drawing a dbgrid cell from a look up
lazarus / 16-Databases

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codifies · 2012-09-11 05:07

I have managed to use a DBLookupComboBox as a custom editor for a
field containing a foreign key.
this works (but I can't see how to change the width of the drop down
bit of the combo box which is way to big compared to the cell and
means you cant see the value properly when closed)

My main issue is the cell renders the key text (i want to be editing a
key value but display it as the looked up text associated with the key
in the foreign table)

I've got as far of attempting to render some custom text in the cell
like this
Code: [Select]procedure TForm1.DBGrid1DrawColumnCell(Sender: TObject;
const Rect: TRect;
  DataCol: Integer; Column: TColumn; State: TGridDrawState);
var
  s: String;
begin
  if (gdFocused in State) then FRect := Rect;
  if (Column.DesignIndex=3) then
     begin
         s:='arrgh! :)';
         (Sender as TDBGrid).Canvas.TextRect(Rect,Rect.Left,Rect.Top,
s);
     end
  else
      (Sender as TDBGrid).DefaultDrawColumnCell(Rect, DataCol, Column,
State);
end;   
is there some way I can set the string by looking up the value via the
DBLookupComboBox somehow? or do I need to make a seperate sql query
for each cell?

With luck I'm doing this the hard way and there's a dead easy way!

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teos · 2012-09-13 18:12

I'm not sure if I understand the problem but DBgrid should be able to
display and use the dbLookupcombobox.

But to get that to work, you should add a field to the fielddefs of
the dataset, defining that field as lookup. Then you fill in the
lookupdataset, lookupkeyfield, resultfield and from that point, DBGrid
should show a combobox for the field.

I think, also from your other question that the components you use
provide much more functionality than you think they do. Those
dbLookupcomboboxes are part of the database framework.

If my remarks don't work like they should, I'm very curious to learn
what the problem is and if you can post the settings of the datafield
that you need the lookupcombobox for.

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codifies · 2012-09-13 18:44

I discovered later that you didn't need a separate drop down, you used
to need to in Delphi years ago I seem to remember and I'm only just
getting back into things

I attempted to get the approach you suggested working earlier, but
could only get the drop down bit working but not the cell display. 
Eventually on each run it just said some data component wasn't active
without identifying which component it was, and I couldn't resurrect
it and ended up used a different approach...  

If you're confident you can replicate a foreign key look up to edit a
dbgrid table I'm positive not only myself but quite a large number of
people would find it useful.