Path: utzoo!attcan!uunet!zephyr.ens.tek.com!tektronix!psueea!jove.cs.pdx.edu!bartonr
From: bartonr@jove.cs.pdx.edu (Robert Barton)
Newsgroups: comp.sys.amiga
Subject: Help changing custom screen's palette
Message-ID: <2374@psueea.UUCP>
Date: 13 Feb 90 17:56:26 GMT
Sender: news@psueea.UUCP
Reply-To: bartonr@jove.cs.pdx.edu (Robert Barton)
Organization: Dept. of Computer Science, Portland State University; Portland OR
Lines: 20

>    I am trying to change the colors of a custom screen. But instead the
> workbench screen's palette changes, and my custom screen's colors remain
> unchanged.
>
>       move.l intbase,a6
>       lea newscreenstructure,a0
>       jsr openscrn(a6)       ;The above just opened a custom screen.
>       move.l d0,screenhd     ;Saves the screen stucture for later use.

  You should check screenhd for a non-NULL value at this point.

>       move.l screenhd,a0
>       move.l 44(a0),a0   ;Loads screen's viewport into register a0.

  This is where you have the problem.  The viewport field is a substructure of
the screen structure, and not a pointer.  So the move.l 44(a0),a0 is putting
the first longword of the viewport into a0, rather than the address of the vp.
This longword just happens to be a pointer to the next viewport, which in this
case is the Workbench's viewport.  So that's where the new colors show up.
You need to use lea 44(a0),a0.