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From: "Brent Ritchie" <Juicer_X AT hotmail DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Implementing a double buffer
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Message-ID: <8ZUa8.25984$Hv5.3040659@news20.bellglobal.com>
Date: Thu, 14 Feb 2002 15:19:19 -0500
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Hello,

    I 've got a small problem. I can't get a double buffer to work. I don't
know why it wouldn't? To me it looks ok. But if you can see anything wrong I
would appreciate any input.

bool end_game = TRUE;
character hero("George","Knight",10,10,12,12);

void init()
{
 allegro_init();
 install_keyboard();
 set_gfx_mode(GFX_AUTODETECT,800,600,0,0);
 install_timer();
 BITMAP *buffer = create_bitmap(800, 600);    // make a bitmap in system RAM
 clear_bitmap(buffer); // zero the memory bitmap
 vsync();
}

void shutdown()
{
 allegro_exit();
}

void input()
{
 if (key[KEY_ESC]) end_game = FALSE;
 hero.update(buffer);
 blit(buffer, screen, 0, 0, 0, 0, 800, 600);
 clear_bitmap(buffer);
}
 the calling order of the functions is init(), input(), shutdown().

the error message is:
test.h: In function `void input()':
test.h:23: `buffer' undeclared (first use this function)
test.h:23: (Each undeclared identifier is reported only once for each
function it appears in.)