[Mesa3d-dev] Modularization of software rasterizer

[Keith W. <ke...@va...>]

Brian,

I'm currently tightening up the interfaces between the software rasterizer and
the rest of the world.

Specifically this involves:

	- a _swrast_InvalidateState( ctx, new_state ) routine, which must be called
with state updates to allow swrast to maintain an internal state.

	- a SWvertex structure:

	typedef struct {
	   GLfloat win[4];
	   GLfloat eye[4];		/* for GL_EXT_point_param only */
	   GLfloat texcoord[MAX_TEXTURE_UNITS][4];
	   GLchan color[4];
	   GLchan specular[4];
	   GLfloat fog;
	   GLuint index;
	   GLuint flags;
	} SWvertex;


	All software primitive rasterization functions will expect such a vertex
instead of grabbing the values out of the VB directly.  This has a lot of
subtle benefits, including being able to call the software rasterizer from a
hardware driver (after translating hardware vertices to software ones), and
being able to call the software rasterizer from non-standard geometry
pipelines, like the fastpath.

	- A set of entry points:

		_swrast_Quad
		_swrast_Triangle
		_swrast_Line
		_swrast_Point

	which can be called at any time and will always call the correct
quad/tri/line/point for the current state.  These feel a lot like
grDrawTriangle, etc.

All in all the effect is to make the software rasterizer look a lot more like
the hardware rasterizers, or like glide - an abstraction layer above a
hardware rasterizer.  

I'm also providing some helper functions to build SWvertices from vertex
buffer indices, and to help with special drivers like X11 that want to extend
the software rasterizer.

This interface will be documented by a text file in the swrast directory.

Keith