Auto merge of #21461 - jdm:webgltmp2, r=nox

Various webgl fixes for framebuffer attachment test

These changes resolve all panics on macOS when running framebuffer-object-attachment.html in headless and headful testing.

---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] There are tests for these changes OR
- [x] Fixes #13710. Fixes #20570.

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/21461)
<!-- Reviewable:end -->

1 files changed, 31 insertions, 32 deletions

diff --git a/components/script/dom/webglrenderingcontext.rs b/components/script/dom/webglrenderingcontext.rs
index ab7178ffa16..ea45fd69ce5 100644
--- a/components/script/dom/webglrenderingcontext.rs
+++ b/components/script/dom/webglrenderingcontext.rs
@@ -39,7 +39,7 @@ use dom::webgl_validations::types::{TexDataType, TexFormat, TexImageTarget};
 use dom::webglactiveinfo::WebGLActiveInfo;
 use dom::webglbuffer::WebGLBuffer;
 use dom::webglcontextevent::WebGLContextEvent;
-use dom::webglframebuffer::{WebGLFramebuffer, WebGLFramebufferAttachmentRoot};
+use dom::webglframebuffer::{WebGLFramebuffer, WebGLFramebufferAttachmentRoot, CompleteForRendering};
 use dom::webglobject::WebGLObject;
 use dom::webglprogram::WebGLProgram;
 use dom::webglrenderbuffer::WebGLRenderbuffer;
@@ -339,10 +339,14 @@ impl WebGLRenderingContext {
     // this: clear() and getParameter(IMPLEMENTATION_COLOR_READ_*).
     fn validate_framebuffer(&self) -> WebGLResult<()> {
         match self.bound_framebuffer.get() {
-            Some(ref fb) if fb.check_status() != constants::FRAMEBUFFER_COMPLETE => {
-                Err(InvalidFramebufferOperation)
+            Some(fb) => match fb.check_status_for_rendering() {
+                CompleteForRendering::Complete => Ok(()),
+                CompleteForRendering::Incomplete =>
+                    Err(InvalidFramebufferOperation),
+                CompleteForRendering::MissingColorAttachment =>
+                    Err(InvalidOperation),
             },
-            _ => Ok(()),
+            None => Ok(()),
         }
     }
 
@@ -1057,6 +1061,21 @@ impl WebGLRenderingContext {
             _ => Err(InvalidEnum),
         }
     }
+
+    pub fn initialize_framebuffer(&self, clear_bits: u32) {
+        if clear_bits == 0 {
+            return;
+        }
+        self.send_command(WebGLCommand::InitializeFramebuffer {
+            color: clear_bits & constants::COLOR_BUFFER_BIT != 0,
+            depth: clear_bits & constants::DEPTH_BUFFER_BIT != 0,
+            stencil: clear_bits & constants::STENCIL_BUFFER_BIT != 0,
+        });
+    }
+
+    pub fn bound_framebuffer(&self) -> Option<DomRoot<WebGLFramebuffer>> {
+        self.bound_framebuffer.get()
+    }
 }
 
 impl Drop for WebGLRenderingContext {
@@ -1572,6 +1591,10 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
                 renderbuffer.bind(target);
             }
             _ => {
+                if renderbuffer.is_some() {
+                    self.webgl_error(InvalidOperation);
+                }
+
                 self.bound_renderbuffer.set(None);
                 // Unbind the currently bound renderbuffer
                 self.send_command(WebGLCommand::BindRenderbuffer(target, None));
@@ -1971,20 +1994,6 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
             handle_potential_webgl_error!(self, self.validate_ownership(renderbuffer), return);
             handle_object_deletion!(self, self.bound_renderbuffer, renderbuffer,
                                     Some(WebGLCommand::BindRenderbuffer(constants::RENDERBUFFER, None)));
-            // From the GLES 2.0.25 spec, page 113:
-            //
-            //     "If a renderbuffer object is deleted while its
-            //     image is attached to the currently bound
-            //     framebuffer, then it is as if
-            //     FramebufferRenderbuffer had been called, with a
-            //     renderbuffer of 0, for each attachment point to
-            //     which this image was attached in the currently
-            //     bound framebuffer."
-            //
-            if let Some(fb) = self.bound_framebuffer.get() {
-                fb.detach_renderbuffer(renderbuffer);
-            }
-
             renderbuffer.delete()
         }
     }
@@ -2020,18 +2029,6 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
                 ));
             }
 
-            // From the GLES 2.0.25 spec, page 113:
-            //
-            //     "If a texture object is deleted while its image is
-            //      attached to the currently bound framebuffer, then
-            //      it is as if FramebufferTexture2D had been called,
-            //      with a texture of 0, for each attachment point to
-            //      which this image was attached in the currently
-            //      bound framebuffer."
-            if let Some(fb) = self.bound_framebuffer.get() {
-                fb.detach_texture(texture);
-            }
-
             texture.delete()
         }
     }
@@ -2723,10 +2720,12 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.3
     fn StencilMaskSeparate(&self, face: u32, mask: u32) {
         match face {
-            constants::FRONT | constants::BACK | constants::FRONT_AND_BACK =>
+            constants::FRONT |
+            constants::BACK |
+            constants::FRONT_AND_BACK =>
                 self.send_command(WebGLCommand::StencilMaskSeparate(face, mask)),
             _ => return self.webgl_error(InvalidEnum),
-        }
+        };
     }
 
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.3