Using the Keyboard

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

Font *f = NULL;
Point location = {0,0};

void key_down(Control *c, unsigned long key)
{
  char utf8[8];
  int width, max_width;

  max_width = get_control_area(c).width;

  unicode_char_to_utf8(key, utf8);
  width = font_width(f, utf8, strlen(utf8));
  if (location.x + width > max_width) {
    location.x = 0;
    location.y += font_height(f);
  }
  draw_utf8(g, location, utf8, strlen(utf8));
  location.x += width;
}

int main(int argc, char *argv[])
{
  App *app;
  Window *w;
  Control *c;

  app = new_app(argc, argv);
  f = find_default_font(app);

  w = newwindow(app, rect(50,50,200,200),
                "Press a Key", STANDARD_WINDOW);
  set_window_background(w, LIGHT_GREY);

  c = new_control(w, rect(10,10,180,180));
  on_control_key_down(c, key_down);

  show_window(w);
  main_loop(app);
  return 0;
}

Notes:

• Keyboard call-back functions are sent an unsigned long Unicode character value.
• Various functions exist to translate Unicode to and from the UTF-8 encoding.
• UTF-8 strings are used when drawing text.
• There is a default font, which can be found using find_default_font.
• Fonts can be used to find the pixel size of strings drawn using that font.