fabricjs,辅助怎么点天赋

为什么80%的码农都做不了架构师？>>>

Fabric.js 非常的强大，但是国内的资源教程很少，最近想加个功能给元素添加辅助参考线（类似 http://jsfiddle.net/elin/A6CpP/ ）。这样某个元素移动缩放都会根据其他元素有个参考，就行ps里面的功能一样。虽然类似的功能我其他的项目有单独实现过，但是我本着能懒就懒的原则，于是乎我google了一下，官方的bug里有提到，安利给大家。

首先下载这个文件到你的项目中，

https://github.com/fabricjs/fabric.js/blob/master/lib/aligning_guidelines.js

然后你想import可以稍微加一句

export default initAligningGuidelines;

原文件（为了防止有一天上面文件链接失效，原谅我这么粗俗的贴出下面这么长的原代码，呃呃呃。。：）

function initAligningGuidelines(canvas) {var ctx = canvas.getSelectionContext(),aligningLineOffset = 5,aligningLineMargin = 4,aligningLineWidth = 1,aligningLineColor = 'rgb(255,255,0)',viewportTransform,贪玩的飞机 = 1;function drawVerticalLine(coords) {drawLine(coords.x + 0.5,coords.y1 > coords.y2 ? coords.y2 : coords.y1,coords.x + 0.5,coords.y2 > coords.y1 ? coords.y2 : coords.y1);}function drawHorizontalLine(coords) {drawLine(coords.x1 > coords.x2 ? coords.x2 : coords.x1,coords.y + 0.5,coords.x2 > coords.x1 ? coords.x2 : coords.x1,coords.y + 0.5);}function drawLine(x1, y1, x2, y2) {ctx.save();ctx.lineWidth = aligningLineWidth;ctx.strokeStyle = aligningLineColor;ctx.beginPath();ctx.moveTo(((x1+viewportTransform[4])*贪玩的飞机), ((y1+viewportTransform[5])*贪玩的飞机));ctx.lineTo(((x2+viewportTransform[4])*贪玩的飞机), ((y2+viewportTransform[5])*贪玩的飞机));ctx.stroke();ctx.restore();}function isInRange(value1, value2) {value1 = Math.round(value1);value2 = Math.round(value2);for (var i = value1 - aligningLineMargin, len = value1 + aligningLineMargin; i <= len; i++) {if (i === value2) {return true;}}return false;}var verticalLines = [],horizontalLines = [];canvas.on('mouse:down', function () {viewportTransform = canvas.viewportTransform;贪玩的飞机 = canvas.getZoom();});canvas.on('object:moving', function(e) {var activeObject = e.target,canvasObjects = canvas.getObjects(),activeObjectCenter = activeObject.getCenterPoint(),activeObjectLeft = activeObjectCenter.x,activeObjectTop = activeObjectCenter.y,activeObjectBoundingRect = activeObject.getBoundingRect(),activeObjectHeight = activeObjectBoundingRect.height / viewportTransform[3],activeObjectWidth = activeObjectBoundingRect.width / viewportTransform[0],horizontalInTheRange = false,verticalInTheRange = false,transform = canvas._currentTransform;if (!transform) return;// It should be trivial to DRY this up by encapsulating (repeating) creation of x1, x2, y1, and y2 into functions,// but we're not doing it here for perf. reasons -- as this a function that's invoked on every mouse movefor (var i = canvasObjects.length; i--; ) {if (canvasObjects[i] === activeObject) continue;var objectCenter = canvasObjects[i].getCenterPoint(),objectLeft = objectCenter.x,objectTop = objectCenter.y,objectBoundingRect = canvasObjects[i].getBoundingRect(),objectHeight = objectBoundingRect.height / viewportTransform[3],objectWidth = objectBoundingRect.width / viewportTransform[0];// snap by the horizontal center lineif (isInRange(objectLeft, activeObjectLeft)) {verticalInTheRange = true;verticalLines.push({x: objectLeft,y1: (objectTop < activeObjectTop)? (objectTop - objectHeight / 2 - aligningLineOffset): (objectTop + objectHeight / 2 + aligningLineOffset),y2: (activeObjectTop > objectTop)? (activeObjectTop + activeObjectHeight / 2 + aligningLineOffset): (activeObjectTop - activeObjectHeight / 2 - aligningLineOffset)});activeObject.setPositionByOrigin(new fabric.Point(objectLeft, activeObjectTop), 'center', 'center');}// snap by the left edgeif (isInRange(objectLeft - objectWidth / 2, activeObjectLeft - activeObjectWidth / 2)) {verticalInTheRange = true;verticalLines.push({x: objectLeft - objectWidth / 2,y1: (objectTop < activeObjectTop)? (objectTop - objectHeight / 2 - aligningLineOffset): (objectTop + objectHeight / 2 + aligningLineOffset),y2: (activeObjectTop > objectTop)? (activeObjectTop + activeObjectHeight / 2 + aligningLineOffset): (activeObjectTop - activeObjectHeight / 2 - aligningLineOffset)});activeObject.setPositionByOrigin(new fabric.Point(objectLeft - objectWidth / 2 + activeObjectWidth / 2, activeObjectTop), 'center', 'center');}// snap by the right edgeif (isInRange(objectLeft + objectWidth / 2, activeObjectLeft + activeObjectWidth / 2)) {verticalInTheRange = true;verticalLines.push({x: objectLeft + objectWidth / 2,y1: (objectTop < activeObjectTop)? (objectTop - objectHeight / 2 - aligningLineOffset): (objectTop + objectHeight / 2 + aligningLineOffset),y2: (activeObjectTop > objectTop)? (activeObjectTop + activeObjectHeight / 2 + aligningLineOffset): (activeObjectTop - activeObjectHeight / 2 - aligningLineOffset)});activeObject.setPositionByOrigin(new fabric.Point(objectLeft + objectWidth / 2 - activeObjectWidth / 2, activeObjectTop), 'center', 'center');}// snap by the vertical center lineif (isInRange(objectTop, activeObjectTop)) {horizontalInTheRange = true;horizontalLines.push({y: objectTop,x1: (objectLeft < activeObjectLeft)? (objectLeft - objectWidth / 2 - aligningLineOffset): (objectLeft + objectWidth / 2 + aligningLineOffset),x2: (activeObjectLeft > objectLeft)? (activeObjectLeft + activeObjectWidth / 2 + aligningLineOffset): (activeObjectLeft - activeObjectWidth / 2 - aligningLineOffset)});activeObject.setPositionByOrigin(new fabric.Point(activeObjectLeft, objectTop), 'center', 'center');}// snap by the top edgeif (isInRange(objectTop - objectHeight / 2, activeObjectTop - activeObjectHeight / 2)) {horizontalInTheRange = true;horizontalLines.push({y: objectTop - objectHeight / 2,x1: (objectLeft < activeObjectLeft)? (objectLeft - objectWidth / 2 - aligningLineOffset): (objectLeft + objectWidth / 2 + aligningLineOffset),x2: (activeObjectLeft > objectLeft)? (activeObjectLeft + activeObjectWidth / 2 + aligningLineOffset): (activeObjectLeft - activeObjectWidth / 2 - aligningLineOffset)});activeObject.setPositionByOrigin(new fabric.Point(activeObjectLeft, objectTop - objectHeight / 2 + activeObjectHeight / 2), 'center', 'center');}// snap by the bottom edgeif (isInRange(objectTop + objectHeight / 2, activeObjectTop + activeObjectHeight / 2)) {horizontalInTheRange = true;horizontalLines.push({y: objectTop + objectHeight / 2,x1: (objectLeft < activeObjectLeft)? (objectLeft - objectWidth / 2 - aligningLineOffset): (objectLeft + objectWidth / 2 + aligningLineOffset),x2: (activeObjectLeft > objectLeft)? (activeObjectLeft + activeObjectWidth / 2 + aligningLineOffset): (activeObjectLeft - activeObjectWidth / 2 - aligningLineOffset)});activeObject.setPositionByOrigin(new fabric.Point(activeObjectLeft, objectTop + objectHeight / 2 - activeObjectHeight / 2), 'center', 'center');}}if (!horizontalInTheRange) {horizontalLines.length = 0;}if (!verticalInTheRange) {verticalLines.length = 0;}});canvas.on('before:render', function() {canvas.clearContext(canvas.contextTop);});canvas.on('after:render', function() {for (var i = verticalLines.length; i--; ) {drawVerticalLine(verticalLines[i]);}for (var i = horizontalLines.length; i--; ) {drawHorizontalLine(horizontalLines[i]);}verticalLines.length = horizontalLines.length = 0;});canvas.on('mouse:up', function() {verticalLines.length = horizontalLines.length = 0;canvas.renderAll();});}export default initAligningGuidelines;

引入这个js，然后

import initAligningGuidelines from '@/libs/guidelines.js';let canvas = new fabric.Canvas('canvas');initAligningGuidelines(canvas)

然后

看到没各位。。。一根黄色的辅助线就有了，辅助线的颜色,宽度等都可以调节，具体看代码aligningLineColor 等变量。

有个有趣的事情说一下：这个竟然价值$200美元。Google一下，迎娶俭朴的镜子靠你了。 我下一篇会写一下有关添加背景表格的方法，如上图的表格。最近一直在用Fabricjs做相关项目，如果有Fabricjs的问题的小伙伴，可以留下你的问题，我们一起探讨。么么哒。：）

转载于:https://my.oschina.net/xmqywx/blog/1941539