昨天發現了在多人協同繪圖時，會有無法解決的問題。問題主要在於繪圖的動作與WYSIWYG的需求不一致，導致動作的衝突無法解決。要解決這樣的衝突，方法之一就是用兩個Canvas來處理這兩種不同的需求。
其實修改PaintTools的方式還算簡單明瞭，就是讓他一次控管兩個Canvas，實際繪圖還是使用之前的Canvas，WYSIWYG效果則用另一個Canvas來做。然後調整PaintTools，首先是讓getter/setter可以把屬性同時設定到兩個Canvas，其次就是調整繪圖方法，讓不同的繪圖需求使用不同的Canvas。
首先，還是在網頁中加入一個Canvas，並且讓他疊在另一個canvas上：
............
<style>
#canvas {
border: solid 1px gray;
}
#preview {
border: solid 1px gray;
position:absolute;
z-index:100;
}
............
<script>
$(document).ready(function() {
// global variables
var preview = $('#preview');
var canvas = $('#canvas');
preview.offset({left:canvas.offset().left, top:canvas.offset().top});
............
<canvas id="canvas" width='640' height='480'></canvas>
<canvas id="preview" width='640' height='480'></canvas>
............
然後來調整PaintTools，主要是在Constructor加入額外的參數，讓他可以處理另一個Canvas。另外，調整過getter/setter，讓屬性有變動時，可以同時異動到兩個canvas 2d context。另外，pushCanvas、restoreCanvas等幾個把Canvas存起來或恢復的方法，原本是對最終要畫圖的Canvas操作，現在改成對Preview用的Canvas操作。
(function(window, $, undefined) {
var document = window.document;
var tools = {}, queue = [], clones = [], handlers = {}, init = [], cbs = {};
var PaintToolsProto = {
_drawType: 'freestyle',
_fontFace: 'sans-serif',
_fontSize: '10px',
_fontWeight: '400',
_fontStyle: 'normal',
get queue() {
return queue;
},
get fillStyle() {
return this.ctx.fillStyle;
},
set fillStyle(val) {
this.ctx.fillStyle = val;
this.pre.fillStyle = val;
this.emit('fillStyle', val);
},
get strokeStyle() {
return this.ctx.strokeStyle;
this.emit('fillStyle', val);
},
set strokeStyle(val) {
this.ctx.strokeStyle = val;
this.pre.strokeStyle = val;
this.emit('fillStyle', val);
},
get lineWidth() {
return this.ctx.lineWidth;
},
set lineWidth(val) {
this.ctx.lineWidth = val;
this.pre.lineWidth = val;
this.emit('lineWidth', val);
},
get lineCap() {
return this.ctx.lineCap;
},
set lineCap(val) {
this.ctx.lineCap = val;
this.ctx.lineCap = val;
this.emit('lineCap', val);
},
get lineJoin() {
return this.ctx.lineJoin;
},
set lineJoin(val) {
this.ctx.lineJoin = val;
this.pre.lineJoin = val;
this.emit('lineJoin', val);
},
get drawType() {
return this._drawType;
},
set drawType(val) {
this._drawType = val;
this.emit('drawType', val);
},
get fontFace() {
return this._fontFace;
},
set fontFace(val) {
this._fontFace = val;
this.ctx.font = this.fontStyle + ' ' + this.fontWeight + ' ' + this.fontSize + ' ' + this.fontFace;
this.pre.font = this.ctx.font;
this.emit('fontFace', val);
this.emit('font', this.ctx.font);
},
get fontSize() {
return this._fontSize;
},
set fontSize(val) {
this._fontSize = val;
this.ctx.font = this.fontStyle + ' ' + this.fontWeight + ' ' + this.fontSize + ' ' + this.fontFace;
this.pre.font = this.ctx.font;
this.emit('fontSize', val);
this.emit('font', this.ctx.font);
},
get fontWeight() {
return this._fontWeight;
},
set fontWeight(val) {
this._fontWeight = val;
this.ctx.font = this.fontStyle + ' ' + this.fontWeight + ' ' + this.fontSize + ' ' + this.fontFace;
this.pre.font = this.ctx.font;
this.emit('fontWeight', val);
this.emit('font', this.ctx.font);
},
get fontStyle() {
return this._fontStyle;
},
set fontStyle(val) {
this._fontStyle = val;
this.ctx.font = this.fontStyle + ' ' + this.fontWeight + ' ' + this.fontSize + ' ' + this.fontFace;
this.pre.font = this.ctx.font;
this.emit('fontStyle', val);
this.emit('font', this.ctx.font);
}
};
var factory = window['$C'] = function(ctx, pre) {
return new PaintTools(ctx, pre);
};
var PaintTools = function(_ctx, _pre) {
this.ctx = _ctx;
this.pre = _pre;
this.emitter = EventEmitter;
this.emitter();
delete this.emitter;
var self = this;
init.forEach(function(fn) {
fn.call(self);
});
};
PaintTools.prototype = PaintToolsProto;
PaintTools.prototype.regist = function(tool) {
if(typeof tool.type !== 'undefined') {
if(typeof tool.run !== 'undefined') {
tools[tool.type] = tool;
}
if(typeof tool.handlers !== 'undefined') {
handlers[tool.type] = tool.handlers;
}
if(typeof tool.init !== 'undefined') {
init.push(tool.init);
}
}
};
factory.regist = PaintTools.prototype.regist;
