Add Support for WebGL Transormfeedback

Reference: https://www.khronos.org/registry/webgl/specs/latest/2.0/#3.7.15

components/canvas/webgl_limits.rs

@@ -20,6 +20,8 @@ impl GLLimitsDetect for GLLimits {
         let max_renderbuffer_size = gl.get_integer(gl::MAX_RENDERBUFFER_SIZE);
         let max_texture_image_units = gl.get_integer(gl::MAX_TEXTURE_IMAGE_UNITS);
         let max_vertex_texture_image_units = gl.get_integer(gl::MAX_VERTEX_TEXTURE_IMAGE_UNITS);
+        let max_transform_feedback_separate_attribs =
+            gl.get_integer(gl::MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS);
 
         // TODO: better value for this?
         let max_client_wait_timeout_webgl = std::time::Duration::new(1, 0);
@@ -67,6 +69,7 @@ impl GLLimitsDetect for GLLimits {
             max_vertex_texture_image_units,
             max_vertex_uniform_vectors,
             max_client_wait_timeout_webgl,
+            max_transform_feedback_separate_attribs,
         }
     }
 }

components/canvas/webgl_thread.rs

@@ -1180,6 +1180,41 @@ impl WebGLImpl {
             WebGLCommand::GetRenderbufferParameter(target, pname, ref chan) => {
                 Self::get_renderbuffer_parameter(gl, target, pname, chan)
             },
+            WebGLCommand::CreateTransformFeedback(ref sender) => {
+                let value = gl.gen_transform_feedbacks();
+                sender.send(value).unwrap()
+            },
+            WebGLCommand::DeleteTransformFeedback(id) => {
+                gl.delete_transform_feedbacks(id);
+            },
+            WebGLCommand::IsTransformFeedback(id, ref sender) => {
+                let value = gl.is_transform_feedback(id);
+                sender.send(value).unwrap()
+            },
+            WebGLCommand::BindTransformFeedback(target, id) => {
+                gl.bind_transform_feedback(target, id);
+            },
+            WebGLCommand::BeginTransformFeedback(mode) => {
+                gl.begin_transform_feedback(mode);
+            },
+            WebGLCommand::EndTransformFeedback() => {
+                gl.end_transform_feedback();
+            },
+            WebGLCommand::PauseTransformFeedback() => {
+                gl.pause_transform_feedback();
+            },
+            WebGLCommand::ResumeTransformFeedback() => {
+                gl.resume_transform_feedback();
+            },
+            WebGLCommand::GetTransformFeedbackVarying(program, index, ref sender) => {
+                let (size, ty, mut name) = gl.get_transform_feedback_varying(program.get(), index);
+                // We need to split, because the name starts with '_u' prefix.
+                name = name.split_off(2);
+                sender.send((size, ty, name)).unwrap();
+            },
+            WebGLCommand::TransformFeedbackVaryings(program, ref varyings, buffer_mode) => {
+                gl.transform_feedback_varyings(program.get(), varyings.as_slice(), buffer_mode);
+            },
             WebGLCommand::GetFramebufferAttachmentParameter(
                 target,
                 attachment,
@@ -1814,9 +1849,10 @@ impl WebGLImpl {
                 linked: false,
                 active_attribs: vec![].into(),
                 active_uniforms: vec![].into(),
+                transform_feedback_length: Default::default(),
+                transform_feedback_mode: Default::default(),
             };
         }
-
         let mut num_active_attribs = [0];
         unsafe {
             gl.get_program_iv(
@@ -1868,11 +1904,28 @@ impl WebGLImpl {
             })
             .collect::<Vec<_>>()
             .into();
-
+        let mut transform_feedback_length = [0];
+        unsafe {
+            gl.get_program_iv(
+                program.get(),
+                gl::TRANSFORM_FEEDBACK_VARYINGS,
+                &mut transform_feedback_length,
+            );
+        }
+        let mut transform_feedback_mode = [0];
+        unsafe {
+            gl.get_program_iv(
+                program.get(),
+                gl::TRANSFORM_FEEDBACK_BUFFER_MODE,
+                &mut transform_feedback_mode,
+            );
+        }
         ProgramLinkInfo {
             linked: true,
             active_attribs,
             active_uniforms,
+            transform_feedback_length: transform_feedback_length[0],
+            transform_feedback_mode: transform_feedback_mode[0],
         }
     }
 

