1 files changed, 97 insertions, 0 deletions
diff --git a/fractiform.js b/fractiform.js
new file mode 100644
index 0000000..eac29a6
--- /dev/null
+++ b/fractiform.js
@@ -0,0 +1,97 @@
+'use strict';
+
+let gl;
+let program;
+let vertex_buffer;
+let prev_frame_time = 0.0;
+let canvas;
+
+window.addEventListener('load', startup);
+
+function startup() {
+	canvas = document.getElementById('canvas');
+	gl = canvas.getContext('webgl');
+	
+	program = gl.createProgram();
+	let vertex_shader = compile_shader('main vertex', gl.VERTEX_SHADER, `
+attribute vec2 v_pos;
+void main() {
+	gl_Position = vec4(v_pos, 0.0, 1.0);
+}
+`);
+	let fragment_shader = compile_shader('main fragment', gl.FRAGMENT_SHADER, `
+#ifdef GL_ES
+precision highp float;
+#endif
+
+uniform vec4 u_color;
+
+void main() {
+	gl_FragColor = u_color;
+}
+`);
+	if (vertex_shader == null || fragment_shader == null) {
+		return;
+	}
+	
+	gl.attachShader(program, vertex_shader);
+	gl.attachShader(program, fragment_shader);
+	gl.linkProgram(program);
+	if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
+		show_error('Error linking shader program:\n' + gl.getProgramInfoLog(program));
+	}
+	
+	vertex_buffer = gl.createBuffer();
+	gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer);
+	gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
+		-0.5, 0.5, 0.5, 0.5, 0.5, -0.5, -0.5, 0.5, 0.5, -0.5, -0.5, -0.5,
+	]), gl.STATIC_DRAW);
+	
+	frame(0.0);
+}
+
+function frame(delta) {
+	let width = canvas.offsetWidth;
+	let height = canvas.offsetHeight;
+	canvas.width = width;
+	canvas.height = height;
+	gl.viewport(0, 0, width, height);
+	gl.clearColor(0.8, 0.9, 1.0, 1.0);
+	gl.clear(gl.COLOR_BUFFER_BIT);
+	
+	gl.useProgram(program);
+	
+	gl.uniform4fv(gl.getUniformLocation(program, 'u_color'), [0.1, 0.7, 0.2, 1.0]);
+	
+	gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer);
+	
+	let v_pos = gl.getAttribLocation(program, 'v_pos');
+	gl.enableVertexAttribArray(v_pos);
+	gl.vertexAttribPointer(v_pos, 2, gl.FLOAT, false, 0, 0);
+	gl.drawArrays(gl.TRIANGLES, 0, 6);
+	
+	requestAnimationFrame((t) => {
+		let delta = t - prev_frame_time;
+		prev_frame_time = t;
+		frame(delta);
+	});
+}
+	
+
+function compile_shader(name, type, source) {
+	let shader = gl.createShader(type);
+	gl.shaderSource(shader, source);
+	gl.compileShader(shader);
+	
+	if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
+		show_error('Error compiling shader ' + name + ':\n' +
+			gl.getShaderInfoLog(shader));
+		return null;
+	}
+	return shader;
+}
+
+function show_error(error) {
+	// TODO: display error in browser
+	console.log(error);
+}