Auto merge of #13309 - anholt:webgl-fbo-prep, r=emilio

webgl: FBO support preparation

<!-- Please describe your changes on the following line: -->
Sending this PR now so that we can get the webrender patches merged.  This is prep for the webgl-fbo series, with one small fix for some conformance tests.

---
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- [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).

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- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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13 files changed, 128 insertions, 48 deletions

diff --git a/components/layout/webrender_helpers.rs b/components/layout/webrender_helpers.rs
index c6da8f2d105..dacc8278306 100644
--- a/components/layout/webrender_helpers.rs
+++ b/components/layout/webrender_helpers.rs
@@ -427,9 +427,12 @@ impl WebRenderDisplayItemConverter for DisplayItem {
                 if let Some(id) = item.webrender_image.key {
                     if item.stretch_size.width > Au(0) &&
                        item.stretch_size.height > Au(0) {
+                        // TODO(gw): Pass through the tile spacing once the other
+                        //           changes related to this land (parsing etc).
                         builder.push_image(item.base.bounds.to_rectf(),
                                            item.base.clip.to_clip_region(frame_builder),
                                            item.stretch_size.to_sizef(),
+                                           Size2D::zero(),
                                            item.image_rendering.to_image_rendering(),
                                            id);
                     }
diff --git a/components/script/dom/webglframebuffer.rs b/components/script/dom/webglframebuffer.rs
index 6e426fa0969..cd212d644bf 100644
--- a/components/script/dom/webglframebuffer.rs
+++ b/components/script/dom/webglframebuffer.rs
@@ -5,6 +5,7 @@
 // https://www.khronos.org/registry/webgl/specs/latest/1.0/webgl.idl
 use canvas_traits::CanvasMsg;
 use dom::bindings::codegen::Bindings::WebGLFramebufferBinding;
+use dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGLRenderingContextConstants as constants;
 use dom::bindings::global::GlobalRef;
 use dom::bindings::js::Root;
 use dom::bindings::reflector::reflect_dom_object;
@@ -79,6 +80,12 @@ impl WebGLFramebuffer {
         self.is_deleted.get()
     }
 
+    pub fn check_status(&self) -> u32 {
+        // Until we build support for attaching renderbuffers or
+        // textures, all user FBOs are incomplete.
+        return constants::FRAMEBUFFER_UNSUPPORTED;
+    }
+
     pub fn target(&self) -> Option<u32> {
         self.target.get()
     }
diff --git a/components/script/dom/webglrenderingcontext.rs b/components/script/dom/webglrenderingcontext.rs
index 3fc63349634..f42eeab4dbf 100644
--- a/components/script/dom/webglrenderingcontext.rs
+++ b/components/script/dom/webglrenderingcontext.rs
@@ -212,6 +212,38 @@ impl WebGLRenderingContext {
         }
     }
 
