Hi,

In Drupal 7 I'm working on a module that deals with node forms.
I must set some values from code. Actually what I do is save some user input
and populate the node form with the values.

I can easily modify field values from hook_form_alter except term_reference_tree.
It looks like that when hook_form_alter gets called, the term_reference_tree field
only has some meta data and doesn't contain the checkboxes for the tree.

They are missing in hook_field_attach_form too. However, when I check the field
upon form submit, the checkboxes are there.

On form submit the field has a key [#options] and an array with the checkbox tree,
but these keys are missing in hook_form_alter. There's a function
term_reference_tree_process_checkbox_tree which I tried to call from my module.
It builds the frame of the checkbox tree, but not the actual checkboxes. Output is like this:

[#options_tree] => Array
    (
    )

[#options] => Array
    (
    )

[0] => Array
    (
        [#type] => checkbox_tree_level
        [#max_choices] => 1
        [#leaves_only] => 
        [#start_minimized] => 
        [#depth] => 1
        [#level_start_minimized] => 
    )

As you can see, the #options array is empty, and the checkbox array only has some default
values.
I tried to simply insert values in the array (and set the keys where they should belong), set
#checked to true like with regular checkboxes, but when the form is presented to the user,
these values got overwritten with empty values.

I also tried to modify weight, to put my module before term_reference_tree, but it didn't help.

Is there a way to check some checkboxes from code before it the form gets displayed
to the user? I am not too familiar with term reference tree module, but I think there must
be some function I can call or another hook I can catch to build the checkbox tree so I
can populate it.

Thanks in advance,
Balazs