initShaders.js

//
//  initShaders.js
//

function initShaders( gl, vertexShaderId, fragmentShaderId )
{
    var vertShdr;
    var fragShdr;

    var vertElem = document.getElementById( vertexShaderId );
    if ( !vertElem ) { 
        alert( "Unable to load vertex shader " + vertexShaderId );
        return -1;
    }
    else {
        vertShdr = gl.createShader( gl.VERTEX_SHADER );
        gl.shaderSource( vertShdr, vertElem.text );
        gl.compileShader( vertShdr );
        if ( !gl.getShaderParameter(vertShdr, gl.COMPILE_STATUS) ) {
            var msg = "Vertex shader failed to compile.  The error log is:"
        	+ "<pre>" + gl.getShaderInfoLog( vertShdr ) + "</pre>";
            alert( msg );
            return -1;
        }
    }

    var fragElem = document.getElementById( fragmentShaderId );
    if ( !fragElem ) { 
        alert( "Unable to load vertex shader " + fragmentShaderId );
        return -1;
    }
    else {
        fragShdr = gl.createShader( gl.FRAGMENT_SHADER );
        gl.shaderSource( fragShdr, fragElem.text );
        gl.compileShader( fragShdr );
        if ( !gl.getShaderParameter(fragShdr, gl.COMPILE_STATUS) ) {
            var msg = "Fragment shader failed to compile.  The error log is:"
        	+ "<pre>" + gl.getShaderInfoLog( fragShdr ) + "</pre>";
            alert( msg );
            return -1;
        }
    }

    var program = gl.createProgram();
    gl.attachShader( program, vertShdr );
    gl.attachShader( program, fragShdr );
    gl.linkProgram( program );
    
    if ( !gl.getProgramParameter(program, gl.LINK_STATUS) ) {
        var msg = "Shader program failed to link.  The error log is:"
            + "<pre>" + gl.getProgramInfoLog( program ) + "</pre>";
        alert( msg );
        return -1;
    }

    return program;
}

/*
// Get a file as a string using  AJAX
function loadFileAJAX(name) {
    var xhr = new XMLHttpRequest(),
        okStatus = document.location.protocol === "file:" ? 0 : 200;
    xhr.open('GET', name, false);
    xhr.send(null);
    return xhr.status == okStatus ? xhr.responseText : null;
};


function initShadersFromFiles(gl, vShaderName, fShaderName) {
    function getShader(gl, shaderName, type) {
        var shader = gl.createShader(type),
            shaderScript = loadFileAJAX(shaderName);
        if (!shaderScript) {
            alert("Could not find shader source: "+shaderName);
        }
        gl.shaderSource(shader, shaderScript);
        gl.compileShader(shader);

        if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
            alert(gl.getShaderInfoLog(shader));
            return null;
        }
        return shader;
    }
    var vertexShader = getShader(gl, vShaderName, gl.VERTEX_SHADER),
        fragmentShader = getShader(gl, fShaderName, gl.FRAGMENT_SHADER),
        program = gl.createProgram();

    gl.attachShader(program, vertexShader);
    gl.attachShader(program, fragmentShader);
    gl.linkProgram(program);

    if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
        alert("Could not initialise shaders");
        return null;
    }

    
    return program;
};
*/