Center primitive after resize

no-reply@allegro.cc (AleX-G Squadron) — Sat, 25 Aug 2012 20:40:38 +0000

I am having some problems centering a primitive after i resize the window using a native dialog box. It will work only if i put 1:1 ratio resolutions such as 300x300 or 500x500, otherwise the primitive object wont be at the center. I want to use a resolution of 800x600 and make the primitive appear at the center. How am i supposed to do that? Here is the logic i am using:

#SelectExpand
  1int resolution = al_show_native_message_box(window, "Change resolution", "800x600?", 
  2    "Do you really want to change resolution?", "Of course!|No",
  3 
  4ALLEGRO_MESSAGEBOX_YES_NO);
  5
  6  if(resolution == 1)
  7  {
  8    width = width + 300;
  9    height = height + 500;
 10    al_resize_display(window, height, width);
 11    al_flip_display();
 12  }

no-reply@allegro.cc (jmasterx) — Sat, 25 Aug 2012 22:02:00 +0000

Can you show the code that draws the primitive (a messagebox is not a primitive).

no-reply@allegro.cc (AleX-G Squadron) — Sat, 25 Aug 2012 22:41:12 +0000

It is a triangle:

al_draw_triangle(x,y-15,x-15,y+15,x+15,y+15,al_map_rgb(0,255,0),2.0);

x is width/2 and y is height/2

no-reply@allegro.cc (Trent Gamblin) — Sat, 25 Aug 2012 22:59:02 +0000

Are you recalculating width, height, x and y after resizing the display?

no-reply@allegro.cc (AleX-G Squadron) — Sat, 25 Aug 2012 23:15:53 +0000

Yes, i have to, because it doesnt work too.

no-reply@allegro.cc (Trent Gamblin) — Sat, 25 Aug 2012 23:20:23 +0000

    width = width + 300;
    height = height + 500;

That looks suspicious. Are you starting out with a 500x100 window?

EDIT: Instead of playing detective, just show the whole code.

no-reply@allegro.cc (jmasterx) — Sat, 25 Aug 2012 23:47:20 +0000

To draw an isosceles triangle of width W and height H at center cx, cy:

cx = al_get_display_width / 2;
cy = al_get_display_height / 2;
p1.x = cx;
p1.y = cy - (H / 2.0f);

p2.x = cx - (W / 2.0f);
p2.y = cy + (H / 2.0f);

p3.x = cx + (W / 2.0f);
p3.y = cy + (H / 2.0f);

no-reply@allegro.cc (AleX-G Squadron) — Sun, 26 Aug 2012 01:31:25 +0000

I changed some things but the idea is exactly the same

#SelectExpand
   1#include 
   2#include 
   3#include 
   4#include 
   5
   6enum BUTTONS{W, S, A, D};
   7
   8int main (void)
   9{
al_init();
al_init_primitives_addon();
al_init_image_addon();
al_install_keyboard();
  14
int width = 300;
int height = 300;
  17
bool quit = false;
bool buttons[4] = {false, false, false, false};
  20
ALLEGRO_DISPLAY *window = al_create_display(width,height);
ALLEGRO_BITMAP *icon = al_load_bitmap("image/1.png");
ALLEGRO_EVENT_QUEUE *event = NULL;

al_set_display_icon(window,icon);
  26
al_flip_display();
  28
int resolution = al_show_native_message_box(window, "Change resolution", "600x600?", 
  "Do you really want to change resolution?", "Of course!|No", ALLEGRO_MESSAGEBOX_YES_NO);
  31
if(resolution == 1)
{
  width += 300;
  height += 500;
  al_resize_display(window, height, width);
  al_flip_display();
}
  39
int x = width / 2;
int y = height / 2;
  42
event = al_create_event_queue();
al_register_event_source(event, al_get_keyboard_event_source());
al_register_event_source(event, al_get_display_event_source(window));
  46
while(!quit)
{
  ALLEGRO_EVENT e;
  al_wait_for_event(event, &e);
  51
  if(e.type == ALLEGRO_EVENT_KEY_DOWN)
  {
    switch(e.keyboard.keycode)
    {
    case ALLEGRO_KEY_W:
      buttons[W] = true;
      break;
  59
    case ALLEGRO_KEY_S:
      buttons[S] = true;
      break;
  63
    case ALLEGRO_KEY_A:
      buttons[A] = true;
      break;
  67
    case ALLEGRO_KEY_D:
      buttons[D] = true;
      break;
    }
  }
  else if (e.type == ALLEGRO_EVENT_KEY_UP)
  {
    switch(e.keyboard.keycode)
    {
    case ALLEGRO_KEY_W:
      buttons[W] = false;
      break;
  80
    case ALLEGRO_KEY_S:
      buttons[S] = false;
      break;
  84
    case ALLEGRO_KEY_A:
      buttons[A] = false;
      break;
  88
    case ALLEGRO_KEY_D:
      buttons[D] = false;
      break;
    case ALLEGRO_KEY_ESCAPE:
      quit = true;
      break;
    }
  }
  else if (e.type == ALLEGRO_EVENT_DISPLAY_CLOSE)
  {
    quit = true;
  }
  else if(x <= 0)
  {
    x += 10;
  }
  else if(y >= height - 15)
  {
    y = height - 15;
  }
  else if(x >= width - 5)
  {
    x = width-15;
  }
  else if(y <= 15)
  {
    y += 10;
  }
  
  x -= buttons[A] * 10;
  x += buttons[D] * 10;
  y -= buttons[W] * 10;
  y += buttons[S] * 10;
 122
al_draw_triangle(x,y-15,x-15,y+15,x+15,y+15,al_map_rgb(0,255,0),2.0);
al_flip_display();
al_clear_to_color(al_map_rgb(0,0,0));
al_set_window_title(window, "Game programming");
 127
}
 129
al_destroy_bitmap(icon);
al_destroy_display(window);
 132
return 0;
 134}

no-reply@allegro.cc (Slartibartfast) — Sun, 26 Aug 2012 16:22:14 +0000

al_resize_display takes the width parameter before the height parameter...