Add `Shader` and `Version`

to simplify and constrain `program::create`

6 files changed, 156 insertions, 134 deletions

diff --git a/glow/src/backend.rs b/glow/src/backend.rs
index 69d04168..89dc1aaa 100644
--- a/glow/src/backend.rs
+++ b/glow/src/backend.rs
@@ -1,9 +1,9 @@
+use crate::program;
 use crate::quad;
 use crate::text;
 use crate::triangle;
 use crate::{Settings, Transformation, Viewport};
 
-use glow::HasContext;
 use iced_graphics::backend;
 use iced_graphics::font;
 use iced_graphics::{Layer, Primitive};
@@ -31,57 +31,7 @@ impl Backend {
             settings.text_multithreading,
         );
 
-        let version = gl.version();
-        let shader_version = match (
-            version.major,
-            version.minor,
-            version.is_embedded,
-        ) {
-            // OpenGL 3.0+
-            (3, 0 | 1 | 2, false) => (
-                format!("#version 1{}0", version.minor + 3),
-                format!(
-                    "#version 1{}0\n#define HIGHER_THAN_300 1",
-                    version.minor + 3
-                ),
-            ),
-            // OpenGL 3.3+
-            (3 | 4, _, false) => (
-                format!("#version {}{}0", version.major, version.minor),
-                format!(
-                    "#version {}{}0\n#define HIGHER_THAN_300 1",
-                    version.major, version.minor
-                ),
-            ),
-            // OpenGL ES 3.0+
-            (3, _, true) => (
-                format!("#version 3{}0 es", version.minor),
-                format!(
-                    "#version 3{}0 es\n#define HIGHER_THAN_300 1",
-                    version.minor
-                ),
-            ),
-            // OpenGL ES 2.0+
-            (2, _, true) => (
-                String::from(
-                    "#version 100\n#define in attribute\n#define out varying",
-                ),
-                String::from("#version 100\n#define in varying"),
-            ),
-            // OpenGL 2.1
-            (2, _, false) => (
-                String::from(
-                    "#version 120\n#define in attribute\n#define out varying",
-                ),
-                String::from("#version 120\n#define in varying"),
-            ),
-            // OpenGL 1.1+
-            _ => panic!("Incompatible context version: {:?}", version),
-        };
-        log::info!(
-            "Shader directive: {}",
-            shader_version.0.lines().next().unwrap()
-        );
+        let shader_version = program::Version::new(gl);
 
         let quad_pipeline = quad::Pipeline::new(gl, &shader_version);
         let triangle_pipeline = triangle::Pipeline::new(gl, &shader_version);
diff --git a/glow/src/program.rs b/glow/src/program.rs
index 13676c70..9a02d578 100644
--- a/glow/src/program.rs
+++ b/glow/src/program.rs
@@ -1,29 +1,118 @@
 use glow::HasContext;
 
-pub unsafe fn create(
-    gl: &glow::Context,
-    shader_sources: &[(u32, &str)],
-    attributes: &[(u32, &str)],
-) -> <glow::Context as HasContext>::Program {
-    let program = gl.create_program().expect("Cannot create program");
+/// The [`Version`] of a `Program`.
+pub struct Version {
+    vertex: String,
+    fragment: String,
+}
+
+impl Version {
+    pub fn new(gl: &glow::Context) -> Version {
+        let version = gl.version();
 
-    let mut shaders = Vec::with_capacity(shader_sources.len());
+        let (vertex, fragment) = match (
+            version.major,
+            version.minor,
+            version.is_embedded,
+        ) {
+            // OpenGL 3.0+
+            (3, 0 | 1 | 2, false) => (
+                format!("#version 1{}0", version.minor + 3),
+                format!(
+                    "#version 1{}0\n#define HIGHER_THAN_300 1",
+                    version.minor + 3
+                ),
+            ),
+            // OpenGL 3.3+
+            (3 | 4, _, false) => (
+                format!("#version {}{}0", version.major, version.minor),
+                format!(
+                    "#version {}{}0\n#define HIGHER_THAN_300 1",
+                    version.major, version.minor
+                ),
+            ),
+            // OpenGL ES 3.0+
+            (3, _, true) => (
+                format!("#version 3{}0 es", version.minor),
+                format!(
+                    "#version 3{}0 es\n#define HIGHER_THAN_300 1",
+                    version.minor
+                ),
+            ),
+            // OpenGL ES 2.0+
+            (2, _, true) => (
+                String::from(
+                    "#version 100\n#define in attribute\n#define out varying",
+                ),
+                String::from("#version 100\n#define in varying"),
+            ),
+            // OpenGL 2.1
+            (2, _, false) => (
+                String::from(
+                    "#version 120\n#define in attribute\n#define out varying",
+                ),
+                String::from("#version 120\n#define in varying"),
+            ),
+            // OpenGL 1.1+
+            _ => panic!("Incompatible context version: {:?}", version),
+        };
 
