Author: Tobias Zimmergren
http://www.zimmergren.net | http://www.tozit.com | @zimmergren

Introduction

SharePoint 2010 developing for performance article series:
In this series of articles I will briefly introduce you to some key concepts when it comes to developing for performance in our SharePoint 2010 applications.

Related articles in this article series

Part 1 – SP 2010: Developing for performance Part 1 – Developer Dashboard
Part 2 – SP 2010: Developing for performance Part 2 – SPMonitoredScope
Part 3 – SP 2010: Developing for performance Part 3 – Caching in SharePoint 2010
Part 4 – SP 2010: Developing for performance Part 4 – Logging
Part 5 – SP 2010: Developing for performance Part 5 – Disposal patterns and tools
Part 6 – SP 2010: Developing for performance Part 6 – CSS Sprites
Part 7 – SP 2010: Developing for performance Part 7 – Crunching those scripts
Part 8 – SP 2010: Developing for performance Part 8 – Control that ViewState

Part 6 (this article):
In web development today its very important to keep performance in mind – this is especially important in any site that is published externally or for whatever reason will have heavy traffic. In this article I will briefly cover the area of CSS Sprites, how they are implemented in SharePoint 2010 and of course how you can create them yourself.

Introduction to CSS Sprites

What are CSS sprites anyway?

CSS sprites is a technique used to reduce the number of requests for images on a site when visiting it. Normally when you see a web site today there’s plenty of files being requested and loaded upon the request made. With the use of CSS sprites we can reduce the amount of files that we need to request from the server by consolidating many image files into one file and use CSS to display the correct part of that consolidated image when it needs to depict your specific image.

Short in short: Take a bunch of separate images and smack them together to one single file. Voila, you’ll only need to request one file from the server.

SharePoint 2010 and CSS Sprites

So why are we talking about CSS sprites here anyway, isn’t this supposed to be all about SharePoint and awesomeness? But of course, and that’s exactly why we’re talking about it – CSS sprites are a natural part of a normal SharePoint 2010 installation. By default, there’s CSS sprite techniques used to render and display images in (for example) the Ribbon menu.

These are some samples of images used with CSS sprites in SharePoint 2010:

FGIMG.PNG	jsgridcluster.png

As you can see in any of the two images above the many small images/icons have been smashed together into one single image file and then there’s some CSS magic to position it. This is basically what it’s all about.

Why should I bother learning to use CSS sprites?

This would be like asking yourself the question "Why would I develop something that is of great performance" or "Why would I do something awesome". No more rhetorical questions please

Of course the reasoning behind creating CSS sprites are that you can develop web applications that can reduce the page load and enhance the performance of your sites and make them load quicker and be more responsive.

Creating CSS sprites for my applications? How?

There’s a few ways to create CSS sprites for you own applications.

For obvious reasons mentioned above I will not be demonstrating how to do this manually but will rather be using any of the hundreds of tools out there to create the sprites.

In this example I’m going to use my main man Waldek’s tool called SpriteGenerator.

There’s a bunch of other tools available to create and generate these sprites as well of course, bing.com is thy friend.

How to: Generate CSS sprites using a tool

In this section I’ll talk you through our current application and what it looks like, what we want to achieve and finally how to achieve it.

Our current application, a visual sample

This is my current sample application before we start using sprites.

Control Panel Web Part (dummy):

This is the Visual Studio project, containing all the images and resources:

As you can see there’s quite some images being loaded. The images used in the application (my Web Part) will be fetched using a normal HTTP-request and that’s when one could realize how quickly those small requests can add up to impact performance.

This application uses some generic HTML markup like this:

         <div  class="width300p"> 

             <div  class="leftalign floatleft width30"> 

                 <div  class="height70p"><asp:Image  ID="Image2"  runat="server"  ImageUrl="/_layouts/images/TOZIT.CSSSprites/mail.png"  /></div> 

                 <div  class="height70p"><asp:Image  ID="Image3"  runat="server"  ImageUrl="/_layouts/images/TOZIT.CSSSprites/message.png"  /></div> 

                 <div  class="height70p"><asp:Image  ID="Image4"  runat="server"  ImageUrl="/_layouts/images/TOZIT.CSSSprites/more.png"  /></div> 

