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Understanding MFC Document/View Architecture in Windows Programming

This document explores the Microsoft Foundation Class (MFC) Document/View architecture, emphasizing its advantages in separating data from its presentation. Unlike traditional App/Window models, the Document/View approach encapsulates data in `CDocument` classes and rendering mechanisms in `CView` classes, allowing for versatile data handling across different views. It also discusses the use of dynamic creation macros for efficient object management and the role of templates within MFC applications. Tools like AppWizard and ClassWizard aid in quickly generating and customizing frameworks for efficient application development.

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Understanding MFC Document/View Architecture in Windows Programming

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  1. MFCWindowsProgramming: Document/ViewApproach Moredetailednotesat: http://dforeman.cs.binghamton.edu/~foreman/360/notes-html/class15.htm

  2. MFCWindowsProgramming: App/WindowApproach vs. Document/View Approach AnApp/Windowapproachprogram createsapplicationandwindowobjects MirrorsWin32 APIprogramorganization Maindifference--MFCautomatesandmasks details… anddoesmanyothernecessarytasks But data&renderingofdataare intertwined Frequently,datamembersexistinwindowclass –ExampleinMSG2005.CPP:Outputstringdefinedin window-basedclass • Butoutputstringisdata • Reallyhasnothingtodowithwindowit’sbeingdisplayedin

  3. �Conceptuallydataisdifferentfrom renderingofdata �InanApp/Windowapproachprogram theyare mixedtogetherinsamewindow class �Frequentlyweneedtohavedifferentviews ofsamedata –(e.g.,displayingdatainawindoworonaprinter) �Soit’sagoodideatoseparatedataanddatapresentation Doc/ViewAchievesSeparationof DataandDataPresentation �EncapsulatesdatainaCDocumentclassobject �Encapsulatesdatadisplaymechanismand userinteractionwith itinaCViewclassobject �ClassesderivedfromCDocument –Shouldhandleanythingaffectinganapplication's data �ClassesderivedfromCView –Shouldhandledisplayofdataanduser interactionswiththatdisplay

  4. OtherClassesareStill Needed �StillneedtocreateCFrameWndand CWinAppclasses �Buttheirrolesarereduced Documents �Document –Containanyforms ofdataassociatedwith the application(puredata) –Notlimitedtotext –Couldbeanything •gamedata,graphicaldata,etc.

  5. DocumentInterfaces �SingleDocumentinterface(SDI)application –Programthatdealswithonedocumentatatime –AllourprogramstodatehavebeenSDIapps �MultipleDocumentInterface(MDI) application –Programorganizedtohandlemultipledocuments simultaneously –Morethanonedocumentcanbedisplayedina windowatthesametime –Example of anMDIapplication:MicrosoftExcel Views �Arenderingofadocument;a physicalrepresentationofthedata �Providesmechanismfordisplaying datastoredinadocument �Defineshowdataistobedisplayedin awindow �Defineshowtheusercaninteractwithit

  6. FrameWindow �Windowinwhichaviewofa documentisdisplayed �Adocumentcanhavemultiple viewsassociatedwithit –differentwaysoflookingatthe samedata �Butaviewhasonlyone documentassociatedwithit

  7. MFCTemplateClassObject �Handlescoordinationbetweendocuments,views,andframewindows �Ingeneral: –Applicationobjectcreatesatemplate... –whichcoordinatesdisplayofdocument'sdata… –in a view… –inside a frame window �i.e.,our CWinAppobjectcreatesaDocument TemplatewhichcreatesaCDocumentobjectand aCFrameWndobject –TheCFrameWndobjectcreatesaCViewobject –Whichdisplaysthedocumentdata Template/Document/View/Window

  8. Serialization �Providesforstorage/retrieval ofdocumentdata �Usuallyto/fromadiskfile �CDocumentclasshasserializationbuiltintoit –SoinDOCUMENT/VIEWapps, saving/storingdataisstraightforward DynamicCreation �InDoc/Viewapproach,objectsaredynamic �Doc/Viewprogramis run –Its frame window, document, and view are created dynamically –Often Doc/View objects are synthesized from file data • Theyneedtobecreatedatloadtime(runtime) –Toallowfordynamiccreation,usedynamic creationmacros • inclassesderivedfromCFrameWnd,CDocument,and CView)

