[Mesa-dev] [PATCH v2 1/4] mesa: introduce MS variants of line width min/max/granularity

[Kenneth Graunke]

On Tuesday, September 6, 2016 11:49:59 PM PDT Ilia Mirkin wrote:
> These are exposed in ES 3.2. However this moves all st/mesa to clamping
> on the MS variants. But for now the MS variants are initialized to the
> AA values.
> 
> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>

So...

- Virtually all implementations have the same line widths and granularity
  regardless of multisampling or antialiasing settings.

- Imagination is a counter example, and has different ranges/granularity
  for normal (aliased) and smooth/multisampled lines:

  https://cvs.khronos.org/bugzilla/show_bug.cgi?id=13828#c2

  Hence, the need for two separate ranges.  This would be useful for
  a theoretical Imagination driver, although none exists today.

- I believe that AA = MS in all cases.  But GLES doesn't have the
  concept of "smooth lines", so they gave the queries a different name.

- The only Mesa driver that sets these differently today is ILO..all
  other drivers set MaxLineWidth and MaxLineWidthAA identically.  (I have
  no idea why ILO does this.  We could probably drop the distinction.)

Maybe it would make sense to drop the distinction and just have one
field for both kinds of queries.  If we don't want to go that route,
then I think I'd rather see only two sets of fields:

- MaxPointWidth
- MaxPointWidthMS (or AA, either name)
- LineWidthGranularity
- LineWidthGranularityMS (or AA, either name)

The MS/AA versions should be used if either MSAA is enabled or
SmoothFlag is enabled.

Does that seem reasonable?

--Ken
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