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use crate::blend::{BlendEquation, BlendFunction, BlendMode};
use crate::depth::DepthTestMode;
use crate::{GlFramebuffer, GlProgram, GlVertexArray, GolemError};
use alloc::rc::Rc;
use core::cell::RefCell;
use glow::HasContext;
/// The context required to interact with the GPU
pub struct Context(pub(crate) Rc<ContextContents>);
pub(crate) struct ContextContents {
pub(crate) gl: glow::Context,
pub(crate) current_program: RefCell<Option<GlProgram>>,
pub(crate) current_surface: RefCell<Option<GlFramebuffer>>,
vao: GlVertexArray,
max_vertex_attrib_index: RefCell<u32>,
}
impl Drop for ContextContents {
fn drop(&mut self) {
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glDeleteVertexArrays.xhtml
// glow handles passing in the pointer to our value, and GL will silently ignore invalid
// values
unsafe {
self.gl.delete_vertex_array(self.vao);
}
}
}
impl Context {
/// Create an instance from an OpenGL context
pub fn from_glow(gl: glow::Context) -> Result<Context, GolemError> {
let vao = unsafe {
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glGenVertexArrays.xhtml
// glow handles passing in '1' and returning the value to us
let vao = gl.create_vertex_array()?;
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glBindVertexArray.xhtml
// In this case, we know 'vao' must be a valid vao because we just constructed it
gl.bind_vertex_array(Some(vao));
vao
};
let contents = Context(Rc::new(ContextContents {
gl,
current_program: RefCell::new(None),
current_surface: RefCell::new(None),
vao,
max_vertex_attrib_index: RefCell::new(0),
}));
contents.set_clear_color(0.0, 0.0, 0.0, 1.0);
Ok(contents)
}
/// Set the section of the framebuffer that will be rendered to
///
/// By default, this is the entire internal area of the window. When switching to a
/// [`Surface`], it's generally important to set the viewport to its area.
///
/// [`Surface`]: crate::Surface
pub fn set_viewport(&self, x: u32, y: u32, width: u32, height: u32) {
unsafe {
self.0
.gl
.viewport(x as i32, y as i32, width as i32, height as i32);
}
}
/// Set the color the render target will be cleared to by [`clear`]
///
/// [`clear`]: Context::clear
pub fn set_clear_color(&self, r: f32, g: f32, b: f32, a: f32) {
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glClearColor.xhtml
// Set the clear color to (r, g, b, a)
unsafe {
self.0.gl.clear_color(r, g, b, a);
}
}
/// Clear the current render target to the render color (see [`set_clear_color`])
///
/// [`set_clear_color`]: Context::set_clear_color
pub fn clear(&self) {
let gl = &self.0.gl;
unsafe {
gl.clear(glow::COLOR_BUFFER_BIT | glow::DEPTH_BUFFER_BIT);
}
}
/// Set the blend mode, with `None` disabling blending
///
/// By default, this is `None`
///
/// See the documentation for [`BlendMode`] for the various blending options
pub fn set_blend_mode(&self, blend_state: Option<BlendMode>) {
let gl = &self.0.gl;
match blend_state {
Some(BlendMode {
equation,
function,
global_color: [r, g, b, a],
}) => unsafe {
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glEnable.xhtml
// gl::BLEND is on the whitelist
gl.enable(glow::BLEND);
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glBlendEquation.xhtml
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glBlendEquationSeparate.xhtml
// The to_gl() function only produces valid values
match equation {
BlendEquation::Same(eq) => gl.blend_equation(eq.to_gl()),
BlendEquation::Separate { color, alpha } => {
gl.blend_equation_separate(color.to_gl(), alpha.to_gl());
}
}
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glBlendFunc.xhtml
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glBlendFuncSeparate.xhtml
// The to_gl() function only produces valid values
match function {
BlendFunction::Same {
source,
destination,
} => {
gl.blend_func(source.to_gl(), destination.to_gl());
}
BlendFunction::Separate {
source_color,
source_alpha,
destination_alpha,
destination_color,
} => {
gl.blend_func_separate(
source_color.to_gl(),
source_alpha.to_gl(),
destination_alpha.to_gl(),
destination_color.to_gl(),
);
}
}
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glBlendColor.xhtml
gl.blend_color(r, g, b, a);
},
None => unsafe {
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glEnable.xhtml
// gl::BLEND is on the whitelist
gl.disable(glow::BLEND);
},
}
}
/// Set the depth test mode, with `None` disabling depth testing
///
/// By default, this is `None`
///
/// See the documentation for [`DepthTestMode`](depth/struct.DepthTestMode.html)
/// for the various depth testing options
pub fn set_depth_test_mode(&self, depth_test_state: Option<DepthTestMode>) {
let gl = &self.0.gl;
match depth_test_state {
Some(DepthTestMode {
function,
range_near,
range_far,
depth_mask,
}) => unsafe {
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glEnable.xhtml
gl.enable(glow::DEPTH_TEST);
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glDepthFunc.xhtml
// The to_gl() function only produces valid values
gl.depth_func(function.to_gl());
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glDepthRange.xhtml
#[cfg(not(target_arch = "wasm32"))]
gl.depth_range_f64(range_near as f64, range_far as f64);
// https://www.khronos.org/registry/OpenGL-Refpages/es3.0/html/glDepthRangef.xhtml
#[cfg(target_arch = "wasm32")]
gl.depth_range_f32(range_near, range_far);
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glDepthMask.xhtml
gl.depth_mask(depth_mask);
},
None => unsafe {
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glEnable.xhtml
gl.disable(glow::DEPTH_TEST);
},
}
}
/// Set the new max attribute, clear the old one
pub(crate) fn max_attrib(&self, index: u32) -> u32 {
let mut attrib_ptr = self.0.max_vertex_attrib_index.borrow_mut();
let attrib = *attrib_ptr;
*attrib_ptr = index;
attrib
}
}