gallium: Replace gl_rasterization_rules with lower_left_origin and half_pixel_center.

Squashed commit of the following:

commit 04c5fa2cbb8e89d6f2fa5a75af1cca03b1f6b852
Author: José Fonseca <[email protected]>
Date:   Tue Apr 23 17:37:18 2013 +0100

    gallium: s/lower_left_origin/bottom_edge_rule/

commit 4dff4f64fa83b9737def136fffd161d55e4f1722
Author: José Fonseca <[email protected]>
Date:   Tue Apr 23 17:35:04 2013 +0100

    gallium: Move diagram to docs.

commit 442a63012c8c3c3797f45e03f2ca20ad5f399832
Author: James Benton <[email protected]>
Date:   Fri May 11 17:50:55 2012 +0100

    gallium: Replace gl_rasterization_rules with lower_left_origin and half_pixel_center.

    This change is necessary to achieve correct results when using OpenGL
    FBOs.

Reviewed-by: Marek Olšák <[email protected]>

1 files changed, 70 insertions, 3 deletions

diff --git a/src/gallium/docs/source/cso/rasterizer.rst b/src/gallium/docs/source/cso/rasterizer.rst
index be4bad56c00..44e5544cdaa 100644
--- a/src/gallium/docs/source/cso/rasterizer.rst
+++ b/src/gallium/docs/source/cso/rasterizer.rst
@@ -238,9 +238,76 @@ scissor
 multisample
     Whether :term:`MSAA` is enabled.
 
-gl_rasterization_rules
-    Whether the rasterizer should use (0.5, 0.5) pixel centers. When not set,
-    the rasterizer will use (0, 0) for pixel centers.
+half_pixel_center
+    When true, the rasterizer should use (0.5, 0.5) pixel centers for
+    determining pixel ownership (e.g, OpenGL, D3D10 and higher)::
+
+           0 0.5 1
+        0  +-----+
+           |     |
+       0.5 |  X  |
+           |     |
+        1  +-----+
+
+    When false, the rasterizer should use (0, 0) pixel centers for determining
+    pixel ownership (e.g., D3D9 or ealier)::
+
+         -0.5 0 0.5
+      -0.5 +-----+
+           |     |
+        0  |  X  |
+           |     |
+       0.5 +-----+
+
+bottom_edge_rule
+    Determines what happens when a pixel sample lies precisely on a triangle
+    edge.
+
+    When true, a pixel sample is considered to lie inside of a triangle if it
+    lies on the *bottom edge* or *left edge* (e.g., OpenGL drawables)::
+
+        0                    x
+      0 +--------------------->
+        |
+        |  +-------------+
+        |  |             |
+        |  |             |
+        |  |             |
+        |  +=============+
+        |
+      y V
+
+    When false, a pixel sample is considered to lie inside of a triangle if it
+    lies on the *top edge* or *left edge* (e.g., OpenGL FBOs, D3D)::
+
+        0                    x
+      0 +--------------------->
+        |
+        |  +=============+
+        |  |             |
+        |  |             |
+        |  |             |
+        |  +-------------+
+        |
+      y V
+
+    Where:
+     - a *top edge* is an edge that is horizontal and is above the other edges;
+     - a *bottom edge* is an edge that is horizontal and is below the other
+       edges;
+     - a *left edge* is an edge that is not horizontal and is on the left side of
+       the triangle.
+
+    .. note::
+
+        Actually all graphics APIs use a top-left rasterization rule for pixel
+        ownership, but their notion of top varies with the axis origin (which
+        can be either at y = 0 or at y = height).  Gallium instead always
+        assumes that top is always at y=0.
+
+    See also:
+     - http://msdn.microsoft.com/en-us/library/windows/desktop/cc627092.aspx
+     - http://msdn.microsoft.com/en-us/library/windows/desktop/bb147314.aspx
 
 clip_halfz
     When true clip space in the z axis goes from [0..1] (D3D).  When false