This is now possible with the new prefs UI framework.

Changes have been made in Git for this ticket:

Request #6711: pref to choose preferred multipart/alternative display part

http://git.horde.org/diff.php/imp/config/prefs.php.dist?rt=horde-git&r1=13dcbf8f824f5aefc3f2add2e7642d5e8fbba1f4&r2=dd7ad25824b6726b89a93d8c08ec1229057aaddf
http://git.horde.org/diff.php/imp/docs/CHANGES?rt=horde-git&r1=48724980857eef05ee6f589a3757263d477b697b&r2=dd7ad25824b6726b89a93d8c08ec1229057aaddf
http://git.horde.org/diff.php/imp/lib/Mime/Viewer/Alternative.php?rt=horde-git&r1=1cecd5d8a0a787eeedf60a26ce38d960bb3e06cd&r2=dd7ad25824b6726b89a93d8c08ec1229057aaddf
http://git.horde.org/diff.php/imp/lib/Prefs/Ui.php?rt=horde-git&r1=8267407b9326e82ce455e88ebd87d5841e0c3268&r2=dd7ad25824b6726b89a93d8c08ec1229057aaddf

I'm going to reject.  Maybe in the future there will be some 
Horde_Prefs_Ui way to interact with mime_drivers.php settings.

That's a good point, it would indeed make the configuration a bit confusing.

I still don't agree with this.  I don't want the same configuration 
option appearing in 2 different locations: mime_driver config needs to 
stay in the mime_driver config files where everything else about that 
driver is configured.

We should lock the preference by default, so that it mimics the 
current behavior of the mime_drivers.php setting.

Should this really be user settable?  This implicates both security 
and server load concerns (XSS/Phishing filtering is not cheap) and 
seems to be better left to the discretion of an admin.

PS, I am sure there is a better way to do this and am hoping the horde 
team can do it better than my hack of a solution.

I can tell you what I did as its not that difficult.  In 
mime_drivers.php I added an if statment and changed the boolean value 
to be a variable name:





if ( $GLOBALS['prefs']->getValue('html_inline_viewing') === '0' ) {

         $viewHtmlInline = false;

} else {

         $viewHtmlInline = true;

}





/**

  * HTML driver settings

  */

$mime_drivers['imp']['html'] = array(

     'inline' => $viewHtmlInline,





and created a new preference in prefs.php:



$_prefs['html_inline_viewing'] = array (

        'value' => 1,

        'locked' => false,

        'shared' => false,

        'type' => 'checkbox',

        'desc' => _("View messages as HTML when both HTML and plain text are 
available (this change takes effect after log out)?"),

        'help' => 'prefs-notavailable'

);

You said you were modifying files for this - can you submit a patch?

Makes sense.

I am currently modifying the prefs.php and mime_drivers.php files to 
add the ability to give users the choice of viewing messages in HTML 
or text by default as a preference option.



Has the Horde team looked at adding this as a user settable option if 
inline HTML and text are being permitted (and a message has both 
formats being sent in message)?



Can this be added as a request for future releases?