gallium: add bits for clipping points as tris (d3d-style)

OpenGL does whole-point clipping, that is a large point is either fully
clipped or fully unclipped (the latter means it may extend beyond the
viewport as long as the center is inside the viewport). d3d9 (d3d10 has
no large points) however requires points to be clipped after they are
expanded to a rectangle. (Note some IHVs are known to ignore GL rules at
least with some hw/drivers.)
Hence add a rasterizer bit indicating which way points should be clipped
(some drivers probably will always ignore this), and add the draw interaction
this requires. Drivers wanting to support this and using draw must support
large points on their own as draw doesn't implement vp clipping on the
expanded points (it potentially could but the complexity doesn't seem
warranted), and the driver needs to do viewport scissoring on such points.

Conflicts:

	src/gallium/drivers/llvmpipe/lp_context.c
	src/gallium/drivers/llvmpipe/lp_state_derived.c

Reviewed-by: Jose Fonseca <[email protected]>

1 files changed, 11 insertions, 4 deletions

diff --git a/src/gallium/docs/source/cso/rasterizer.rst b/src/gallium/docs/source/cso/rasterizer.rst
index 44e5544cdaa..8d473b8446e 100644
--- a/src/gallium/docs/source/cso/rasterizer.rst
+++ b/src/gallium/docs/source/cso/rasterizer.rst
@@ -200,10 +200,11 @@ point_quad_rasterization
 Determines if points should be rasterized according to quad or point
 rasterization rules.
 
-OpenGL actually has quite different rasterization rules for points and
-point sprites - hence this indicates if points should be rasterized as
-points or according to point sprite (which decomposes them into quads,
-basically) rules.
+(Legacy-only) OpenGL actually has quite different rasterization rules
+for points and point sprites - hence this indicates if points should be
+rasterized as points or according to point sprite (which decomposes them
+into quads, basically) rules. Newer GL versions no longer support the old
+point rules at all.
 
 Additionally Direct3D will always use quad rasterization rules for
 points, regardless of whether point sprites are enabled or not.
@@ -217,6 +218,12 @@ generated.
    Some renderers always internally translate points into quads; this state
    still affects those renderers by overriding other rasterization state.
 
+point_tri_clip
+    Determines if clipping of points should happen after they are converted
+    to "rectangles" (required by d3d) or before (required by OpenGL, though
+    this rule is ignored by some IHVs).
+    It is not valid to set this to enabled but have point_quad_rasterization
+    disabled.
 point_smooth
     Whether points should be smoothed. Point smoothing turns rectangular
     points into circles or ovals.