Xref: news2.mv.net comp.os.msdos.djgpp:5123
From: Shawn Hargreaves <slh100 AT york DOT ac DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: A few more DJGPP Questions...
Date: Tue, 18 Jun 1996 11:49:45 +0100
Organization: The University of York, UK
Lines: 53
Message-ID: <Pine.SGI.3.91.960618112844.15738A-100000@sgi16.york.ac.uk>
NNTP-Posting-Host: sgi16.york.ac.uk
Mime-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
In-Reply-To: <834783710snz@flag.demon.co.uk>
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

On Fri, 14 Jun 1996, Ben Ashley wrote:

> Actually, I was gonna Email you about something, but I didn't know if you
> were still around :).  Still, I may aswell ask my Email questions here:

I'm here for a couple more weeks yet (two, to be exact).

> 1.  In my picture boxes, I am going to create a bitmap, with the 
>     dimensions of the client area of the picture boxes.  Any 
>     drawing/writing to this control willl therefore go to the bitmap.  
>     memory bitmap to screen?  Should I create A sub-bitmap or what?  I 

This could be done with or without a sub-bitmap, it really wouldn't make 
much difference. Without a sub-bitmap, your display code would look like:

    blit(image, screen, 0, 0, p_box_x, p_box_y, width, height);

With a sub-bitmap, in your setup code you could do:

    sub_bitmap = create_sub_bitmap(screen, p_box_x, p_box_y, width, height);

and then display it with:

    blit(image, sub_bitmap, 0, 0, 0, 0, width, height);

Using a sub-bitmap has the advantage that you can use zero-based 
coordinates, and the sub-bitmap has it's own clipping so you don't need 
to worry about setting the screen clip rectangle before you draw to it.

> 2.  If the picture box resized, how would I go about resizing the bitmap?
>     Do I just put it in a temporary location, delete the old, make a 
>     new one with the new size, clear it and copy the stored bitmap to 
>     the new one?

That's how the grabber utility does it when you resize bitmap objects. It 
depends if you want the resize to clip them or just scale them: for 
scaling you could keep the original memory bitmap and just use 
stretch_blit() to display it. If you don't want to scale it, try 
something like:

    BITMAP *temp = create_bitmap(new_w, new_h);
    blit(image, temp, 0, 0, 0, 0, MIN(old_w, new_w), MIN(old_h, new_h));
    destroy_bitmap(image);
    image = temp;



/*
 *	Shawn Hargreaves.        Why is 'phonetic' spelt with a ph?
 *	Check out Allegro and FED on http://www.york.ac.uk/~slh100/
 */