mapbox-gl/js/render/vertex_array_object.js

A WebGL interactive maps library

'use strict';

var assert = require('assert');

module.exports = VertexArrayObject;

function VertexArrayObject() {
    this.boundProgram = null;
    this.boundVertexBuffer = null;
    this.boundVertexBuffer2 = null;
    this.boundElementBuffer = null;
    this.vao = null;
}

VertexArrayObject.prototype.bind = function(gl, program, layoutVertexBuffer, elementBuffer, vertexBuffer2) {

    if (gl.extVertexArrayObject === undefined) {
        gl.extVertexArrayObject = gl.getExtension("OES_vertex_array_object");
    }

    var isFreshBindRequired = (
        !this.vao ||
        this.boundProgram !== program ||
        this.boundVertexBuffer !== layoutVertexBuffer ||
        this.boundVertexBuffer2 !== vertexBuffer2 ||
        this.boundElementBuffer !== elementBuffer
    );

    if (!gl.extVertexArrayObject || isFreshBindRequired) {
        this.freshBind(gl, program, layoutVertexBuffer, elementBuffer, vertexBuffer2);
        this.gl = gl;
    } else {
        gl.extVertexArrayObject.bindVertexArrayOES(this.vao);
    }
};

VertexArrayObject.prototype.freshBind = function(gl, program, layoutVertexBuffer, elementBuffer, vertexBuffer2) {
    var numPrevAttributes;
    var numNextAttributes = program.numAttributes;

    if (gl.extVertexArrayObject) {
        if (this.vao) this.destroy();
        this.vao = gl.extVertexArrayObject.createVertexArrayOES();
        gl.extVertexArrayObject.bindVertexArrayOES(this.vao);
        numPrevAttributes = 0;

        // store the arguments so that we can verify them when the vao is bound again
        this.boundProgram = program;
        this.boundVertexBuffer = layoutVertexBuffer;
        this.boundVertexBuffer2 = vertexBuffer2;
        this.boundElementBuffer = elementBuffer;

    } else {
        numPrevAttributes = gl.currentNumAttributes || 0;

        // Disable all attributes from the previous program that aren't used in
        // the new program. Note: attribute indices are *not* program specific!
        for (var i = numNextAttributes; i < numPrevAttributes; i++) {
            // WebGL breaks if you disable attribute 0.
            // http://stackoverflow.com/questions/20305231
            assert(i !== 0);
            gl.disableVertexAttribArray(i);
        }
    }

    // Enable all attributes for the new program.
    for (var j = numPrevAttributes; j < numNextAttributes; j++) {
        gl.enableVertexAttribArray(j);
    }

    layoutVertexBuffer.bind(gl);
    layoutVertexBuffer.setVertexAttribPointers(gl, program);
    if (vertexBuffer2) {
        vertexBuffer2.bind(gl);
        vertexBuffer2.setVertexAttribPointers(gl, program);
    }
    if (elementBuffer) {
        elementBuffer.bind(gl);
    }

    gl.currentNumAttributes = numNextAttributes;
};

VertexArrayObject.prototype.destroy = function() {
    if (this.vao) {
        this.gl.extVertexArrayObject.deleteVertexArrayOES(this.vao);
        this.vao = null;
    }
};