There are two solutions I can think of:
(1) derive combo-field% and override the on-popup method to construct the
choice menu dynamically based on what is selected in the combo box field.
This has a few disadvantages, namely (a) you have to produce the menu
immediately, so if you have to query a database for the list of items,
there might be a long delay for the menu to show up and (b) the menu will
not update when the user types more text in the field, instead it will have
to be closed and reopened.
(2) you can use a combination of text-field% and a list-box%, where the
callback on the text field will populate the list box with the filtered
contents. The user would have to select an item from the list box, but
this can be populated in a separate thread to prevent the GUI from freezing
up during a database query. It does not look as nice as GUI widgets from
other applications though...
Here is some example code for both options, including an animation of what
it looks like:
https://gist.github.com/alex-hhh/20f03dcf2f7f340d20b95cb36da39f61
Alex.
On Friday, February 15, 2019 at 5:39:31 AM UTC+8, James Platt wrote:
>
> I have a situation where I want a Racket GUI combo-field% (or some other
> GUI element) to allow the user to select an exact item (uniquely matching a
> database key) from a list that is too long to display all at once. I'm
> thinking that some form of auto completion would be best. In Framework, I
> see that there is an auto-complete method in text% but I don't see a way to
> give it a specific search space to work from. I see the opposite. You can
> get the list which it is auto completing from but I don't see how to set
> it.
>
> I mention combo-field% because the equivalent item in the LibreOffice
> database module does what I want. I had a LibreOffice document which was
> connecting as client to a PostgreSQL database. The combo-field list items
> were populated with an SQL query which got all the official human gene
> symbols from the database. At the time there were something like 40,000
> unique official gene symbols. The user could start typing and it would
> reduce the list, as you go, to the remaining items that match. Also, when
> there are too many items to display at once, LibreOffice only displays the
> first 10 or 20 items in the combo-field menu and gives you a scroll bar.
> This worked out pretty well for that use case. I now have a very similar
> one.
>
> What would be the best way to handle this situation? The user needs to
> select an exact item from a database but there are too many items for a
> simple menu.
>
> James
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