open chunky screen

[grond]

How can I open a chunky screen on a gfx card through the operating system (more specifically P96)? I assume that the P96 software patches the relevant OS functions so I believe that BestModeIDA() should work at least for modes related to the original Amiga screenmodes (e.g. 8bit CLUT in 320x200 without special modes like EHB). If this were not the case, software that was not aware of graphics cards (but coded in an OS compliant way) could not run on a picasso screen. I have seen some example code that opens a Picasso-Library and then calls some functions from that. This would mean that I have to write code for different ways of opening a screen depending on the gfx subsystem and its drivers. I understand that of course not all features offered by typical graphics cards can be supported through the standard OS functions. So what is the preferred way?

[thomas]

On classic AmigaOS you should stick with CGX because CGX programs also work on P96 while P96 programs don't work on CGX.

If you require a gfx card, you should use CGX functions to find a suitable mode ID. If you fail to open cybergraphics.library, then there is no gfx card in the system.

If you don't require a gfx card, you should not care about chunky/planar. Just use graphics.library functions for everything. Never touch a bitmap directly, use AllocBitMap or OpenScreenTags to create bitmaps and GetBitMapAttr to query information. Use Blt#? or Read/WritePixelArray8 functions to move data around. Keep away from struct BitMap.

[grond]

Thanks a lot, that is helpful.

What if I want to have the option to either use c2p code or write directly in chunky I guess I would want to query the screenmode I get for whether it is chunky or planar? Like call BestModeIDA() with say 320x200, 8 bit CLUT and find out whether it is an AGA screenmode or an RTG screenmode I got?

[thomas]

IsCyberModeID(display_id) will give you TRUE if the mode is from CyberGraphics.

With GetCyberIDAttr() you can determine the pixel format.

With graphics.library only you can't tell, at least for <= 8 bit. If depth is > 8 bit, then it's surely a gfx card mode. And if BMA_FLAGS contains BMF_INTERLEAVED then it's surely a planar bitmap.

[grond]

Thanks again! I wondered whether the rtg libraries had introduced some new tags that would be understood by a presumably patched BestModeIDA. You are referring to cybergraphics functions. Am I right in understanding that this would again work with picasso cards? Could there be users that have a picasso card but no cybergraphics?

[thomas]

Surely they don't have cybergraphics but nevertheless they have cybergraphics.library because picasso96 emulates cybergraphics.library.

[grond]

This seems to imply that apollo could just as well go the cybergraphics route (following AROS) instead of picasso. Interesting...

[Samurai_Crow]

Both P96 and CGX 4 are backward compatible with CGX 3 APIs adding only two incompatible ways of implementing overlay. Since overlay effects use texture blitting on modern graphics cards, those features can be safely removed.