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use crate::error::WasmError;
use wasm_bindgen::JsCast;
use web_sys::WebGl2RenderingContext as GlContext;
use super::webgl;
use super::webgl::{Color4, ShaderType, WebGl2};
use super::shader::{MAIN_VERTEX_SHADER, MAIN_FRAGMENT_SHADER};
use super::shader::ShaderProgram;
pub struct GraphicsContext {
gl: WebGl2,
frame_nr: u64,
shader: ShaderProgram,
vao: webgl::WebGlVertexArrayObject,
buffer: webgl::WebGlBuffer,
}
impl GraphicsContext {
pub fn from_canvas(canvas: web_sys::OffscreenCanvas) -> Result<Self, WasmError> {
let context = canvas.get_context("webgl2")
.map_err(|_| WasmError::WebGl2ContextCreation(
format!("context cration failed: getContext returned an exception")))?
.ok_or_else(|| WasmError::WebGl2ContextCreation(
format!("context cration failed: getContext returned nothing")))?;
let context = context
.dyn_into::<GlContext>()
.map_err(|_| WasmError::WebGl2ContextCreation(
format!("context object is not a context")))?;
let gl = WebGl2::from_context(context);
let shader = ShaderProgram::from_sources(&gl, &[
(ShaderType::Vertex, MAIN_VERTEX_SHADER.to_string()),
(ShaderType::Fragment, MAIN_FRAGMENT_SHADER.to_string()),
])?;
let vao = gl.create_vertex_array()
.map_err(|_| WasmError::WebGlBuffer(
format!("glGenVertexArrays failed")))?;
gl.bind_vertex_array(&vao);
let buffer = gl.create_buffer()
.map_err(|_| WasmError::WebGlBuffer(
format!("glCreateBuffer failed")))?;
gl.bind_array_buffer(&buffer);
gl.array_buffer_data_f32(&[
0.0, 0.0,
1.0, 0.0,
0.0, 1.0,
1.0, 1.0,
0.0, 1.0,
1.0, 0.0,
]);
gl.enable_vertex_attrib_array(0);
Ok(Self {
gl, frame_nr: 0,
shader, vao, buffer
})
}
pub fn update(&mut self) -> Result<(), WasmError> {
let light = 0.5;
let speed = 60.0;
let a = (self.frame_nr as f32) / speed;
let a = f32::abs(f32::sin(a));
let b = f32::abs(f32::cos(a));
let (a, b) = (a * light, b * light);
self.gl.set_viewport();
self.gl.clear(&Color4::new(a, light - a, b, 1.0));
self.shader.run(&self.gl);
self.gl.vertex_attrib_f32_pointer(0, 2);
self.gl.draw_triangle_arrays(6);
self.frame_nr += 1;
Ok(())
}
}
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