RE: [AL] How to do it?

SourceForge Headquarters 225 Broadway Suite 1600 San Diego, CA 92101 +1 (858) 454-5900

I remember a few months ago we were telling *you* how to do this sort of
thing, Will! You know you're getting somewhere when you start giving other
people advice :)

Nice job.

Derek

-----Original Message-----
From: William labbett [mailto:w_l...@ho...]
Sent: Friday, March 22, 2002 10:48 AM
To: al...@ca...
Subject: Re: [AL] How to do it?

> Hi there.
>
> How to move a sprite from A to B ?
> note:
> A is a fixed position, B is the mouseX,Y position
> right after button 1 pressed.
> I would like to do something like do_line() but
> the sprite will move on screen (I don't want a
> continuos line!)

You need to understand how the computer does what you're talking about.If
you were to do
 /*psuedo*/
blit(small sprite to middle of buffer bitmap)
blit(buffer to screen)

/* then */
blit(small sprite a bit to the left of middle of buffer)
blit(buffer to screen)

you'll get your sprite drawn twice, the second time over the top of the
first because the sprite you drew first time is still on the buffer bitmap
when you draw it again.
So what needs to be done before you move it is erase it from the buffer
first, then it won't be there!
  So say your background was black then you need to blit a black rectangle
the size of your sprite to the buffer.Then blit the sprite in it's new
position.You could just clear the screen to black for simpler code but that
wouldn't work if you wanted other things to stay were they were.
 I haven't used the mouse yet in allegro but I suspect your code would be
something like;
/* as part of loop */
/* pseudo*/
get_mouse_position();
clear_the_screen_to_black();
blit(sprite at mouse coordinates);

if you want the sprite to appear centred on the mouse cursor (so the
cursor's in the middle of the sprite when it's drawn) then you need to do a
bit of maths; you need to draw the sprite half the width and height of
itself closer to to 0,0.

hope that helps
Will
>From <all...@ca...> Fri Mar 22 04:18:18 2002
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From: Lo'oRiS il Kabukimono <_l...@li...>
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> I am just curious what does mouse_sprite point to??
> (it is in the mouse section of the help)

it points to the mouse cursor.

-- 
"When the world is in darkness, four warriors will come..."
 - Final Fantasy I
                                . /\ °
Real Name: Lorenzo Petrone       <* >
Web: digilander.iol.it/lano666    \/ ·
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dear allegro,I am being swamped with mail from canvas link =
allegro.PLEASE .UNSUBSCRIBE ALLEGRO in the body of the message.I have =
not requested it and I do not require it.am an old infirm person and can =
do without all this hassle.

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
<META content=3D"MSHTML 5.50.4134.100" name=3DGENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>dear allegro,I am being swamped with =
mail from=20
canvas link allegro.PLEASE .UNSUBSCRIBE ALLEGRO in the body of the =
message.I=20
have not requested it and I do not require it.am an old infirm person =
and can do=20
without all this hassle.</FONT></DIV></BODY></HTML>

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