commit 7268e7d36f8e1ae868916c4f663e2a68039cacf0
author Corentin Wallez <cwallez@chromium.org> Tue Aug 18 12:30:06 2020 +0000
committer Commit Bot service account <commit-bot@chromium.org> Tue Aug 18 12:30:06 2020 +0000
tree 2f73b51e4171a5db1ff5aa7e24d214038cbd9322
parent d95180deded12701abc5e13ee7fa9bd1bcdbb9cb

OpenGL: Unconditionally set glFrontFace

Previously glFrontFace was called only if some cull mode was set. This
was incorrect because the front face also influences whether a triangle
uses stencilFront or stencilBack.

Because OpenGL default to GL_CCW (which with the Y-flip is the inverse
of wgpu::FrontFace::CCW that's default in the descriptor), if
stencilFront != stencilBack and cull mode is none, then the incorrect
stencil face descriptor was used.

Also adds a regression test for this issue.

Bug: dawn:508
Change-Id: I00d93bda6d4f030cf9db472a9f2b0deefc72707f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/26880
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

src/dawn_native/opengl/RenderPipelineGL.cpp

diff --git a/src/dawn_native/opengl/RenderPipelineGL.cpp b/src/dawn_native/opengl/RenderPipelineGL.cpp
index 943dfbb..7c70396 100644
--- a/src/dawn_native/opengl/RenderPipelineGL.cpp
+++ b/src/dawn_native/opengl/RenderPipelineGL.cpp
@@ -43,14 +43,15 @@
         void ApplyFrontFaceAndCulling(const OpenGLFunctions& gl,
                                       wgpu::FrontFace face,
                                       wgpu::CullMode mode) {
+            // Note that we invert winding direction in OpenGL. Because Y axis is up in OpenGL,
+            // which is different from WebGPU and other backends (Y axis is down).
+            GLenum direction = (face == wgpu::FrontFace::CCW) ? GL_CW : GL_CCW;
+            gl.FrontFace(direction);
+
             if (mode == wgpu::CullMode::None) {
                 gl.Disable(GL_CULL_FACE);
             } else {
                 gl.Enable(GL_CULL_FACE);
-                // Note that we invert winding direction in OpenGL. Because Y axis is up in OpenGL,
-                // which is different from WebGPU and other backends (Y axis is down).
-                GLenum direction = (face == wgpu::FrontFace::CCW) ? GL_CW : GL_CCW;
-                gl.FrontFace(direction);
 
                 GLenum cullMode = (mode == wgpu::CullMode::Front) ? GL_FRONT : GL_BACK;
                 gl.CullFace(cullMode);