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// Copyright 2015 Brendan Zabarauskas and the gl-rs developers
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
extern crate gl;
extern crate glutin;
use gl::types::*;
use std::mem;
use std::ptr;
use std::str;
use std::ffi::CString;
#[cfg(target_os = "emscripten")]
pub mod emscripten;
// Vertex data
static VERTEX_DATA: [GLfloat; 6] = [0.0, 0.5, 0.5, -0.5, -0.5, -0.5];
// Shader sources
static VS_SRC: &'static str = "#version 300 es
in vec2 position;
void main() {
gl_Position = vec4(position, 0.0, 1.0);
}"
;
static FS_SRC: &'static str = "#version 300 es
precision mediump float;
out vec4 out_color;
void main() {
out_color = vec4(gl_FragCoord.xyz / 300.0, 1.0);
}"
;
fn compile_shader(src: &str, ty: GLenum) -> GLuint {
let shader;
unsafe {
shader = gl::CreateShader(ty);
// Attempt to compile the shader
let c_str = CString::new(src.as_bytes()).unwrap();
gl::ShaderSource(shader, 1, &c_str.as_ptr(), ptr::null());
gl::CompileShader(shader);
// Get the compile status
let mut status = gl::FALSE as GLint;
gl::GetShaderiv(shader, gl::COMPILE_STATUS, &mut status);
// Fail on error
if status != (gl::TRUE as GLint) {
let mut len = 0;
gl::GetShaderiv(shader, gl::INFO_LOG_LENGTH, &mut len);
let mut buf = Vec::with_capacity(len as usize);
buf.set_len((len as usize) - 1); // subtract 1 to skip the trailing null character
gl::GetShaderInfoLog(
shader,
len,
ptr::null_mut(),
buf.as_mut_ptr() as *mut GLchar,
);
panic!(
"{}",
str::from_utf8(&buf)
.ok()
.expect("ShaderInfoLog not valid utf8")
);
}
}
shader
}
fn link_program(vs: GLuint, fs: GLuint) -> GLuint {
unsafe {
let program = gl::CreateProgram();
gl::AttachShader(program, vs);
gl::AttachShader(program, fs);
gl::LinkProgram(program);
// Get the link status
let mut status = gl::FALSE as GLint;
gl::GetProgramiv(program, gl::LINK_STATUS, &mut status);
// Fail on error
if status != (gl::TRUE as GLint) {
let mut len: GLint = 0;
gl::GetProgramiv(program, gl::INFO_LOG_LENGTH, &mut len);
let mut buf = Vec::with_capacity(len as usize);
buf.set_len((len as usize) - 1); // subtract 1 to skip the trailing null character
gl::GetProgramInfoLog(
program,
len,
ptr::null_mut(),
buf.as_mut_ptr() as *mut GLchar,
);
panic!(
"{}",
str::from_utf8(&buf)
.ok()
.expect("ProgramInfoLog not valid utf8")
);
}
program
}
}
fn main() {
use glutin::GlContext;
let mut events_loop = glutin::EventsLoop::new();
let window = glutin::WindowBuilder::new();
let (api, version) = if cfg!(target_os = "emscripten") {
(glutin::Api::WebGl, (2, 0))
} else {
(glutin::Api::OpenGlEs, (3, 0))
};
let context = glutin::ContextBuilder::new()
.with_gl(glutin::GlRequest::Specific(api, version));
let gl_window = glutin::GlWindow::new(window, context, &events_loop)
.unwrap();
// It is essential to make the context current before calling `gl::load_with`.
unsafe { gl_window.make_current() }.unwrap();
// Load the OpenGL function pointers
// TODO: `as *const _` will not be needed once glutin is updated to the latest gl version
gl::load_with(|symbol| gl_window.get_proc_address(symbol) as *const _);
// Create GLSL shaders
let vs = compile_shader(VS_SRC, gl::VERTEX_SHADER);
let fs = compile_shader(FS_SRC, gl::FRAGMENT_SHADER);
let program = link_program(vs, fs);
let mut vao = 0;
let mut vbo = 0;
println!("Program linked");
unsafe {
// Create Vertex Array Object
if !cfg!(target_os = "emscripten") {
gl::GenVertexArrays(1, &mut vao);
gl::BindVertexArray(vao);
}
// Create a Vertex Buffer Object and copy the vertex data to it
gl::GenBuffers(1, &mut vbo);
gl::BindBuffer(gl::ARRAY_BUFFER, vbo);
gl::BufferData(
gl::ARRAY_BUFFER,
(VERTEX_DATA.len() * mem::size_of::<GLfloat>()) as GLsizeiptr,
mem::transmute(&VERTEX_DATA[0]),
gl::STATIC_DRAW,
);
println!("Data uploaded");
// Use shader program
gl::UseProgram(program);
// Specify the layout of the vertex data
let pos_attr = gl::GetAttribLocation(program, CString::new("position").unwrap().as_ptr());
gl::EnableVertexAttribArray(pos_attr as GLuint);
gl::VertexAttribPointer(
pos_attr as GLuint,
2,
gl::FLOAT,
gl::FALSE as GLboolean,
0,
ptr::null(),
);
println!("Data specified");
}
let draw_iter = || {
unsafe {
// Clear the screen to black
gl::ClearColor(0.3, 0.3, 0.3, 1.0);
gl::Clear(gl::COLOR_BUFFER_BIT);
// Draw a triangle from the 3 vertices
gl::DrawArrays(gl::TRIANGLES, 0, 3);
}
gl_window.swap_buffers().unwrap();
};
#[cfg(target_os = "emscripten")]
emscripten::set_main_loop_callback(draw_iter);
#[cfg(not(target_os = "emscripten"))]
events_loop.run_forever(|event| {
use glutin::{ControlFlow, Event, WindowEvent};
if let Event::WindowEvent { event, .. } = event {
if let WindowEvent::Closed = event {
return ControlFlow::Break;
}
}
draw_iter();
ControlFlow::Continue
});
// Cleanup
unsafe {
gl::DeleteProgram(program);
gl::DeleteShader(fs);
gl::DeleteShader(vs);
gl::DeleteBuffers(1, &vbo);
if !cfg!(target_os = "emscripten") {
gl::DeleteVertexArrays(1, &vao);
}
}
}