OnDragOver (C++)

Description

This code comes from an application that contains a list box and three labels, each with a different font and color. The DragMode property for each of the labels is dmAutomatic. You can select a label, drag it to a list box, and drop it. When the label is dropped, the items in the list box assume the color and font of the dropped label.

This OnDragOver event handler allows the list box to accept a dropped label:

Code

void __fastcall TForm1::ListBox1DragOver(TObject *Sender, TObject *Source, int X, int Y, TDragState State, bool &Accept)
{
   Accept = Source->ClassNameIs("TLabel");
}

/*
This OnDragDrop event handler implements the drop behavior.
*/ 
void __fastcall TForm1::ListBox1DragDrop(TObject *Sender, TObject *Source, int X, int Y)
{
  if (Sender->ClassNameIs("TListBox") && Source->ClassNameIs("TLabel"))
  {
	TListBox *DestList = dynamic_cast<TListBox *>(Sender);
	DestList->Font = (dynamic_cast<TLabel *>(Source))->Font;
	DestList->Color = (dynamic_cast<TLabel *>(Source))->Color;
	DestList->DoubleBuffered = true;
	DestList->Color = clWindow;
  }
}

__fastcall TForm1::TForm1(TComponent* Owner)
  : TForm(Owner)
{
  ListBox1->Items->Add("Not");
  ListBox1->Items->Add("In");
  ListBox1->Items->Add("Alphabetical");
  ListBox1->Items->Add("Order");

}

Uses

• Vcl.Controls.TControl.OnDragOver ( fr | de | ja )
• Vcl.Controls.TControl.OnDragDrop ( fr | de | ja )
• Vcl.Controls.TWinControl.DoubleBuffered ( fr | de | ja )