Saturday, August 28, 2010
So what's new in MFC 10? to answer to this question i tried to compare the two versions MFC 9 and MFC 10 using CppDepend.
Let's begin with breaking changes and search for removed classes:
SELECT TYPES WHERE WasRemoved
It was very strange that this class is removed , and to be sure i searched in the code source and i found it inside #ifdef ENABLE_RIBBON_LAUNCH_BUTTON statement.
The only resource i found in the web talking about this change is here , and i dont know if
adding #define ENABLE_RIBBON_LAUNCH_BUTTON is suficient to compile without problem.
SELECT TYPES WHERE WasAdded AND isClass
What's the new features added by these classes?
When i searched in MSDN the utility of these classes , i didnt found any useful informations, so i searched for methods using CMFCRibbonInfo.
SELECT METHODS WHERE IsDirectlyUsing "CMFCRibbonInfo"
The RibbonBar class use CMFCRibbonInfo to save it to xml or load it.
Jump list is a new useful Window7 feature, it adds a new way of interaction beteween user and application.
here's a good article to add JumpList feature with MFC.
This class provides a CWnd support for MFC Control containment of Feature Pack controls.
And to know which controls can be contained inside this container, let's search for classes used by CMFCControlContainer::CreateDlgControl.
Here's the result:
So only these MFC feature pack controls are concerned by this container.
This class implements ATL::IDocument interface required for "Search and Organize" feature.
My first impression when i discovered that implemention was " WOW, MFC use now interfaces to enforce low coupling".
Let's see the impact of using this interface, for that let's search for classes using CDocumentAdapter :
SELECT TYPES WHERE IsDirectlyUsing "CDocument+CDocumentAdapter"
only CDocument use directly this class.
However IDocument is used by other classes like the new class CMFCPreviewCtrlImpl, so this class can work with CDocumentAdapter and also others classes implementing this interface.
And as explained in the comment of CDocumentAdapter code source:
"Search and Organize handlers are implemented in ATL DLLs, which can be MFC or not-MFC based.Internally handlers refer to IDocument interface, whose implementation in the common case should be supplied by a developer. CDocumentAdapter provides this implementation for MFC and basically calls the appropriate methods of the parent CDocument."
This class autosaves documents and restores them if an application unexpectedly exits, it's used by Restart Manager feature, here's an interesting article talking about it.
Let's search for classes used by CDataRecoveryHandler:
SELECT TYPES WHERE IsDirectlyUsedBy "CDataRecoveryHandler"
Which MFC classes use the recovery feature?
SELECT TYPES WHERE IsDirectlyUsing "CDataRecoveryHandler"
So all these classes benefit of this new feature especially CDocument.
A pop-up dialog box that functions like a message box but can display additional information to the user.
here's an interesting article talking about this feature.
Gives an application the apparence of a VS2008 or Windows 7 application.
Used for touch feature.
CFolderPickerDialog class implements CFileDialog in the folder picker mode.
when i dsicovered these classes, i thouth that is concerning xml parsing but when i searched for methods using them i discovered that only CMFCRibbonInfo use them to save or load its description to xml files.
SELECT METHODS WHERE IsDirectlyUsing "CXMLParserRoot"
CMFCZoomKernel,CMFCScanliner, CMFCScanlinerBitmap :
Not yet documented in MSDN, let's discover which classes use them.
SELECT TYPES WHERE IsDirectlyUsing "CMFCZoomKernel"
And we have the same result for the two other classes.
Extends the integer primitives to help prevent integer overflow and lets you compare different types of integers.
here's a video about using SafeInt.
SELECT METHODS WHERE WasRemoved
Almost all theses methodes are not removed but only the signature is changed , and some optional parameters are added, however some methods are removed like CCommandManager::ResetAllImages or CPanelDialog::ClipPaint, and one method was renamed from CMFCRibbonBar::GetTabTrancateRatio to CMFCRibbonBar::GetTabTruncateRatio.
Let's search for all methods added to MFC10
SELECT METHODS WHERE WasAdded
Which features are added by these new methods?
For that we will focus only in the most used classes.
Here's the methods added for CWnd, and almost all methods added concern touch feature and touch gestures.
Many methods of these classes add CAtlTransactionmanager as optional parameter.
