Yalantis/uCrop · error · CImgDisplayException

CImgDisplay::screen_height(): Failed to open X11 display.

Error message

CImgDisplay::screen_height(): Failed to open X11 display.

What it means

Thrown by CImgDisplay::screen_height() when no X11 display connection is available: the cached X11_attr display pointer is null and a fallback XOpenDisplay(0) also fails to connect to an X server (typically no DISPLAY environment variable or no server running on headless systems).

Solutions

1. Set the DISPLAY environment variable to a reachable X server (e.g. export DISPLAY=:0) before running the program
2. Run the application in a desktop session or under an X server (Xvfb, VNC, or XQuartz for remote/headless use)
3. Link CImg with an alternative display backend supported on your platform instead of X11

When it happens

Trigger: Thrown at ucrop/src/main/jni/CImg.h:10567 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/10d129ffca793256. Report an issue: GitHub.

Appendix: source

Thrown at ucrop/src/main/jni/CImg.h:10567

#ifdef cimg_use_xrandr
        if (X11_attr.resolutions && X11_attr.curr_resolution)
          res = X11_attr.resolutions[X11_attr.curr_resolution].width;
        else res = DisplayWidth(dpy,DefaultScreen(dpy));
#else
        res = DisplayWidth(dpy,DefaultScreen(dpy));
#endif
      }
      return res;
    }

    static int screen_height() {
      cimg::X11_attr &X11_attr = cimg::X11_attr::ref();
      Display *const dpy = X11_attr.display;
      int res = 0;
      if (!dpy) {
        Display *const _dpy = XOpenDisplay(0);
        if (!_dpy)
          throw CImgDisplayException("CImgDisplay::screen_height(): Failed to open X11 display.");
        res = DisplayHeight(_dpy,DefaultScreen(_dpy));
        XCloseDisplay(_dpy);
      } else {

#ifdef cimg_use_xrandr
        if (X11_attr.resolutions && X11_attr.curr_resolution)
          res = X11_attr.resolutions[X11_attr.curr_resolution].height;
        else res = DisplayHeight(dpy,DefaultScreen(dpy));
#else
        res = DisplayHeight(dpy,DefaultScreen(dpy));
#endif
      }
      return res;
    }

    static void wait_all() {
      cimg::X11_attr &X11_attr = cimg::X11_attr::ref();
      if (!X11_attr.display) return;

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