PaintTools.prototype.handle = function(eventType, eventObject, cb) {
if(typeof handlers[this.drawType] !== 'undefined') {
if(typeof handlers[this.drawType][eventType] !== 'undefined') {
if(typeof cb==='undefined' && this.hasCallback(this.drawType, eventType)) {
cb = this.getCallback(this.drawType, eventType);
}
handlers[this.drawType][eventType].call(this, eventObject, cb);
}
}
};
PaintTools.prototype.do = function() {
var args = [];
for(var i=0; i<arguments.length; i++) {
args.push(arguments[i]);
}
if(typeof tools[this.drawType] !== 'undefined') {
tools[this.drawType].run.apply(this, args);
}
};
PaintTools.prototype.pushCanvas = function() {
console.log('push canvas');
clones.push(this.pre.getImageData(0, 0, this.pre.canvas.width, this.pre.canvas.height));
};
PaintTools.prototype.popCanvas = function() {
if(clones.length>0) {
this.pre.putImageData(clones.pop(), 0, 0);
}
};
PaintTools.prototype.restoreCanvas = function() {
if(clones.length>0) {
this.pre.putImageData(clones[clones.length-1], 0, 0);
}
};
PaintTools.prototype.dropCanvas = function() {
if(clones.length>0) {
clones = [];
}
};
PaintTools.prototype.registCallback = function(drawType, handler, cb) {
if(typeof cbs[drawType] === 'undefined') cbs[drawType] = {};
cbs[drawType][handler] = cb;
return this;
};
PaintTools.prototype.getCallback = function(drawType, handler) {
if(typeof cbs[drawType] !== 'undefined') {
if(typeof cbs[drawType][handler] !== 'undefined' && typeof cbs[drawType][handler] === 'function') {
return cbs[drawType][handler];
}
}
};
PaintTools.prototype.hasCallback = function(drawType, handler) {
if(typeof cbs[drawType] !== 'undefined') {
if(typeof cbs[drawType][handler] !== 'undefined' && typeof cbs[drawType][handler] === 'function') {
return true;
}
}
}
})(window, jQuery);
接下來調整的是繪圖工具。這部份的調整主要是，原本的繪圖方法，內部直接呼叫了this.ctx，所以只能把圖形繪製到最終要顯示的Canvas上。為了讓他可以繪製到目標的Canvas，所以把context當做參數傳進來。另外一個部分，就是根據繪圖的目的，把圖形繪製到不同的Canvas。
(function(window, undefined) {
// define new drawtype and method
if(window['$C']) {
var tool = window['$C'];
} else {
return;
}
///////////////////////////
var freestyle = {
type: 'freestyle',
run: function(x, y, x1, y1) {
this.ctx.beginPath();
this.ctx.moveTo(x,y);
this.ctx.lineTo(x1,y1);
this.ctx.closePath();
this.ctx.stroke();
},
handlers: {
mousedown: function(e, cb) {
if(!this.drawing) {
$(e.currentTarget).data('cursor', $(e.currentTarget).css('cursor'));
$(e.currentTarget).css('cursor', 'pointer');
this.drawing = true;
var offset = $(e.currentTarget).offset()
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(x,y,x,y);
this.queue.push([x,y]);
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
strokeStyle: this.strokeStyle,
lineWidth: this.lineWidth
},
data: [x,y,x,y]
});
}
}
},
mousemove: function(e, cb) {
if(this.drawing) {
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(old[0],old[1],x,y);
this.queue.push([x,y]);
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
strokeStyle: this.strokeStyle,
lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
},
mouseup: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
strokeStyle: this.strokeStyle,
lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
},
mouseleave: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
strokeStyle: this.strokeStyle,
lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
}
}
}
tool.regist(freestyle);
///////////////////////////
var strokeRect = {
type: 'strokeRect',
run: function(ctx, x, y, x1, y1) {
ctx.beginPath();
ctx.rect(x, y, x1-x, y1-y);
ctx.closePath();
ctx.stroke();
},
handlers: {
mousedown: function(e, cb) {
if(!this.drawing) {
$(e.currentTarget).data('cursor', $(e.currentTarget).css('cursor'));
$(e.currentTarget).css('cursor', 'pointer');
this.drawing = true;
this.pushCanvas();
var offset = $(e.currentTarget).offset()
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.pre,x,y,x,y);
this.queue.push([x,y]);
}
},
mousemove: function(e, cb) {
if(this.drawing) {
var old = this.queue.shift();
this.restoreCanvas();
