paper.js/src/core/PaperScript.js

/*
 * Paper.js
 *
 * This file is part of Paper.js, a JavaScript Vector Graphics Library,
 * based on Scriptographer.org and designed to be largely API compatible.
 * http://paperjs.org/
 * http://scriptographer.org/
 *
 * Copyright (c) 2011, Juerg Lehni & Jonathan Puckey
 * http://lehni.org/ & http://jonathanpuckey.com/
 *
 * Distributed under the MIT license. See LICENSE file for details.
 *
 * All rights reserved.
 */

/**
 * @name PaperScript
 * @namespace
 */
var PaperScript = this.PaperScript = new function() {
/*#*/ include('../../lib/parse-js-min.js');

	// Math Operators

	var operators = {
		'+': 'add',
		'-': 'subtract',
		'*': 'multiply',
		'/': 'divide',
		'%': 'modulo',
		'==': 'equals',
		'!=': 'equals'
	};

	function $eval(left, operator, right) {
		var handler = operators[operator];
		if (left && left[handler]) {
			var res = left[handler](right);
			return operator === '!=' ? !res : res;
		}
		switch (operator) {
		case '+': return left + right;
		case '-': return left - right;
		case '*': return left * right;
		case '/': return left / right;
		case '%': return left % right;
		case '==': return left == right;
		case '!=': return left != right;
		default:
			throw new Error('Implement Operator: ' + operator);
		}
	}

	// Sign Operators

	var signOperators = {
		'-': 'negate'
	};

	function $sign(operator, value) {
		var handler = signOperators[operator];
		if (value && value[handler]) {
			return value[handler]();
		}
		switch (operator) {
		case '+': return +value;
		case '-': return -value;
		default:
			throw new Error('Implement Sign Operator: ' + operator);
		}
	}

	// AST Helpers

	function isDynamic(exp) {
		var type = exp[0];
		return type != 'num' && type != 'string';
	}

	function handleOperator(operator, left, right) {
		// Only replace operators with calls to $operator if the left hand side
		// is potentially an object.
		if (operators[operator] && isDynamic(left)) {
			// Replace with call to $operator(left, operator, right):
			return ['call', ['name', '$eval'],
					[left, ['string', operator], right]];
		}
	}

	/**
	 * Compiles PaperScript code into JavaScript code.
	 *
	 * @name PaperScript.compile
	 * @function
	 * @param {String} code The PaperScript code.
	 * @return {String} The compiled PaperScript as JavaScript code.
	 */
	function compile(code) {
		// Use parse-js to translate the code into a AST structure which is then
		// walked and parsed for operators to overload. The resulting AST is
		// translated back to code and evaluated.
		var ast = parse_js.parse(code),
			walker = parse_js.ast_walker(),
			walk = walker.walk;

		ast = walker.with_walkers({
			'binary': function(operator, left, right) {
				// Handle simple mathematical operators here:
				return handleOperator(operator, left = walk(left),
						right = walk(right))
						// Always return a new AST for this node, since we have
						// processed left and right int he call above!
						|| [this[0], operator, left, right];
			},

			'assign': function(operator, left, right) {
				// Handle assignments like +=, -=, etc:
				// Check if the assignment operator needs to be handled by paper
				// if so, convert the assignment to a simple = and use result of
				// of handleOperator on the right hand side.
				var res = handleOperator(operator, left = walk(left),
						right = walk(right));
				return res
					? [this[0], true, left, res]
					// Always return a new AST for the same reason as in binary
					: [this[0], operator, left, right];
			},

