tree 7b375b9fe377f37a8d92afebfc8929f1d7b56e56
parent 2959749f85cc117d6361848b62b5a8e91460451a
author Chris Dalton <csmartdalton@google.com> 1573020081 -0700
committer Skia Commit-Bot <skia-commit-bot@chromium.org> 1573080139 +0000

Rename stencil face terminology to clockwise/counter-clockwise

"Front" and "back" actually refer to opposite triangles in GL vs
Vulkan. Both APIs define counter-clockwise as the default winding
direction for the front face, but since GL uses a bottom-up coordinate
system, they are reversed from one another.

The idea of this CL is to define Ganesh's stencil settings in terms of
clockwise and counter-clockwise in skia device space, just like how we
use "sk_Clockwise" insead of "gl_FrontFacing" in SkSL. We
intentionally avoid the "front"/"back" terminology so there is no
ambiguity. The individual backends are now responsible to translate
cw/ccw into whatever that means for front and back in their own
particular APIs.

This change also swaps the front and back stencil faces in vulkan and
metal, since they were previously backwards from GL. This should have
no actual effect yet, because the only code so far where this matters
is ccpr.

Change-Id: Ife6afbe0a83899edc7eacc3f00a4507d065cccab
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/252977
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>