4 files changed, 457 insertions, 0 deletions
diff --git a/gfx/wr/webrender_build/Cargo.toml b/gfx/wr/webrender_build/Cargo.toml
new file mode 100644
index 0000000000..862d2a77b1
--- /dev/null
+++ b/gfx/wr/webrender_build/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "webrender_build"
+authors = ["The Servo Project Developers"]
+version = "0.0.1"
+license = "MPL-2.0"
+repository = "https://github.com/servo/webrender"
+description = "Code shared between precompilation (build.rs) and the rest of WebRender"
+edition = "2018"
+
+[features]
+serialize_program = ["serde"]
+
+[dependencies]
+bitflags = "1.2"
+lazy_static = "1"
+serde = { optional = true, version = "1.0", features = ["serde_derive"] }
diff --git a/gfx/wr/webrender_build/src/lib.rs b/gfx/wr/webrender_build/src/lib.rs
new file mode 100644
index 0000000000..23438a478e
--- /dev/null
+++ b/gfx/wr/webrender_build/src/lib.rs
@@ -0,0 +1,19 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#[macro_use]
+extern crate bitflags;
+
+#[macro_use]
+extern crate lazy_static;
+
+#[cfg(any(feature = "serde"))]
+#[macro_use]
+extern crate serde;
+
+pub mod shader;
+pub mod shader_features;
+
+/// This must be known at build-time as the shaders depend on it.
+pub const MAX_VERTEX_TEXTURE_WIDTH: usize = 1024;
diff --git a/gfx/wr/webrender_build/src/shader.rs b/gfx/wr/webrender_build/src/shader.rs
new file mode 100644
index 0000000000..3c15f4f414
--- /dev/null
+++ b/gfx/wr/webrender_build/src/shader.rs
@@ -0,0 +1,222 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! Functionality for managing source code for shaders.
+//!
+//! This module is used during precompilation (build.rs) and regular compilation,
+//! so it has minimal dependencies.
+
+use std::borrow::Cow;
+use std::fs::File;
+use std::io::Read;
+use std::path::Path;
+use std::collections::HashSet;
+use std::collections::hash_map::DefaultHasher;
+use crate::MAX_VERTEX_TEXTURE_WIDTH;
+
+pub use crate::shader_features::*;
+
+lazy_static! {
+    static ref MAX_VERTEX_TEXTURE_WIDTH_STRING: String = MAX_VERTEX_TEXTURE_WIDTH.to_string();
+}
+
+#[derive(Clone, Copy, Debug)]
+pub enum ShaderKind {
+    Vertex,
+    Fragment,
+}
+
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
+pub enum ShaderVersion {
+    Gl,
+    Gles,
+}
+
+impl ShaderVersion {
+    /// Return the full variant name, for use in code generation.
+    pub fn variant_name(&self) -> &'static str {
+        match self {
+            ShaderVersion::Gl => "ShaderVersion::Gl",
+            ShaderVersion::Gles => "ShaderVersion::Gles",
+        }
+    }
+}
+
+#[derive(PartialEq, Eq, Hash, Debug, Clone, Default)]
+#[cfg_attr(feature = "serialize_program", derive(Deserialize, Serialize))]
+pub struct ProgramSourceDigest(u64);
+
+impl ::std::fmt::Display for ProgramSourceDigest {
+    fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        write!(f, "{:02x}", self.0)
+    }
+}
+
+impl From<DefaultHasher> for ProgramSourceDigest {
+    fn from(hasher: DefaultHasher) -> Self {
+        use std::hash::Hasher;
+        ProgramSourceDigest(hasher.finish())
+    }
+}
+
+const SHADER_IMPORT: &str = "#include ";
+
+pub struct ShaderSourceParser {
+    included: HashSet<String>,
+}
+
+impl ShaderSourceParser {
+    pub fn new() -> Self {
+        ShaderSourceParser {
+            included: HashSet::new(),
+        }
+    }
+
+    /// Parses a shader string for imports. Imports are recursively processed, and
+    /// prepended to the output stream.
+    pub fn parse<F: FnMut(&str), G: Fn(&str) -> Cow<'static, str>>(
+        &mut self,
+        source: Cow<'static, str>,
+        get_source: &G,
+        output: &mut F,
+    ) {
+        for line in source.lines() {
+            if line.starts_with(SHADER_IMPORT) {
+                let imports = line[SHADER_IMPORT.len() ..].split(',');
+
+                // For each import, get the source, and recurse.