+    // Helper function for validating framebuffer completeness in
+    // calls touching the framebuffer.  From the GLES 2.0.25 spec,
+    // page 119:
+    //
+    //    "Effects of Framebuffer Completeness on Framebuffer
+    //     Operations
+    //
+    //     If the currently bound framebuffer is not framebuffer
+    //     complete, then it is an error to attempt to use the
+    //     framebuffer for writing or reading. This means that
+    //     rendering commands such as DrawArrays and DrawElements, as
+    //     well as commands that read the framebuffer such as
+    //     ReadPixels and CopyTexSubImage, will generate the error
+    //     INVALID_FRAMEBUFFER_OPERATION if called while the
+    //     framebuffer is not framebuffer complete."
+    //
+    // The WebGL spec mentions a couple more operations that trigger
+    // this: clear() and getParameter(IMPLEMENTATION_COLOR_READ_*).
+    fn validate_framebuffer_complete(&self) -> bool {
+        match self.bound_framebuffer.get() {
+            Some(fb) => match fb.check_status() {
+                constants::FRAMEBUFFER_COMPLETE => return true,
+                _ => {
+                    self.webgl_error(InvalidFramebufferOperation);
+                    return false;
+                }
+            },
+            // The default framebuffer is always complete.
+            None => return true,
+        }
+    }
+
     fn tex_parameter(&self, target: u32, name: u32, value: TexParameterValue) {
         let texture = match target {
             constants::TEXTURE_2D => self.bound_texture_2d.get(),
@@ -591,6 +623,7 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
         let error_code = if let Some(error) = self.last_error.get() {
             match error {
                 WebGLError::InvalidEnum => constants::INVALID_ENUM,
+                WebGLError::InvalidFramebufferOperation => constants::INVALID_FRAMEBUFFER_OPERATION,
                 WebGLError::InvalidValue => constants::INVALID_VALUE,
                 WebGLError::InvalidOperation => constants::INVALID_OPERATION,
                 WebGLError::OutOfMemory => constants::OUT_OF_MEMORY,
@@ -748,9 +781,11 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
             // case: Chromium currently unbinds, and Gecko silently
             // returns.  The conformance tests don't cover this case.
             Some(renderbuffer) if !renderbuffer.is_deleted() => {
-                renderbuffer.bind(target)
+                self.bound_renderbuffer.set(Some(renderbuffer));
+                renderbuffer.bind(target);
             }
             _ => {
+                self.bound_renderbuffer.set(None);
                 // Unbind the currently bound renderbuffer
                 self.ipc_renderer
                     .send(CanvasMsg::WebGL(WebGLCommand::BindRenderbuffer(target, None)))
@@ -773,6 +808,7 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
                 Err(err) => return self.webgl_error(err),
             }
         } else {
+            slot.set(None);
             // Unbind the currently bound texture
             self.ipc_renderer
                 .send(CanvasMsg::WebGL(WebGLCommand::BindTexture(target, None)))
@@ -882,6 +918,10 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.8
     fn CopyTexImage2D(&self, target: u32, level: i32, internal_format: u32,
                       x: i32, y: i32, width: i32, height: i32, border: i32) {
+        if !self.validate_framebuffer_complete() {
+            return;
+        }
+
         let validator = CommonTexImage2DValidator::new(self, target, level,
                                                        internal_format, width,
                                                        height, border);
@@ -935,6 +975,10 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.8
     fn CopyTexSubImage2D(&self, target: u32, level: i32, xoffset: i32, yoffset: i32,
                          x: i32, y: i32, width: i32, height: i32) {
+        if !self.validate_framebuffer_complete() {
+            return;
+        }
+
         // NB: We use a dummy (valid) format and border in order to reuse the
         // common validations, but this should have its own validator.
         let validator = CommonTexImage2DValidator::new(self, target, level,
@@ -974,6 +1018,10 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
 
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.11
     fn Clear(&self, mask: u32) {
+        if !self.validate_framebuffer_complete() {
+            return;
+        }
+
         self.ipc_renderer.send(CanvasMsg::WebGL(WebGLCommand::Clear(mask))).unwrap();
         self.mark_as_dirty();
     }
@@ -1200,6 +1248,10 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
                     return self.webgl_error(InvalidValue);
                 }
 
+                if !self.validate_framebuffer_complete() {
+                    return;
+                }
+
                 self.ipc_renderer
                     .send(CanvasMsg::WebGL(WebGLCommand::DrawArrays(mode, first, count)))
                     .unwrap();
@@ -1236,6 +1288,10 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
             return self.webgl_error(InvalidOperation);
         }
 
+        if !self.validate_framebuffer_complete() {
+            return;
+        }
+
         match mode {
             constants::POINTS | constants::LINE_STRIP |
             constants::LINE_LOOP | constants::LINES |
@@ -1504,6 +1560,10 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
             None => return self.webgl_error(InvalidValue),
         };
 
