[Scummvm-devel] 256 color overlay mode

Max Horn max at quendi.de
Mon Apr 17 03:41:03 CEST 2006

Hi Chris, (and maybe other ports),

this is an inquiry about NEWGUI_256, defined in scummsys.h, which is  
used to indicate that the overlay only provides a 256 color palette  

First off: Are there any other ports that need this? (Maybe MorphOS,  
though that port seems to be unmaintained since 2003-08-23). If so,  
please tell me, and tell me soon!

Secondly: Chris, this is disabled for OS5 and Zodiac. Looking through  
the PalmOS code in current Subversion, I am not sure if any of the  
current code even makes use of that feature. Could you clarify: Is  
the 256 color overlay mode still used by the PalmOS port? If so, does  
it even use the regular GUI code?

Background: I am investigating the replacement of  
OSystem::RGBToColor. So far, it seems we'll not go the pixel format  
route I originally had in mind, but rather, we'll take the gBitFormat  
hack and refine it to something less hackish. That is, backends will  
be able to specify the bitformat as an int, allowing for 555, 565,  
1555, 4444 and possibly more formats. Client code can then directly  
optimize for each format. In many cases, using graphics/colormasks.h,  
one can write the code once and compile it for every needed bitformat.

However, that approach won't work with a palette mode overlay. We can  
design everything so that a palette mode overlay is still possible --  
however, before spending time on designing and implementing this, I'd  
like to know whether it's even needed / used. And if it is, we  
probably need to adjust the new GUI code anyway, to work properly in  
this case.


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