Question about ALLEGRO_EVENT_KEY

Question about ALLEGRO_EVENT_KEY_CHAR

Bob Keane

Member #7,342

June 2006

I am playing with ALLEGRO_EVENT_KEY_CHAR and having some success. However, When typing characters, it draws the character twice. Here is the code:

#SelectExpand
  1#include "allegro5/allegro.h"
  2#include "allegro5/allegro_image.h"
  3#include "allegro5/allegro_primitives.h"
  4#include <stdio.h>
  5#include <allegro5/allegro_font.h>
  6#include <allegro5/allegro_ttf.h>
  7#define white al_map_rgb(255,255,255)
  8#define black al_map_rgb(0,0,0)
  9#define line_size 2
 10bool done = false;
 11bool redraw = false;
 12
 13int main(int argc, char **argv){
 14
 15   ALLEGRO_DISPLAY *display = NULL;
 16   ALLEGRO_EVENT_QUEUE *event_queue = NULL;
 17   ALLEGRO_USTR *input;
 18   input = al_ustr_new("");
 19
 20
 21   if(!al_init()) {
 22      fprintf(stderr, "failed to initialize allegro!\n");
 23      return -1;
 24   }
 25
 26   display = al_create_display(640, 480);
 27   if(!display) {
 28      fprintf(stderr, "failed to create display!\n");
 29      return -1;
 30   }
 31
 32   event_queue = al_create_event_queue();
 33      if(!event_queue) {
 34      fprintf(stderr, "failed to create event_queue!\n");
 35      al_destroy_display(display);
 36      return -1;
 37   }
 38
 39   if(!al_install_keyboard()) {
 40      fprintf(stderr, "failed to initialize the keyboard!\n");
 41      return -1;
 42   }
 43
 44   ALLEGRO_FONT *font = al_create_builtin_font();
 45
 46   if (!font){
 47      fprintf(stderr, "Could not create font.\n");
 48      return -1;
 49   }
 50
 51   al_register_event_source(event_queue, al_get_display_event_source(display));
 52
 53   al_register_event_source(event_queue, al_get_keyboard_event_source());
 54
 55   al_clear_to_color(black);
 56
 57   al_flip_display();
 58
 59   while(!done)
 60   {
 61      ALLEGRO_EVENT ev;
 62      ALLEGRO_TIMEOUT timeout;
 63      al_init_timeout(&timeout, 0.06);
 64      int position = 0;
 65
 66      bool get_event = al_wait_for_event_until(event_queue, &ev, &timeout);
 67
 68      if(get_event && ev.type == ALLEGRO_EVENT_DISPLAY_CLOSE) {
 69         done = true;
 70      }
 71
 72      if(get_event && ev.keyboard.keycode == ALLEGRO_KEY_ESCAPE)
 73        done = true;
 74
 75    if(ev.type == ALLEGRO_EVENT_KEY_CHAR){
 76       al_ustr_append_chr(input, ev.keyboard.unichar);
 77       redraw = true;
 78       }
 79
 80    if(!al_event_queue_is_empty(&ev) && redraw){
 81        redraw = false;
 82        al_draw_textf(font, white, 10, 30, 0, "%s", al_cstr(input));
 83        al_flip_display();}
 84   }// end of while loop
 85
 86//   fprintf(stderr, "You entered %u", al_cstr(input));
 87
 88   al_destroy_display(display);
 89   al_destroy_event_queue(event_queue);
 90
 91   return 0;
 92}

I suspect either my loop is faulty, or allegro_event_key_char reads pressing and releasing the key is read as two keystrokes. Which is the case?

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Edgar Reynaldo

Major Reynaldo

May 2007

You are ignoring your get event variable in the line that checks were a character event. This means the next time you wait and there's time out as mist it will repeat the character. Sorry I'm on my phone some of this may not make sense.

Eagle and Allegro 5 binaries | Older Allegro 4 and 5 binaries | Allegro 5 compile guide
King Piccolo will make it so Then I could just flip it with some sweet, sweet matrix math.

Bob Keane

Member #7,342

June 2006

That was it. The line should be:

 if(get_event && ev.type == ALLEGRO_EVENT_KEY_CHAR){
       al_ustr_append_chr(input, ev.keyboard.unichar);
       redraw = true;
       }

Thanks.