Handling the OnPopup Event

You may want to adjust pop-up menu items before displaying the menu, just as you may want to enable or disable items on a regular menu. With a regular menu, you can handle the OnClick event for the item at the top of the menu.

With a pop-up menu, however, there is no top-level menu bar, so to prepare the pop-up menu commands, you handle the event in the menu component itself. The pop-up menu component provides an event just for this purpose, called OnPopup.

To adjust menu items on a pop-up menu before displaying them:

Select the pop-up menu component.
Attach an event handler to its OnPopup event.
Write code in the event handler to enable, disable, hide, or show menu items.

In the following code, the Edit1Click event handler described previously in Disabling menu items is attached to the pop-up menu component's OnPopup event. A line of code is added to Edit1Click for each item in the pop-up menu.

Copy Code

procedure TEditForm.Edit1Click(Sender: TObject);
var
  HasSelection: Boolean;
begin
  Paste1.Enabled := Clipboard.HasFormat(CF_TEXT);
  Paste2.Enabled := Paste1.Enabled;{Add this line}
  HasSelection := Editor.SelLength <> 0;
  Cut1.Enabled := HasSelection;
  Cut2.Enabled := HasSelection;{Add this line}
  Copy1.Enabled := HasSelection;
  Copy2.Enabled := HasSelection;{Add this line}
  Delete1.Enabled := HasSelection;
end;

Copy Code

void __fastcall TMainForm::EditEditClick(TObject *Sender)
{
  // enable or disable the Paste menu item
  Paste1->Enabled = Clipboard()->HasFormat(CF_TEXT);
  Paste2->Enabled = Paste1->Enabled;            // add this line
  bool HasSelection = (RichEdit1->SelLength > 0);  // true if text is selected
  Cut1->Enabled = HasSelection;    // enable menu items if HasSelection is true
  Cut2->Enabled = HasSelection;    // add this line
  Copy1->Enabled = HasSelection;
  Copy2->Enabled = HasSelection;   // add this line
  Delete1->Enabled = HasSelection;
}

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