+        if !self.validate_framebuffer_complete() {
+            return;
+        }
+
         match unsafe { JS_GetArrayBufferViewType(pixels) } {
             Type::Uint8 => (),
             _ => return self.webgl_error(InvalidOperation)
diff --git a/components/servo/Cargo.lock b/components/servo/Cargo.lock
index 647b62e58ae..e3b03e9f8bb 100644
--- a/components/servo/Cargo.lock
+++ b/components/servo/Cargo.lock
@@ -2643,7 +2643,7 @@ dependencies = [
 [[package]]
 name = "webrender"
 version = "0.5.1"
-source = "git+https://github.com/servo/webrender#61b8f8bfefd472bd71dd9a06c1d16dab28c1fcc0"
+source = "git+https://github.com/servo/webrender#58b9e983a5e74ac1670fcf67f9c2ba68740ab2cc"
 dependencies = [
  "app_units 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "bincode 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2668,7 +2668,7 @@ dependencies = [
 [[package]]
 name = "webrender_traits"
 version = "0.5.1"
-source = "git+https://github.com/servo/webrender#61b8f8bfefd472bd71dd9a06c1d16dab28c1fcc0"
+source = "git+https://github.com/servo/webrender#58b9e983a5e74ac1670fcf67f9c2ba68740ab2cc"
 dependencies = [
  "app_units 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "byteorder 0.5.3 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/ports/cef/Cargo.lock b/ports/cef/Cargo.lock
index 92108a43380..6c5f8cd1394 100644
--- a/ports/cef/Cargo.lock
+++ b/ports/cef/Cargo.lock
@@ -2503,7 +2503,7 @@ dependencies = [
 [[package]]
 name = "webrender"
 version = "0.5.1"
-source = "git+https://github.com/servo/webrender#61b8f8bfefd472bd71dd9a06c1d16dab28c1fcc0"
+source = "git+https://github.com/servo/webrender#58b9e983a5e74ac1670fcf67f9c2ba68740ab2cc"
 dependencies = [
  "app_units 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "bincode 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -2528,7 +2528,7 @@ dependencies = [
 [[package]]
 name = "webrender_traits"
 version = "0.5.1"
-source = "git+https://github.com/servo/webrender#61b8f8bfefd472bd71dd9a06c1d16dab28c1fcc0"
+source = "git+https://github.com/servo/webrender#58b9e983a5e74ac1670fcf67f9c2ba68740ab2cc"
 dependencies = [
  "app_units 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "byteorder 0.5.3 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/resources/shaders/prim_shared.glsl b/resources/shaders/prim_shared.glsl
index 7336a400624..2220a7de34d 100644
--- a/resources/shaders/prim_shared.glsl
+++ b/resources/shaders/prim_shared.glsl
@@ -375,38 +375,44 @@ PrimitiveInfo fetch_text_run_glyph(int index, out vec4 color, out vec4 uv_rect)
 
 struct Image {
     PrimitiveInfo info;
-    vec4 st_rect;               // Location of the image texture in the texture atlas.
-    vec4 stretch_size_uvkind;   // Size of the actual image.
+    vec4 st_rect;                        // Location of the image texture in the texture atlas.
+    vec4 stretch_size_and_tile_spacing;  // Size of the actual image and amount of space between
+                                         //     tiled instances of this image.
+    vec4 uvkind;                         // Type of texture coordinates.
 };
 
 Image fetch_image(int index) {
     Image image;
 
-    int offset = index * 5;
+    int offset = index * 6;
 
     image.info = unpack_prim_info(offset);
     image.st_rect = data[offset + 3];
-    image.stretch_size_uvkind = data[offset + 4];
+    image.stretch_size_and_tile_spacing = data[offset + 4];
+    image.uvkind = data[offset + 5];
 
     return image;
 }
 
 struct ImageClip {
     PrimitiveInfo info;
-    vec4 st_rect;               // Location of the image texture in the texture atlas.
-    vec4 stretch_size_uvkind;   // Size of the actual image.
+    vec4 st_rect;                        // Location of the image texture in the texture atlas.
+    vec4 stretch_size_and_tile_spacing;  // Size of the actual image and amount of space between
+                                         //     tiled instances of this image.
+    vec4 uvkind;                         // Type of texture coordinates.
     Clip clip;
 };
 
