web page last updated Wednesday 20th August 2003 #?am

=========== Wed 20th Aug. 2003 #?am =====

As of today, a colour viewer via -sDEVICE=whoosh24 and a b/w viewer via -sDEVICE=whoosh1 are now available for 256 colour WB screens on graphics cards. Also available now on graphics cards are depth-8 custom screen viewers.


Tue.29.jul.2003.1230am: the Picasso card problem below seems to be a technical usage problem. All the viewers appear to be functioning on Picasso. There is a slight bug on the release program where env variable whooshscreen is ignored if it is local! This problem is fixed on the next upload, to get around it for now you have to type:

setenv whooshscreen magic_number

instead of using set. As a result of the correspondence with the Picasso owner I have decided to upload some info about Graphics cards. Graphics cards are very tricky, being used to AGA when I programmed the viewers for Cyber I used my AGA knowledge, this caused total viewer failure! It took possibly a month before I made the breakthrough, anyway I summarise here important differences between graphics cards and AGA.

This info is important for using the gs8 Cyber viewers as well as of interest to programmers.

=========== graphics cards vs AGA facts: ==============

I discovered these facts after several weeks of viewers not functioning:

1. For an AGA screen, you can give any depth: 1 , 2 , ..., 8

2. For a truecolour screen depth *cannot* be changed,
     so if you clone a depth-16 WB via whooshwbres it can only be depth 16,
     ie 8,15,24 are *impossible*!
   So if you clone AGA WB depth-3 screen this could be given depth 8,
	   *NOT* true for Cyber,
2.a. So for truecolour you select the depth from the requester,
3. Cyber depth-8 screen is *not* AGA! so it cannot be done in eg depth 1
   Cyber depth-8 differs from AGA by probably being byte-per-pixel,
   also various AGA-bugs are absent! SetRGB32CM() has a bug with AGA 
   where it doesnt set lower 4 bits of blue component, no such bug 
   for Cyber depth-8.
   Cyber depth-8 screens are similar to AGA though,
3.a. Cyber depth-8 also cannot have the depth changed! It can only be in 
     depth 8, never 15,16,24!
3.a.i So as with 2.a. above depth-8 is also selected from the requester,
      for AGA machines depth does *not* come from the requester
      with Cyber depth *only* comes from the requester!
      I wasted maybe a month figuring this out! its very confusing,
4. Every screen on a graphics card is either AGA or Cyber, there is a 
   cybergraphics.library OS call which will tell you if a screen is Cyber!
   I think actually there are no AGA screens on Cyber,
Summary: for Cyber depth is incorporated into the magic number,
for AGA depth is independent of the magic number!
depth-1 screens appear to be impossible for Cyber.

Sunday 27th July: I have had feedback from someone with a Picasso card saying there are problems with some of the viewers. He had a 256 colour WB, unfortunately the WB viewers have been designed for truecolour WBs so they will currently not function for Cyber 256 colour WB. As long as you use a depth 15,16 or 24 Cyber WB the Cyber WB viewers are an option. If you use 256 colour WB then only the custom screen viewers are an option. The AGA WB viewers are fine for a 256 colour AGA screen. Because of the program logic it may require some effort to make 256 colour function for Cyber WB viewers, not sure if its worth the trouble.

Now the above Picasso card owner said only some of the custom screen viewers functioned. Anyway I am trying to resolve this, firstly whether its a usage problem or whether its a program problem. If its a program problem I will try to fix it.

If anyone else with Picasso card can send feedback positive or negative I am interested. If possible can you send me a jpeg screenshot for the screen requester that appears for the custom screen viewers. Also when trying out the 24 bit custom screen viewer please try in sequence all the screens in the screen requester till success, note that AGA screens in the requester will almost certainly fail.

I am interested to hear feedback from G3 (or G4) users, either Pegasos or A1.
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