Add support for WebGL2 framebuffer invalidation

Adds support for the `invalidateFramebuffer` and `invalideSubFramebuffer`
WebGL2 calls.

See: https://www.khronos.org/registry/webgl/specs/latest/2.0/#3.7.4

components/canvas/Cargo.toml

@@ -35,7 +35,7 @@ raqote = {git = "https://github.com/jrmuizel/raqote"}
 time = { version = "0.1.0", optional = true }
 pixels = {path = "../pixels"}
 servo_config = {path = "../config"}
-sparkle = "0.1.17"
+sparkle = "0.1.19"
 webrender = {git = "https://github.com/servo/webrender"}
 webrender_api = {git = "https://github.com/servo/webrender"}
 webrender_traits = {path = "../webrender_traits"}

components/canvas/webgl_thread.rs

@@ -1968,6 +1968,12 @@ impl WebGLImpl {
             WebGLCommand::ClearBufferfi(buffer, draw_buffer, depth, stencil) => {
                 gl.clear_buffer_fi(buffer, draw_buffer, depth, stencil)
             },
+            WebGLCommand::InvalidateFramebuffer(target, ref attachments) => {
+                gl.invalidate_framebuffer(target, attachments)
+            },
+            WebGLCommand::InvalidateSubFramebuffer(target, ref attachments, x, y, w, h) => {
+                gl.invalidate_sub_framebuffer(target, attachments, x, y, w, h)
+            },
         }
 
         // If debug asertions are enabled, then check the error state.

components/canvas_traits/webgl.rs

@@ -533,6 +533,8 @@ pub enum WebGLCommand {
     ClearBufferiv(u32, i32, Vec<i32>),
     ClearBufferuiv(u32, i32, Vec<u32>),
     ClearBufferfi(u32, i32, f32, i32),
+    InvalidateFramebuffer(u32, Vec<u32>),
+    InvalidateSubFramebuffer(u32, Vec<u32>, i32, i32, i32, i32),
 }
 
 macro_rules! nonzero_type {

components/script/dom/webgl2renderingcontext.rs

@@ -603,6 +603,51 @@ impl WebGL2RenderingContext {
 
         self.base.send_command(msg(buffer, draw_buffer, array));
     }
+
+    fn valid_fb_attachment_values(&self, target: u32, attachments: &[u32]) -> bool {
+        let fb_slot = match target {
+            constants::FRAMEBUFFER | constants::DRAW_FRAMEBUFFER => {
+                self.base.get_draw_framebuffer_slot()
+            },
+            constants::READ_FRAMEBUFFER => self.base.get_read_framebuffer_slot(),
+            _ => {
+                self.base.webgl_error(InvalidEnum);
+                return false;
+            },
+        };
+
+        if let Some(fb) = fb_slot.get() {
+            if fb.check_status() != constants::FRAMEBUFFER_COMPLETE {
+                return false;
+            }
+
+            for &attachment in attachments {
+                match attachment {
+                    constants::DEPTH_ATTACHMENT |
+                    constants::STENCIL_ATTACHMENT |
+                    constants::DEPTH_STENCIL_ATTACHMENT => {},
+                    constants::COLOR_ATTACHMENT0..=constants::COLOR_ATTACHMENT15 => {
+                        let last_slot = constants::COLOR_ATTACHMENT0 +
+                            self.base.limits().max_color_attachments -
+                            1;
+                        if last_slot < attachment {
+                            return false;
+                        }
+                    },
+                    _ => return false,
+                }
+            }
+        } else {
+            for &attachment in attachments {
+                match attachment {
+                    constants::COLOR | constants::DEPTH | constants::STENCIL => {},
+                    _ => return false,
+                }
+            }
+        }
+
+        true
+    }
 }
 
 impl WebGL2RenderingContextMethods for WebGL2RenderingContext {
@@ -3497,6 +3542,45 @@ impl WebGL2RenderingContextMethods for WebGL2RenderingContext {
             stencil,
         ));
     }
+
+    /// https://www.khronos.org/registry/webgl/specs/latest/2.0/#3.7.4
+    fn InvalidateFramebuffer(&self, target: u32, attachments: Vec<u32>) {
+        if !self.valid_fb_attachment_values(target, &attachments) {
+            return;
+        }
+
+        self.base
+            .send_command(WebGLCommand::InvalidateFramebuffer(target, attachments))
+    }
+
+    /// https://www.khronos.org/registry/webgl/specs/latest/2.0/#3.7.4
+    fn InvalidateSubFramebuffer(
+        &self,
+        target: u32,
+        attachments: Vec<u32>,
+        x: i32,
+        y: i32,
+        width: i32,
+        height: i32,
+    ) {
+        if !self.valid_fb_attachment_values(target, &attachments) {
+            return;
+        }
+
+        if width < 0 || height < 0 {
+            return;
+        }
+
+        self.base
+            .send_command(WebGLCommand::InvalidateSubFramebuffer(
+                target,
+                attachments,
+                x,
+                y,
+                width,
+                height,
+            ))
+    }
 }
 
 impl LayoutCanvasWebGLRenderingContextHelpers for LayoutDom<WebGL2RenderingContext> {

components/script/dom/webidls/WebGL2RenderingContext.webidl

@@ -314,9 +314,9 @@ interface mixin WebGL2RenderingContextBase
   //                      GLint dstX1, GLint dstY1, GLbitfield mask, GLenum filter);
   // void framebufferTextureLayer(GLenum target, GLenum attachment, WebGLTexture? texture, GLint level,
   //                              GLint layer);
-  // void invalidateFramebuffer(GLenum target, sequence<GLenum> attachments);
-  // void invalidateSubFramebuffer(GLenum target, sequence<GLenum> attachments,
-  //                               GLint x, GLint y, GLsizei width, GLsizei height);
+  void invalidateFramebuffer(GLenum target, sequence<GLenum> attachments);
+  void invalidateSubFramebuffer(GLenum target, sequence<GLenum> attachments,
+                                GLint x, GLint y, GLsizei width, GLsizei height);
   // void readBuffer(GLenum src);
 
   /* Renderbuffer objects */