xftwidth.c

#include <X11/Xft/Xft.h>
#include <X11/Xlib.h>
#include <X11/extensions/Xrender.h>
#include <fontconfig/fontconfig.h>

#include <stdio.h>
#include <string.h>

int main(int argc, char** argv)
{
        if (argc < 3)
        {
                printf("xftwidth font string\n");
                return 1;
        }

        char *name = argv[1];
        size_t len = strlen(argv[2]);

        Display *dpy;
        XftFont *fn;
        XGlyphInfo ext;
        FcChar8 str[len]; 

        memcpy(str, argv[2], len);

        dpy = XOpenDisplay(NULL);
        fn = XftFontOpenName(dpy, 0, name);

        if (fn == NULL)
        {
                puts("Font not found.");
                return 1;
        }

        XftTextExtents8(dpy, fn, str, (int)len, &ext);
        printf("%d\n", ext.width);

        XCloseDisplay(dpy);

        return 0;
}