 ImageClip fetch_image_clip(int index) {
     ImageClip image;
 
-    int offset = index * 14;
+    int offset = index * 15;
 
     image.info = unpack_prim_info(offset);
     image.st_rect = data[offset + 3];
-    image.stretch_size_uvkind = data[offset + 4];
-    image.clip = unpack_clip(offset + 5);
+    image.stretch_size_and_tile_spacing = data[offset + 4];
+    image.uvkind = data[offset + 5];
+    image.clip = unpack_clip(offset + 6);
 
     return image;
 }
diff --git a/resources/shaders/ps_image.fs.glsl b/resources/shaders/ps_image.fs.glsl
index e787b9bbd65..b685e4772e1 100644
--- a/resources/shaders/ps_image.fs.glsl
+++ b/resources/shaders/ps_image.fs.glsl
@@ -11,16 +11,19 @@ void main(void) {
 
     // We clamp the texture coordinate calculation here to the local rectangle boundaries,
     // which makes the edge of the texture stretch instead of repeat.
-    vec2 uv = clamp(pos, vLocalRect.xy, vLocalRect.xy + vLocalRect.zw);
-
-    uv = (uv - vLocalRect.xy) / vStretchSize;
+    vec2 relative_pos_in_rect =
+         clamp(pos, vLocalRect.xy, vLocalRect.xy + vLocalRect.zw) - vLocalRect.xy;
 #else
-    vec2 uv = vUv;
+    float alpha = 1.0;;
+    vec2 relative_pos_in_rect = vLocalPos;
 #endif
-    vec2 st = vTextureOffset + vTextureSize * fract(uv);
-#ifdef WR_FEATURE_TRANSFORM
+
+    // We calculate the particular tile this fragment belongs to, taking into
+    // account the spacing in between tiles. We only paint if our fragment does
+    // not fall into that spacing.
+    vec2 position_in_tile = mod(relative_pos_in_rect, vStretchSize + vTileSpacing);
+    vec2 st = vTextureOffset + ((position_in_tile / vStretchSize) * vTextureSize);
+    alpha = alpha * float(all(bvec2(step(position_in_tile, vStretchSize))));
+
     oFragColor = vec4(1, 1, 1, alpha) * texture(sDiffuse, st);
-#else
-    oFragColor = texture(sDiffuse, st);
-#endif
 }
diff --git a/resources/shaders/ps_image.glsl b/resources/shaders/ps_image.glsl
index b89a421789b..0ca0ac57211 100644
--- a/resources/shaders/ps_image.glsl
+++ b/resources/shaders/ps_image.glsl
@@ -4,11 +4,13 @@
 
 flat varying vec2 vTextureOffset; // Offset of this image into the texture atlas.
 flat varying vec2 vTextureSize;   // Size of the image in the texture atlas.
+flat varying vec2 vTileSpacing;   // Amount of space between tiled instances of this image.
 
 #ifdef WR_FEATURE_TRANSFORM
 varying vec3 vLocalPos;
 flat varying vec4 vLocalRect;
 flat varying vec2 vStretchSize;
 #else
-varying vec2 vUv;                 // Location within the CSS box to draw.
+varying vec2 vLocalPos;
+flat varying vec2 vStretchSize;
 #endif
diff --git a/resources/shaders/ps_image.vs.glsl b/resources/shaders/ps_image.vs.glsl
index d146e98c8c3..1f5a997b0af 100644
--- a/resources/shaders/ps_image.vs.glsl
+++ b/resources/shaders/ps_image.vs.glsl
@@ -10,17 +10,18 @@ void main(void) {
     TransformVertexInfo vi = write_transform_vertex(image.info);
     vLocalRect = vi.clipped_local_rect;
     vLocalPos = vi.local_pos;
-    vStretchSize = image.stretch_size_uvkind.xy;
+    vStretchSize = image.stretch_size_and_tile_spacing.xy;
 #else
     VertexInfo vi = write_vertex(image.info);
-    vUv = (vi.local_clamped_pos - vi.local_rect.p0) / image.stretch_size_uvkind.xy;
+    vStretchSize = image.stretch_size_and_tile_spacing.xy;
+    vLocalPos = vi.local_clamped_pos - vi.local_rect.p0;
 #endif
 
