Passing values to turbogears widgets at display time (the general case)

Last time I dug this up I was not clear enough in documenting my findings, so I had to find them again. Here is the second attempt.

In Turbogears, in order to pass parameters to arbitrary widgets in a compound widget, the syntax is:

form.display(PARAMNAME=dict(WIDGETNAME=VALUE))

And if you have more complex nested widgets and would like to know what goes on, this monkey patch is good for inspecting the params lookup functions:

import turbogears.widgets.forms
old_rpbp = turbogears.widgets.forms.retrieve_params_by_path
def inspect_rpbp(params, path):
    print "RPBP", repr(params), repr(path)
    res = old_rpbp(params, path)
    print "RPBP RES", res
    return res
turbogears.widgets.forms.retrieve_params_by_path = inspect_rpbp

The code for the lookup itself is, as the name suggests, in the retrieve_params_by_path function in the file widgets/forms.py in the Turbogears source code.