html - How to indent multiple levels of select optgroup with CSS?

Question

Just trying to indent optgroup blocks by nesting depth really, I've tried a general margin-left rule, nested elements then trying to apply the same rule, tried padding-left... is indenting like this possible? It seems elementary :P

In the example below, the optgroup labelled 'client2_a' should be indented more than the others, because it is nested inside 'client2'.

http://jsfiddle.net/Tb5Rc/5/

Answer 1

8/29/2016 Edit

The original answer below is no longer functional in modern browsers. For those who still need to use a tag instead of doing magic with HTML lists, a better solution was found on this stackoverflow thread: Rendering a hierarchy of "OPTION"s in a "SELECT" tag

I would recommend the solution suggested by igor-krupitsky who suggests dropping   and using the binary   instead. At least on Chrome, this does not break using the keyboard to find the first character of an item in the list.

End Edit

The current HTML specification does not provide for nested tags adding any functionality (such as indentation). See this link.

In the mean time, you can manually style your levels with CSS. I tried using styles in your sample, but for some reason they did not render correctly, so at the very least the following will work:

<select name="select_projects" id="select_projects">
        <option value="">project.xml</option>
        <optgroup label="client1">
            <option value="">project2.xml</option>
        </optgroup>
        <optgroup label="client2">
            <option value="">project5.xml</option>
            <option value="">project6.xml</option>
            <optgroup label="client2_a">
                <option value="" style="margin-left:23px;">project7.xml</option>
                <option value="" style="margin-left:23px;">project8.xml</option>
            </optgroup>
            <option value="">project3.xml</option>
            <option value="">project4.xml</option>
       </optgroup>
       <option value="">project0.xml</option>
       <option value="">project1.xml</option>
    </select>