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Fabric. JS right click menu

2022-07-02 05:17:00 【Director of Moral Education Department】

Brief introduction

Fabric.js Default No Right mouse button event , Only Click the mouse button 、 Mouse button up 、 Mouse movement Other events . But you may need to use... In your work “ Right click ” event , such as “ Right-click menu ” . So there is this article .

This article focuses on Fabric.js The main api Yes ：

fireRightClick： Allow right clicking
stopContextMenu： Disable the default right-click menu
mouse:down： Mouse click event

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If you don't know Fabric.js Classmate , You can see 《Fabric.js From the beginning to ___》

This case is developed in a native way , Not based on Vue 、React Other framework , So don't worry too much about the running environment and other problems .

The case code is placed at the end of the text ~

Environment and version

Chrome Browser version ：96.0.4664.45
Fabric.js edition ：4.6.0

Ideas

Let's talk about the needs first ：

Right click the element , Pop up menu ;
Pop up menu sub 4 In this case （ The menu is on the right side of the mouse , The menu is on the left side of the mouse , The menu is above the mouse , The menu is under the mouse ）;
Left click elsewhere on the canvas , The hidden menu ;

Realize the idea ：

Create a canvas ;
establish “ menu ” Of DOM Elements ;
Go to the official website to find “ Right click related events ”;
Right click on the element , According to the distance between the mouse and the edge of the canvas , Calculate where the menu is to be displayed ;
Left click on the canvas , The hidden menu ;

Realization

Look up the documents

In the above idea , In fact, the only difficulty is “ Right click related events ” .

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stay Object related documents in , There seems to be no right button for the mouse event , What is slightly touched is the mouse click （ Here I choose mousedown）.

So I went to Document on canvas I looked in the , Find these two properties ：

fireRightClick ： Whether the canvas can trigger the right-click event
stopContextMenu： Disable the default right-click menu

Ha ha ha ha , Developed ~

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After my careful observation , Find out mouse:down There was a in the incident button attribute ：

left-click ：button The value of is 1
Right click ：button The value of is 3
In the key （ That is, click the scroll wheel ）,button The value of is 2, The premise needs to be set fireMiddleClick: true

Hands on Development

Layout

<style>  /*  Containers , Relative positioning  */  .box {    position: relative;  }  /*  canvas , Give me a border  */  #canvas {    border: 1px solid #ccc;  }  /*  menu  */  .menu-x {    visibility: hidden; /*  The hidden menu  */    z-index: -100;    position: absolute;    top: 0;    left: 0;    box-sizing: border-box;    border-radius: 4px;    box-shadow: 0 0 4px rgba(0, 0, 0, 0.3);    background-color: #fff;  }  /*  Menu each option  */  .menu-li {    box-sizing: border-box;    padding: 4px 8px;    border-bottom: 1px solid #ccc;    cursor: pointer;  }  /*  Mouse over options , Change the background color  */  .menu-li:hover {    background-color: antiquewhite;  }  /*  First option , The top two corners are rounded  */  .menu-li:first-child {    border-top-left-radius: 4px;    border-top-right-radius: 4px;  }  /*  The last option , The bottom two corners are rounded , No border at the bottom  */  .menu-li:last-child {    border-bottom: none;    border-bottom-left-radius: 4px;    border-bottom-right-radius: 4px;  }</style><!--  Containers （ Relative positioning ） --><div class="box">  <!--  canvas  -->  <canvas id="canvas" width="600" height="600"></canvas>  <!--  Right-click menu （ Absolute positioning , And the default is hidden ） -->  <div    id="menu"    class="menu-x"  >    <div class="menu-li"> Don't do anything? </div>    <div class="menu-li"> Don't do anything? </div>    <div class="menu-li"> Don't do anything? </div>    <div class="menu-li"> Don't do anything? </div>    <div class="menu-li" onclick="delEl()"> Delete </div>  </div></div>

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The effect at this time is shown in the figure above .

Initialize canvas , And generate graphics

<script>//  After the document is loaded, execute window.onload = function() {  //  Output current  fabric  edition   console.log(`Facrib.js edition ：${fabric.version}`)  //  Initialize canvas   init()  //  Disable the default right-click event on the menu   menu.oncontextmenu = function(e) {    e.preventDefault()  }}//  initialization function init() {  canvas = new fabric.Canvas('canvas', {    fireRightClick: true, //  Enable right click ,button The number of 3    stopContextMenu: true, //  Disable the default right-click menu   })  //  rectangular   const rect1 = new fabric.Rect({    left: 10,    top: 510,    fill: 'orange',    width: 40,    height: 40  })  //  Rounded rectangle   const rect2 = new fabric.Rect({    left: 510,    top: 10,    fill: 'pink',    width: 40,    height: 40,    rx: 10, //  Round corners x    ry: 10, //  Round corners y  })  //  circular   const circle = new fabric.Circle({    radius: 30, //  radius     fill: 'green',    left: 20,    top: 20,  })  //  triangle   let triangle = new fabric.Triangle({    width: 80, //  Bottom edge width     height: 100, //  The distance from the bottom edge to the fixed point     fill: 'blue',    left: 500,    top: 480  })  //  Add rectangle to canvas   canvas.add(rect1, rect2, circle, triangle)}</script>

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Add click event （ Judgment right button ）

<script>//  Omit some of the above code function init() {  //  Omitted code ......  //  Add rectangle to canvas   canvas.add(rect1, rect2, circle, triangle)  //  Press mouse   canvas.on('mouse:down', canvasOnMouseDown)}    //  Click event of mouse on canvas function canvasOnMouseDown(opt) {  //  Judge ： Right click , And right click on the element   // opt.button: 1- left-click ;2- In the key ;3- Right click   //  Click... On the canvas ：opt.target  by  null  if (opt.button === 3 && opt.target) {    //  Get current element     activeEl = opt.target    menu.domReady = function() {      console.log(123)    }    //  Show menu , Set the position of the right-click menu     //  Get the width and height of the menu component     const menuWidth = menu.offsetWidth    const menuHeight = menu.offsetHeight    //  Current mouse position     let pointX = opt.pointer.x    let pointY = opt.pointer.y    //  Calculate where the menu appears     //  If the mouse is close to the right side of the canvas , The menu appears to the left of the mouse pointer     if (canvas.width - pointX <= menuWidth) {      pointX -= menuWidth    }    //  If the mouse is near the bottom of the canvas , The menu appears just above the mouse pointer     if (canvas.height - pointY <= menuHeight) {      pointY -= menuHeight    }    //  Show the menu     menu.style = `      visibility: visible;      left: ${pointX}px;      top: ${pointY}px;      z-index: 100;    `  } else {    hiddenMenu()  }}//  The hidden menu function hiddenMenu() {  menu.style = `    visibility: hidden;    left: 0;    top: 0;    z-index: -100;  `  activeEl = null}//  Remove elements function delEl() {  canvas.remove(activeEl)  hiddenMenu()}</script>

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