⤷ Change meanings of mouse buttons

Use SystemParametersInfo function with SPI_SETMOUSEBUTTONSWAP parameter.

procedure TForm1.Button1Click(Sender: TObject);
begin
  SystemParametersInfo(SPI_SETMOUSEBUTTONSWAP, 1, nil, 0);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  SystemParametersInfo(SPI_SETMOUSEBUTTONSWAP, 0, nil, 0);
end;
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