+                for import in imports {
+                    if self.included.insert(import.into()) {
+                        let include = get_source(import);
+                        self.parse(include, get_source, output);
+                    } else {
+                        output(&format!("// {} is already included\n", import));
+                    }
+                }
+            } else {
+                output(line);
+                output("\n");
+            }
+        }
+    }
+}
+
+/// Reads a shader source file from disk into a String.
+pub fn shader_source_from_file(shader_path: &Path) -> String {
+    assert!(shader_path.exists(), "Shader not found {:?}", shader_path);
+    let mut source = String::new();
+    File::open(&shader_path)
+        .expect("Shader not found")
+        .read_to_string(&mut source)
+        .unwrap();
+    source
+}
+
+/// Creates heap-allocated strings for both vertex and fragment shaders.
+pub fn build_shader_strings<G: Fn(&str) -> Cow<'static, str>>(
+    gl_version: ShaderVersion,
+    features: &[&str],
+    base_filename: &str,
+    get_source: &G,
+) -> (String, String) {
+   let mut vs_source = String::new();
+   do_build_shader_string(
+       gl_version,
+       features,
+       ShaderKind::Vertex,
+       base_filename,
+       get_source,
+       |s| vs_source.push_str(s),
+   );
+
+   let mut fs_source = String::new();
+   do_build_shader_string(
+       gl_version,
+       features,
+       ShaderKind::Fragment,
+       base_filename,
+       get_source,
+       |s| fs_source.push_str(s),
+   );
+
+   (vs_source, fs_source)
+}
+
+/// Walks the given shader string and applies the output to the provided
+/// callback. Assuming an override path is not used, does no heap allocation
+/// and no I/O.
+pub fn do_build_shader_string<F: FnMut(&str), G: Fn(&str) -> Cow<'static, str>>(
+   gl_version: ShaderVersion,
+   features: &[&str],
+   kind: ShaderKind,
+   base_filename: &str,
+   get_source: &G,
+   mut output: F,
+) {
+   build_shader_prefix_string(gl_version, features, kind, base_filename, &mut output);
+   build_shader_main_string(base_filename, get_source, &mut output);
+}
+
+/// Walks the prefix section of the shader string, which manages the various
+/// defines for features etc.
+pub fn build_shader_prefix_string<F: FnMut(&str)>(
+   gl_version: ShaderVersion,
+   features: &[&str],
+   kind: ShaderKind,
+   base_filename: &str,
+   output: &mut F,
+) {
+    // GLSL requires that the version number comes first.
+    let gl_version_string = match gl_version {
+        ShaderVersion::Gl => "#version 150\n",
+        ShaderVersion::Gles => "#version 300 es\n",
+    };
+    output(gl_version_string);
+
+    // Insert the shader name to make debugging easier.
+    output("// shader: ");
+    output(base_filename);
+    output(" ");
+    for (i, feature) in features.iter().enumerate() {
+        output(feature);
+        if i != features.len() - 1 {
+            output(",");
+        }
+    }
+    output("\n");
+
+    // Define a constant depending on whether we are compiling VS or FS.
+    let kind_string = match kind {
+        ShaderKind::Vertex => "#define WR_VERTEX_SHADER\n",
+        ShaderKind::Fragment => "#define WR_FRAGMENT_SHADER\n",
+    };
+    output(kind_string);
+
+    // Define a constant for the vertex texture width.
+    output("#define WR_MAX_VERTEX_TEXTURE_WIDTH ");
+    output(&MAX_VERTEX_TEXTURE_WIDTH_STRING);
+    output("U\n");
+
+    // Add any defines for features that were passed by the caller.
+    for feature in features {
+        assert!(!feature.is_empty());
+        output("#define WR_FEATURE_");
+        output(feature);
+        output("\n");
+    }
+}
+
+/// Walks the main .glsl file, including any imports.
