Path: utzoo!attcan!uunet!van-bc!
From: lphillips@lpami.wimsey.bc.ca (Larry Phillips)
Newsgroups: comp.sys.amiga
Subject: Re: Help changing custom screen's palette
Keywords: Assembly, LOADRGB4
Message-ID: <1135@lpami.wimsey.bc.ca>
Date: 12 Feb 90 00:28:10 GMT
Lines: 38
Return-Path: <lpami!lphillips>
To: van-bc!rnews

In <2300@ucqais.uc.edu>, rbatra@ucqais.uc.edu (pri=2 Rajesh Batra) writes:
>	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. I used the library call LOADRGB4. Would someone
>please tell me what I am doing wrong? Here is some of the source:
>
>       [ code deleted ]
>
>       move.l 44(a0),a0   ;Loads screen's viewport into register a0.
>
> [code deleted
>
>----------------
>	If you think the error is so obvious that you would rather spare
>me the embarrassment please email me the solution to: 

I don't think you have to be too embarrassed.

What you have done in the abover excerpted line is to load up a pointer to the
_next_ ViewPort. This is because a ViewPort structure is contained in the
Screen struct, rather than a pointer to a ViewPort. The operation you want is:

       add.l  #sc_ViewPort,a0   ; ( or  add.l #44,a0 to use your terms )

Since the pointer to the Screen struct is in a0, adding 44 to it will make it a
pointer to the ViewPort. Your line moved the contents of the first longword in
the ViewPort struct to a0, which pointed you at the next ViewPort.

-larry

--
Gallium Arsenide is the technology of the future;
  always has been, always will be.
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|   //   Larry Phillips                                                 |
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