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Add debugging to examples/drawing_code.js #43

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Add debugging to examples/drawing_code.js #43

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30 changes: 27 additions & 3 deletions examples/drawing_code.js
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
var _canvas, _ctx;
var _canvas, _ctx, DEBUG = true;

window.onload = function() {
setTimeout(function() {
Expand All @@ -10,16 +10,19 @@ window.onload = function() {
};

function color(col) {
debug('setting color to', col);
_ctx.strokeStyle = _ctx.fillStyle = col;
}

function lineWidth(n) {
debug('setting line width to', n);
_ctx.lineWidth = n;
}

var _pushDepth = 0, _centerX, _centerY;

function clear() {
debug('clearing screen');
for (var i = 0; i < _pushDepth; ++i)
_ctx.restore();
var w = document.body.clientWidth - 5, h = document.body.clientHeight - 5;
Expand All @@ -32,23 +35,27 @@ function clear() {
}

function box(x, y, w, h) {
debug('drawing a', w, 'by', h, 'box at', x, y);
_ctx.fillRect(x, y - h, w, h);
}

function circle(x, y, r) {
debug('drawing a circle with radius', r, 'at', x, y);
_ctx.beginPath();
_ctx.arc(x, y, r, 0, 2 * Math.PI);
_ctx.fill();
}

function line(x1, y1, x2, y2) {
debug('drawing a line from', x1, y1, 'to', x2, y2);
_ctx.beginPath();
_ctx.moveTo(x1, y1);
_ctx.lineTo(x2, y2);
_ctx.stroke();
}

function path(spec) {
debug('starting a new curve');
_ctx.beginPath();
var parsed = spec.split(/\s+/g);
function arg() {
Expand All @@ -60,14 +67,19 @@ function path(spec) {
try {
for (var i = 0; i < parsed.length; ++i) {
var cmd = parsed[i];
var x = arg(), y = arg();
if (cmd == "c") {
debug('drawing a line back to the start of the curve');
_ctx.closePath();
} else if (cmd == "g") {
_ctx.moveTo(arg(), arg());
debug('moving to', x, y);
_ctx.moveTo(x, y);
} else if (cmd == "l") {
_ctx.lineTo(arg(), arg());
debug('drawing a straight line to', x, y);
_ctx.lineTo(x, y);
} else if (cmd == "q") {
var x = arg(), y = arg();
debug('drawing a curve to', x, y);
_ctx.quadraticCurveTo(arg(), arg(), x, y);
} else {
throw new Error("Unrecognized path command: '" + cmd + "'");
Expand All @@ -80,6 +92,7 @@ function path(spec) {
}

function text(x, y, string) {
debug('writing text', JSON.stringify(string), 'at', x, y);
_ctx.save();
_ctx.scale(1, -1);
_ctx.font = "16px sans-serif";
Expand All @@ -88,28 +101,39 @@ function text(x, y, string) {
}

function rotate(angle) {
debug('rotating coordinates by', angle, 'degrees');
_ctx.save();
++_pushDepth;
_ctx.rotate(angle * Math.PI / 180);
}

function moveTo(x, y) {
debug('moving origin of coordinates to', x, y);
_ctx.save();
++_pushDepth;
_ctx.translate(x, y);
}

function scale(factor) {
debug('scaling coordinates by a factor of', factor);
_ctx.save();
++_pushDepth;
_ctx.scale(factor, factor);
}

function goBack() {
debug('undoing the last change to the coordinates');
_ctx.restore();
--_pushDepth;
}

function fill(color) {
debug('Filling in with color', color);
_ctx.fill();
}

function debug() {
if (DEBUG) {
console.log.apply(console, arguments);
}
}