+pub fn build_shader_main_string<F: FnMut(&str), G: Fn(&str) -> Cow<'static, str>>(
+   base_filename: &str,
+   get_source: &G,
+   output: &mut F,
+) {
+   let shared_source = get_source(base_filename);
+   ShaderSourceParser::new().parse(
+       shared_source,
+       &|f| get_source(f),
+       output
+   );
+}
diff --git a/gfx/wr/webrender_build/src/shader_features.rs b/gfx/wr/webrender_build/src/shader_features.rs
new file mode 100644
index 0000000000..45efd72532
--- /dev/null
+++ b/gfx/wr/webrender_build/src/shader_features.rs
@@ -0,0 +1,200 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::collections::HashMap;
+
+bitflags! {
+    #[derive(Default)]
+    pub struct ShaderFeatureFlags: u32 {
+        const GL = 1 << 0;
+        const GLES = 1 << 1;
+
+        const ADVANCED_BLEND_EQUATION = 1 << 8;
+        const DUAL_SOURCE_BLENDING = 1 << 9;
+        const DITHERING = 1 << 10;
+        const TEXTURE_EXTERNAL = 1 << 11;
+        const DEBUG = 1 << 12;
+    }
+}
+
+pub type ShaderFeatures = HashMap<&'static str, Vec<String>>;
+
+/// Builder for a list of features.
+#[derive(Clone)]
+struct FeatureList<'a> {
+    list: Vec<&'a str>,
+}
+
+impl<'a> FeatureList<'a> {
+    fn new() -> Self {
+        FeatureList {
+            list: Vec::new(),
+        }
+    }
+
+    fn add(&mut self, feature: &'a str) {
+        assert!(!feature.contains(','));
+        self.list.push(feature);
+    }
+
+    fn with(&self, feature: &'a str) -> Self {
+        let mut other = self.clone();
+        other.add(feature);
+        other
+    }
+
+    fn concat(&self, other: &Self) -> Self {
+        let mut list = self.list.clone();
+        list.extend_from_slice(&other.list);
+        FeatureList {
+            list
+        }
+    }
+
+    fn finish(&mut self) -> String {
+        self.list.sort_unstable();
+        self.list.join(",")
+    }
+}
+
+/// Computes available shaders and their features for the given feature flags.
+pub fn get_shader_features(flags: ShaderFeatureFlags) -> ShaderFeatures {
+    let mut shaders = ShaderFeatures::new();
+
+    // Clip shaders
+    shaders.insert("cs_clip_rectangle", vec![String::new(), "FAST_PATH".to_string()]);
+    shaders.insert("cs_clip_image", vec!["TEXTURE_2D".to_string()]);
+    shaders.insert("cs_clip_box_shadow", vec!["TEXTURE_2D".to_string()]);
+
+    // Cache shaders
+    shaders.insert("cs_blur", vec!["ALPHA_TARGET".to_string(), "COLOR_TARGET".to_string()]);
+
+    for name in &["cs_line_decoration", "cs_gradient", "cs_border_segment", "cs_border_solid", "cs_svg_filter"] {
+        shaders.insert(name, vec![String::new()]);
+    }
+
+    let mut base_prim_features = FeatureList::new();
+
+    // Brush shaders
+    let mut brush_alpha_features = base_prim_features.with("ALPHA_PASS");
+    for name in &["brush_solid", "brush_blend", "brush_mix_blend"] {
+        let mut features: Vec<String> = Vec::new();
+        features.push(base_prim_features.finish());
+        features.push(brush_alpha_features.finish());
+        features.push("DEBUG_OVERDRAW".to_string());
+        shaders.insert(name, features);
+    }
+    for name in &["brush_conic_gradient", "brush_radial_gradient", "brush_linear_gradient"] {
+        let mut features: Vec<String> = Vec::new();
+        let mut list = FeatureList::new();
+        if flags.contains(ShaderFeatureFlags::DITHERING) {
+            list.add("DITHERING");
+        }
+        features.push(list.concat(&base_prim_features).finish());
+        features.push(list.concat(&brush_alpha_features).finish());
+        features.push(list.with("DEBUG_OVERDRAW").finish());
+        shaders.insert(name, features);
+    }
+
+    {
+        let mut features: Vec<String> = Vec::new();
+        features.push(base_prim_features.finish());
+        features.push(brush_alpha_features.finish());
+        features.push(base_prim_features.with("ANTIALIASING").finish());
+        features.push(brush_alpha_features.with("ANTIALIASING").finish());
