Combo_boxes and how to use them

Question

I'd like to be able to type a search term into a combo box and, with each typed character, i'd like to perform a SQLite query and get back results that influence what items appear in the popup menu part of the combo-box.  I've been able to do this with a popup_menu and a separate edit_field, but it takes up too much room in the user interface. ideally i'd like to be able to do it from a combo_box.  but there don't seem to be enough hooks into a combo_box to do this. take for example the value parameter.  while a variable bound to it will contain the text typed into the combo_box, it also contains the value of whatever item is pulled down in the popup menu.  this leads to confusion and none of my experiments have been able to get values typed into the combo_box to actually produce new SQLite queries on a character-by-character basis (yes, i tried adding immediate=true to the combo_box instance when i created it).
that said, i'm going to guess that (like everything else in the SDK), there are parameters i can set in a combo_box to deal with the text typed into it and the item selected by the popup separately. i just don't know what they are because they are not mentioned in the documentation for a combo_box.  or i'm wrong and what i am requesting is impossible.  but i thought i'd ask here first.

Answer 1

HI Victor,
I meant the validate function - it would be clarified if you download the test plugin (see link a few posts up).
Here is guts of the code:
vf:push_button {
    title = "Push me... (perform test)",
    action = function( button )
        LrFunctionContext.postAsyncTaskWithContext( "Test", function( context )
            local efValidated = false
            local cbValidated = false
            context:addCleanupHandler( function( status, message )
                if status then
                    local m = {}
                    local c = 0
                    if efValidated then
                        m[#m + 1] = "edit-field validator was called"
                        c = c + 1
                    else
                        m[#m + 1] = "*** edit-field validator was NOT called"
                    end
                    if cbValidated then
                        m[#m + 1] = "combo-box validator was called"
                        c = c + 1
                    else
                        m[#m + 1] = "*** combo-box validator was NOT called"
                    end
                    if c > 0 then
                        LrDialogs.message( section.title.." completed without an error being thrown - "..table.concat( m, ", " ).."." )
                    else
                        LrDialogs.message( section.title.." failed! - no validators were called." )
                    end
                else
                    LrDialogs.message( "*** "..section.title.." ended - an error was thrown: " .. ( message or "?" ) .. " - push '"..button.title.."' button to perform test again, if desired." )
                end
            end )
            props.efValue = "Edit this - validator should get called when you do"
            props.cbValue = "Edit this - validator should get called when you do"
            props.items = {
                "No worthwhile items...",
            --[[ validate function spec -
                Parameters:
                    view (LrView) This control.
                    value (any) The value to validate.
                Returns three values:
                    result (Boolean) True if value was valid.
                    value (any) The new value.
                    message (string) If result is false, an error message.
            local function validate( viewObject, value )
                props.items = {
                    "One", "Two", "Three", "...",
                return true, value
            end
            local vi = {
                vf:row {
                    vf:static_text {
                        title = "Edit field:",
                        width = share 'label_width',
                    vf:edit_field {
                        bind_to_object = props,
                        value = bind 'efValue',
                        --items = { 'no worthwhile items' },
                        immediate = true,
                        validate = function( vo, value )
                            efValidated = true
                            return true, value -- false, "edit-field validator was called", "edit-field validator is ok"
                        end,
                        width_in_chars = 30,
                vf:row {
                    vf:static_text {
                        title = "Combo box:",
                        width = share 'label_width',
                    vf:combo_box {
                        bind_to_object = props,
                        value = bind 'cbValue',
                        items = { 'no worthwhile items' },
                        immediate = true,
                        validate = function( vo, value)
                            cbValidated = true
                            return true, value -- false, "combo-box validator was called", "combo-box validator is ok"
                        end,
                        width_in_chars = 30,
            local args = {}
            args.title = "Test"
            args.contents = vf:view( vi )
            LrDialogs.presentModalDialog( args )
        end )
    end, -- action func
Problem: validate function (of combo box) not getting called - what am I doing wrong?
PS - validate function of edit-field is getting called.
Rob