How to implement HTML5 Canvas undo function

HTML 5 is awesome. My most favorite feature is the canvas. It has many uses and of them is to allow the users of your website to draw free shapes.

If that’s what your website utilizes the canvas element for, by no doubt you have already identified the need for an ‘undo’ function. Perhaps you have already tried the .save() and .restore() functions, only to realize that they only save and restore the fill style of the drawing shapes.

This is exactly the problem I had, while creating my online Rage Comic Editor. Fortunately, I implemented a solution, which I would like to share with you.

The following tutorial assumes that you are familiar with the canvas element and its usage. It will only explain the technique I have discovered to save and restore a canvas drawing state. The implementation is (naturally) in JavaScript.

First, and most important, I have an online demo illustrating the tutorial, here. If you are inpatient or want to get straight to the code, feel free to navigate there and ‘view source’. It is well commented and should be self-explanatory.

In the demo I didn’t bother to implement a ‘free hand drawing’ tool. Instead, I have two buttons only – one of them draw lines on the canvas and the other button undoes one step at a time.

Now to the point… The whole technique consists of three parts:

  1. You need an array, to store the ‘restore points’ (much like Windows Restore Points). We will push states in it, when performing changes on the canvas, and will pop (and restore) states, out of it, when we press the ‘undo’ button. Here is how I have declared it: var restorePoints = [];
  2. As mentioned, before performing any change on the canvas, we need to store its state. We do this, by calling the toDataURL of the canvas, which exports the current drawing in your canvas, to a (PNG) image, encoded as base64. Basically, we ask the canvas to give us a text representation of the image that is drawn. Now we only need to insert this text, as an element of our restorePoints array. We do this using the restorePoints.push(…) command. The implementation of this step is in the saveRestorePoint() function in the example. Again – you have to call this method, before performing a change on the canvas!
  3. Now, how do we restore the canvas to its previous state, when the user clicks on an ‘undo’ button? We call a javascript method in which we have to create a new Image object in the memory, set its ‘src’ property to the last element in the restorePoints array (we do this using the array pop() method, which also removes the element from the array – exactly what we need!) and draw this image on the canvas (using the drawImage() function). So effectively what we do is: we take the last restoration point (image) and overlay it on top of the current state of the canvas. This will cause the effect of removing only the last change on your canvas, because we have restored to a point, which is previous to that change. We also need to remove the restoration point from the array, because we are currently ‘in it’ anyway.

And that’s about it. To summarize: maintain a javascript array of the previous states of the canvas. Before you perform a change on the canvas, save the current state, by exporting the canvas to a base64 encoded image. Store that state in the array of states, then do your change. When you want to ‘undo’, .pop() the last state from the canvas and draw it on top of everything. This will overwrite the whole canvas, but will only remove your last change, because the restoration point is before it.

I think there is no better explanation than a code sample, so go ahead and view the source of the demo. You can download the complete solution from here.

Cheers and Merry Christmas!


ChartPart for SharePoint

If you would like to generate some charts in Microsoft SharePoint 2007, after a quick search you will find that there is no such out-of-the-box functionality. You shouldn’t worry, though, as there is a free web part available at Codeplex, which has everything you need for your list-based charting needs. It is called “ChartPart for SharePoint” and is available here.


In order to get it working on your server, you will need to have Microsoft .NET 3.5 SP1 and Microsoft Chart Controls for Microsoft .NET Framework 3.5 installed. The ‘installation package’ does not check for those prerequisites, so make sure you do that manually before you install. Most probably you already have .NET 3.5 SP1 installed, but chances are, the MS Chart Controls are not installed.


The deployment package consists of two WSP files (SharePoint solution deployment packages) – MSChartControls.wsp and ChartPart 2.0.wsp. First, you have to install the MSChartControls package. Login on your SharePoint server, start the Console (Start -> Run -> cmd) and type:

stsadm -o addsolution –filename MSChartControls.wsp
stsadm -o execadmsvcjobs

STSADM NOTE: Of course, you will have to choose between the convenience of not typing the full path to the stsadm.exe file or not having to type the full path to the WSP. So, you have to be in one of the two folders and type the full path to the other file.

