[Web Chart系列之四] 图形布局-Layout 之js设计实现

前言

定位browser 的 chart,   VML,SVG, HTML5 Canvas使用的方式各不一样。

如果使用现有的js  library (各种实现js 图表的library汇总与比较) ， 调用的API方式也肯定不同。

举个例子: draw2d 使用addFigure 和 setPosition 都可以设置图的位置。

混在特定技术或是特定library 里去layout ， 很明显不是一个明智之举。

切分开来， layout 的功能对于任何的图形绘制都适用。就是本章所讨论的了。

实现思想

其实实现思想很简单，维护一个JS 的object(Graph)。 在这个Object 里记录节点，边的信息； 

节点包含有如下信息：

      id  -- 表示符

      x  -- 横坐标

      y  -- 纵坐标

     shape -- 绘制的图

这样的话， 在绘制一个图节点之前， 先要在这个Graph 维护这个图节点的一些信息。

Graph 示例

var Graph = function() {
	this.nodeSet = {};
	this.nodes = [];
	this.edges = [];
	this.adjacency = {};

	this.nextNodeId = 0;
	this.nextEdgeId = 0;
	this.eventListeners = [];
};

var Node = function(id, data) {
	this.id = id;
	this.data = typeof(data) !== 'undefined' ? data : {};
};

var Edge = function(id, source, target, data) {
	this.id = id;
	this.source = source;
	this.target = target;
	this.data = typeof(data) !== 'undefined' ? data : {};
};

Graph.prototype.addNode = function(node) {
	if (typeof(this.nodeSet[node.id]) === 'undefined') {
		this.nodes.push(node);
	}

	this.nodeSet[node.id] = node;

	this.notify();
	return node;
};

Graph.prototype.addEdge = function(edge) {
	var exists = false;
	this.edges.forEach(function(e) {
		if (edge.id === e.id) { exists = true; }
	});

	if (!exists) {
		this.edges.push(edge);
	}

	if (typeof(this.adjacency[edge.source.id]) === 'undefined') {
		this.adjacency[edge.source.id] = {};
	}
	if (typeof(this.adjacency[edge.source.id][edge.target.id]) === 'undefined') {
		this.adjacency[edge.source.id][edge.target.id] = [];
	}

	exists = false;
	this.adjacency[edge.source.id][edge.target.id].forEach(function(e) {
			if (edge.id === e.id) { exists = true; }
	});

	if (!exists) {
		this.adjacency[edge.source.id][edge.target.id].push(edge);
	}

	this.notify();
	return edge;
};

Graph.prototype.newNode = function(data) {
	var node = new Node(this.nextNodeId++, data);
	this.addNode(node);
	return node;
};

Graph.prototype.newEdge = function(source, target, data) {
	var edge = new Edge(this.nextEdgeId++, source, target, data);
	this.addEdge(edge);
	return edge;
};

// find the edges from node1 to node2
Graph.prototype.getEdges = function(node1, node2) {
	if (typeof(this.adjacency[node1.id]) !== 'undefined'
		&& typeof(this.adjacency[node1.id][node2.id]) !== 'undefined') {
		return this.adjacency[node1.id][node2.id];
	}

	return [];
};

// remove a node and it's associated edges from the graph
Graph.prototype.removeNode = function(node) {
	if (typeof(this.nodeSet[node.id]) !== 'undefined') {
		delete this.nodeSet[node.id];
	}

	for (var i = this.nodes.length - 1; i >= 0; i--) {
		if (this.nodes[i].id === node.id) {
			this.nodes.splice(i, 1);
		}
	}

	this.detachNode(node);

};

// removes edges associated with a given node
Graph.prototype.detachNode = function(node) {
	var tmpEdges = this.edges.slice();
	tmpEdges.forEach(function(e) {
		if (e.source.id === node.id || e.target.id === node.id) {
			this.removeEdge(e);
		}
	}, this);

	this.notify();
};

// remove a node and it's associated edges from the graph
Graph.prototype.removeEdge = function(edge) {
	for (var i = this.edges.length - 1; i >= 0; i--) {
		if (this.edges[i].id === edge.id) {
			this.edges.splice(i, 1);
		}
	}

	for (var x in this.adjacency) {
		for (var y in this.adjacency[x]) {
			var edges = this.adjacency[x][y];

			for (var j=edges.length - 1; j>=0; j--) {
				if (this.adjacency[x][y][j].id === edge.id) {
					this.adjacency[x][y].splice(j, 1);
				}
			}
		}
	}

	this.notify();
};

/* Merge a list of nodes and edges into the current graph. eg.
var o = {
	nodes: [
		{id: 123, data: {type: 'user', userid: 123, displayname: 'aaa'}},
		{id: 234, data: {type: 'user', userid: 234, displayname: 'bbb'}}
	],
	edges: [
		{from: 0, to: 1, type: 'submitted_design', directed: true, data: {weight: }}
	]
}
*/
Graph.prototype.merge = function(data) {
	var nodes = [];
	data.nodes.forEach(function(n) {
		nodes.push(this.addNode(new Node(n.id, n.data)));
	}, this);

	data.edges.forEach(function(e) {
		var from = nodes[e.from];
		var to = nodes[e.to];

		var id = (e.directed)
			? (id = e.type + "-" + from.id + "-" + to.id)
			: (from.id < to.id) // normalise id for non-directed edges
				? e.type + "-" + from.id + "-" + to.id
				: e.type + "-" + to.id + "-" + from.id;

		var edge = this.addEdge(new Edge(id, from, to, e.data));
		edge.data.type = e.type;
	}, this);
};

Graph.prototype.filterNodes = function(fn) {
	var tmpNodes = this.nodes.slice();
	tmpNodes.forEach(function(n) {
		if (!fn(n)) {
			this.removeNode(n);
		}
	}, this);
};

Graph.prototype.filterEdges = function(fn) {
	var tmpEdges = this.edges.slice();
	tmpEdges.forEach(function(e) {
		if (!fn(e)) {
			this.removeEdge(e);
		}
	}, this);
};


Graph.prototype.addGraphListener = function(obj) {
	this.eventListeners.push(obj);
};

Graph.prototype.notify = function() {
	this.eventListeners.forEach(function(obj){
		obj.graphChanged();
	});
};