[Discuss-gnuradio] Load Preset parameters in block

[Mark Arlinghaus]

Hello,

Is there a way to load preset default parameters in a block.  For example, I have a channel model block that takes several parameters, such as the doppler spread, path delays, path gains, doppler spectrum, etc., and I want to have presets that will auto-populate the parameters in the GRC block for pre-defined channel models.  I can make a drop-down menu that has the pre-defined channel models, but I don't know how to change the values that populate in the other parameters.  I would like to do this using the xml file.  Is there a way to put a conditional parameter in the <value> tags that would depend on the setting in the drop down menu (It seems conditionals can be used in the <hide> and <import> tags, but not inside the <value> tags)?  Is there a way to do it using the <opt> tags?  Is there a list of valid options and what they do anywhere?  It seems the <opt> val:XXX <\opt> tags might do it, but I can't seem to get any of them to work. 

Although I could pass in a preset parameter to the C++ function and simply override everything coming from the GUI, I'd rather have it populate the parameters in the block, but still let them be changed.  This way, if someone wanted to load the settings for a "Channel X" preset, except with a different Doppler spread, it could be done easily.  

Note this is a similar problem as posted here:
https://lists.gnu.org/archive/html/discuss-gnuradio/2015-02/msg00016.html, but it doesn't appear the previous question was ever answered.

Thank you in advance for your help.

Mark Arlinghaus