[RCD] reduce network requests by consolidating icon images

Nathan Kinkade nath at nkinka.de
Sat Mar 28 15:27:25 CET 2009

I've been spending a lot of time in Firebug with RoundCube the past few
weeks.  One thing I've noticed is that there are quite a lot of network
requests to freshly load the front page.  With the default theme there are
around 45 separate requests for a little less than 250K.  I was asking
myself how to reduce the number of requests and was reminded of something
interesting that I had noticed Gmail doing, and that is to consolidate many
icons into a single image and then use CSS to position the image as the
background of a fixed width/height block-level element.

As I went to implement this, I began to realize that not only does this
approach reduce the number of network requests, but it also seems to
simplify the code a bit.  With this method the code doesn't have to worry
at all about images or file names, but becomes somewhat image-agnostic by
only specifying the *type* of behavior it would like to see in a given
location.  How that bahavior is implemented then becomes a simple matter of

Here is the consolidated image with not all but most of the usual icons:


And here are the patches to implement this:


I found that doing this reduced the number of requests on a clean load of
the main mailbox view from 45 to 35, which is fairly significant.  It does
add about 5K to the page size because it brings along a number of unneeded
icons for that page.  10 less requests may not be perceptible for many
people running on a fast machine with broadband Internet to a server that
isn't very loaded.  However, for a busy machine, perhaps an installation of
RoundCube serving webmail for a university, for example, 10 less requests
per fresh page load could make a noticeable difference.  10 less requests
will probably also make a noticeable difference for those on a high latency
connection, where 5K extra is less of a problem than 10 more network

I have no idea whether this is of any use or interest to anyone else, but I
thought I'd share my experiment with the list.

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