-    for (shader_type, shader_source) in shader_sources.iter() {
-        let shader = gl
-            .create_shader(*shader_type)
-            .expect("Cannot create shader");
+        log::info!("Shader directive: {}", vertex.lines().next().unwrap());
 
-        gl.shader_source(shader, shader_source);
-        gl.compile_shader(shader);
+        Version { vertex, fragment }
+    }
+}
+
+pub struct Shader(<glow::Context as HasContext>::Shader);
+
+impl Shader {
+    fn compile(gl: &glow::Context, stage: u32, content: &str) -> Shader {
+        unsafe {
+            let shader = gl.create_shader(stage).expect("Cannot create shader");
 
-        if !gl.get_shader_compile_status(shader) {
-            panic!("{}", gl.get_shader_info_log(shader));
+            gl.shader_source(shader, &content);
+            gl.compile_shader(shader);
+
+            if !gl.get_shader_compile_status(shader) {
+                panic!("{}", gl.get_shader_info_log(shader));
+            }
+
+            Shader(shader)
         }
+    }
 
-        gl.attach_shader(program, shader);
+    /// Creates a vertex [`Shader`].
+    pub fn vertex(
+        gl: &glow::Context,
+        version: &Version,
+        content: &'static str,
+    ) -> Self {
+        let content = format!("{}\n{}", version.vertex, content);
 
-        shaders.push(shader);
+        Shader::compile(gl, glow::VERTEX_SHADER, &content)
+    }
+
+    /// Creates a fragment [`Shader`].
+    pub fn fragment(
+        gl: &glow::Context,
+        version: &Version,
+        content: &'static str,
+    ) -> Self {
+        let content = format!("{}\n{}", version.fragment, content);
+
+        Shader::compile(gl, glow::FRAGMENT_SHADER, &content)
+    }
+}
+
+pub unsafe fn create(
+    gl: &glow::Context,
+    shaders: &[Shader],
+    attributes: &[(u32, &str)],
+) -> <glow::Context as HasContext>::Program {
+    let program = gl.create_program().expect("Cannot create program");
+
+    for shader in shaders {
+        gl.attach_shader(program, shader.0);
     }
 
     for (i, name) in attributes {
@@ -36,8 +125,8 @@ pub unsafe fn create(
     }
 
     for shader in shaders {
-        gl.detach_shader(program, shader);
-        gl.delete_shader(shader);
+        gl.detach_shader(program, shader.0);
+        gl.delete_shader(shader.0);
     }
 
     program
diff --git a/glow/src/quad.rs b/glow/src/quad.rs
index e965f3c9..d9f1c6ae 100644
--- a/glow/src/quad.rs
+++ b/glow/src/quad.rs
@@ -1,6 +1,7 @@
 mod compatibility;
 mod core;
 
+use crate::program;
 use crate::Transformation;
 use glow::HasContext;
 use iced_graphics::layer;
@@ -15,12 +16,12 @@ pub enum Pipeline {
 impl Pipeline {
     pub fn new(
         gl: &glow::Context,
-        shader_version: &(String, String),
+        shader_version: &program::Version,
     ) -> Pipeline {
-        let version = gl.version();
+        let gl_version = gl.version();
 