This will add the solution to the SharePoint Central Administration -> Operations -> Solution Management. You can either use the User Interface it provides to deploy the added solution, or you can continue executing console commands, like this:

stsadm -o deploysolution -name MSChartControls.wsp -immediate –allowgacdeployment
stsadm -o execadmsvcjobs

Then, you have to activate the installed solution on Web Application level:

  1. Go to Central Administration
  2. Go to Application Management
  3. Select Manage Web Application Features
  4. Verify that you have selected the correct Web Application in the top right corner
  5. Click Activate on the Microsoft Chart Controls Feature

Now, you have to do something similar for the other WSP (Chart Part 2.0.wsp):

stsadm -o addsolution -filename “ChartPart 2.0.wsp”
stsadm -o execadmsvcjobs

Deploy the solution, either from Central Admin, or by using the console:

stsadm -o deploysolution -name “Chartpart 2.0.wsp” -immediate -allowCasPolicies -url <url>
stsadm -o execadmsvcjobs

Where <url> is the address of the web site you wish to deploy the webpart to. Now all you have to do is activate the feature on the selected Site Collection.

  1. Go to Site Settings for your top-level site
  2. Go To Site Collection Features
  3. Activate the ChartPart for SharePoint feature
  4. Now you can add ChartParts on every site in your Site Collection.


I created a new ‘Web Part Page’ on my site, to use for experimenting with the web parts. I chose ‘Full Page, Vertical’ layout template, as it  is one of the simplest and I preferred to have full width.

I chose to ‘Edit Page’ and clicked on ‘Add a Web Part’ link in the design mode of the page. A pop-up showing all available web parts appears and from there, I chose to add on the page the ‘ChartPart’ web part.

Once added on the page, you have to configure it. While the page is still in design mode, click on the little arrow down in the right upper corner of the web part. It will open a side menu. Click on ‘Modify Shared Web Part’. This will open the options of the web part.

Here, you can set the title of the web part (as it will appear on the page it is added to), the web site to pull data from, the specific list and its view. Then you have to select X and Y “Series” column. A bit of explanation… Only Number fields can be choses as “X-Series”. “Item Count” is always available to you. As “Y-Series” you have to specify a column of the SharePoint list.

To illustrate all this, I will configure my list to contain only two columns – “City” (single line of text) and “Population” (number field). Here is what my list looks like:

Now, I want to configure the Chart web part to visualize this statistics. I will set it up this way:

We click OK button and the generated chart looks like:


You can customize the chart in many ways. First. by selecting the ‘Chart Type’ for the chart. Choices are Column, Bar, Pie and so many others. Additionally, you can select ‘Style’ (Cylinder, Emboss, LightToDark, Wedge), which seems to work only on specific ‘Chart Types’. For example, it clearly works on a ‘Column’ chart type. Here is the difference between ‘Cylinder’ and ‘Wedge’:

There is many other fine tunings you can do, like color palette, size and etc. Also what’s really nice is that in the tooltip (when you hover a column in the chart) you will see an exact value, of the column.


ChartPart for SharePoint is a great component, if you want to visualize some statistics based on SharePoint list items. It is highly customizable, easy to install and use.

ASP.NET MVC: Create Facebook-like search box

In today’s article I will show you how to create your own Facebook-like (or LinkedIn-like) search box. If you haven’t seen what it looks like, here is an example:

You will notice that it features: autocomplete, icon, matches what you type and when you click a result item, it takes you to the appropriate page. That’s what our control in MVC will feature too. We will implement this in ASP.NET MVC2 and jQuery.

The Plan:
We will create an attribute and use it to decorate the action methods of our controllers. When we decorate an action, we will be adding metadata, such as the display name it should appear with in the search results and an optional icon. When the user types something in the search control, we will use jQuery to POST to a special controller, which will be enumerating all action methods in all controllers. While enumerating, it will be looking for a match between the search query and the metadata of each ‘indexed’ action method.


Note: You can download the working demo project from here.

The Attribute
Ok, let’s start with the attribute. In your Code folder (if you don’t have one – go ahead and create it) add a new class and name it ‘ActivitySearchAttribute’. It will have two string properties – Text and ImageUrl. Implement it like that:

This is the attribute we will be using to decorate our action methods in the controllers. That way we will mark them as ‘searchable’.

Action-Method Decorations
Let’s create a couple of dummy controllers, with a couple of actions in each of them and decorate them with the newly created attribute. Like this:

As you can see, the icon property (“group.png” in the example) in the metadata is optional. Non-decorated action methods will not be returned as search results.

The Search Controller
Now let’s implement the search controller. Basically, what it will be doing is: receive a query string (e.g. “the”, as in the first image of this post), get all controllers, enumerate the action method of each controller, match the ‘Text’ property of the ‘ActivitySearch’ attribute (which we use to decorate the action) and then return an array of the matches with the appropriate URL to each result. Just like Facebook. I won’t paste the code here, as it is big, but you will find it in the attached sample project. The file is in Controllers and is named “SearchController.cs”.

