The TIB_Grid logic for deselecting multiple rows already selected should, I
think, be inserted in the grids MouseUp event, as it is not yet performed by
TIB_GRID.

if ((AButton = mbLeft) or (Abutton=mbRight)) and
not ((ssShift in AShift)or (ssCtrl inAShift)) and
(not ((Sender as TIB_Grid).DataSource.Dataset as
TIB_Query).Selected[(Sender as TIB_Grid).FocusedCell.Y ) and
( not ((Sender as TIB_Grid).IndicateTitles) or ((Sender as
TIB_Grid).DefaultRowHeight < Y))
then
((Sender as TIB_Grid).DataSource.Dataset as
TIB_Query).SelectAll(False);

Y is the mouse coordinate supplied by the grid's OnMouseUp event.
Both Left and Right buttons can be used to select and deselect rows.
Selection requires Ctrl or Shift to be pressed.
Clicking inside a selected row does not deselect rows.
Clicking a title bar will not deselect rows.

The prior logic posted here in the past few days has missed at least one of
these requirements.

Regards

Russell