     // vUv will contain how many times this image has wrapped around the image size.
     vec2 st0 = image.st_rect.xy;
     vec2 st1 = image.st_rect.zw;
 
-    switch (uint(image.stretch_size_uvkind.z)) {
+    switch (uint(image.uvkind.x)) {
         case UV_NORMALIZED:
             break;
         case UV_PIXEL: {
@@ -33,4 +34,5 @@ void main(void) {
 
     vTextureSize = st1 - st0;
     vTextureOffset = st0;
+    vTileSpacing = image.stretch_size_and_tile_spacing.zw;
 }
diff --git a/resources/shaders/ps_image_clip.fs.glsl b/resources/shaders/ps_image_clip.fs.glsl
index 2ee0f8ee0c7..62da5a846f9 100644
--- a/resources/shaders/ps_image_clip.fs.glsl
+++ b/resources/shaders/ps_image_clip.fs.glsl
@@ -11,17 +11,22 @@ void main(void) {
 
     // We clamp the texture coordinate calculation here to the local rectangle boundaries,
     // which makes the edge of the texture stretch instead of repeat.
-    vec2 uv = clamp(local_pos.xy, vLocalRect.xy, vLocalRect.xy + vLocalRect.zw);
-
-    uv = (uv - vLocalRect.xy) / vStretchSize;
+    vec2 pos_for_texture =
+         clamp(pos, vLocalRect.xy, vLocalRect.xy + vLocalRect.zw) - vLocalRect.xy;
 #else
     float alpha = 1;
     vec2 local_pos = vLocalPos;
-    vec2 uv = vUv;
+    vec2 relative_pos_in_rect = vLocalPos - vLocalRect.xy;
 #endif
 
-    vec2 st = vTextureOffset + vTextureSize * fract(uv);
-
     alpha = min(alpha, do_clip(local_pos, vClipRect, vClipRadius));
+
+    // We calculate the particular tile this fragment belongs to, taking into
+    // account the spacing in between tiles. We only paint if our fragment does
+    // not fall into that spacing.
+    vec2 position_in_tile = mod(relative_pos_in_rect, vStretchSize + vTileSpacing);
+    vec2 st = vTextureOffset + ((position_in_tile / vStretchSize) * vTextureSize);
+    alpha = alpha * float(all(bvec2(step(position_in_tile, vStretchSize))));
+
     oFragColor = texture(sDiffuse, st) * vec4(1, 1, 1, alpha);
 }
diff --git a/resources/shaders/ps_image_clip.glsl b/resources/shaders/ps_image_clip.glsl
index 8b5f263fe72..fe4333271d9 100644
--- a/resources/shaders/ps_image_clip.glsl
+++ b/resources/shaders/ps_image_clip.glsl
@@ -4,13 +4,14 @@
 
 flat varying vec2 vTextureOffset; // Offset of this image into the texture atlas.
 flat varying vec2 vTextureSize;   // Size of the image in the texture atlas.
+flat varying vec2 vTileSpacing;   // Amount of space between tiled instances of this image.
+flat varying vec2 vStretchSize;
 flat varying vec4 vClipRect;
 flat varying vec4 vClipRadius;
+flat varying vec4 vLocalRect;
 
