3 files changed, 76 insertions, 2 deletions

diff --git a/components/script/dom/webgl_extensions/ext/extfragdepth.rs b/components/script/dom/webgl_extensions/ext/extfragdepth.rs
new file mode 100644
index 00000000000..182b30bf754
--- /dev/null
+++ b/components/script/dom/webgl_extensions/ext/extfragdepth.rs
@@ -0,0 +1,62 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use super::{WebGLExtension, WebGLExtensionSpec, WebGLExtensions};
+use crate::dom::bindings::reflector::{reflect_dom_object, DomObject, Reflector};
+use crate::dom::bindings::root::DomRoot;
+use crate::dom::webglrenderingcontext::WebGLRenderingContext;
+use canvas_traits::webgl::{WebGLSLVersion, WebGLVersion};
+use dom_struct::dom_struct;
+
+#[dom_struct]
+pub struct EXTFragDepth {
+    reflector_: Reflector,
+}
+
+impl EXTFragDepth {
+    fn new_inherited() -> EXTFragDepth {
+        Self {
+            reflector_: Reflector::new(),
+        }
+    }
+}
+
+impl WebGLExtension for EXTFragDepth {
+    type Extension = Self;
+
+    fn new(ctx: &WebGLRenderingContext) -> DomRoot<Self> {
+        reflect_dom_object(Box::new(Self::new_inherited()), &*ctx.global())
+    }
+
+    fn spec() -> WebGLExtensionSpec {
+        WebGLExtensionSpec::Specific(WebGLVersion::WebGL1)
+    }
+
+    fn is_supported(ext: &WebGLExtensions) -> bool {
+        let min_glsl_version = if ext.is_gles() {
+            WebGLSLVersion { major: 3, minor: 0 }
+        } else {
+            WebGLSLVersion {
+                major: 1,
+                minor: 10,
+            }
+        };
+        match (
+            ext.is_gles(),
+            ext.is_min_glsl_version_satisfied(min_glsl_version),
+        ) {
+            // ANGLE's shader translator can't translate ESSL1 exts to ESSL3. (bug
+            // 1524804)
+            (true, true) => false,
+            (true, false) => ext.supports_gl_extension("GL_EXT_frag_depth"),
+            (false, is_min_glsl_version_satisfied) => is_min_glsl_version_satisfied,
+        }
+    }
+
+    fn enable(_ext: &WebGLExtensions) {}
+
+    fn name() -> &'static str {
+        "EXT_frag_depth"
+    }
+}
diff --git a/components/script/dom/webgl_extensions/ext/mod.rs b/components/script/dom/webgl_extensions/ext/mod.rs
index e2bba1c713f..229d09d56f5 100644
--- a/components/script/dom/webgl_extensions/ext/mod.rs
+++ b/components/script/dom/webgl_extensions/ext/mod.rs
@@ -8,6 +8,7 @@ use crate::dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGL
 pub mod angleinstancedarrays;
 pub mod extblendminmax;
 pub mod extcolorbufferhalffloat;
+pub mod extfragdepth;
 pub mod extshadertexturelod;
 pub mod exttexturefilteranisotropic;
 pub mod oeselementindexuint;
diff --git a/components/script/dom/webgl_extensions/extensions.rs b/components/script/dom/webgl_extensions/extensions.rs
index 9609dea88ad..3a3ec2591b3 100644
--- a/components/script/dom/webgl_extensions/extensions.rs
+++ b/components/script/dom/webgl_extensions/extensions.rs
@@ -18,7 +18,7 @@ use crate::dom::oestexturehalffloat::OESTextureHalfFloat;
 use crate::dom::webglcolorbufferfloat::WEBGLColorBufferFloat;
 use crate::dom::webglrenderingcontext::WebGLRenderingContext;
 use crate::dom::webgltexture::TexCompression;
-use canvas_traits::webgl::{GlType, TexFormat, WebGLVersion};
+use canvas_traits::webgl::{GlType, TexFormat, WebGLSLVersion, WebGLVersion};
 use fnv::{FnvHashMap, FnvHashSet};
 use js::jsapi::JSObject;
 use malloc_size_of::MallocSizeOf;
@@ -165,15 +165,21 @@ pub struct WebGLExtensions {
     features: DomRefCell<WebGLExtensionFeatures>,
     webgl_version: WebGLVersion,
     api_type: GlType,
+    glsl_version: WebGLSLVersion,
 }
 
 impl WebGLExtensions {
-    pub fn new(webgl_version: WebGLVersion, api_type: GlType) -> WebGLExtensions {
+    pub fn new(
+        webgl_version: WebGLVersion,
+        api_type: GlType,
+        glsl_version: WebGLSLVersion,
+    ) -> WebGLExtensions {
         Self {
             extensions: DomRefCell::new(HashMap::new()),
             features: DomRefCell::new(WebGLExtensionFeatures::new(webgl_version)),
             webgl_version,
             api_type,
+            glsl_version,
         }
     }
 
@@ -399,6 +405,7 @@ impl WebGLExtensions {
         self.register::<ext::angleinstancedarrays::ANGLEInstancedArrays>();
         self.register::<ext::extblendminmax::EXTBlendMinmax>();
         self.register::<ext::extcolorbufferhalffloat::EXTColorBufferHalfFloat>();
+        self.register::<ext::extfragdepth::EXTFragDepth>();
         self.register::<ext::extshadertexturelod::EXTShaderTextureLod>();
         self.register::<ext::exttexturefilteranisotropic::EXTTextureFilterAnisotropic>();
         self.register::<ext::oeselementindexuint::OESElementIndexUint>();
@@ -433,6 +440,10 @@ impl WebGLExtensions {
         self.is_enabled::<WEBGLColorBufferFloat>() || self.is_enabled::<OESTextureFloat>()
     }
 
+    pub fn is_min_glsl_version_satisfied(&self, min_glsl_version: WebGLSLVersion) -> bool {
+        self.glsl_version >= min_glsl_version
+    }
+
     pub fn is_half_float_buffer_renderable(&self) -> bool {
         self.is_enabled::<EXTColorBufferHalfFloat>() || self.is_enabled::<OESTextureHalfFloat>()
     }