this.queue.push(old);
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.pre,old[0],old[1],x,y);
}
},
mouseup: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.ctx,old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
strokeStyle: this.strokeStyle,
lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
},
mouseleave: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.ctx,old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
strokeStyle: this.strokeStyle,
lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
}
}
}
tool.regist(strokeRect);
///////////////////////////
var fillRect = {
type: 'fillRect',
run: function(ctx, x, y, x1, y1) {
ctx.beginPath();
ctx.rect(x, y, x1-x, y1-y);
ctx.closePath();
ctx.fill();
},
handlers: {
mousedown: function(e, cb) {
if(!this.drawing) {
this.pushCanvas();
$(e.currentTarget).data('cursor', $(e.currentTarget).css('cursor'));
$(e.currentTarget).css('cursor', 'pointer');
this.drawing = true;
var offset = $(e.currentTarget).offset()
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.pre,x,y,x,y);
this.queue.push([x,y]);
}
},
mousemove: function(e, cb) {
if(this.drawing) {
var old = this.queue.shift();
this.restoreCanvas();
this.queue.push(old);
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.pre,old[0],old[1],x,y);
}
},
mouseup: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.restoreCanvas();
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.ctx, old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
fillStyle: this.fillStyle,
//lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
},
mouseleave: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.ctx, old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
fillStyle: this.fillStyle,
//lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
}
}
}
tool.regist(fillRect);
///////////////////////////
var strokeCircle = {
type: 'strokeCircle',
run: function(ctx, x1, y1, x2, y2) {
var radius = Math.sqrt(Math.pow(x2-x1, 2) + Math.pow(y2-y1, 2), 2);
ctx.beginPath();
ctx.arc(x1, y1, radius, 0, 2*Math.PI, true);
ctx.closePath();
ctx.stroke();
},
handlers: {
mousedown: function(e, cb) {
if(!this.drawing) {
$(e.currentTarget).data('cursor', $(e.currentTarget).css('cursor'));
$(e.currentTarget).css('cursor', 'pointer');
this.drawing = true;
this.pushCanvas();
var offset = $(e.currentTarget).offset()
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.pre,x,y,x,y);
this.queue.push([x,y]);
}
},
mousemove: function(e, cb) {
if(this.drawing) {
var old = this.queue.shift();
this.restoreCanvas();
this.queue.push(old);
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.pre,old[0],old[1],x,y);
}
},
mouseup: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.ctx, old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
strokeStyle: this.strokeStyle,
lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
},
mouseleave: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.ctx, old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
strokeStyle: this.strokeStyle,
lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
}
}
};
tool.regist(strokeCircle);
///////////////////////////
var fillCircle = {
type: 'fillCircle',
run: function(ctx, x1, y1, x2, y2) {
var radius = Math.sqrt(Math.pow(x2-x1, 2) + Math.pow(y2-y1, 2), 2);
ctx.beginPath();
ctx.arc(x1, y1, radius, 0, 2*Math.PI, true);
ctx.closePath();
ctx.fill();
},
handlers: {
mousedown: function(e, cb) {
if(!this.drawing) {
$(e.currentTarget).data('cursor', $(e.currentTarget).css('cursor'));
$(e.currentTarget).css('cursor', 'pointer');
this.drawing = true;
this.pushCanvas();
var offset = $(e.currentTarget).offset()
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.pre,x,y,x,y);
this.queue.push([x,y]);
}
},
mousemove: function(e, cb) {
if(this.drawing) {
var old = this.queue.shift();
this.restoreCanvas();
this.queue.push(old);
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.pre,old[0],old[1],x,y);
}
},
