Auto merge of #16893 - MortimerGoro:webgl_extensions, r=emilio

Implement WebGL extensions

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This PR provides the base for implementing WebGL extensions. It comes with the following ones already implemented and passing all related WebGL conformance tests:

- OES_texture_float
- OES_texture_float_linear
- OES_texture_half_float
- OES_texture_half_float_linear
- OES_vertex_array_object

I'll submit other extensions like compressed textures in a separate PR to ease the review process. I included the 5 extensions in this PR because it's easier to show/review how the WebGL extension base works.

To pass all OES_texture_float_xxx tests I had to add some missing format conversions in WebGLRenderingContext.rs

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- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [x] There are tests for these changes OR
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1 files changed, 166 insertions, 0 deletions

diff --git a/components/script/dom/webgl_extensions/ext/oesvertexarrayobject.rs b/components/script/dom/webgl_extensions/ext/oesvertexarrayobject.rs
new file mode 100644
index 00000000000..596af11ceff
--- /dev/null
+++ b/components/script/dom/webgl_extensions/ext/oesvertexarrayobject.rs
@@ -0,0 +1,166 @@
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+use canvas_traits::CanvasMsg;
+use dom::bindings::codegen::Bindings::OESVertexArrayObjectBinding::{self, OESVertexArrayObjectMethods};
+use dom::bindings::codegen::Bindings::OESVertexArrayObjectBinding::OESVertexArrayObjectConstants;
+use dom::bindings::js::{JS, MutNullableJS, Root};
+use dom::bindings::reflector::{DomObject, Reflector, reflect_dom_object};
+use dom::webglrenderingcontext::WebGLRenderingContext;
+use dom::webglvertexarrayobjectoes::WebGLVertexArrayObjectOES;
+use dom_struct::dom_struct;
+use js::conversions::ToJSValConvertible;
+use js::jsapi::JSContext;
+use js::jsval::{JSVal, NullValue};
+use std::iter;
+use super::{WebGLExtension, WebGLExtensions};
+use webrender_traits::{self, WebGLCommand, WebGLError};
+
+#[dom_struct]
+pub struct OESVertexArrayObject {
+    reflector_: Reflector,
+    ctx: JS<WebGLRenderingContext>,
+    bound_vao: MutNullableJS<WebGLVertexArrayObjectOES>,
+}
+
+impl OESVertexArrayObject {
+    fn new_inherited(ctx: &WebGLRenderingContext) -> OESVertexArrayObject {
+        Self {
+            reflector_: Reflector::new(),
+            ctx: JS::from_ref(ctx),
+            bound_vao: MutNullableJS::new(None)
+        }
+    }
+
+    #[allow(unsafe_code)]
+    fn get_current_binding(&self, cx:*mut JSContext) -> JSVal {
+        rooted!(in(cx) let mut rval = NullValue());
+        if let Some(bound_vao) = self.bound_vao.get() {
+            unsafe {
+                bound_vao.to_jsval(cx, rval.handle_mut());
+            }
+        }
+        rval.get()
+    }
+}
+
+impl OESVertexArrayObjectMethods for OESVertexArrayObject {
+    // https://www.khronos.org/registry/webgl/extensions/OES_vertex_array_object/
+    fn CreateVertexArrayOES(&self) -> Option<Root<WebGLVertexArrayObjectOES>> {
+        let (sender, receiver) = webrender_traits::channel::msg_channel().unwrap();
+        self.ctx.send_renderer_message(CanvasMsg::WebGL(WebGLCommand::CreateVertexArray(sender)));
+
+        let result = receiver.recv().unwrap();
+        result.map(|vao_id| WebGLVertexArrayObjectOES::new(&self.global(), vao_id))
+    }
+
+    // https://www.khronos.org/registry/webgl/extensions/OES_vertex_array_object/
+    fn DeleteVertexArrayOES(&self, vao: Option<&WebGLVertexArrayObjectOES>) {
+        if let Some(vao) = vao {
+            if vao.is_deleted() {
+                return;
+            }
+
+            // Unbind deleted VAO if currently bound
+            if let Some(bound_vao) = self.bound_vao.get() {
+                if bound_vao.id() == vao.id() {
+                    self.bound_vao.set(None);
+                    self.ctx.send_renderer_message(CanvasMsg::WebGL(WebGLCommand::BindVertexArray(None)));
+                }
