TwwDataGrid: Custom title button sorting of some fields.

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kyle

• October 09, 2021 03:15
• Edited

Given a dataset attached to a grid, how can I manually sort fields the grid has determined to be not sortable while maintaining usual sorting look?

If an event passes the field name, I can adjust dataset SQL to order by the field. I need TwwDataGrid to display the sorting arrow & maintain descending value as if it's an auto-sorting column.

This is the beginnings of my attempt to code special sorting handling for a field the grid can't sort, but SQL can. It falls way short. I figure there has to be an easier way.

procedure TOrdersFrm.LinesGrdTitleButtonClick(Sender: TObject; AFieldName: string);
begin
  inherited;
  var lTitleButton := LinesGrd.ColumnByName(sLineDesc).HeaderTitleButton;

  if lTitleButton <> nil then
  begin
    if SameText(aFieldName, sLineDesc) then
    begin
      begin
        TPath(lTitleButton.ImageForButton).Fill.Color :=
          THackwwDataGrid(LinesGrd).GetEffectiveTitleIconColor;

        if LinesGrd.SortDescending then
        begin
          lTitleButton.ImageForButton.RotationAngle := 180;
        end
        else
        begin
          lTitleButton.ImageForButton.RotationAngle := 0;
        end;

        THackwwGridTitleButton(lTitleButton).SetImageForButtonVisible(True);
      end;
    end
    else
    begin
      THackwwGridTitleButton(lTitleButton).SetImageForButtonVisible(False);
    end;
  end;
end;

0

• 

  Michael Verhagen

  • October 10, 2021 03:05

  If I understand you correctly, you wish to preserve the UI appearance that indicates sort-ability of the column even when the grid would suppress that display because it is incapable of doing the sorting in its usual way.

  You can make the SQL achieve the sorting, but you want this to be triggered the way a user would sort by clicking on a column header.

  I have no experience with replacing title button images, but doing that sounds like the most natural approach and hacking the code of TwwDBGrid would be the last thing I would try.

  You say your approach "falls way short" but can you describe how it is inadequate?  Have you looked for clues in the TwwDBGrid code to see how it manages the presence of the sort arrows?

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• 

  kyle

  • October 10, 2021 13:19
  • Edited

  Your understanding is correct. Grid sorting performs exactly the same except the actual sorting is decided to do default sorting or call an OnCustomSort event.

  Grid source would be something like ...

  if assigned(fOnCustomSort) then
    fOnCustomSort(Self)
  else
    DoDefaultSort;

  Much of what I wrote was extracted from the grid source. The arrow almost works as it should. When clicking the custom sorted column after a std sort column, the std sort column doesn't clear its arrow.

  Also, after reading more grid source, there is more to do, e.g. clearing open editors. I pulling in a lot of code from source and cracking open classes for protected members to get custom sort capability. It's getting a little messy.

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• 

  kyle

  • October 12, 2021 13:08

  Better than the code above is...

  lDoDefaultSort := True;
  
  if assigned(fOnCustomSort) then
    fOnCustomSort(lDoDefaultSort);
  
  if lDoDefaultSort then
    DoDefaultSort;

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• 

  Roy Woll

  • October 12, 2021 22:53

  You can control the icon with the following properties.

  procedure TDataGridCustomColorsForm.Button1Click(Sender: TObject);
  begin
   dgfish.sortfieldname:= 'LengthIn'; // Set which column should show icon
   dgfish.RefreshTitleButtons();
  end;
  

  You may also want to set the grid's SortDescending property to true if the grid is descending order.

   

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