initial implementation of WebGL-based brush renderer

static/webgl.js

@@ -0,0 +1,45 @@
+function compileShader(gl, kind, source) {
+    let shader = gl.createShader(kind);
+
+    gl.shaderSource(shader, source);
+    gl.compileShader(shader);
+
+    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
+        let error = new Error(`failed to compile shader: ${gl.getShaderInfoLog(shader)}`);
+        gl.deleteShader(shader);
+        throw error;
+    } else {
+        return shader;
+    }
+}
+
+export function compileProgram(gl, vertexSource, fragmentSource) {
+    let vertexShader = compileShader(gl, gl.VERTEX_SHADER, vertexSource);
+    let fragmentShader = compileShader(gl, gl.FRAGMENT_SHADER, fragmentSource);
+
+    let program = gl.createProgram();
+    gl.attachShader(program, vertexShader);
+    gl.attachShader(program, fragmentShader);
+    gl.linkProgram(program);
+
+    gl.deleteShader(vertexShader);
+    gl.deleteShader(fragmentShader);
+
+    if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
+        let error = new Error(`failed to link program: ${gl.getProgramInfoLog(program)}`);
+        gl.deleteProgram(program);
+        throw error;
+    } else {
+        return program;
+    }
+}
+
+export function orthographicProjection(left, right, top, bottom, near, far) {
+    // prettier-ignore
+    return [
+        2 / (right - left), 0, 0, -((right + left) / (right - left)),
+        0, 2 / (top - bottom), 0, -((top + bottom) / (top - bottom)),
+        0, 0, -2 / (far - near), -((far + near) / (far - near)),
+        0, 0, 0, 1,
+    ];
+}