From 3965df80883b76568f949f38170e6c645577114d Mon Sep 17 00:00:00 2001
From: Nicolas Silva <nical@fastmail.com>
Date: Fri, 16 Nov 2018 11:07:51 +0100
Subject: [PATCH] Add debug checks for some global GL states.

---
 webrender/src/device/gl.rs | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/webrender/src/device/gl.rs b/webrender/src/device/gl.rs
index 8731daddc8..3d8eacf91c 100644
--- a/webrender/src/device/gl.rs
+++ b/webrender/src/device/gl.rs
@@ -1020,6 +1020,11 @@ impl Device {
             )
         };
 
+        // Explicitly set some global states to the values we expect.
+        gl.disable(gl::FRAMEBUFFER_SRGB);
+        gl.disable(gl::MULTISAMPLE);
+        gl.disable(gl::POLYGON_SMOOTH);
+
         Device {
             gl,
             resource_override_path,
@@ -1152,10 +1157,20 @@ impl Device {
         }
     }
 
+    // If an assertion is hit in this function, something outside of WebRender is likely
+    // messing with the GL context's global state.
+    pub fn check_gl_state(&self) {
+        debug_assert!(self.gl.is_enabled(gl::FRAMEBUFFER_SRGB) == 0);
+        debug_assert!(self.gl.is_enabled(gl::MULTISAMPLE) == 0);
+        debug_assert!(self.gl.is_enabled(gl::POLYGON_SMOOTH) == 0);
+    }
+
     pub fn begin_frame(&mut self) -> GpuFrameId {
         debug_assert!(!self.inside_frame);
         self.inside_frame = true;
 
+        self.check_gl_state();
+
         // Retrieve the currently set FBO.
         let mut default_read_fbo = [0];
         unsafe {