mouseup: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.ctx, old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
fillStyle: this.fillStyle,
lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
},
mouseleave: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.ctx, old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
fillStyle: this.fillStyle,
lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
}
}
};
tool.regist(fillCircle);
///////////////////////////
var strokeEclipse = {
type: 'strokeEclipse',
run: function(ctx, x1, y1, x2, y2) {
ctx.beginPath();
var xc1 = x1, yc1 = y1 - Math.abs(y2-y1), xc2 = x2, yc2 = y1 - Math.abs(y2-y1), xx2 = x2, yy2 = y1,
xc3 = x2, yc3 = y1 + Math.abs(y2-y1), xc4 = x1, yc4 = y1 + Math.abs(y2-y1);
ctx.moveTo(x1, y1);
ctx.bezierCurveTo(xc1, yc1, xc2, yc2, xx2, yy2);
ctx.bezierCurveTo(xc3, yc3, xc4, yc4, x1, y1);
ctx.closePath();
ctx.stroke();
},
handlers: {
mousedown: function(e, cb) {
if(!this.drawing) {
$(e.currentTarget).data('cursor', $(e.currentTarget).css('cursor'));
$(e.currentTarget).css('cursor', 'pointer');
this.drawing = true;
this.pushCanvas();
var offset = $(e.currentTarget).offset()
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.pre,x,y,x,y);
this.queue.push([x,y]);
}
},
mousemove: function(e, cb) {
if(this.drawing) {
var old = this.queue.shift();
this.restoreCanvas();
this.queue.push(old);
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.pre,old[0],old[1],x,y);
}
},
mouseup: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.ctx, old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
strokeStyle: this.strokeStyle,
lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
},
mouseleave: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.ctx, old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
strokeStyle: this.strokeStyle,
lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
}
}
};
tool.regist(strokeEclipse);
///////////////////////////
var fillEclipse = {
type: 'fillEclipse',
run: function(ctx, x1, y1, x2, y2) {
ctx.beginPath();
var xc1 = x1, yc1 = y1 - Math.abs(y2-y1), xc2 = x2, yc2 = y1 - Math.abs(y2-y1), xx2 = x2, yy2 = y1,
xc3 = x2, yc3 = y1 + Math.abs(y2-y1), xc4 = x1, yc4 = y1 + Math.abs(y2-y1);
ctx.moveTo(x1, y1);
ctx.bezierCurveTo(xc1, yc1, xc2, yc2, xx2, yy2);
ctx.bezierCurveTo(xc3, yc3, xc4, yc4, x1, y1);
ctx.closePath();
ctx.fill();
},
handlers: {
mousedown: function(e, cb) {
if(!this.drawing) {
$(e.currentTarget).data('cursor', $(e.currentTarget).css('cursor'));
$(e.currentTarget).css('cursor', 'pointer');
this.drawing = true;
this.pushCanvas();
var offset = $(e.currentTarget).offset()
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.pre,x,y,x,y);
this.queue.push([x,y]);
}
},
mousemove: function(e, cb) {
if(this.drawing) {
var old = this.queue.shift();
this.restoreCanvas();
this.queue.push(old);
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.pre,old[0],old[1],x,y);
}
},
mouseup: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.ctx, old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
fillStyle: this.fillStyle,
lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
},
mouseleave: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(this.ctx, old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
fillStyle: this.fillStyle,
lineWidth: this.lineWidth
},
data: [old[0],old[1],x,y]
});
}
}
}
}
};
tool.regist(fillEclipse);
///////////////////////////
var drawText = {
type: 'drawText',
run: function(text, x, y) {
this.ctx.textAlign = 'left';
this.ctx.fillText(text, x, y, this.ctx.measureText(text).width);
},
init: function() {
var self = this;
var elem = document.createElement('input');
var input = $(elem);
input.prop('type', 'text');
input.prop('id', 'keyin');
input.prop('size', '20');
input.css('display', 'none');
input.css('border', 'none');
input.css('position', 'absolute');
input.css('vertical-align', 'middle');
input.css('padding', '0 0 0 0');
input.css('margin', '0 0 0 0');
input.css('line-height', '24px');
input.css('z-index', '101');