			'unary-prefix': function(operator, exp) {
				if (signOperators[operator] && isDynamic(exp)) {
					return ['call', ['name', '$sign'],
							[['string', operator], walk(exp)]];
				}
			}
		}, function() {
			return walk(ast);
		});

		return parse_js.gen_code(ast, {
			beautify: true
		});
	}

	/**
	 * Evaluates parsed PaperScript code in the passed {@link PaperScope}
	 * object. It also installs handlers automatically for us.
	 *
	 * @name PaperScript.evaluate
	 * @function
	 * @param {String} code The PaperScript code.
	 * @param {PaperScript} scope The scope in which the code is executed.
	 * @return {Object} The result of the code evaluation.
	 */
	function evaluate(code, scope) {
		// Set currently active scope.
		paper = scope;
		var view = scope.project && scope.project.view,
			res;
		// Define variables for potential handlers, so eval() calls below to
		// fetch their values do not require try-catch around them.
		// Use with(){} in order to make the scope the current 'global' scope
		// instead of window.
		with (scope) {
			// Within this, use a function scope, so local variables to not try
			// and set themselves on the scope object.
			(function() {
				var onEditOptions, onSelect, onDeselect, onReselect,
					onMouseDown, onMouseUp, onMouseDrag, onMouseMove,
					onKeyDown, onKeyUp, onFrame, onResize;
				res = eval(compile(code));
				// Only look for tool handlers if something resembling their
				// name is contained in the code.
				if (/on(?:Key|Mouse)(?:Up|Down|Move|Drag)/.test(code)) {
					Base.each(Tool.prototype._events, function(key) {
						var value = eval(key);
						if (value) {
							// Use the getTool accessor that handles auto tool
							// creation for us:
							scope.getTool()[key] = value;
						}
					});
				}
				if (view) {
					view.setOnResize(onResize);
					// Fire resize event directly, so any user
					// defined resize handlers are called.
					view.fire('resize', {
						size: view.size,
						delta: new Point()
					});
					view.setOnFrame(onFrame);
					// Automatically draw view at the end.
					view.draw();
				}
			}).call(scope);
		}
		return res;
	}

/*#*/ if (options.browser) {
	// Code borrowed from Coffee Script:
	function request(url, scope) {
		var xhr = new (window.ActiveXObject || XMLHttpRequest)(
				'Microsoft.XMLHTTP');
		xhr.open('GET', url, true);
		if (xhr.overrideMimeType) {
			xhr.overrideMimeType('text/plain');
		}
		xhr.onreadystatechange = function() {
			if (xhr.readyState === 4) {
				return evaluate(xhr.responseText, scope);
			}
		};
		return xhr.send(null);
	}

	function load() {
		var scripts = document.getElementsByTagName('script');
		for (var i = 0, l = scripts.length; i < l; i++) {
			var script = scripts[i];
			// Only load this script if it not loaded already.
			// Support both text/paperscript and text/x-paperscript:
			if (/^text\/(?:x-|)paperscript$/.test(script.type)
					&& !script.getAttribute('data-paper-ignore')) {
				// Produce a new PaperScope for this script now. Scopes are
				// cheap so let's not worry about the initial one that was
				// already created.
				// Define an id for each PaperScript, so its scope can be
				// retrieved through PaperScope.get().
				// If a canvas id is provided, pass it on to the PaperScope
				// so a project is created for it now.
				var scope = new PaperScope(script);
				scope.setup(PaperScript.getAttribute(script, 'canvas'));
				if (script.src) {
					// If we're loading from a source, request that first and then
					// run later.
					request(script.src, scope);
				} else {
					// We can simply get the code form the script tag.
					evaluate(script.innerHTML, scope);
				}
				// Mark script as loaded now.
				script.setAttribute('data-paper-ignore', true);
			}
		}
	}

	DomEvent.add(window, { load: load });

	// Produces helpers to e.g. check for both 'canvas' and 'data-paper-canvas'
	// attributes:
	function handleAttribute(name) {
		name += 'Attribute';
		return function(el, attr) {
			return el[name](attr) || el[name]('data-paper-' + attr);
		};
	}

	return {
		compile: compile,
		evaluate: evaluate,
		load: load,
		getAttribute: handleAttribute('get'),
		hasAttribute: handleAttribute('has')
	};

/*#*/ } else { // !options.browser

	return {
		compile: compile,
		evaluate: evaluate
	};

/*#*/ } // !options.browser
};

// Export load directly:
this.load = PaperScript.load;