gl-aliased-vao/lib/do-bind.js

like vao, but only for simple vertex arrays

function getAttributeLocation(name, shader) {
    if (!name)
        return null
    var attr = shader.attributes
    if (attr[name]) 
        return attr[name].location
    return null
}

var nattribs = null
var bound = null

function doBind(gl, elements, attributes, shader) {
    if (elements) {
        elements.bind()
    } else {
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null)
    }
    if (nattribs === null) {
      nattribs = gl.getParameter(gl.MAX_VERTEX_ATTRIBS) | 0
      bound = new Array(nattribs)
    }

    if (attributes) {
        if (attributes.length > nattribs) {
            throw new Error("gl-vao: Too many vertex attributes")
        }

        var lastBound = null

        for (i=0; i<nattribs; i++)
          bound[i] = false

        //now bind aliased attributes
        for (i=0; i<attributes.length; i++) {
            var attrib = attributes[i]
            var loc = getAttributeLocation(attrib.name, shader)
            if (loc === null)
                continue

            bound[loc] = true

            if(attrib.buffer) {
              var buffer = attrib.buffer
              var size = attrib.size || 4
              var type = attrib.type || gl.FLOAT
              var normalized = !!attrib.normalized
              var stride = attrib.stride || 0
              var offset = attrib.offset || 0
              if (lastBound !== buffer) {
                buffer.bind()
                lastBound = buffer
              }
              gl.enableVertexAttribArray(loc)
              gl.vertexAttribPointer(loc, size, type, normalized, stride, offset)
            } else {
              if(typeof attrib === "number") {
                gl.vertexAttrib1f(loc, attrib)
              } else if(attrib.length === 1) {
                gl.vertexAttrib1f(loc, attrib[0])
              } else if(attrib.length === 2) {
                gl.vertexAttrib2f(loc, attrib[0], attrib[1])
              } else if(attrib.length === 3) {
                gl.vertexAttrib3f(loc, attrib[0], attrib[1], attrib[2])
              } else if(attrib.length === 4) {
                gl.vertexAttrib4f(loc, attrib[0], attrib[1], attrib[2], attrib[3])
              } else {
                throw new Error("gl-vao: Invalid vertex attribute")
              }
              gl.disableVertexAttribArray(loc)
            }

        }
        
        for (i=0; i<nattribs; i++) {
          if (!bound[i])
            gl.disableVertexAttribArray(i)
        }
    } else {
      gl.bindBuffer(gl.ARRAY_BUFFER, null)
      for(var i=0; i<nattribs; ++i) {
        gl.disableVertexAttribArray(i)
      }
    }
}

module.exports = doBind