MICROSOFT FOUNDATION CLASSES

MFC:
CObject is the base class for most of the MFC Classes.

Features:
i) RUNTIME_CLASS
ii) Serialize

What is a Message Map?

          a) Message Maps are the way by which MFC handles the application messages.
b) Gets message from the OS, translates the message and dispatches the message to the window procedure.
c) In MFC, 'Run' method, starts the message map.
d) Classes derived from 'CCmdTarget' can contain a message map.

            .h  -> DECLARE_MESSAGE_MAP()

                                

    a) Declares MessageMap Structure.

    b) Tells the application that the class in which this is called is going to have a 

 messagemap and handle messages.

    c) Adds three members to the class declaration.

i) MessageEntries[] array (AFX_MSGMAP_ENTRY)

       ii) MessageMap Structure

      iii) GetMessageMap() -> Virtual Function that returns MessageMap's address 

  
.cpp -> BEGIN_MESSAGE_MAP() -> Initializes MessageMap Structure
... -> Fills MessageEntries[] array
END_MESSAGE_MAP() -> Terminates MessageEntries[] array

           e.g:

BEGIN_MESSAGE_MAP(MyFrame, CFrameWnd)

ON_WM_LBUTTONDOWN()    --> Macro, which declares that MyFrame is                                                                                         going to handle left button

END_MESSAGE_MAP()

CFrameWnd -> The base class

MyFrame -> The class name which implements the message map

Refer: Application Messages

MessageMap Macros:
ON_COMMAND_RANGE(id1, id2,...., eventhandlers)

Difference between PostMessage and SendMessage functions:
PostMessage:
Posts the message to the application queue(follows FIFO) -> asynchronous call
    SendMessage:
Sends the message to the particular control or window -> synchronous call

Serialization in MFC:
To make a class serializable it is necessary to add two macros.
.h -> DECLARE_SERIAL(<classname>)
.cpp         -> IMPLEMENT_SERIAL(<classname>, CObject)

Serializing: (application -> disk)
void <classname>::Serialize(CArchive& ar)
{
CObject::Serialize(ar);
...
}

DeSerializing: (disk -> application)
void <clasname>::DeleteContents()
{
CDocument::DeleteContents();
...
}

Types of Applications in MFC:
a) Document Interface
  SDI -> Single Document Interface
    Supports one open document at a time.

MDI -> Multi Document Interface

     Supports two or more documents open simultaneously.

     Document/View Architecture in MFC:
a) In a Doc/View application, the application data is represented by a document object.
     b) Views of that data are represented by one or more view objects
    CDocument class is the base class for the document objects.
    CView class and its derivates are base classes for view objects.
UpdateAllViews
GetFirstViewPosition
GetNextView

b) Dialog based
DDX -> Data Exchange
DDV -> Data Verification
UpdateData(TRUE) -> data from controls to variables
UpdateData(FALSE) -> data from variables to control

Dialogs: (CDialog -- Derived from CWnd)

Initialization  --> OnInitDialog()

Closing        --> EndDialog()

Difference between Modal and Modeless dialog:
Modal      :  Without closing the dialog, the user cannot activate the parent window.
    DoModal() -  is used to display a modal dialog box.
Modeless :  Modeless dialog is a container component that appears on top of the main 
   content without blocking user interaction with the underlying page.
   ShowWindow() - ShowWindow function sets the specified window's show state.  Both are derived from CDialog.

Collection Classes in MFC:
MFC provides collection classes of three categories:
A) MFC Array Classes
B) MFC List Classes
C) MFC Map Classes

A) MFC Array Classes:  can be accessed using index.
a) CByteArray -> 8 bit bytes
b) CWordArray -> 16 bit bytes
c) CUIntArray         -> unsigned integers
d) CStringArray -> CString
e) CPtrArray         -> void pointers
f) CObArray -> CObject pointers

important functions:
SetAt(), SetSize(), GetSize(), GetUpperBound(), Copy(), RemoveAt(), RemoveAll()

B) MFC List Classes: 
a) CObList -> CObject pointers
     b) CPtrList -> void pointers
     c) CStringList -> CString

datatype: POSITION -> pointer to a CNode

important functions:
AddHead(), RemoveHead(), RemoveTail(), GetAt(), SetAt(), GetPrev(), 
GetHeadPosition, GetTailPosition(), RemoveAt(), InsertAfter(), InsertBefore()

