I'm using a ESRI.ArcGIS.Desktop.AddIns.ComboBox. I configure the size of the combobox in config.esriaddinx with the following xml:

    <ComboBox id="my_id"
              message="Everything is awesome!"
              caption="Everything is awesome!"
              tip="Everything is awesome!"
              category="Add-In Controls" 
              sizeString =     "WWWWWWWWWWWWW" 
              itemSizeString = "WWWWWWWWWWWWW" />

It work fine, but it really baffles me that the width is configured with a bunch of 'W's.

Can anyone explain the reasoning behind it?


This is just conjecture, but there is probably some variable-width text measurement logic going on behind the scenes, and the character W was probably chosen because it is one of the widest characters available in variable-width fonts. I agree that it is a bit nonsensical to do it this way.

  • I think this is the closest we'll get to an answer. Would be wonderful with some esri insider knowledge to shed light on the reasoning behind. – steenhulthin Jan 6 '15 at 8:10

That string represent the maximum length of string that you can show on that combo-box.That mean if it shows "WWW" you can add items of maximum 3 character.If you entered otherwise the arc-map split that string by the maximum length and balance will shown as next item.This also mentioned in Add-in _wizard. See image below addin-wizard

  • This is not (entirely) correct. I use 12 Ws which still shows all of my longest element of about 20 chars. And it does not answer the question about the 'why'? Is there some standard where W is a magic representation of string length? I would this to make sense. – steenhulthin Dec 3 '14 at 12:40
  • i have tested that also.You have enter string in to "item size string" text-box to restrict the number of characters in the item."W" is just a representation of width. But you can enter any character to that text-box.Number of the string is that only matters.. – Subin Dec 3 '14 at 13:54
  • 1
    That is not entirely correct either. The size of the combobox is not the same when I use sizeString="aaaa" in stead of sizeString="WWWW" for instance. Maybe this question can really only be answered by esri. I makes no sense to me at least. – steenhulthin Dec 4 '14 at 8:05
  • yeah that's right. – Subin Dec 4 '14 at 8:35

As stated previously, this defines the width of the drop-down box, as shown here in the ESRI help. This doesn't have to be a 'W'. You can use any repeated character. It does bring up the question of why not just use a numeric value where the number is equivalent to the width value in some predefined units.

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