Delphi7 API's MDI window creation

Continue to the previous section, we still create an MDI window with the project file. The code is as follows:

 ProgramMdiapp;usesWindows, Messages;varthemessage:tmsg; Framewindow,clientwindow,childwindow:hwnd;ConstIdchildwnd= -; //First MDI child window ID{$R *. RES}//callback functionfunctionFramewindowproc (Theframewindow:hwnd; Themessage,wparam,lparam:longint): Longint;stdcall;varclientstruct:tclientcreatestruct;begin   CaseThemessage ofwm_create:beginClientstruct.hwindowmenu:=0; Clientstruct.idfirstchild:=Idchildwnd; Clientwindow:= CreateWindowEx (0,                  'mdiclient',                  Nil, Ws_childorWs_clipchildrenorws_visible,0,                  0,                  0,                  0, Theframewindow,0, HINSTANCE, @ClientStruct); ifClientwindow =0  Then        beginMessageBox (0,'CreateWindow faild',Nil, MB_OK);        Exit; End; End; Wm_destroy:beginPostQuitMessage (0);    Exit; End; End; Result:=Defframeproc (theframewindow,clientwindow,themessage,wparam,lparam);End;//Register the main windowfunctionRegisterframeclass:boolean;varWindowclass:twndclass;beginWindowclass.style:=cs_hredraworCs_vredraw; Windowclass.lpfnwndproc:=@FrameWindowProc; Windowclass.cbclsextra:=0; Windowclass.cbwndextra:=0; Windowclass.hinstance:=hinstance; Windowclass.hicon:= LoadIcon (0, Idi_winlogo); Windowclass.hcursor:= LoadCursor (0, Idc_arrow); Windowclass.hbrbackground:=Color_window; Windowclass.lpszmenuname:=Nil; Windowclass.lpszclassname:='Frameclass'; Result:= Windows. RegisterClass (Windowclass) <>0;End;//Registering child windowsfunctionRegisterchildclass:boolean;varWindowclass:twndclass;beginWindowclass.style:= Cs_hredraworCs_vredraw; Windowclass.lpfnwndproc:=@DefMDICHildProc; Windowclass.cbclsextra:=0; Windowclass.cbwndextra:=0; Windowclass.hinstance:=hinstance; Windowclass.hicon:= LoadIcon (0, idi_application); Windowclass.hcursor:= LoadCursor (0, Idc_arrow); Windowclass.hbrbackground:=Color_window; Windowclass.lpszmenuname:=Nil; Windowclass.lpszclassname:='ChildClass'; Result:= Windows. RegisterClass (Windowclass) <>0;End;//start the main programbegin  if  notRegisterframeclass Then  beginMessageBox (0,'Registerframeclass faild',Nil, MB_OK);  Exit; End; FrameWindow:= CreateWindowEx (0,                              'Frameclass',                              'Frame Window', Ws_overlappedwindoworWs_clipchildren, Cw_usedefault,                              Cw_usedefault, Cw_usedefault, Cw_usedefault, 0,                              0, HINSTANCE,Nil); ifFrameWindow <>0  Then  beginShowWindow (Framewindow,sw_shownormal);  UpdateWindow (FrameWindow); End  Else  beginMessageBox (0,'Createframewindow failed',Nil, MB_OK);  Exit; End; if  notRegisterchildclass Then   beginMessageBox (0,'Registerchildclass failed',Nil, MB_OK);   Exit; End; ChildWindow:= Createmdiwindow ('ChildClass',                        'Child Window', Ws_visible, Cw_usedefault, Cw_usedefault,                        Cw_usedefault, Cw_usedefault, Clientwindow, HINSTANCE,0); ifChildWindow <>0  Then   beginShowWindow (Childwindow,sw_shownormal);   UpdateWindow (ChildWindow); End   Else   beginMessageBox (0,'Createchildwindow Falid',Nil, MB_OK);   Exit; End;  whileGetMessage (Themessage,0,0,0) Do   beginTranslateMessage (themessage);   DispatchMessage (themessage); End;End.

The effect is as follows:

Delphi7 API's MDI window creation