Finish the shader docs

src/graphics/shader.rs

@@ -12,15 +12,41 @@ use crate::Context;
 pub use crate::graphics::opengl::UniformValue;
 
 /// The default vertex shader.
+///
+/// The source code for this shader is available in [`src/resources/shader.vert`](https://github.com/17cupsofcoffee/tetra/blob/master/src/resources/shader.vert).
 pub static DEFAULT_VERTEX_SHADER: &str = include_str!("../resources/shader.vert");
 
 /// The default fragment shader.
+///
+/// The source code for this shader is available in [`src/resources/shader.vert`](https://github.com/17cupsofcoffee/tetra/blob/master/src/resources/shader.frag).
 pub static DEFAULT_FRAGMENT_SHADER: &str = include_str!("../resources/shader.frag");
 
 /// A shader program, consisting of a vertex shader and a fragment shader.
 ///
 /// This type acts as a lightweight handle to the associated graphics hardware data,
 /// and so can be cloned with little overhead.
+///
+/// # Vertex Shaders
+///
+/// Vertex shaders take in data via three attributes:
+///
+/// * `a_position` - A `vec2` representing the position of the vertex in world space.
+/// * `a_uv` - A `vec2` representing the texture co-ordinates that are associated with the vertex.
+/// * `a_color` - A `vec4` representing a color to multiply the output by.
+///
+/// # Fragment Shaders
+///
+/// Fragment shaders have a single `vec4` output called `o_color` - this should be set to the desired output color for the
+/// fragment.
+///
+/// # Uniforms
+///
+/// By default, the shader is provided with two uniform variables:
+///
+/// * `u_projection` - A `mat4` which can be used to translate world space co-ordinates into screen space.
+/// * `u_texture` - A `sampler2D` which can be used to access color data from the currently active texture.
+///
+/// You can also set data into your own uniform variables via the `set_uniform` method.
 #[derive(Debug, Clone, PartialEq)]
 pub struct Shader {
     pub(crate) handle: Rc<GLProgram>,