+            }
+
+            // Remove VAO references from buffers
+            let buffers = vao.bound_attrib_buffers();
+            for buffer in buffers {
+                buffer.remove_vao_reference(vao.id());
+            }
+            if let Some(buffer) = vao.bound_buffer_element_array() {
+                buffer.remove_vao_reference(vao.id());
+            }
+
+            // Delete the vao
+            self.ctx.send_renderer_message(CanvasMsg::WebGL(WebGLCommand::DeleteVertexArray(vao.id())));
+            vao.set_deleted();
+        }
+    }
+
+    // https://www.khronos.org/registry/webgl/extensions/OES_vertex_array_object/
+    fn IsVertexArrayOES(&self, vao: Option<&WebGLVertexArrayObjectOES>) -> bool {
+        // Conformance tests expect false if vao never bound
+        vao.map_or(false, |vao| !vao.is_deleted() && vao.ever_bound())
+    }
+
+    // https://www.khronos.org/registry/webgl/extensions/OES_vertex_array_object/
+    fn BindVertexArrayOES(&self, vao: Option<&WebGLVertexArrayObjectOES>) {
+        if let Some(bound_vao) = self.bound_vao.get() {
+            // Store buffers attached to attrib pointers
+            let buffers = self.ctx.borrow_bound_attrib_buffers();
+            bound_vao.set_bound_attrib_buffers(buffers.iter().map(|(key, buffer)| {
+                (*buffer).add_vao_reference(bound_vao.id());
+                (*key, &**buffer)
+            }));
+            // Store element array buffer
+            let element_array = self.ctx.bound_buffer_element_array();
+            bound_vao.set_bound_buffer_element_array(element_array.as_ref().map(|buffer| {
+                buffer.add_vao_reference(bound_vao.id());
+                &**buffer
+            }));
+        }
+
+        if let Some(vao) = vao {
+            if vao.is_deleted() {
+                self.ctx.webgl_error(WebGLError::InvalidOperation);
+                return;
+            }
+
+            self.ctx.send_renderer_message(CanvasMsg::WebGL(WebGLCommand::BindVertexArray(Some(vao.id()))));
+            vao.set_ever_bound();
+            self.bound_vao.set(Some(&vao));
+
+            // Restore WebGLRenderingContext current bindings
+            let buffers = vao.borrow_bound_attrib_buffers();
+            self.ctx.set_bound_attrib_buffers(buffers.iter().map(|(k, v)| (*k, &**v)));
+            let element_array = vao.bound_buffer_element_array();
+            self.ctx.set_bound_buffer_element_array(element_array.as_ref().map(|buffer| &**buffer));
+        } else {
+            self.ctx.send_renderer_message(CanvasMsg::WebGL(WebGLCommand::BindVertexArray(None)));
+            self.bound_vao.set(None);
+            self.ctx.set_bound_attrib_buffers(iter::empty());
+        }
+    }
+}
+
+impl WebGLExtension for OESVertexArrayObject {
+    type Extension = OESVertexArrayObject;
+    fn new(ctx: &WebGLRenderingContext) -> Root<OESVertexArrayObject> {
+        reflect_dom_object(box OESVertexArrayObject::new_inherited(ctx),
+                           &*ctx.global(),
+                           OESVertexArrayObjectBinding::Wrap)
+    }
+
+    fn is_supported(ext: &WebGLExtensions) -> bool {
+        ext.supports_any_gl_extension(&["GL_OES_vertex_array_object",
+                                        "GL_ARB_vertex_array_object",
+                                        "GL_APPLE_vertex_array_object"])
+    }
+
+    fn enable(ext: &WebGLExtensions) {
+        let query = OESVertexArrayObjectConstants::VERTEX_ARRAY_BINDING_OES;
+        ext.add_query_parameter_handler(query, Box::new(|cx, webgl_ctx| {
+            match webgl_ctx.get_extension_manager().get_dom_object::<OESVertexArrayObject>() {
+                Some(dom_object) => {
+                    Ok(dom_object.get_current_binding(cx))
+                },
+                None => {
+                    // Extension instance not found!
+                    Err(WebGLError::InvalidOperation)
+                }
+            }
+        }));
+    }
+
+    fn name() -> &'static str {
+        "OES_vertex_array_object"
+    }
+}