Title: show system menu for form
As you know, every form/window in MS Windows (TForm in VCL terms) have a
system menu. Usually there are pre-defined items like Close, Mimimize,
Maximize, Move etc
But, of course, you also may add any own item in this system menu - see my
tip#30 for sample (http://www.scalabium.com/faq/dct0030.htm)
So sometimes you may want to show this system menu for form but in any own
position and from any your event. For example, user'll click on some your
button and will see this system menu:
procedure TForm1.Button1Click(Sender: TObject);
var
hMenuHandle: hMENU;
hMenuItem: dWord;
p: TPoint;
begin
{recalculate button coordinates to screen coordinates}
p.X := Button1.Left;
p.Y := Button1.Top;
p := Button4.ClientToScreen(p);
hMenuHandle := GetSystemMenu(Handle, False);
hMenuItem := LongWord(Windows.TrackPopupMenu(hMenuHandle, TPM_LEFTBUTTON or TPM_RIGHTBUTTON or TPM_RETURNCMD,
p.X, p.Y, 0, Handle, nil));
if hMenuItem 0 then
SendMessage(Handle, WM_SYSCOMMAND, hMenuItem, 0);
end;
This could be really useful if you replace standard caption and draw own
"header". Generally better for this task to process the WM_NCPAINT and
WM_NCHITTEST messages but I saw a few implementations without these messages
too...