Create a special window [6]

In this example:

Unit unit1; interfaceuses windows, messages, sysutils, variants, classes, graphics, controls, forms, dialogs, extctrls; Type tform1 = Class (tform) Panel1: tpanel; Procedure formcreate (sender: tobject); Procedure panel1click (Sender: tobject); end; var form1: tform1; implementation {$ R *. DFM} var F: Boolean; Procedure tform1.formcreate (Sender: tobject); Begin self. color: = clwhite; panel1.parentbackground: = false; end; Procedure tform1.panel1click (Sender: tobject); var RGN: hrgn; begin F: = not F; if F then RGN: = createellipticrgn (0, 0, panel1.width, panel1.height) else RGN: = createrectrgn (0, 0, panel1.width, panel1.height); setcancwrgn (panel1.handle, RGN, true) end; end.