[Mesa-dev] [PATCH 1/3] gallium: add resource normalization flags (v4)

[Luca Barbieri]

> Hmm this is indeed rather complicated, though I guess it could work.

A possibly less complicated simplified restatement, from the state
tracker point of view:
- If PIPE_CAP_FLEXIBLE_SAMPLER is supported, you can do anything and
PIPE_RESOURCE_FLAG_TEXTURE_RECT_SEMANTICS is ignored
- If you use PIPE_RESOURCE_FLAG_TEXTURE_RECT_SEMANTICS, then it's like
GL_TEXTURE_RECTANGLE, except normalized coordinates are supported and
preferred if PIPE_RESOURCE_FLAG_PREFER_NORMALIZED_COORDS gets set by
the driver
- If you don't use PIPE_RESOURCE_FLAG_TEXTURE_RECT_SEMANTICS, then:
A. If NPOT and no PIPE_CAP_NPOT_TEXTURES, then you must respect the
driver normalization preference
B. If POT or NPOT with PIPE_CAP_NPOT_TEXTURES, then it's like
GL_TEXTURE_2D, except that unnormalized coordinates are supported and
preferred (but only with clamp wrap modes) if
PIPE_RESOURCE_FLAG_PREFER_UNNORMALIZED_COORDS gets set by the driver.

For internal drawing, respect the driver preference if any, and
otherwise choose yourself. Don't attempt to use non-clamp wrap modes
for internal drawing (we should introduce an "I guarantee the
coordinate is in bounds" mode for this).
If you really need non-clamp modes, either require
PIPE_CAP_FLEXIBLE_SAMPLING or always use normalized coordinates and
either use POT textures or require PIPE_CAP_NPOT_TEXTURES.

If you don't respect the driver preference for internal drawing and
always use normalized, then you must either only use POT textures or
require PIPE_CAP_NPOT_TEXTURES.
If you don't respect the driver preference for internal drawing and
always use unnormalized, then you must either use
PIPE_RESOURCE_FLAG_TEXTURE_RECT_SEMANTICS or require
PIPE_CAP_FLEXIBLE_SAMPLING.


And from the driver point of view:
- If you have two texture layouts tied to normalization, use the
unnormalized one if either PIPE_RESOURCE_FLAG_TEXTURE_RECT_SEMANTICS
or the texture is NPOT, otherwise use the normalized one. Don't expose
PIPE_CAP_NPOT_TEXTURES.
- If you have only one texture layout, do nothing and ignore
PIPE_RESOURCE_FLAG_TEXTURE_RECT_SEMANTICS.
- If only one normalization is supported for the given layout, or if
one of them is faster, set the preference flag for that one, otherwise
do nothing.