fttest.c

/* $ gcc -W -Wall -Wextra -o fttest fttest.c -lX11 -lXft `pkg-config --cflags freetype2`
 * $ ./fttest "DejaVu Sans Mono"
 * $ ./fttest "Noto Color Emoji"
 * X Error of failed request:  BadLength (poly request too large or internal Xlib length error)
 *   Major opcode of failed request:  139 (RENDER)
 *   Minor opcode of failed request:  20 (RenderAddGlyphs)
 *   Serial number of failed request:  21
 *   Current serial number in output stream:  23
 */

#include <unistd.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/Xft/Xft.h>

#define ELEMS(x) (sizeof(x) / sizeof((x)[0]))
XftChar32 msg[] = { ':', ')', ' ', 0x263a }; // ":) ☺"

void redraw(XftDraw *d, XftColor *c, XftFont *f) {
    XftDrawString32(d, c, f, 20, 70, msg, ELEMS(msg));
}

int main(int argc, char **argv)
{
    Display *display;
    XftFont *font;
    XftDraw *xftdraw;
    XEvent event;

    if (argc != 2) {
        fprintf(stderr, "Usage: %s <font>\n", argv[0]);
        return 1;
    }

    display = XOpenDisplay(0);
    Window w = XCreateSimpleWindow(display, DefaultRootWindow(display), 0, 0, 360, 90, 0, 0, 0);
    XMapWindow(display, w);
    XSelectInput(display, w, ExposureMask | KeyPressMask);

    font = XftFontOpenName(display, 0, argv[1]);
    if (!font) {
        fprintf(stderr, "XftFontOpenName failed\n");
        return 1;
    }

    xftdraw = XftDrawCreate(display, w, DefaultVisual(display, 0), DefaultColormap(display, 0));

    XRenderColor xrcolor = {.red = 0xffff,.alpha = 0xffff };
    XftColor xftcolor;
    XftColorAllocValue(display, DefaultVisual(display, 0), DefaultColormap(display, 0), &xrcolor, &xftcolor);

    redraw(xftdraw, &xftcolor, font);

    while (1) {
        XNextEvent(display, &event);
        if (event.type == Expose)
            redraw(xftdraw, &xftcolor, font);

        if (event.type == KeyPress)
            break;
    }

    XftColorFree(display, DefaultVisual(display, 0),
                 DefaultColormap(display, 0), &xftcolor);
    XftDrawDestroy(xftdraw);

    return 0;
}