components/canvas_traits/webgl.rs

@@ -292,6 +292,16 @@ pub enum WebGLCommand {
     GetProgramInfoLog(WebGLProgramId, WebGLSender<String>),
     GetFramebufferAttachmentParameter(u32, u32, u32, WebGLSender<i32>),
     GetRenderbufferParameter(u32, u32, WebGLSender<i32>),
+    CreateTransformFeedback(WebGLSender<u32>),
+    DeleteTransformFeedback(u32),
+    IsTransformFeedback(u32, WebGLSender<bool>),
+    BindTransformFeedback(u32, u32),
+    BeginTransformFeedback(u32),
+    EndTransformFeedback(),
+    PauseTransformFeedback(),
+    ResumeTransformFeedback(),
+    GetTransformFeedbackVarying(WebGLProgramId, u32, WebGLSender<(i32, u32, String)>),
+    TransformFeedbackVaryings(WebGLProgramId, Vec<String>, u32),
     PolygonOffset(f32, f32),
     RenderbufferStorage(u32, u32, i32, i32),
     ReadPixels(Rect<u32>, u32, u32, IpcBytesSender),
@@ -660,6 +670,10 @@ pub struct ProgramLinkInfo {
     pub active_attribs: Box<[ActiveAttribInfo]>,
     /// The list of active uniforms.
     pub active_uniforms: Box<[ActiveUniformInfo]>,
+    /// The number of varying variables
+    pub transform_feedback_length: i32,
+    /// The buffer mode used when transform feedback is active
+    pub transform_feedback_mode: i32,
 }
 
 /// Description of a single active attribute.
@@ -733,6 +747,8 @@ parameters! {
         Bool(ParameterBool {
             DepthWritemask = gl::DEPTH_WRITEMASK,
             SampleCoverageInvert = gl::SAMPLE_COVERAGE_INVERT,
+            TransformFeedbackActive = gl::TRANSFORM_FEEDBACK_ACTIVE,
+            TransformFeedbackPaused = gl::TRANSFORM_FEEDBACK_PAUSED,
         }),
         Bool4(ParameterBool4 {
             ColorWritemask = gl::COLOR_WRITEMASK,
@@ -774,6 +790,12 @@ parameters! {
             StencilValueMask = gl::STENCIL_VALUE_MASK,
             StencilWritemask = gl::STENCIL_WRITEMASK,
             SubpixelBits = gl::SUBPIXEL_BITS,
+            TransformFeedbackBinding = gl::TRANSFORM_FEEDBACK_BINDING,
+            MaxTransformFeedbackInterleavedComponents = gl::MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS,
+            MaxTransformFeedbackSeparateAttribs = gl::MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS,
+            MaxTransformFeedbackSeparateComponents = gl::MAX_TRANSFORM_FEEDBACK_SEPARATE_COMPONENTS,
+            TransformFeedbackBufferSize = gl::TRANSFORM_FEEDBACK_BUFFER_SIZE,
+            TransformFeedbackBufferStart = gl::TRANSFORM_FEEDBACK_BUFFER_START,
         }),
         Int2(ParameterInt2 {
             MaxViewportDims = gl::MAX_VIEWPORT_DIMS,
@@ -968,4 +990,5 @@ pub struct GLLimits {
     pub max_vertex_texture_image_units: u32,
     pub max_vertex_uniform_vectors: u32,
     pub max_client_wait_timeout_webgl: std::time::Duration,
+    pub max_transform_feedback_separate_attribs: u32,
 }

components/script/dom/mod.rs

@@ -532,6 +532,7 @@ pub mod webglshader;
 pub mod webglshaderprecisionformat;
 pub mod webglsync;
 pub mod webgltexture;
+pub mod webgltransformfeedback;
 pub mod webgluniformlocation;
 pub mod webglvertexarrayobjectoes;
 pub mod websocket;