Transactional File System is a new technology first introduced in Windows Vista. It enables you to roll back operations made on the file system and registry.
here's a good article about this feature.
New possibilities to add item to recent file list are now available.
Here's the methods added by CDocument:
Two new features concern methods added :
-Supporting Windows Search with MFC
Let's discover the changes concerning dependency of CDocument to other MFC classes,and which additional dependencies are added in MFC10, for that Dependency Matrix can be useful, and the sign "+" in the cell representing the dependency indicate that this dependency is new.
So many dependencies are added, especially with new classes added to MFC10 like CDataRecoveryHandler,and also some other inner classes added to CDocument.
Here's the methods added by CFileDialog:
A good news is we can now customize CFileDialog by adding what we want in the dialog.
Here's the methods added by CMDIChildWndEx:
Windows7 add a new interesting features like:taskbar Tabs,Taskbar thumbnails and thumbnail previews, and almost all methods added to CMDIChildWndEx concern theses features.
Windows 7 add also some useful features like OverlayIcon and progressbar in the taskbar, and the methods added to CFrameWnd concern these features.
Almost all methods added to CWinApp concern the ApplicationRecovery support.
Other useful methods are added like CMFCControlRenderer::SmoothResize and CDrawingmanager::DrawRotated.
Methods where visibility was changed:
SELECT METHODS WHERE VisibilityWasChanged
Almost the visibility of all CMFCRibbonTab methods is changed from private to public.
But when i checked the code source the only modification in the class declaration is the adding of DECLARE_DYNAMIC(CMFCRibbonTab) , this macro include "public:" , so i wonder if this visibility changes is only a side effect of adding this macro.
Methods Not Used Anymore:
Some methods become obsolete when upgrading framework version, did MFC10 not use anymore some methods?
To answer to this question let's execute the query :
SELECT METHODS WHERE IsNotUsedAnymore
here's the result:
Theses methods was declared before in multimon.h , the origin of this file goes back to Windows 98 to let compatibility with Windows 95 in the case of multi monitor, here's an interesting article talking about it.
In MFC10 this file is no longer included in mfc files. and MFC10 use directly GetSystemMetrics instead of xGetSystemmetrics.
Wednesday, August 18, 2010
MFC is a good library that wraps Windows API, and it’s also a framework so it provides a structure for your application and influent the design.
We have to be careful when using frameworks, because it impact also the design, and accepting the structure imposed by a specific framework without understanding its impact could be dangerous.
Let’s take a look into Doc/View architecture proposed by MFC and discuss how MVC pattern could be implemented.
Did CDocument/CView implements MVC pattern?
Doc/View architecture as described by many articles is implementing MVC pattern, but where’s the Model, the controller and the view?
Here’s a description from this msdn article:
“The Document-View variant recognizes all three roles of Model-View-Controller but merges the controller into the view. The document corresponds to the model role in MVC. This variant is present in many existing GUI platforms. An excellent example of Document-View is the Microsoft Foundation Class Library (MFC) in the Microsoft Visual C++ environment. The tradeoff of using this variant is that the view and the controller are more tightly coupled.”
So the CDocument is the model and CView merge the view and controller.
But actually the CDocument is not representing only the model , and to proof it let’s discover some CDocument design and methods:
CDocument derives from CCmdTarget to receive events and commands and contains the following methods : AddView, GetFirstViewPosition,GetNextView,UpdateAllViews.
So this class treats events,refresh and manage views, so it have some controller responsability.
Why CDocument is not the good candidate to be the model?
As described below the CDocument contains controller logic, and considering it also as model impact a lot the cohesion of classes, each classe must have a specific responsibility; it makes the design more flexible.
The model must be independent of any framework used, if it can be a POCO classes it will be wonderful, the question is why coupling the model with a specific framework?
high coupling makes the design more rigid, and any evolution or changes will be very difficult, for example if some client ask to provides also webservices, and if our model is highly coupled with CDocument , this evolution will cost a lot, on the other side if it’s independent to CDocument it can be developed more easily.
What’s the conclusion of this story?
- High cohesion and low coupling are two powerful concepts that assist your design, but their benefits are more visible only if evolutions or changes are needed.
- Be careful when using external frameworks, and not understanding the design provided by the framework could impact a lot the design quality of your application.