From 8b601714035f2cc4925e7f1007c4bfe593c30164 Mon Sep 17 00:00:00 2001
From: Dzmitry Malyshau <kvarkus@gmail.com>
Date: Mon, 17 May 2021 22:00:05 -0400
Subject: [PATCH] [glsl-out] emit sample variables extension

---
 src/back/glsl/features.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/back/glsl/features.rs b/src/back/glsl/features.rs
index b78352fdea..7b99c9c22b 100644
--- a/src/back/glsl/features.rs
+++ b/src/back/glsl/features.rs
@@ -30,6 +30,8 @@ bitflags::bitflags! {
         const SAMPLE_QUALIFIER = 1 << 12;
         const CLIP_DISTANCE = 1 << 13;
         const CULL_DISTANCE = 1 << 14;
+        // Sample ID
+        const SAMPLE_VARIABLES = 1 << 15;
     }
 }
 
@@ -95,6 +97,7 @@ impl FeaturesManager {
         // gl_ClipDistance is supported by core versions > 1.3 and aren't supported by an es versions without extensions
         check_feature!(CLIP_DISTANCE, 130, 300);
         check_feature!(CULL_DISTANCE, 450, 300);
+        check_feature!(SAMPLE_VARIABLES, 300, 300);
 
         // Return an error if there are missing features
         if missing.is_empty() {
@@ -183,6 +186,11 @@ impl FeaturesManager {
             // writeln!(out, "#extension GL_EXT_clip_cull_distance : require")?;
         }
 
+        if self.0.contains(Features::SAMPLE_VARIABLES) && version.is_es() {
+            // https://www.khronos.org/registry/OpenGL/extensions/OES/OES_sample_variables.txt
+            writeln!(out, "#extension GL_OES_sample_variables : require")?;
+        }
+
         Ok(())
     }
 }
@@ -310,6 +318,9 @@ impl<'a, W> Writer<'a, W> {
                             crate::BuiltIn::CullDistance => {
                                 self.features.request(Features::CULL_DISTANCE)
                             }
+                            crate::BuiltIn::SampleIndex => {
+                                self.features.request(Features::SAMPLE_VARIABLES)
+                            }
                             _ => {}
                         },
                         Binding::Location {