Auto merge of #20317 - gootorov:webgl-getFramebufferAttachmentParameter, r=jdm

Implement WebGL getFrameBufferAttachmentParameter API

<!-- Please describe your changes on the following line: -->
Implementation of `getFramebufferAttachmentParameter` as in WebGL1 specification.

Part of https://github.com/servo/servo/issues/10209.

r? emilio or jdm.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

<!-- Either: -->
- [x] There are tests for these changes

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- 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/20317)
<!-- Reviewable:end -->

1 files changed, 14 insertions, 0 deletions

diff --git a/components/canvas/webgl_thread.rs b/components/canvas/webgl_thread.rs
index e27d85c4395..785df7fd6c2 100644
--- a/components/canvas/webgl_thread.rs
+++ b/components/canvas/webgl_thread.rs
@@ -750,6 +750,8 @@ impl WebGLImpl {
                 Self::active_uniform(ctx.gl(), program_id, index, chan),
             WebGLCommand::GetAttribLocation(program_id, name, chan) =>
                 Self::attrib_location(ctx.gl(), program_id, name, chan),
+            WebGLCommand::GetFramebufferAttachmentParameter(target, attachment, pname, chan) =>
+                Self::get_framebuffer_attachment_parameter(ctx.gl(), target, attachment, pname, chan),
             WebGLCommand::GetVertexAttrib(index, pname, chan) =>
                 Self::vertex_attrib(ctx.gl(), index, pname, chan),
             WebGLCommand::GetVertexAttribOffset(index, pname, chan) =>
@@ -1165,6 +1167,18 @@ impl WebGLImpl {
         chan.send(gl.get_string(gl::EXTENSIONS)).unwrap();
     }
 
+    // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.6
+    fn get_framebuffer_attachment_parameter(
+        gl: &gl::Gl,
+        target: u32,
+        attachment: u32,
+        pname: u32,
+        chan: WebGLSender<i32>
+    ) {
+        let parameter = gl.get_framebuffer_attachment_parameter_iv(target, attachment, pname);
+        chan.send(parameter).unwrap();
+    }
+
     fn uniform_location(gl: &gl::Gl,
                         program_id: WebGLProgramId,
                         name: String,