  9. DynamicCreationMacros �DECLARE_DYNCREATE(class_name) –indeclaration(.hfile) �IMPLEMENT_DYNCREATE(class_name, parent_class_name) –(in .cpp file) �AfterIMPLEMENT_DYNCREATE()macroisinvoked: –Classisenabledfordynamiccreation –Nowatemplatecanbecreated SDIDoc/ViewCWinApp’sClass InitInstance() �Create document template and window: CSingleDocTemplate*pDocTemplate( IDR_MAINFRAME //ResourceID RUNTIME_CLASS(CPgmDoc) // the document RUNTIME_CLASS(CMainFrame)//mainSDIframewindow RUNTIME_CLASS(CPgmView)); //theview //RUNTIME_CLASS():amacroreturnspointerstoapp,doc,viewclasses //Willonlyworkafterdynamicdeclaration/creationmacrosareinvoked AddDocTemplate(pDocTemplate): //Addstemplateandcreateswindow �Finally,showwindowandupdateclientareaasusual: m_pMainWnd->ShowWindow(SW_SHOW); m_pMainWnd->UpdateWindow();

  10. Document/ViewPrograms �Almostalwayshaveatleastfourclassesderived from: – CFrameWnd – CDocument – CView – CWinApp �Usuallyputintoseparatedeclaration(.h)and implementation (.cpp) files �Becauseoftemplateanddynamiccreation,there’s lotsofinitialization �Couldbedonebyhand,butnobodydoesitthatway MicrosoftDeveloperStudio AppWizardandClassWizard Tools

  11. AppWizard �ToolthatgeneratesaDoc/ViewMFCprogramframework automatically �Canbe builton andcustomizedby programmer �Fast,efficientwayofproducingWindowsApps �Performsrequiredinitializationautomatically �CreatesfunctionalCFrameWnd,CView,CDocument,CWinAppclasses �AfterAppWizarddoesit'sthing: –Applicationcanbebuiltandrun –Full-fledged window with all common menu items, tools,etc. ClassWizards �Facilitatemessagehandlinginaframework-basedMFCapplication �Toolsthatconnectresourcesanduser-generatedeventstoprogramresponsecode �WriteC++skeletonroutinestohandlemessages �Insertcodeintoappropriateplacesinprogram –Codethencanthenbecustomizedbyhand �Can beusedtocreatenewclassesorderiveclassesfromMFCbaseclasses –Addnewmembervariables/functionstoclasses �In.NETmany“classwizards”areavailablethroughPropertieswindow

  12. SKETCHApplication �ExampleofUsingAppWizardand ClassWizard �Usercanusemouseasadrawingpencil Leftmousebuttondown: –linesin windowfollowmousemotion �Leftmousebuttonup: –sketchingstops �Userclicks"Clear"menuitem –windowclientareaiserased �Sketchdata(points)won'tbesaved –Soleavedocument(CSketchDoc)class createdbyAppWizardalone �Basefunctionalityofapplication (CSketchApp) andframewindow(CMainFrame)classesareadequate –Leavethemalone �UseClassWizardtoaddsketchingtoCView class

  13. SketchingRequirements �Ifleftmousebuttonisdown: –Eachtimemousemoves: •GetaDC •Createapenofdrawingcolor •SelectpenintoDC •Movetooldpoint •Drawalinetothenewpoint •Makecurrentpointtheoldpoint •SelectpenoutofDC Variables �BOOLEANm_butdn �CPointm_pt,m_ptold �COLORREFm_color �CDC*pDC

  14. StepsinPreparingSKETCH �1.“File/New/Project” –ProjectType:“VisualC++Projects” –Template:“MFCApplication” –Entername:Sketch �2.In“WelcometoMFCApplicationWizard” –Applicationtype:“SingleDocument”Application –Takedefaultsforallotherscreens �3.BuildApplication-->Full-fledgedSDIAppwith emptywindowandno functionality �4.AddmembervariablestoCSketchView –Candomanuallyin.hfile –Easierto: • SelectClassViewpane • ClickonSketchViewclass –Notememberfunctions&variables • RightclickonCSketchViewclass –Choose“Add”/“Variable” –Launches“AddMemberVariableWizard” –VariableType:enterCPoint –Name:m_pt –Access:Public(default) –Noteafter“Finish”thatit’sbeenaddedtothe.hfile • Repeatforothervariables(oradddirectlyin.hfile): –CPoint m_ptold –bool m_butdn –COLORREF m_color –CDC* pDC

