Question

When a Delphi Form is declared and instantiated inside a DLL and the DLL loaded by the host application, Arrow and Tab keys are not passed across the Host/DLL boundary. This means that TEdit boxes and TMemo controls that may be used on the form will not respond to these key strokes. Is there anyway to ensure that these key strokes are passed from the main application form to the form in the dll? Note there may be multiple DLLs, each containing a form. KeyPreview makes no difference.

Answer 1

Forms in DLL’s miss this support, as well as support of menu shortcuts (actions). You can write some code to simulate this behaviour.

////////////////////////////////////////////////////////////////
// If you display a form from inside a DLL/COM server, you will miss
// the automatic navigation between the controls with the "TAB" key.
// The "KeyPreview" property of the form has to be set to "True".
procedure TForm1.FormKeyPress(Sender: TObject; var Key: Char);
var
  bShift: Boolean;
begin
  // Check for tab key and switch focus to next or previous control.
  // Handle this in the KeyPress event, to avoid a messagebeep.
  if (Ord(Key) = VK_TAB) then
  begin
    bShift := Hi(GetKeyState(VK_SHIFT)) <> 0;
    SelectNext(ActiveControl, not(bShift), True);
    Key := #0; // mark as handled
  end;
end;