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Canvas Drag and Drop Region Using HTML 5

Introduction

 
In this article, we will understand canvas drag and drop regions using HTML 5. Here in this article, you can move the rectangular shape as well as the circle when the application is running in the browser.
 
Here we will use some JavaScript and some styles along with HTML code. Just go through the steps to see how to create this application. Let's see how the canvasclippingregion application can be created. To do so use the following steps.
 
Step 1 : Open a HTML editor or Visual Studio.
 
sd.gif
 
Open File menu ->select new ->Choose Website then.
 
0000.jpg
 
This is where we will create an HTML5 application.   
  • Go to Solution Explorer
  • Right-click on the Application name
  • Select Add-->add new item
  • Now in the window that opens, select an HTML page or a new Webform
  • Rename it to dragdropclippingregion.aspx
dragndrop.gif
 
Step 2: In this section, we will create the style for the media and create the .css on the media screen. Put the given script in the Head section of the HTML or between the <head>--</head> tags. Here the CSS is used for design purposes.
 
CSS Script
  1. <style>  
  2. body  
  3. {  
  4.   margin: 0px;  
  5.   padding: 0px;  
  6. }  
  7. Canvas  
  8. {  
  9.    border: 2px solid #9C9898;  
  10.    margin-top: 50px;  
  11.    margin-left: 50px;  
  12.    background-color: #009999;  
  13.    box-shadow: 5px 5px 8px #222;  
  14.  }  
  15. .title  
  16. {  
  17.    text-align: center;  
  18.    font-family: Segoe UI Light, Arial, Helvetica;  
  19.    font-size: 2.2em;  
  20.    margin: 1em;  
  21. }  
  22. .info  
  23. {  
  24.    text-align: center;  
  25.    font-family: Segoe UI Light, Arial, Helvetica;  
  26.    font-size: 1.2em;  
  27.    margin: 0.25em;  
  28. }  
  29. </style> 
Step 3 : In this part we need to work on some JavaScript. To fully understand how JavaScript works, download the attached .rar file and run the canvasclippingregion application.
 
The whole JavaScript looks as in the following
  1. window.onload = function ()  
  2.          {  
  3.             var stage = new Kinetic.Stage("container", 500, 200);  
  4.             var layer = new Kinetic.Layer();  
  5.             var draggingShape = undefined;  
  6.             var draggingRectOffsetX = 0;  
  7.             var draggingRectOffsetY = 0;  
  8.             var box = new Kinetic.Shape({  
  9.                 drawFunc: function () {  
  10.                     var context = this.getContext();  
  11.                     context.beginPath();  
  12.                     context.rect(this._x, this._y, 200, 100);  
  13.                     context.fillStyle = "#ddd";  
  14.                     context.fill();  
  15.                     context.closePath();  
  16.                 },  
  17.                _x: 100,  
  18.                 _y: 50  
  19.             });  
  20.             box.on("mousedown", function () {  
  21.                 draggingShape = this;  
  22.                 var mousePos = stage.getMousePosition();  
  23.                 draggingRectOffsetX = mousePos.x - box._x;  
  24.                 draggingRectOffsetY = mousePos.y - box._y;  
  25.             });  
  26.             box.on("mouseover", function () {  
  27.                 document.body.style.cursor = "pointer";  
  28.             });  
  29.             box.on("mouseout", function () {  
  30.                 document.body.style.cursor = "default";  
  31.             });  
  32.             layer.add(box);  
  33.             var circle = new Kinetic.Shape({  
  34.                 drawFunc: function () {  
  35.                     var context = this.getContext();  
  36.                     context.beginPath();  
  37.                     context.rect(box._x, box._y, 200, 100);  
  38.                     context.clip();  
  39.                     context.beginPath();  
  40.                     context.arc(this._x, this._y, 50, 0, 2 * Math.PI, false);  
  41.                     context.fillStyle = "yellow";  
  42.                     context.fill();  
  43.                     context.closePath();  
  44.                 },  
  45.                 _x: 300,  
  46.                 _y: 50  
  47.             }); 
Step 4: In this section, we are going to become familiar with the body part of HTML scripting. Replace this script from the body section of the dragdropclippingregion.aspx page. Here we pass a Canvas in the canvas tag.
  1. <body style="background-color: #FFFFCC">  
  2.     <center>  
  3.         <h2>  
  4.             Canvas Drag and Drop Region  
  5.         </h2>  
  6.     </center>  
  7.     <hr />  
  8.     <div id="container">  
  9.     </div>  
  10. </body> 
Step 5 : The complete code for the canvasclippingregion application:
  1. <%@ Page Language="C#" AutoEventWireup="true" CodeFile="dragdropclippingregion.aspx.cs" Inherits="dragdropclippingregion" %>  
  2. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">  
  3. <html xmlns="http://www.w3.org/1999/xhtml">  
  4. <head runat="server">  
  5.     <style>  
  6.     </style>  
  7.     <script src="jscript.js">  
  8.     </script>  
  9.     <script>  
  10.     </script>  
  11. </head>  
  12. <body style="background-color: #FFFFCC">  
  13.     <center>  
  14.         <h2>  
  15.             Canvas Drag and Drop Region  
  16.         </h2>  
  17.     </center>  
  18.     <hr />  
  19.     <div id="container">  
  20.     </div>  
  21. </body>  
  22. </html> 
Step 6: Output Press F5 Note: For the accurate output of HTML5 applications, you must have the Google Chrome browser in your PC. You can move the rectangular shape as well as the circle when the application is running in the browser.
 
dragndrop1.gif
 
After changing the rectangular and circle shape.
 
dragndrop2.gif
 
Here are some useful resources.


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