  15. �5.Addmessagehandlerfunctions: –SelectCSketchViewinClassView –Select“Messages”icon in Properties window • ResultsinalistofWM_messages –ScrolltoWM_LBUTTONDOWN&selectit –Add the handler by clicking on down arrow and “<Add>OnLButtonDown” • Notethatthefunctionisaddedintheeditwindowandthe cursorispositionedoverit: –After“TODO…”enterfollowingcode: m_butdn=TRUE; m_ptold=point;

  16. �RepeatprocessforWM_LBUTTONUP handler: –ScrolltoWM_LBUTTONUP –Click:“<Add>OnLButtonUp”, –EditCodeby adding: m_butdn=FALSE;

  17. �RepeatforWM_MOUSEMOVE –ScrolltoWM_MOUSEMOVE –Click:“<Add>OnMouseMove” –Editbyaddingcode: if(m_butdn) { pDC=GetDC(); m_pt=point; CPennewPen(PS_SOLID,1,m_color); CPen*pPenOld=pDC->SelectObject(&newPen); pDC->MoveTo(m_ptold); pDC->LineTo(m_pt); m_ptold=m_pt; pDC->SelectObject(pPenOld); } �6.Initializevariablesin CSketchViewconstructor –DoubleclickonCSketchViewconstructor •CSketchView(void)inClassView –After“TODO…”,Addcode: m_butdn=FALSE; m_pt=m_ptold=CPoint(0,0); m_color=RGB(0,0,0);

  18. �7.ChangingWindow’sProperties –Usewindow’sSetWindowXxxxx()functions •InCWinApp-derivedclassbeforewindowis shown and updated –Example:Changingthedefaultwindowtitle m_pMainWnd->SetWindowText( TEXT(“SketchingApplication”)); –TherearemanyotherSetWindowXxxxx() functionsthatcanbeusedtochangeother propertiesofthewindow �8.Buildandruntheapplication MenusandCommand Messages �Userclickson menuitem �WM_COMMANDmessageissent �ID_XXXidentifieswhichmenuitem(itsID) �Nopredefinedhandlers �Somessagemappingmacroisdifferent �ON_COMMAND(ID_XXX,OnXxx) –OnXxx()isthehandlerfunction –Mustbedeclaredin.hfileanddefinedin.cppfile

  19. AddingColorandClearMenu ItemstoSKETCHApp �ResourceView(sketch.rcfolder) –DoubleclickMenufolder –DoubleclickIDR_MAINFRAMEmenu –Add:“DrawingColor”popupmenuitemwithitems: •“Red”,ID_DRAWING_COLOR_RED(default) •“Blue”, ID_DRAWINGCOLOR_BLUE •“Green”, ID_DRAWINGCOLOR_GREEN •“Black”, ID_DRAWINGCOLOR_BLACK –Addanothermainmenuitem: •“ClearScreen”, ID_CLEARSCREEN •SetPopuppropertytoFalse AddMenuItemCommand HandlerFunction –Oneway:Use“EventHandlerWizard” –In“ResourceView”bring up menu editor –Right click on“Red”menuitem –Select“AddEventHandler”�“EventHandler Wizard” dialogbox •Classlist:CSketchView •Messagetype:COMMAND •Function handler name: accept default –OnDrawingcolorRed •Clickon“Addandedit” •After“TODO…”ineditorenterfollowingcode: m_color=RGB(255,0,0);

  20. AnotherMethodofAddinga MenuItemCommandHandler –InClassViewSelectCSketchView –InPropertieswindowselectEvents(lightning bolticon) –Scrolldownto:ID_DRAWINGCOLOR_RED –Select“COMMAND” –Click “<Add>OnDrawingcolorRed”handler –Editcodebyadding: m_color=RGB(255,0,0);

  21. RepeatforID_DRAWINGCOLOR_BLUE Code:m_color=RGB(0,0,255); RepeatforID_DRAWINGCOLOR_GREEN Code:m_color=RGB(0,255,0); RepeatforID_DRAWINGCOLOR_BLACK Code:m_color=RGB(0,0,0); RepeatforID_CLEAR Code:Invalidate();

  22. DestroyingtheWindow �JustneedtocallDestroyWindow() –DothisintheCMainFrameclass–usually inresponsetoa“Quit”menuitem

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