allegro_main.dpr

著名的游戏开发库Allegro4.2.0 for DELPHI

{*
 *    Example program for the Allegro library, by Shawn Hargreaves.
 *
 *    This program demonstrates how to use fixed point numbers, which
 *    are signed 32-bit integers storing the integer part in the
 *    upper 16 bits and the decimal part in the 16 lower bits. This
 *    example also uses the unusual approach of communicating with
 *    the user exclusively via the allegro_message() function.
 *}

program Allegro_Main;
uses
  SysUtils, Allegro;

procedure allegro_message(msg: string; args: array of const);
begin
  allegro.allegro_message(PChar(Format(msg, args)));
end;

var
  // declare three 32 bit (16.16) fixed point variables
  x, y, z: fixed;
begin
  if allegro_init() <> 0 then
    Exit;

  // convert integers to fixed point like this
  x := itofix(10);

  // convert floating point to fixed point like this
  y := ftofix(3.14);

  {* fixed point variables can be assigned, added, subtracted, negated,
   * and compared just like integers, eg:
   *}
  z := fixadd(x, y); //x + y;
  allegro_message('%f + %f = %f', [fixtof(x), fixtof(y), fixtof(z)]);

  {* you can't add integers or floating point to fixed point, though:
   *    z = x + 3;
   * would give the wrong result.
   *}

  {* fixed point variables can be multiplied or divided by integers or
   * floating point numbers, eg:
   *}
  z := y * 2; //y * 2;
  allegro_message('%f * 2 = %f', [fixtof(y), fixtof(z)]);

  {* you can't multiply or divide two fixed point numbers, though:
   *    z = x * y;
   * would give the wrong result. Use fixmul() and fixdiv() instead, eg:
   *}
  z := fixmul(x, y);
  allegro_message('%f * %f = %f', [fixtof(x), fixtof(y), fixtof(z)]);

  // fixed point trig and square root are also available, eg:
  z := fixsqrt(x);
  allegro_message('fixsqrt(%f) = %f', [fixtof(x), fixtof(z)]);
end.