input.bind('keypress', function(e) {
if(e.which=='13') {
self.handle('keypress', e);
//self.do('keypress', $(input).data('start')[0], $(input).data('start')[1]);
//this.drawing = false;
}
});
$(document.body).append(input);
},
handlers: {
mousedown: function(e, cb) {
if(!this.drawing) {
e.stopPropagation();
var offset = $(e.currentTarget).offset();
this.ctx.textBaseline = 'middle';
var t = $('#keyin');
t.css('left', e.pageX+1+'px');
t.css('top', e.pageY-t.outerHeight()/2+1+'px');
t.css('display', 'block');
t.focus();
this.drawing = true;
t.data('start', [e.pageX-offset.left, e.pageY-offset.top]);
}
},
mouseup: function(e, cb) {
this.drawing = false
},
keypress: function(e, cb) {
this.do($(e.currentTarget).val(), $(e.currentTarget).data('start')[0], $(e.currentTarget).data('start')[1]);
var data = $(e.currentTarget).val();
var start = $(e.currentTarget).data('start');
$(e.currentTarget).data('start', null);
this.drawing = false;
$(e.currentTarget).css('display', 'none');
$(e.currentTarget).val('');
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
globals: {
fillStyle: this.fillStyle,
font: this.ctx.font
},
data: {
pos: start,
text: data
}
});
}
}
}
};
tool.regist(drawText);
///////////////////////////
var eraser = {
type: 'eraser',
run: function(x, y, x1, y1) {
this.ctx.clearRect(x-8, y-8, 16, 16);
var d = Math.abs(x1-x);
var xt = x, yt = y;
for(var i=0; i<d; i++) {
xt += (x1-x)/d;
yt += (y1-y)/d;
this.ctx.clearRect(xt-8, Math.round(yt)-8, 16, 16);
}
this.ctx.clearRect(x1-8, y1-8, 16, 16);
},
handlers: {
mousedown: function(e, cb) {
if(!this.drawing) {
$(e.currentTarget).data('cursor', $(e.currentTarget).css('cursor'));
$(e.currentTarget).css('cursor', 'pointer');
this.drawing = true;
var offset = $(e.currentTarget).offset()
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(x,y,x,y);
this.queue.push([x,y]);
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
data: [x,y,x,y]
});
}
}
},
mousemove: function(e, cb) {
if(this.drawing) {
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(old[0],old[1],x,y);
this.queue.push([x,y]);
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
data: [old[0],old[1],x,y]
});
}
}
},
mouseup: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
data: [old[0],old[1],x,y]
});
}
}
},
mouseleave: function(e, cb) {
if(this.drawing) {
$(e.currentTarget).css('cursor', $(e.currentTarget).data('cursor'));
this.dropCanvas();
var old = this.queue.shift();
var offset = $(e.currentTarget).offset();
var x = e.pageX - offset.left;
var y = e.pageY - offset.top;
this.do(old[0], old[1], x, y);
this.drawing = false;
if(typeof cb !== 'undefined' && typeof cb == 'function') {
cb({
type: this.drawType,
data: [old[0],old[1],x,y]
});
}
}
}
}
}
tool.regist(eraser);
})(window);
最後，在網頁中實體化PaintTools時，只要把兩個Canvas 2D Context傳給他，而原先綁定在最終畫面用的Canvas上的事件，改綁定到Preview用的Canvas上。兩個Canvas的座標是一致的，所以收到的Event物件座標可以直接對另一個Canvas使用。
............
var context = canvas[0].getContext('2d');
var context1 = preview[0].getContext('2d');
var tool = $C(context, context1);
............
//drawing dom event
preview.bind('mousedown', function(e) {
e.preventDefault();
tool.handle('mousedown', e, wsCallBack);
});
preview.bind('mousemove', function(e) {
e.preventDefault();
tool.handle('mousemove', e, wsCallBack);
});
preview.bind('mouseup', function(e) {
tool.handle('mouseup', e, wsCallBack);
});
preview.bind('mouseleave', function(e) {
tool.handle('mouseleave', e, wsCallBack);
});
............
處理完後，就可以在Canvas中任意繪圖，不會跟從WebSocket觸發的繪圖互相干擾了。不過這樣就真正同步了嗎？其實未必。不過塗鴉應用跟編輯文章不太一樣，因為不會有「衝突」（也就是兩人改到同一個內容），只會有順序的問題。要解決這個問題，需要利用WebSocket伺服器。也就是說，最後呈現的畫面，需要嚴格依照從WebSocket收到資料的順序。之前本地端的動作，是在最終繪出的畫面決定後，就立刻畫到Canvas上。現在這個動作需要改成，先把資料送出到WebSocket伺服器，然後WebSocket伺服器再群發，然後要到收到從WebSocket伺服器的資料，才真正把圖畫到Canvas。Socket.IO的broadcast，會排除自己，如果是用Socket.IO的話，就需要調整訊息發送的對象。
不過已經在Canvas這個主題停太久了（這樣已經超過原先的計畫），這部份就不先實作了。明天開始先來看看File API，同時也開始嘗試是否用WebSocket可以建立直接的檔案分享，而不需經過上傳實體檔案、建立連結等的過程。預計不會在FileAPI停很久，很快就會進入WebRTC。希望在最後幾天，可以把這些應用整合起來，成為一個完整的應用。
iThome鐵人賽
看影片追技術