基本上每个消息都有一个Result，代表是否（正确）处理过了（但是是否继续传递，还得研究）

TWMContextMenu = packed record
Msg: Cardinal;
hWnd: HWND;
case Integer of
0: (
XPos: Smallint;
YPos: Smallint);
1: (
Pos: TSmallPoint;
Result: Longint);
end;

TWMShowWindow = packed record
Msg: Cardinal;
Show: BOOL;
Status: Longint;
Result: Longint;
end;

TWMSize = packed record
Msg: Cardinal;
SizeType: Longint; { SIZE_MAXIMIZED, SIZE_MINIMIZED, SIZE_RESTORED,
SIZE_MAXHIDE, SIZE_MAXSHOW }
Width: Word;
Height: Word;
Result: Longint;
end;

procedure TControl.WMContextMenu(var Message: TWMContextMenu);
var
Pt, Temp: TPoint;
Handled: Boolean;
PopupMenu: TPopupMenu;
begin
if Message.Result <> 0 then Exit;
if csDesigning in ComponentState then
begin
inherited;
Exit;
end;

Pt := SmallPointToPoint(Message.Pos);
if InvalidPoint(Pt) then
Temp := Pt
else
begin
Temp := ScreenToClient(Pt);
if not PtInRect(ClientRect, Temp) then
begin
inherited;
Exit;
end;
end;

Handled := False;
DoContextPopup(Temp, Handled);
Message.Result := Ord(Handled);
if Handled then Exit;

PopupMenu := GetPopupMenu;
if (PopupMenu <> nil) and PopupMenu.AutoPopup then
begin
SendCancelMode(nil);
PopupMenu.PopupComponent := Self;
if InvalidPoint(Pt) then
Pt := ClientToScreen(Point(0, 0));
PopupMenu.Popup(Pt.X, Pt.Y);
Message.Result := 1;
end;

if Message.Result = 0 then
inherited;
end;