Adding a custom button to WMD (Stack Overflow) editor

How can I add a new button in the WMD editor, like the code button? If I click on the button <info></info> tag will add开发者_如何学编程 on the selected text like code button.

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There is a newer version of the repository called wmd-new. As described on the StackOverflow blog this version uses CSS sprites for better performance. So the toolbar is a single graphic:

There is a PSD (Photoshop) file for the toolbar in the repository that you can edit. Basically you need to add a new button to the wmd.css and the wmd.js files. Look around line 93 in the CSS and you'll see:

/* sprite button slicing style information */
#wmd-button-bar #wmd-bold-button    {left: 0px;   background-position: 0px 0;}
#wmd-button-bar #wmd-italic-button  {left: 25px;  background-position: -20px 0;}
#wmd-button-bar #wmd-spacer1        {left: 50px;}
#wmd-button-bar #wmd-link-button    {left: 75px;  background-position: -40px 0;}
#wmd-button-bar #wmd-quote-button   {left: 100px;  background-position: -60px 0;}
#wmd-button-bar #wmd-code-button    {left: 125px;  background-position: -80px 0;}
#wmd-button-bar #wmd-image-button   {left: 150px;  background-position: -100px 0;}
#wmd-button-bar #wmd-spacer2        {left: 175px;}
#wmd-button-bar #wmd-olist-button   {left: 200px;  background-position: -120px 0;}
#wmd-button-bar #wmd-ulist-button   {left: 225px; background-position: -140px 0;}
#wmd-button-bar #wmd-heading-button {left: 250px; background-position: -160px 0;}
#wmd-button-bar #wmd-hr-button      {left: 275px; background-position: -180px 0;}
#wmd-button-bar #wmd-spacer3        {left: 300px;}
#wmd-button-bar #wmd-undo-button    {left: 325px; background-position: -200px 0;}
#wmd-button-bar #wmd-redo-button    {left: 350px; background-position: -220px 0;}
#wmd-button-bar #wmd-help-button    {right: 0px; background-position: -240px 0;}

Note how the original styling of wmd-button-bar and the how left is being used above.