Study for the colored-emoji-font drawing using cairo and freetype2.5

cairo_colored_font_experiment.c

/* vim:fileencoding=utf-8 tabstop=2 expandtab shiftwidth=2 softtabstop=0:
 *
 *            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
 *                    Version 2, December 2004
 *  
 * Copyright (C) 2014 @cat_in_136
 * 
 * Everyone is permitted to copy and distribute verbatim or modified
 * copies of this license document, and changing it is allowed as long
 * as the name is changed.
 *  
 *            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
 *   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
 *  
 *  0. You just DO WHAT THE FUCK YOU WANT TO.
 * 
 * 
 * How to compile:
 *     % gcc cairo_colored_font_experiment.c -o cairo_colored_font_experiment `pkg-config --cflags --libs gtk+-3.0 freetype2`
 */
#include <cairo.h>
#include <gtk/gtk.h>

#include <ft2build.h>
#include FT_FREETYPE_H

char *ttf_file = NULL;
char *text = NULL;

static gboolean on_draw_event(GtkWidget *widget, cairo_t *cr, 
    gpointer user_data)
{      
  FT_Library ft_library;
  FT_Face ft_face;
  cairo_font_face_t * cairo_face = NULL;

  FT_Init_FreeType(&ft_library);
  FT_New_Face(ft_library, ttf_file, 0, &ft_face);
  cairo_face = cairo_ft_font_face_create_for_ft_face(ft_face, FT_LOAD_COLOR);

  cairo_set_source_rgb(cr, 0, 0, 0);
//  cairo_select_font_face(cr, "Noto Color Emoji", CAIRO_FONT_SLANT_NORMAL,
//      CAIRO_FONT_WEIGHT_NORMAL);
  cairo_set_font_face(cr, cairo_face);
  cairo_set_font_size(cr, 128);

  cairo_move_to(cr, 2, 128);
  cairo_show_text(cr, text);

  return FALSE;
}


int main(int argc, char *argv[])
{
  GtkWidget *window;
  GtkWidget *darea;
  GdkRGBA white = {255, 255, 255, 255};

  gtk_init(&argc, &argv);

  if (argc != 3) {
    g_fprintf(stderr, "Usage: %s ttffile.ttf text\n", argv[0]);
    return -1;
  }
  ttf_file = argv[1];
  text = argv[2];

  window = gtk_window_new(GTK_WINDOW_TOPLEVEL);

  darea = gtk_drawing_area_new();
  gtk_container_add(GTK_CONTAINER(window), darea);

  g_signal_connect(G_OBJECT(darea), "draw", G_CALLBACK(on_draw_event), NULL); 
  g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);

  gtk_window_set_default_size(GTK_WINDOW(window), 400, 192); 
  gtk_widget_override_background_color(GTK_WIDGET(window), GTK_STATE_NORMAL, &white);

  gtk_widget_show_all(window);
  gtk_main();

  return 0;
}