+        features.push("ANTIALIASING,DEBUG_OVERDRAW".to_string());
+        features.push("DEBUG_OVERDRAW".to_string());
+        shaders.insert("brush_opacity", features);
+    }
+
+    // Image brush shaders
+    let mut texture_types = vec!["TEXTURE_2D_ARRAY", "TEXTURE_2D"];
+    if flags.contains(ShaderFeatureFlags::GL) {
+        texture_types.push("TEXTURE_RECT");
+    }
+    if flags.contains(ShaderFeatureFlags::TEXTURE_EXTERNAL) {
+        texture_types.push("TEXTURE_EXTERNAL");
+    }
+    let mut image_features: Vec<String> = Vec::new();
+    for texture_type in &texture_types {
+        let mut fast = FeatureList::new();
+        if !texture_type.is_empty() {
+            fast.add(texture_type);
+        }
+        image_features.push(fast.concat(&base_prim_features).finish());
+        image_features.push(fast.concat(&brush_alpha_features).finish());
+        image_features.push(fast.with("DEBUG_OVERDRAW").finish());
+        let mut slow = fast.clone();
+        slow.add("REPETITION");
+        slow.add("ANTIALIASING");
+        image_features.push(slow.concat(&base_prim_features).finish());
+        image_features.push(slow.concat(&brush_alpha_features).finish());
+        image_features.push(slow.with("DEBUG_OVERDRAW").finish());
+        if flags.contains(ShaderFeatureFlags::ADVANCED_BLEND_EQUATION) {
+            let advanced_blend_features = brush_alpha_features.with("ADVANCED_BLEND");
+            image_features.push(fast.concat(&advanced_blend_features).finish());
+            image_features.push(slow.concat(&advanced_blend_features).finish());
+        }
+        if flags.contains(ShaderFeatureFlags::DUAL_SOURCE_BLENDING) {
+            let dual_source_features = brush_alpha_features.with("DUAL_SOURCE_BLENDING");
+            image_features.push(fast.concat(&dual_source_features).finish());
+            image_features.push(slow.concat(&dual_source_features).finish());
+        }
+    }
+    shaders.insert("brush_image", image_features);
+
+    let mut composite_features: Vec<String> = Vec::new();
+    for texture_type in &texture_types {
+        let base = texture_type.to_string();
+        composite_features.push(base);
+    }
+    shaders.insert("cs_scale", composite_features.clone());
+
+    // YUV image brush shaders
+    let mut yuv_features: Vec<String> = Vec::new();
+    for texture_type in &texture_types {
+        let mut list = FeatureList::new();
+        if !texture_type.is_empty() {
+            list.add(texture_type);
+        }
+        list.add("YUV");
+        composite_features.push(list.finish());
+        yuv_features.push(list.concat(&base_prim_features).finish());
+        yuv_features.push(list.concat(&brush_alpha_features).finish());
+        yuv_features.push(list.with("DEBUG_OVERDRAW").finish());
+    }
+    shaders.insert("composite", composite_features);
+    shaders.insert("brush_yuv_image", yuv_features);
+
+    // Prim shaders
+    let mut text_types = vec![""];
+    if flags.contains(ShaderFeatureFlags::DUAL_SOURCE_BLENDING) {
+        text_types.push("DUAL_SOURCE_BLENDING");
+    }
+    let mut text_features: Vec<String> = Vec::new();
+    for text_type in &text_types {
+        let mut list = base_prim_features.with("TEXTURE_2D");
+        if !text_type.is_empty() {
+            list.add(text_type);
+        }
+        let mut alpha_list = list.with("ALPHA_PASS");
+        text_features.push(alpha_list.finish());
+        text_features.push(alpha_list.with("GLYPH_TRANSFORM").finish());
+        text_features.push(list.with("DEBUG_OVERDRAW").finish());
+    }
+    shaders.insert("ps_text_run", text_features);
+
+    shaders.insert("ps_split_composite", vec![base_prim_features.finish()]);
+
+    shaders.insert("ps_clear", vec![base_prim_features.finish()]);
+
+    if flags.contains(ShaderFeatureFlags::DEBUG) {
+        for name in &["debug_color", "debug_font"] {
+            shaders.insert(name, vec![String::new()]);
+        }
+    }
+
+    shaders
+}
+