xserver and mesa git update 28-12-2010

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+INTRODUCTION

+

+A helper module which provides glue to bind the software rasterizer to

+the software t&l module.  The main task of this module is to build

+swrast vertices from the t&l vertex_buffer structs, and to use them to

+perform triangle setup functions not implemented in the software

+rasterizer.

+

+The module implements a full set of functions to plug into the

+t_vb_render.c driver interface (tnl->Driver.Render.*).  

+

+There are strong advantages to decoupling the software rasterizer from

+the t&l module, primarily allowing hardware drivers better control

+over fallbacks, the removal of implicit knowledge about the software

+rasterizer in the t&l module, allowing the two modules to evolve

+independently and allowing either to be substituted with equivalent

+functionality from another codebase.

+

+This module implements triangle/quad setup for offset, unfilled and

+twoside-lit triangles.  The software rasterizer doesn't handle these

+primitives directly.

+

+Hardware rasterization drivers typically use this module in situations

+where no hardware rasterization is possible, ie during total

+fallbacks. 

+

+STATE

+

+To create and destroy the module:

+

+	GLboolean _swsetup_CreateContext( struct gl_context *ctx );

+	void _swsetup_DestroyContext( struct gl_context *ctx );

+

+The module is not active by default, and must be installed by calling

+_swrast_Wakeup().  This function installs internal swrast_setup

+functions into all the tnl->Driver.Render driver hooks, thus taking

+over the task of rasterization entirely:

+

+        void _swrast_Wakeup( struct gl_context *ctx );

+

+   

+This module tracks state changes internally and maintains derived

+values based on the current state.  For this to work, the driver

+ensure the following funciton is called whenever the state changes and

+the swsetup module is 'awake':

+

+	void _swsetup_InvalidateState( struct gl_context *ctx, GLuint new_state );

+

+There is no explicit call to put the swsetup module to sleep.  Simply

+install other function pointers into all the tnl->Driver.Render.*

+hooks, and (optionally) cease calling _swsetup_InvalidateState().

+

+DRIVER INTERFACE

+

+The module offers a minimal driver interface:

+

+	 void (*Start)( struct gl_context *ctx );

+	 void (*Finish)( struct gl_context *ctx );

+	 

+These are called before and after the completion of all swrast drawing

+activity.  As swrast doesn't call callbacks during triangle, line or

+point rasterization, these are necessary to provide locking hooks for

+some drivers.  They may otherwise be left null.

+

+