I need help with my text drawing function

no-reply@allegro.cc (ISDcaptain) — Wed, 12 Mar 2014 09:30:12 +0000

Okay Im making a Zelda clone, and Im trying to implement that iconic Zelda text box style. You know where it makes a small beep with each letter?
Any ways here is my code

#SelectExpand
  1
  2//Draw text function
  3void drawText(char text[], int x, int y)
  4{
  5  //Get the size of the text
  6  int n = strlen(text);
  7
  8  //Should the program draw the text on screen?
  9  if(drawingtext)
 10  {
 11    //Now draw each letter in the char array
 12    for(int i = 0; i < n; i++)
 13    {
 14      //Draw the letter
 15      al_draw_text(font, al_map_rgb(255, 255, 255), x, y, NULL, text);
 16
 17      //Play the beep
 18      al_play_sample_instance(beepInstance);
 19
 20      //Rest the program
 21      al_rest(10);
 22    }
 23  }
 24  else
 25    return;
 26}

My problem is in the function al_draw_text(), how do I draw each piece of char array at a time, rather than all of it? I want use text[i] as my parameter instead of just text. What should I do?

no-reply@allegro.cc (DanielH) — Wed, 12 Mar 2014 09:57:25 +0000

#SelectExpand
//Draw text function
void drawText(char text[], int x, int y)
{
//Get the size of the text
int n = strlen(text); 

//Should the program draw the text on screen?
if(drawingtext)
{
  char s[2]={0,0};
  int px = x;

  //Now draw each letter in the char array
  for(int i = 0; i < n; i++)
  {
    //Draw the letter
    //al_draw_text(font, al_map_rgb(255, 255, 255), x, y, NULL, text);
    s[0]=text[i];
    
    al_draw_text(font, al_map_rgb(255, 255, 255), px, y, NULL, s);
    
    px += al_get_text_width(font,s);
    
    //Play the beep
    al_play_sample_instance(beepInstance);
    
    //Rest the program
    al_rest(10);
  }
}
else
  return;
 33}

no-reply@allegro.cc (SiegeLord) — Wed, 12 Mar 2014 16:35:55 +0000

I'm not sure that will respect glyph kerning... I'd personally use ALLEGRO_USTR for this:

ALLEGRO_USTR_INFO info;

const ALLEGRO_USTR* ustr = al_ref_buffer(&info, text, (size_t)i);
al_draw_ustr(font, al_map_rgb(255, 255, 255), x, y, 0, ustr);

Note that that will redraw the initial letters every time, so you need to clear the textbox every frame. I certainly would not use al_rest like that. Instead, I would increment i every 10 ticks or something (and not use a loop). Or, alternatively, I'd pass the start tick and the current tick to the drawText function and have it figure out the value of i from that.

no-reply@allegro.cc (ISDcaptain) — Thu, 13 Mar 2014 08:13:46 +0000

Yeah im running into problems. The beep keeps on going on, and it doesn't draw each letter one at a time, I don't know what to do.

no-reply@allegro.cc (Kris Asick) — Thu, 13 Mar 2014 10:42:02 +0000

al_draw_textf(font, al_map_rgb(255, 255, 255), x, y, NULL, "%c", text[i]);

no-reply@allegro.cc (Edgar Reynaldo) — Thu, 13 Mar 2014 11:00:59 +0000

Kris - see what SiegeLord said about kerning.

ISDcaptain said:

Yeah im running into problems. The beep keeps on going on, and it doesn't draw each letter one at a time, I don't know what to do.

Create a timer that beats as often as you want your letters to appear. Each time you get a timer event you increment a counter like n. Then when you draw, you draw n out of the total number of letters where n is the number of timer ticks passed since you started it. Each time you get a timer event play the sound. That should solve your problems.

Draw it like SiegeLord suggested, with al_ref_buffer or al_ref_ustr.

no-reply@allegro.cc (Kris Asick) — Thu, 13 Mar 2014 12:28:23 +0000

Edgar Reynaldo said:

Kris - see what SiegeLord said about kerning.

*nods* Yeah, for variable width fonts, simply looping through all the characters isn't going to work very nicely without some extra code, though I thought I'd inject that little bit of code into the conversation as a quick "make it work right now" approach. Refinements can come afterwards.

no-reply@allegro.cc (ISDcaptain) — Fri, 14 Mar 2014 10:00:26 +0000

Okay how would I go about doing that with a timer? I don't know much about them other than how to use them to regulate the FPS.

no-reply@allegro.cc (Edgar Reynaldo) — Fri, 14 Mar 2014 21:58:33 +0000

These should get you started :
http://wiki.allegro.cc/index.php?title=Allegro_5_API_Tutorials
http://wiki.allegro.cc/index.php?title=Allegro_5_Tutorial/Events
http://wiki.allegro.cc/index.php?title=Allegro_5_Tutorial/Timers

You just need to wait for a timer event, then increment n and play a beep every time you get one.

no-reply@allegro.cc (ISDcaptain) — Sun, 16 Mar 2014 04:20:06 +0000

K I created a timer:

ALLEGRO_TIMER *textTimer = NULL

How do I get it to tick with each letter:

textTimer = al_create_timer(?/?); ??

I don't know what to do here.

no-reply@allegro.cc (Edgar Reynaldo) — Sun, 16 Mar 2014 10:53:33 +0000

The manual said:

al_create_timer

ALLEGRO_TIMER* al_create_timer(double speed_secs)

Introduced in 5.0.0

Install a new timer. If successful, a pointer to a new timer object is returned, otherwise NULL is returned. speed_secs is in seconds per "tick", and must be positive. The new timer is initially stopped.

The system driver must be installed before this function can be called.

Usage note: typical granularity is on the order of microseconds, but with some drivers might only be milliseconds.

See also: al_start_timer, al_destroy_timer

Waiting on an event queue for a timer event :

#SelectExpand
  1int letterCount = 0;
  2ALLEGRO_TIMER* textTimer = al_create_timer(seconds_per_letter);
  3ALLEGRO_EVENT_QUEUE* queue = al_create_event_queue();
  4
  5if (!textTimer || !queue) {Fail();}
  6
  7al_register_event_source(queue , al_get_timer_event_source(textTimer));
  8
  9// When you start writing your text :
 10letterCount = 0;
 11al_start_timer(textTimer);
 12
 13// In your program loop
 14do {
 15
 16  ALLEGRO_EVENT ev;
 17  al_wait_for_event(queue , &ev);
 18
 19  if (ev.type == ALLEGRO_EVENT_TIMER) {
 20    ++letterCount;
 21    PlayBeep();
 22    redraw = true;
 23  }
 24} while(!al_is_event_queue_empty());
 25
 26if (redraw) {
 27   // draw your text here
 28}