 #ifdef WR_FEATURE_TRANSFORM
 varying vec3 vLocalPos;
-flat varying vec4 vLocalRect;
-flat varying vec2 vStretchSize;
 #else
 varying vec2 vLocalPos;
 varying vec2 vUv;                 // Location within the CSS box to draw.
diff --git a/resources/shaders/ps_image_clip.vs.glsl b/resources/shaders/ps_image_clip.vs.glsl
index 6165f535ad9..3ba4bc3b49f 100644
--- a/resources/shaders/ps_image_clip.vs.glsl
+++ b/resources/shaders/ps_image_clip.vs.glsl
@@ -8,13 +8,11 @@ void main(void) {
 
 #ifdef WR_FEATURE_TRANSFORM
     TransformVertexInfo vi = write_transform_vertex(image.info);
-    vLocalRect = vi.clipped_local_rect;
     vLocalPos = vi.local_pos;
-    vStretchSize = image.stretch_size_uvkind.xy;
 #else
     VertexInfo vi = write_vertex(image.info);
-    vUv = (vi.local_clamped_pos - vi.local_rect.p0) / image.stretch_size_uvkind.xy;
     vLocalPos = vi.local_clamped_pos;
+    vLocalRect = image.info.local_rect;
 #endif
 
     vClipRect = vec4(image.clip.rect.xy, image.clip.rect.xy + image.clip.rect.zw);
@@ -26,7 +24,7 @@ void main(void) {
     vec2 st0 = image.st_rect.xy;
     vec2 st1 = image.st_rect.zw;
 
-    switch (uint(image.stretch_size_uvkind.z)) {
+    switch (uint(image.uvkind.x)) {
         case UV_NORMALIZED:
             break;
         case UV_PIXEL: {
@@ -39,4 +37,6 @@ void main(void) {
 
     vTextureSize = st1 - st0;
     vTextureOffset = st0;
+    vStretchSize = image.stretch_size_and_tile_spacing.xy;
+    vTileSpacing = image.stretch_size_and_tile_spacing.zw;
 }
diff --git a/tests/wpt/metadata/webgl/conformance-1.0.3/conformance/misc/object-deletion-behaviour.html.ini b/tests/wpt/metadata/webgl/conformance-1.0.3/conformance/misc/object-deletion-behaviour.html.ini
index 3232baffd25..5561797ccd9 100644
--- a/tests/wpt/metadata/webgl/conformance-1.0.3/conformance/misc/object-deletion-behaviour.html.ini
+++ b/tests/wpt/metadata/webgl/conformance-1.0.3/conformance/misc/object-deletion-behaviour.html.ini
@@ -48,9 +48,6 @@
   [WebGL test #45: getError expected: NO_ERROR. Was INVALID_OPERATION : after evaluating: gl.bindTexture(gl.TEXTURE_CUBE_MAP, texCubeMap)]
     expected: FAIL
 
-  [WebGL test #68: gl.getParameter(gl.RENDERBUFFER_BINDING) should be [object WebGLRenderbuffer\]. Was null.]
-    expected: FAIL
-
   [WebGL test #69: gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo) threw exception TypeError: gl.framebufferRenderbuffer is not a function]
     expected: FAIL
 
@@ -66,12 +63,6 @@
   [WebGL test #74: gl.isRenderbuffer(rbo) should be false. Threw exception TypeError: gl.isRenderbuffer is not a function]
     expected: FAIL
 
-  [WebGL test #79: gl.getParameter(gl.RENDERBUFFER_BINDING) should be [object WebGLRenderbuffer\]. Was null.]
-    expected: FAIL
-
-  [WebGL test #81: gl.getParameter(gl.RENDERBUFFER_BINDING) should be [object WebGLRenderbuffer\]. Was null.]
-    expected: FAIL
-
   [WebGL test #83: gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGBA4, 16, 16) threw exception TypeError: gl.renderbufferStorage is not a function]
     expected: FAIL