[cells-devel] Celtk: mk-entry: How to set initial value?

[Frank Goenninger]

Ok - so here goes the use case:

1. A user is present a list of devices (PowerMasters, "pm") (in  
listbox :pm-list).

2. The entry field :call-sign entry is empty.

3. The user selects an item in the listbox. This sets a slot in the  
parent model (named :pmutil-gui) with the value  of the corresponding  
element of the listbox's item-factory.

4. *** Now the entry field - as it does a c?n on that "selected-pm" -  
should get the callsign of that selected pm. The user is then able to  
change that value to a new one by overtyping it.

5. The user selects a button that reads the value of :callsign-entry  
and sends that value to the pm device (this works already).

6. After programming the device with the new callsign the listbox has  
to refresh,it is re-reading the items such that no item is selected.  
The :callsign-entry should be set to "" (= cleared) because no pm is  
selected.

7. Goto step 3

That's it.  Does this make it more clear. Meanhwile I am chewing on  
your details below ... Thx!!!

Frank

Am 22.11.2007 um 14:42 schrieb Ken Tilton:

> Frank Goenninger wrote:
>> Hi Kenny, hi all (would be interesting to see who actually  
>> monitors  this ?)
>> I have an entry widget like this:
>>     (mk-entry :id :callsign-entry
>>               :value (c?n (let ((pm (selected-pm (fm^ :pmutil-gui))))
>>                             (if pm
>>                                 (callsign pm))))
>>               :enabled (c? (pm-selected-p (fm^ :pmutil-gui)))
>>               :width 17
>>               :tk-justify 'left
>>               :relief 'sunken
>>               :borderwidth 1
>>               :parent-x 424
>>               :parent-y 321
>>               :background (c_? (required-field-color .parent))
>>               :tile? nil)
>> Intention is to be able to set the value initially and afterwards   
>> have the rule kick-in and setting the value automagically. Alas,   
>> neither the initial setting of the value really works nor does  
>> the  cell rule fire ...
>
> You do not show nor can I guess what you mean by "set the value  
> initially". If you are supplying a value initarg, then none of the  
> above applies. If you are making the instance and then in the next  
> line of code setf'ing the value that is still not "initially".  
> Please elucidate.
>
> Meanwhile, c?n goes the other way: the rule runs once to come up  
> with an initial value and then becomes a classic input cell.
>
> As for what you want, it seems a little ugly in that callsign-entry  
> is somewhat a slave to pmutil-gui and somewhat not, and this  
> confusion is making the cells code hard to write. this may be  
> clearer, btw, when we understand better how you meant to supply a  
> value "initially".
>
> There is/was something called c-drifter and c-drifter-absolute is  
> close to what you want, but a quick look suggests they are broken  
> precisely at the initialization point, and any fix makes no sense:  
> does this thing depend on its rule or not?
>
> If you really need to do this...
>
> (c? (let ((x <rule>))
> 	(if .cache-bound-p
>            <initial-value>
>            x)))
>
> You need the rule to run even if not cache-bound-p (ie, initially)  
> to set up the dependencies.
>
> That too is ugly, again I think because of the original confusion  
> over whether the one widget really is a slave to the other. I would  
> resolve that and not get caught up with clever cells tricks.
>
> kt

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