗口，并且中间不需要 XCloseDisplay/XOpenDisplay。

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <X11/Xlib.h>
 
int main (int argc, char *argv[])
{
    Display *display;
    Window window;
    XSetWindowAttributes attributes;
    XGCValues gr_values;
    XFontStruct *fontinfo;
    GC gr_context;
    Visual *visual;
    int depth;
    int screen;
    XEvent event;
    XColor color, dummy;

    display = XOpenDisplay (NULL);
    screen = DefaultScreen (display);
    visual = DefaultVisual (display,screen);
    depth  = DefaultDepth (display,screen);
    attributes.background_pixel = XWhitePixel (display,screen);
 
    window = XCreateWindow (display, XRootWindow (display, screen), 200, 200, 350, 200, 5, depth, InputOutput, visual, CWBackPixel, &attributes);
    XSelectInput (display, window, ExposureMask | KeyPressMask) ;
    fontinfo = XLoadQueryFont (display, "6x10");

    XAllocNamedColor (display, DefaultColormap (display, screen), "red", &color, &dummy);
 
    gr_values.font = fontinfo->fid;
    gr_values.foreground = color.pixel;
    gr_context = XCreateGC (display, window, GCFont + GCForeground, &gr_values);
    XFlush (display);
    XMapWindow (display, window);
    XFlush (display);

    int keypressed = 0;
    while (!keypressed) {
        XNextEvent (display, &event);

        switch (event.type) {
            case Expose:
                XDrawLine (display, window, gr_context, 0, 0, 100, 100);
                XDrawString (display, window, gr_context, 100, 100, "hello1", 6);
                break;
            case KeyPress: 
                keypressed = 1;
                XUnmapWindow (display, window);
                XFlush (display);
                break;
        }
    }

    sleep (1);
    XMapWindow (display, window);
    XFlush (display);

    while (1) {
        XNextEvent (display, &event);

        switch (event.type) {
            case Expose:
                XDrawLine (display, window, gr_context, 50, 50, 100, 100);
                XDrawString (display, window, gr_context, 50, 50, "hello2", 6);
                break;
            case KeyPress: 
                XCloseDisplay (display); 
                exit (0);
        }
    }
}

该程序会等待，直到您按下某个键。然后它会取消映射并再次映射。下一次按键时它将退出。编译它

gcc -o programname programname.c -lX11

样本取自这里：http://www-h.eng.cam.ac.uk/help/tpl/graphics/X/X11R5/node21.html

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