webgl: Add support for renderbufferStorage().

This is not a complete implementation yet: It doesn't clear the
contents of the renderbuffer on creation.  However, Gecko's plan to
only clear renderbuffers when the first FBO using them is the
simplest.

components/script/dom/webglrenderbuffer.rs

@@ -5,13 +5,14 @@
 // https://www.khronos.org/registry/webgl/specs/latest/1.0/webgl.idl
 use canvas_traits::CanvasMsg;
 use dom::bindings::codegen::Bindings::WebGLRenderbufferBinding;
+use dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGLRenderingContextConstants as constants;
 use dom::bindings::js::Root;
 use dom::bindings::reflector::reflect_dom_object;
 use dom::globalscope::GlobalScope;
 use dom::webglobject::WebGLObject;
 use ipc_channel::ipc::{self, IpcSender};
 use std::cell::Cell;
-use webrender_traits::{WebGLCommand, WebGLRenderbufferId};
+use webrender_traits::{WebGLCommand, WebGLRenderbufferId, WebGLResult, WebGLError};
 
 #[dom_struct]
 pub struct WebGLRenderbuffer {
@@ -19,6 +20,7 @@ pub struct WebGLRenderbuffer {
     id: WebGLRenderbufferId,
     ever_bound: Cell<bool>,
     is_deleted: Cell<bool>,
+    internal_format: Cell<Option<u32>>,
     #[ignore_heap_size_of = "Defined in ipc-channel"]
     renderer: IpcSender<CanvasMsg>,
 }
@@ -33,6 +35,7 @@ impl WebGLRenderbuffer {
             ever_bound: Cell::new(false),
             is_deleted: Cell::new(false),
             renderer: renderer,
+            internal_format: Cell::new(None),
         }
     }
 
@@ -81,4 +84,28 @@ impl WebGLRenderbuffer {
     pub fn ever_bound(&self) -> bool {
         self.ever_bound.get()
     }
+
+    pub fn storage(&self, internal_format: u32, width: i32, height: i32) -> WebGLResult<()> {
+        // Validate the internal_format, and save it for completeness
+        // validation.
+        match internal_format {
+            constants::RGBA4 |
+            constants::DEPTH_STENCIL |
+            constants::DEPTH_COMPONENT16 |
+            constants::STENCIL_INDEX8 =>
+                self.internal_format.set(Some(internal_format)),
+
+            _ => return Err(WebGLError::InvalidEnum),
+        };
+
+        // FIXME: Check that w/h are < MAX_RENDERBUFFER_SIZE
+
+        // FIXME: Invalidate completeness after the call
+
+        let msg = CanvasMsg::WebGL(WebGLCommand::RenderbufferStorage(constants::RENDERBUFFER,
+                                                                     internal_format, width, height));
+        self.renderer.send(msg).unwrap();
+
+        Ok(())
+    }
 }

components/script/dom/webglrenderingcontext.rs

@@ -2569,6 +2569,39 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
             None => return constants::FRAMEBUFFER_COMPLETE,
         }
     }
+
+    fn RenderbufferStorage(&self, target: u32, internal_format: u32,
+                           width: i32, height: i32) {
+        // From the GLES 2.0.25 spec:
+        //
+        //    "target must be RENDERBUFFER."
+        if target != constants::RENDERBUFFER {
+            return self.webgl_error(InvalidOperation)
+        }
+
+        // From the GLES 2.0.25 spec:
+        //
+        //     "If either width or height is greater than the value of
+        //      MAX_RENDERBUFFER_SIZE , the error INVALID_VALUE is
+        //      generated."
+        //
+        // and we have to throw out negative-size values as well just
+        // like for TexImage.
+        //
+        // FIXME: Handle max_renderbuffer_size, which doesn't seem to
+        // be in limits.
+        if width < 0 || height < 0 {
+            return self.webgl_error(InvalidValue);
+        }
+
+        match self.bound_renderbuffer.get() {
+            Some(rb) => handle_potential_webgl_error!(self, rb.storage(internal_format, width, height)),
+            None => self.webgl_error(InvalidOperation),
+        };
+
+        // FIXME: We need to clear the renderbuffer before it can be
+        // accessed.  See https://github.com/servo/servo/issues/13710
+    }
 }
 
 pub trait LayoutCanvasWebGLRenderingContextHelpers {

components/script/dom/webidls/WebGLRenderingContext.webidl

@@ -626,8 +626,8 @@ interface WebGLRenderingContextBase
     void readPixels(GLint x, GLint y, GLsizei width, GLsizei height,
                     GLenum format, GLenum type, object? pixels);
 
-    //void renderbufferStorage(GLenum target, GLenum internalformat,
-    //                         GLsizei width, GLsizei height);
+    void renderbufferStorage(GLenum target, GLenum internalformat,
+                             GLsizei width, GLsizei height);
     void sampleCoverage(GLclampf value, GLboolean invert);
     void scissor(GLint x, GLint y, GLsizei width, GLsizei height);