C) MFC Map Classes: [Key-Value pair]
  a) CMapWordToPtr     -> void pointers keyed by WORDs
    b) CMapPtrToWord     -> WORDs keyed by void pointers
    c) CMapPtrToPtr     -> void pointers keyed by other void pointers
    d) CMapWordToOb     -> Object pointers keyed by WORDs
    e) CMapStringToOb     -> CObject pointers keyed by strings
    f) CMapStringToPtr     -> void pointer keyed by strings
    g) CMapStringToString -> Strings keyed by Strings

important functions:
Lookup(), GetStartPosition(), GetNextAssoc(), RemoveKey(), RemoveAll(), GetCount(), IsEmpty()

Classes which are not derived from CObject:
MFC Simple Value Types and Typed Template Collection Classes are not derived from CObject.

Simple Value Types: CPoint, CRect, CSize, CString, CTime, CTimeSpan 
Typed Template Collection Classes: CTypedPtrArray, CTypedPtrList, CTypedPtrMap

DeviceContext:
a) Provides access to GdiObjects.
b) Provides a logical display area for drawing.
-OS transfers it to the actual device drawing.

CDC:
  CPaintDC -> draws in Windows Client Area
   sends WM_ERASEBKGND (marks the invalid region to valid)
CClientDC -> draws in Windows Client Area
CWindowDC -> draws in client and non-client area
CMetaFileDC -> draws in meta file

CGdiObject:
  CBitMap, CBrush, CFont, CPalette, CPen, CRegn

SelectObject : Selects the current object, returns the address of the passed object
DeleteObject : Deletes the selected Object

User Interface thread and Worker thread in MFC:
CWinThread is the base class for threads.
CWinThread is derived from CCmdTarget.

UI Thread  :  The main thread of MFC is an UI thread.
            UI threads can handle user messages.
WorkerThread:  Background threads are called as Worker Threads.
           AfxBeginThread() - AfxEndThread()
           BeginThread() - EndThread()
           BeginThreadEx() - EndThreadEx()
   
Synchronization methods in MFC:
CSyncObject: A pure virtual class that provides functionality common to the synchronization objects in Win32.
CCriticalSection   : A synchronization object that allows one thread at a time to access a resource or section of code (Mutual Exclusion).
CMutex : A synchronization object that allows one thread mutually exclusive access to a resource(Mutual Exclusion - multiple applications).
CSemaphore : Semaphores are useful in controlling access to a shared resource that can only support a limited number of users (Limited Thread).
CEvent : Represents an event, which is a synchronization object that enables one thread to notify another that an event has occurred.
  SetEvent() - Releases the thread (signaled state)
  ReleaseEvent() - Resets to non-signaled state
  
WinSock:  
Sockets are used to communicate with different applications running in the same machine or on a different machine.

  (i) network communication
       (ii) client/server application
   
client-server application:
(i)  Initialize Sockets, create/listen/accept/connection.
       (ii) The address of the computer on which the application is running.
      (iii) The port on which it is listening.
a) requests for connection
b) establishes connection
c) sends/receives information
d) closes the connection

Socket Classes:
a) CAsynSocket
b) CSocket

Methods:
a) OnAccept
b) OnClose
c) OnConnect
d) OnReceive
e) OnSend

Create -> Creates the socket
Connect -> Connects the server
Listen -> Server Listens
Accept -> Accepts socket communication
Send -> Sending information
Receive -> Receiving information
Close -> Closing Connection

Client Server
Create Create
Connect Listen
Send/Receive         Accept
Send/Receive
Close Close

Stream/Datagram Protocols:
  TCP/IP -> Transmission Control Protocols
[establishes a connection,
retains the connection throughout the communication]
    UDP -> Datagram Protocols
[receiver sends back the acknowledgement]

MFC DLLs:
(i) MFC Extension DLLs:
Can a used by other MFC application.
Add AFX_EXT_CLASS to the class declaration.

         (ii) Regular DLLs:
To export a function
a) extern "C"
b) AFX_MANAGE_STATE(AfxGetStaticModuleStatic())
used to make the exported functions threads safe
AfxGetStaticModuleStatic - returns AFX_MODULE_STATE
b) Module Definition File(.def)
Contains the exported functions in a dll, with its ordinals.