From: Marcus Sundberg <e94_msu@elixir.e.kth.se>
  To  : ggi-develop@eskimo.com
  Date: Tue, 14 Jul 1998 01:00:01 +0200

New ggi_graphtype

Hi!

In the true spirit of DTJC I have implemented a new ggi_graphtype
scheme after looking through the libggi-issues document:

#define        GGI_AUTO     (0)

typedef uint32 ggi_graphtype;

#define GT_DEPTH_MASK		0x000000ff
#define GT_ACCESS_MASK		0x0000ff00
#define GT_SUBSCHEME_MASK	0x00ff0000
#define GT_SCHEME_MASK		0xff000000

#define GT_DEPTH_SHIFT		(0)
#define GT_ACCESS_SHIFT		(8)
#define GT_SUBSCHEME_SHIFT	(16)
#define GT_SCHEME_SHIFT		(24)

/* Macros to extract info from a ggi_graphtype. */
#define GT_DEPTH(x)		(((x) & GT_DEPTH_MASK) >> GT_DEPTH_SHIFT)
#define GT_ACCESS(x)		(((x) & GT_ACCESS_MASK) >> GT_ACCESS_SHIFT)
#define GT_SUBSCHEME(x)		((x) & GT_SUBSCHEME_MASK)
#define GT_SCHEME(x)		((x) & GT_SCHEME_MASK)

/* Enumerated schemes */
#define GT_TEXT			((0x01) << GT_SCHEME_SHIFT)
#define GT_RGB			((0x02) << GT_SCHEME_SHIFT)
#define GT_GREYSCALE		((0x03) << GT_SCHEME_SHIFT)
/* Scheme flags */
#define GT_INDEXED		((1<<7) << GT_SCHEME_SHIFT)

/* Subschemes */
#define GT_SUB_LSB_NORMAL	((0x01) << GT_SUBSCHEME_SHIFT)
#define GT_SUB_MSB_NORMAL	((0x02) << GT_SUBSCHEME_SHIFT)
#define GT_SUB_LSB_REVERSE	((0x03) << GT_SUBSCHEME_SHIFT)
#define GT_SUB_MSB_REVERSE	((0x04) << GT_SUBSCHEME_SHIFT)

/* Macro that constructs a graphtype */
#define GT_CONSTRUCT(depth,scheme,access) \
( (depth) | \
  (scheme) | \
  ((access) << GT_ACCESS_SHIFT) )


/* Common graphtypes */
#define GT_TEXT16	GT_CONSTRUCT(16,GT_TEXT,16)
#define GT_TEXT32	GT_CONSTRUCT(32,GT_TEXT,32)
#define GT_1BIT		GT_CONSTRUCT(1, GT_GREYSCALE, 1)
#define GT_4BIT		GT_CONSTRUCT(4, GT_RGB | GT_INDEXED, 4)
#define GT_8BIT		GT_CONSTRUCT(8, GT_RGB | GT_INDEXED, 8)
#define GT_15BIT	GT_CONSTRUCT(15, GT_RGB, 16)
#define GT_16BIT	GT_CONSTRUCT(16, GT_RGB, 16)
#define GT_24BIT	GT_CONSTRUCT(24, GT_RGB, 24)
#define GT_32BIT	GT_CONSTRUCT(24, GT_RGB, 32)
#define GT_AUTO		(0)
#define GT_INVALID	(0xffffffff)

#if 0
#define MASK(X) GM_##X = (1 << GT_##X) 	
typedef enum
{	MASK(TEXT16),
	MASK(TEXT32),
	MASK(1BIT),
	MASK(4BIT),
	MASK(8BIT),
	MASK(15BIT),
	MASK(16BIT),
	MASK(24BIT),
	MASK(32BIT),
	GM_ALL	=  ((1 << GT_LAST) - 1)
} ggi_graphmask;
#undef MASK
#else
#define ggi_graphmask ggi_graphmask_does_not_exist_anymore
#endif

#ifdef NEED_GRAPHTYPE_SYMS
#define GRAPHTYPE(X) ("THIS CODE NEEDS FIXING FOR THE NEW GT_* SCHEME!")
#endif


My comments:
* Changing GGI_AUTO to 0 is genarally a Good Thing as it will simplify lots
  of things and doesn't break any source-compability.
* Having GT_INDEXED as a flag instead of a searate scheme is also the right
  thing to do as you can have both indexed and non-indexed RGB, greyscale,
  YUV or whatever modes.
* The MSB/LSB part of the subscheme should cause no confusion. The 
  NORMAL/REVERSE part refers to RBG or BGR style pixelformats.
  This is the two parts that users is likely to want to change.
  And If we should ever feel the need to have more combinations we
  have 5 bits left in the subscheme.
* The GT_CONSTRUCT macro doesn't take a subscheme argument as you simply
  'or' an eventual subscheme together with the scheme.
* This scheme will maintain source compability for all apps, unless they
  do something special (Everything in demos/ worked out-of-the-box, except
  checkmode.c which took 2 mins to fix).
* I've not added entrys for YUV, CMYK, FNUL, GROK or DIRT colorspaces, and
  neither the 5red17blue10unused3alpha8green subscheme supported by
  WizBang graphicboards, simply because that there's no driver supporting
  them yet. When the need arises for those they can easily be plugged in
  without breaking anything.

Your comments?

Unless anyone finds any important flaw in this scheme that can't be
fixed without breaking anything I'll commit this tomorrow so we can
start updating targets and drivers.

//Marcus