Title: add a double-click event to the header of a Listview?
{
MS did not see fit to send a notification to the listview when the user
Double - clicks on the header. But the header control class does have the
CS_DBLCLKS Style, so it does get WM_LBUTTONDBLCLK messages, it just does
not do anything with them. To get at these messages requires API - Style
subclassing of the header control.
}
uses commctrl;
function HeaderProc(wnd: HWND; Msg: Cardinal; wParam: wParam; lParam: lParam): Longint;
stdcall;
var
hti: THDHitTestInfo;
begin
Result := CallWindowProc(Pointer(GetWindowLong(wnd, GWL_USERDATA)),
wnd, Msg, wParam, lParam);
if Msg = WM_LBUTTONDBLCLK then
begin
FillChar(hti, SizeOf(hti), 0);
hti.Point := SmallPointToPoint(TSmallPoint(lParam));
if SendMessage(wnd, HDM_HITTEST, 0, Longint(@hti)) = 0 then
if hti.Flags = HHT_ONHEADER then
// would usually send a custom notification to GetParent(wnd) here
Form1.Memo1.Lines.Add(Format('doubleclick on header item %d', [hti.Item]));
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
var
wnd: HWND;
buffer: array [0..80] of Char;
oldProc: Integer;
begin
wnd := GetWindow(Listview1.Handle, GW_CHILD);
if wnd 0 then
begin
Windows.GetClassname(wnd, buffer, SizeOf(buffer));
memo1.Text := buffer;
if (GetClassLong(wnd, GCL_STYLE) and CS_DBLCLKS) 0 then
begin
Memo1.Lines.Add('Has doubleclicks style');
oldproc := GetWIndowLong(wnd, GWL_WNDPROC);
if GetWindowLong(wnd, GWL_USERDATA) 0 then
raise Exception.Create('Cannot sublcass header, USERDATA already in use');
SetWIndowLong(wnd, GWL_USERDATA, oldproc);
SetWindowLong(wnd, GWL_WNDPROC, Integer(@HeaderProc));
end;
end
else
Memo1.Text := 'No child';
end;