Delphi Adding Items to ComboBox Speed

Question

I have a fairly complex and large application that hands loads and loads of data. Is there a speedy way to add items to ComboBox that doesn't take so long? On my P3 3.2ghz, the following snippet takes just under a second to add around 32,000 items. (MasterCIList is a StringList with strings typically 20 - 30 bytes long).

with LookupComboBox do
 begin
  Items.BeginUpdate;
  Items.Clear;
  for i := 0 to MasterCIList.Count - 1 do
   Items.Add(MasterCIList[i]);
  Items.EndUpdate;
 end;

Drilling down into the VCL, it appears that in TComboBoxStrings.Add, there is a call to

Result := SendMessage(ComboBox.Handle, CB_ADDSTRING, 0, Longint(PChar(S)));

I'm guessing this is really taking up time (okay, I know it is). Is there another way to populate the Items that is speedier? Any high-speed combo boxes available? I have the TMS components but they seem to be extensions of TComboBox.

For instance, I have the PlusMemo which seems to be a total rewrite of a TMemo. I can easily add a million line in a second to a PlusMemo. A TMemo, I don't think so.

Thank you so much for your time!

Answer 1

Sorry if I'm a nuisance, but I doubt a TComboBox with 32,000 items is even remotely ''usable'' --- I'd say there's a reason why it's slow: it was never meant to do this :)

Would there be a possibility to filter the data, and only load a subset? To be more concrete, in one particular database application I've been working on, the user can search for a person. We let the user type at least 3 or 4 characters of the name, and only then begin to return results in a listbox. This has greatly increased usability of the search form, also greatly speeding up the whole process.

Would you be able to follow a similar approach?

Or, on a completely different take, perhaps you could take a look at the VirtualTreeView component --- either for direct use, or for inspiration.