Json Response
The search will be a dynamic thing. While the user types, we will be sending a request to a controller and we will be receiving a response. We need to create a class which we will serialize to JSON and use it as a response. In your Code folder, create another class and name it ‘ActivitySearchResultItem’. It will have three properties: Text, Url and Image. Implement it like that:

The Search controller will be returning an array of those, to the jQuery UI, as a JSON response.

The JavaScript / jQuery
Now, when we have the back-end, we just need to implement the front-end in jQuery and html. Note that our solution will be using a 3rd party library – jquery.autocomplete.pack.js
Additionally, we will put our javascript, in a file named “activitySearch.js”.

The auto-complete jQuery plugin will take care of attaching to the text-box and submitting/receiving data to/from the back-end controller. We just need to process and format the results. When the user clicks a result, he will be redirected to the URL property associated with the result item (see ‘Json Response’ above). Like that:

As you can see, the jQuery code expects that if there is an Image associated with the search result it should be in the /Content/images folder.

Here is how to setup your page which will contain the search-box control.

Now, when you have everything in place, start the project and just type in the search box some phrase which you know will hit a result. You should see something like:

The search results are clickable and when clicked, it will take you to the appropriate action. You can optimize the whole solution with various caching settings and techniques.

You can download the whole demo project here –

ASP.NET MVC2 – Creating a Display Template

ASP.NET MVC philosophy is “Skinny Controller, Fat Model, Stupid View“. The focus of today’s post is “stupid view”. What does this mean? Well, it means that you should avoid writing any logic in your views. A view should be as simple as wrapping the model’s properties in html tags.

If you are cornered, and must have some kind of a login in your view, it would be nice if it is neatly wrapped in a DisplayTemplate, so your code remains reusable, easy to read and maintain. What follows now is a tutorial on how to create one.

Problem: We have a Model which has a property “RemainingTime”, which is an integer and represents the estimated remaining seconds of some operation. We want to neatly format this time in the view, so that if it has a value of, let’s say, “5”, to be displayed as “5 seconds”. If it has value of “70”, to be displayed as “1 min, 10 seconds”, etc…

Solution: Create a reusable DisplayTemplate and use it to visualize the property.

We start by creating a new ASP.NET MVC2 “empty” project template. We don’t need the default authentication and home controllers, so that would do just fine.

As a first step, let’s create our Model. We’ll call it “RemainingTimeModel” and will have the integer property “EstimatedSeconds”. We will name the DisplayTemplate “SecondsFormatting”. So we go ahead and decorate the “EstimatedSeconds” property with the UIHint attribute, passing “SecondsFormatting” (which is the name of the DisplayTemplate we want to use) in its constructor. This attribute tells ASP.NET MVC which DisplayTemplate to use by default, for this property. Your code should look like this:

Second step is to create the actual DisplayTemplate. It needs to reside in the “Views/Shared/DisplayTemplates” folder, and be named “SecondsFormatting.ascx”. So, create a “DisplayTemplates” folder in your Shared views, then right click it and Add -> View. Check the ‘create partial view’ checkbox and give it the name we mentioned above. By default, this will create non-strongly typed ViewUserControl. We will extend this, to an integer. Open the “SecondsFormatting.ascx” file and change the Inherits=”System.Web.Mvc.ViewUserControl” to Inherits=”System.Web.Mvc.ViewUserControl . Now, when you refer to the Model object in this control, you are working with an integer. The Model that will be passed to this DisplayTemplate is the “EstimatedSeconds” property of the “RemainingTimeModel” model.

Now we just need to implement some logic in the control. Let’s do this:

Ok, we have the model, which has the seconds property, and we have a DisplayTemplate for it. Now we jsut need to use it. For this purpose, we will create one simple controller, which creates a new instance of the model and initializes it, then passes the model to a view. In the view, we will have: Html.DisplayFor(model => model.EstimatedSeconds). Like that:



See how clean your View remains? No logic in there, just a DisplayFor html helper call.

We can now go ahead and try it out, with a couple of different values. It formats it accordingly. Please note that there are much easier ways to format the time and it was used here just as an example of what we should do if our view requires to have a logic. If we try with 3732 seconds, it should display “1 hours, 2 minutes, 12 seconds”.

Now you know how to encapsulate your logic in DisplayTemplates and keep your main Views clean and neat.

You can download the demo project from here.

jQuery in SharePoint

There are rumors jQuery might be included as part of SharePoint 2010. In an anticipation for that, today’s article aims to show what the integration between SharePoint 2007 and jQuery looks like, how to use it and what are the benefits.

So what is jQuery?
jQuery is a lightweight JavaScript library that emphasizes interaction between JavaScript and HTML. It was released in January 2006 at BarCamp NYC by John Resig. jQuery is free, open source software Dual-licensed under the MIT License and the GNU General Public License. Microsoft and Nokia have announced plans to bundle jQuery on their platforms, Microsoft adopting it initially within Visual Studio for use within Microsoft’s ASP.NET AJAX framework and ASP.NET MVC Framework whilst Nokia will integrate it into their Web Run-Time platform.

