Re: [AL] Video Bitmaps - is it bug?

[Sven S. <svs...@st...>]

Jindrich Sarson wrote:
> thanx to all with help with page flipping. But when I implemented it,
> my graphics began flipping very much.

I'm not sure exactly what you mean with flipping here: if you implement
page flipping, it surely would be a pity if it didn't flip? :-)

> <begin code>----
[snip]
>          textout(bmp,font,"After show_video_bitmap() ",30,30,2000);
>          show_video_bitmap(bmp); 

Probably you meant to do these lines in reverse order? With this in
mind, your program behaves as expected on my computer.

> I sow, that first video bitmap overlap screen bitmap, so it is written
> directly to screen, istead of any other place in video ram.

`screen' covers all of video memory, so there is no "other place". This
is not a bug, it's a feature -- see the docs on `create_video_bitmap()'.

Sven
>From <all...@ca...> Mon Nov 12 06:37:05 2001
Received: from raven.upol.cz [158.194.120.4] by canvaslink.com with ESMTP
  (SMTPD32-6.00) id A45F9EDF025E; Mon, 12 Nov 2001 06:37:03 -0500
Received: from aix.upol.cz (root@localhost)
	by raven.upol.cz (AIX4.3/8.9.3/8.9.3) with ESMTP id MAA43196
	for <al...@ca...>; Mon, 12 Nov 2001 12:37:05 +0100
Received: from [158.194.208.29] (root@localhost) by aix.upol.cz (AIX4.2/UCB 8.7/8.7) with ESMTP id MAA18318 for <al...@ca...>; Mon, 12 Nov 2001 12:32:55 +0100 (NFT)
From: Jindrich Sarson <js...@sa...>
To: allegro <al...@ca...>
In-Reply-To: <3BE...@st...>
References: <3BEEF822.5844.C5C92D@localhost>
	<100...@vi...> 
	<3BE...@st...>
Content-Type: text/plain
Content-Transfer-Encoding: 7bit
X-Mailer: Evolution/0.14 (Preview Release)
Date: 12 Nov 2001 12:34:03 +0100
Message-Id: <100...@vi...>
Mime-Version: 1.0
Subject: Re: [AL] Video Bitmaps - is it bug?
Precedence: bulk
Sender: all...@ca...
Reply-To: al...@ca...
X-UIDL: 308772634
Status: O
Content-Length: 1934
Lines: 65

On Po, 2001-11-12 at 12:15, Sven Sandberg wrote:
> 
> I'm not sure exactly what you mean with flipping here: if you implement
> page flipping, it surely would be a pity if it didn't flip? :-)
Yes, I thought flickering... So my small pgm again, with comments, what
I thought, that it will do:


#include <allegro.h>

void main() {
    allegro_init ();
    install_keyboard ();
    install_mouse ();
    install_timer ();
    set_color_depth (16);
    set_gfx_mode (GFX_AUTODETECT, 640, 480, 640*2, 480*2);	
    BITMAP *page1 = create_video_bitmap(640,480);
    BITMAP *page2 = create_video_bitmap(640,480);

//  I thought, that if I create video bitmap, it is created in video 
// memory, but not in part of memory, that is currently visible.
// So I tried to use two pages, that I want to switch to screen
// after redraw. When I used double buffering - with writing to
// memory bitmap and then to screen, it works, but it is slow....
    BITMAP *bmp = page1;
    int key;
    int page = 1;
    do {
	    acquire_bitmap(bmp);
	    clear_to_color(bmp,page*500);
// So here I'm writing to first video bitmap, I thought, that it is
// invisible, but is it not true. Everything is written to screen..
	    textout(bmp,font,"Before show_video_bitmap()",30,30,2000);
	    release_bitmap(bmp);
	    key = readkey();
// As you can see here - I excepted, that here will not be
// any graphics on screen
	    acquire_bitmap(bmp);
// And here I excepted, that my video bitmap is showed...
	    show_video_bitmap(bmp); 
	    textout(bmp,font,"After show_video_bitmap() ",30,30,2000);
	    release_bitmap(bmp);
	    if (page == 1) {
		    bmp = page2;
		    page = 2;
	    } else {
		    bmp = page1;
		    page = 1;
	    }
	    key = readkey();
    } while ((key & 0xff) != 'q');
    remove_keyboard ();
    remove_mouse ();
    remove_timer ();
    allegro_exit ();
}
END_OF_MAIN()


So it doesn't work - what I'm doing wrong?

Thanx,

	Jindra