         // OpenGL 3.0+ and OpenGL ES 3.0+ have instancing (which is what separates `core` from `compatibility`)
-        if version.major >= 3 {
+        if gl_version.major >= 3 {
             log::info!("Mode: core");
             Pipeline::Core(core::Pipeline::new(gl, shader_version))
         } else {
diff --git a/glow/src/quad/compatibility.rs b/glow/src/quad/compatibility.rs
index 28ad214d..76f98ab7 100644
--- a/glow/src/quad/compatibility.rs
+++ b/glow/src/quad/compatibility.rs
@@ -1,4 +1,4 @@
-use crate::program;
+use crate::program::{self, Shader};
 use crate::Transformation;
 use glow::HasContext;
 use iced_graphics::layer;
@@ -27,29 +27,23 @@ pub struct Pipeline {
 impl Pipeline {
     pub fn new(
         gl: &glow::Context,
-        (vertex_version, fragment_version): &(String, String),
+        shader_version: &program::Version,
     ) -> Pipeline {
         let program = unsafe {
+            let vertex_shader = Shader::vertex(
+                gl,
+                shader_version,
+                include_str!("../shader/compatibility/quad.vert"),
+            );
+            let fragment_shader = Shader::fragment(
+                gl,
+                shader_version,
+                include_str!("../shader/compatibility/quad.frag"),
+            );
+
             program::create(
                 gl,
-                &[
-                    (
-                        glow::VERTEX_SHADER,
-                        &format!(
-                            "{}\n{}",
-                            vertex_version,
-                            include_str!("../shader/compatibility/quad.vert")
-                        ),
-                    ),
-                    (
-                        glow::FRAGMENT_SHADER,
-                        &format!(
-                            "{}\n{}",
-                            fragment_version,
-                            include_str!("../shader/compatibility/quad.frag")
-                        ),
-                    ),
-                ],
+                &[vertex_shader, fragment_shader],
                 &[
                     (0, "i_Pos"),
                     (1, "i_Scale"),
diff --git a/glow/src/quad/core.rs b/glow/src/quad/core.rs
index 274ade67..f37300f6 100644
--- a/glow/src/quad/core.rs
+++ b/glow/src/quad/core.rs
@@ -1,4 +1,4 @@
-use crate::program;
+use crate::program::{self, Shader};
 use crate::Transformation;
 use glow::HasContext;
 use iced_graphics::layer;
@@ -22,29 +22,23 @@ pub struct Pipeline {
 impl Pipeline {
     pub fn new(
         gl: &glow::Context,
-        (vertex_version, fragment_version): &(String, String),
+        shader_version: &program::Version,
     ) -> Pipeline {
         let program = unsafe {
+            let vertex_shader = Shader::vertex(
+                gl,
+                shader_version,
+                include_str!("../shader/core/quad.vert"),
+            );
+            let fragment_shader = Shader::fragment(
+                gl,
+                shader_version,
+                include_str!("../shader/core/quad.frag"),
+            );
+
             program::create(
                 gl,
-                &[
-                    (
-                        glow::VERTEX_SHADER,
-                        &format!(
-                            "{}\n{}",
-                            vertex_version,
-                            include_str!("../shader/core/quad.vert")
-                        ),
-                    ),
-                    (
-                        glow::FRAGMENT_SHADER,
-                        &format!(
-                            "{}\n{}",
-                            fragment_version,
-                            include_str!("../shader/core/quad.frag")
-                        ),
-                    ),
-                ],
+                &[vertex_shader, fragment_shader],
                 &[
                     (0, "i_Pos"),
                     (1, "i_Scale"),
diff --git a/glow/src/triangle.rs b/glow/src/triangle.rs
index 91bb96ba..ae4f83ef 100644
--- a/glow/src/triangle.rs
+++ b/glow/src/triangle.rs
@@ -1,5 +1,5 @@
 //! Draw meshes of triangles.
-use crate::program;
+use crate::program::{self, Shader};
 use crate::Transformation;
 use glow::HasContext;
 use iced_graphics::layer;
@@ -23,29 +23,23 @@ pub(crate) struct Pipeline {
 impl Pipeline {
     pub fn new(
         gl: &glow::Context,
-        (vertex_version, fragment_version): &(String, String),
+        shader_version: &program::Version,
     ) -> Pipeline {
         let program = unsafe {
+            let vertex_shader = Shader::vertex(
+                gl,
+                shader_version,
+                include_str!("shader/common/triangle.vert"),
+            );
+            let fragment_shader = Shader::fragment(
+                gl,
+                shader_version,
+                include_str!("shader/common/triangle.frag"),
+            );
+
             program::create(
                 gl,
-                &[
-                    (
-                        glow::VERTEX_SHADER,
-                        &format!(
-                            "{}\n{}",
-                            vertex_version,
-                            include_str!("shader/common/triangle.vert")
-                        ),
-                    ),
-                    (
-                        glow::FRAGMENT_SHADER,
-                        &format!(
-                            "{}\n{}",
-                            fragment_version,
-                            include_str!("shader/common/triangle.frag")
-                        ),
-                    ),
-                ],
+                &[vertex_shader, fragment_shader],
                 &[(0, "i_Position"), (1, "i_Color")],
             )
         };