             </div> 

             <div  class="centeralign floatleft width30"> 

                 <div  class="height70p"><asp:Image  ID="Image5"  runat="server"  ImageUrl="/_layouts/images/TOZIT.CSSSprites/notebook.png"  /></div> 

                 <div  class="height70p"><asp:Image  ID="Image9"  runat="server"  ImageUrl="/_layouts/images/TOZIT.CSSSprites/search.png"  /></div> 

                 <div  class="height70p"><asp:Image  ID="Image13"  runat="server"  ImageUrl="/_layouts/images/TOZIT.CSSSprites/favorites.png"  /></div> 

             </div> 

             <div  class="width30 floatright"> 

                 <div  class="height70p"><asp:Image  ID="Image6"  runat="server"  ImageUrl="/_layouts/images/TOZIT.CSSSprites/info.png"  /></div> 

                 <div  class="height70p"><asp:Image  ID="Image7"  runat="server"  ImageUrl="/_layouts/images/TOZIT.CSSSprites/logoff.png"  /></div> 

                 <div  class="height70p"><asp:Image  ID="Image8"  runat="server"  ImageUrl="/_layouts/images/TOZIT.CSSSprites/question.png"  /></div> 

             </div> 

         </div>

Now, in order for us to utilize the CSS sprites instead, and not have to make a request for each of the images separately – we’ll use the SpriteGenerator and create us some nice CSS sprite magic.

Using the Sprite Generator to make some magic

Like I said before, we’ll be using Waldek’s SpriteGenerator for this sample.

Just open it, put in the images you’d like for it to make some magic with and then simply hit the magic button.

Tip: Check out how to use the SpriteGenerator here

The result of using the SpriteGenerator can look something like this:

This is one consolidated image containing all the graphic from my application. But instead of having about 30 different icons in my project, I now have only one.

The generator will create the CSS needed as well, and it can look something like this:

Now, what this really means is that you now have the ability to actually use only one single image to portray several.

New Visual Studio structure

Obviously, with the new update and only using one single image – the Visual Studio project might look something like this:

New HTML markup

And finally, there needs to be some changes in the HTML markup to reflect the changes with the images. The markup could look something like this:

         <div  class="leftalign floatleft width30"> 

             <div  class="height70p sprite mail">&nbsp;</div> 

             <div  class="height70p sprite message"  >&nbsp;</div> 

             <div  class="height70p sprite more"  >&nbsp;</div> 

         </div>

How does using CSS Sprites affect requests, hence performance?

Dealing with sprites isn’t very hard to get started with as you saw in the previous short samples. But what’s more interesting from a performance perspective is of course how it can affect the performance of the requests being made towards the server.

Let’s do some generic Fiddler-magic to see what the requests look like without using sprites and then what the requests look like with the use of sprites.

Fiddler test 1: NOT using CSS sprites

Fiddler test 2: Using CSS sprites

What you can easily conclude from the initial tests is that there’s more requests without the CSS sprites, while the size can be slightly larger for a consolidated image when using the sprites.
It’ll load and render quicker by downloading only the 3 files instead of the 17 files due to the aggregation time it takes to render the content.

Visualize the results, please!

Using CSS sprites (Time in seconds to load the data)	NOT using CSS sprites (Time in seconds to load the data)
RESPONSE BYTES image/png:    120 250 text/html:    16 593 ~headers~:    1 748 text/css:    778	RESPONSE BYTES image/png:    52 417 text/html:    16 709 ~headers~:    6 260 text/css:    778
ACTUAL PERFORMANCE Aggregate Session time:    00:00:00.531 (0.5 seconds) Sequence (clock) time: 00:00:00.4281250 (0.4 seconds)	ACTUAL PERFORMANCE Aggregate Session time: 00:00:01.390 (1.3 seconds) Sequence (clock) time: 00:00:00.5625000 (0.5 seconds)

I did some tests with two machines, two different projects and a couple of clients to request the pages and the results (on average) was something like this in rendering time. The chart below is a relative visualization of the results per average.

Summary

The impact of a system with a lot more requests for data than these samples, more users and in generally more traffic would differ a bit more than the charts here. Using sprites in combination with caching the data is a good practice to keep the amount of requests to the server to a minimum.

Even if this minor change don’t have any critical impact on improving the performance it’s important to consider. "All improvements are good improvements".