Simply put, it is a high performance rapid development, AJAX-enabled library on top of JavaScript.

There are a lot of articles and tutorials out there, on how to use jQuery in general. Here is the most essential documentation you will need – the jQuery API.

SharePoint integration
Integration between jQuery and SharePoint boils down to finding a smart way to get a jQuery reference in your pages.

Basically you can do this ‘manually’, which is well described here or you can use an automated integration solution (see below).

The manual approach essentially consists of two steps:
1) Deploying the libraries (js) to a location which can be accessed by the pages – that would be the LAYOUTS folder in the 12 hive
2) Loading the libraries on the pages – by modifying the master page, load the library specifically in the page you want to use it or other… It is all well described in the posted article.

The automated solution is a better one. You can get “SmartTools jQueryLoader for SharePoint” which does the integration for you. There is a good article which walks you through the installation process, so we are not going to that here. Make sure you watch the video, though.

Just try it out

If you just want to quickly try the magic of jQuery in SharePoint out, without bothering with the full integration you can do what is described here. The example in this article uses jQuery library which is hosted on Google Code (rather than in your 12 hive) and it dynamically queries the SharePoint web service to retrieve your current tasks, then visualizes them on the page. No need to develop a web part, it is just as simple as that!

You should also check this out, although for some reason I couldn’t get it to work. Basically this is supposed to let you test any jQuery code, from a small ‘editor’ on your home page.

So what are the benefits of using jQuery in SharePoint?

Well, obviously it adds AJAX functionality to your SharePoint web application. You can now retrieve and visualize data asynchronously, without putting any load on the SharePoint server. It also allows you to create more appealing and faster UI.

Page elements control and flexibility
Additionally, SharePoint allows you to change content structure for subsites, lists, libraries, views, columns, content types and the Web parts, but sometimes that’s not enough. Sometimes developers/designers or users need to make changes to the functionality and appearance of a SharePoint site in a way that is not allowed by the IT department. Since SharePoint Designer is usually restricted, we need an alternative way. That would be jQuery. Just to give you a concrete example of such situation, here is a guy who had to make the corners of the quick launch menu rounded.

jQuery saves development time
jQuery simplifies the way you traverse HTML documents, handle events, perform animations, and add Ajax interactions to your web pages. To summarize it one sentence only: couple of lines in jQuery allow you to do better what you could do with over 20 lines of JavaScript.

Many other…

  • You don’t have to check for null objects
  • CSS3 compliant and has a great CSS selector integration
  • Huge community which supports it. Many tutorials out there…
  • Simple and fast development
  • Lightweight!
  • etc…

jQuery 1.3 is fast. As in the “fastest JS framework out there”. Here are some nice tips on how to write a fast jQuery code.

Debugging jQuery in SharePoint
FireBug is the preferred way to debug jQuery (and JavaScript in general). Here is a nice article which goes into details.

Examples “jQuery & SharePoint” website.
jQuery sparklines
Showing random images in SharePoint 2007 using jQuery
Highlight SharePoint List rows conditionally
Paging large content in SharePoint using jQuery
Many other…

SharePoint Web Services Wrapper

Recently I noticed that a common reason for developers to seek help on the MSDN forum is related to difficulties understanding and/or utilizing the SharePoint Web Services. You can’t blame the developers. It’s much more convenient to work with an Object Oriented API, rather than exchanging XML messages with a Web Service. For example, take a look at the Lists.asmx -> GetListItems. Of course it’s no rocket science, but it will sure save time if you could avoid dealing with the XML directly.

I spent some time researching if there is some kind of a library out there which provides ‘managed’ access to those Web Services. I.e. – work with .NET objects, rather than construct and parse XML elements. The closest thing I have found is this and it’s totally outdated and incomplete. At least it’s some reassurance to me that I am not missing the big picture and indeed, there might be people who would appreciate such framework.

So, I decided to start a project which will try to implement such .NET Object Oriented API around the SharePoint Web Services. Of course, for those corner weird cases (as well for the advanced developers), the underlying XML will still be accessible. Here is a good description of all the SharePoint services. My goal is to cover them all, eventually. I will start with the most commonly used ones.

It is hosted on CodePlex –
The project is not published yet, as there is no single line of code written yet. I will be doing this in my spare time. Once I shape it to my liking, it will become open source and everyone is welcome to contribute.

Got comments? Suggestions/Objections? There is a similar library already implemented? Please do let me know.