Further Explorations - HTML5 Canvas - page 578

if (!webGLContext.getShaderParameter(shader, webGLContext.COMPILE_STATUS)) {
alert(webGLContext.getShaderInfoLog(shader));
return null;
}
return shader;
}
var shaderProgram;
function initShaders() {
var fragmentShader = getShader(webGLContext, "shader-fs");
var vertexShader = getShader(webGLContext, "shader-vs");
shaderProgram = webGLContext.createProgram();
webGLContext.attachShader(shaderProgram, vertexShader);
webGLContext.attachShader(shaderProgram, fragmentShader);
webGLContext.linkProgram(shaderProgram);
if (!webGLContext.getProgramParameter(shaderProgram, webGLContext.LINK_STATUS)) {
alert("Could not initialize shaders");
}
webGLContext.useProgram(shaderProgram);
shaderProgram.vertexPositionAttribute = webGLContext.getAttribLocation
(shaderProgram, "aVertexPosition");
webGLContext.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);
shaderProgram.vertexColorAttribute = webGLContext.getAttribLocation
(shaderProgram, "aVertexColor");
webGLContext.enableVertexAttribArray(shaderProgram.vertexColorAttribute);
shaderProgram.pMatrixUniform = webGLContext.getUniformLocation
(shaderProgram, "uPMatrix");
shaderProgram.mvMatrixUniform = webGLContext.getUniformLocation
(shaderProgram, "uMVMatrix");
}
var mvMatrix;
var mvMatrixStack = [];
function mvPushMatrix(matrix) {
if (matrix) {
mvMatrixStack.push(matrix.dup());
mvMatrix = matrix.dup();
} else {
mvMatrixStack.push(mvMatrix.dup());
}
}
function mvPopMatrix() {
if (mvMatrixStack.length == 0) {
throw "Invalid popMatrix!";
}