Today

1
Lecture 12

• Today
• Questions
• Increment and Decrement operators
• DLLs
• Announcements
• Project 5 (Checkers) due 9pm Tuesday
• Project 6 (Checkers II) due 9pm Friday before
  Spring Break
• Project 7 Friday after Spring Break
• Exam 2 Week Following Spring BReak

2
MapObjects

• See the zip File
• Dialog Bug -- Chase Option
• Is not remembering previous setting
• Fix this
• Add another Option to dialog box
• Change the colors of the chasing Objects
• Make text background transparent
• Make default settings all off
• Make background blue to black rather than
  chromatic

3
Change train of thought

• Trace this code
• int a 5
• cout ltlt "a is " ltlt a
• cout ltlt " a afterward is " ltlt a ltlt endl
• a5
• cout ltlt "a is " ltlt a
• cout ltlt " a afterward is " ltlt a ltlt endl
• a5
• cout ltlt "a-- is " ltlt a--
• cout ltlt " a afterward is " ltlt a ltlt endl
• a5
• cout ltlt "--a is " ltlt --a
• cout ltlt " a afterward is " ltlt a ltlt endl

4
What do you think about this?

• int notfoo(int x)
• return x
• int main()
• int a0
• anotfoo(a)
• cout ltlt a ltlt endl
• return 0

5
Overloading --

• What are some properties of and - - we will
  need to maintain when we overload these?
• Question 1 What does it mean to increment or
  decrement concerning the type we want to or
• Question 2 Where are the and - - ops used?
• Question 3 Is it prefix or postfix
• A How do we tell the difference between the two
• B What should it return and when

6
Lets do the Fraction class

• Q1 Incrementing a Fraction means adding the
  value of the denominator to the numerator
• Q2 Can be stand-alone, or inside another
  expression that means it needs to return a value
• Q3A C tells us how to write these methods so
  the compiler can tell the difference
• Prefix takes no parameters
• Postfix takes a dummy integer parameter
• Q3B
• Prefix should return the changed value
• Postfix should return value before it is changed

7
Prefix and Postfix

• Fraction operator()
• //prefix
• this-gtnumthis-gtden
• return this
• Fraction operator(int)
• //postfix
• Fraction temp this
• this-gtnumthis-gtden
• return temp

8
Class Exercises

• Modify Zip13
• Add the code for the operators that we just
  did.
• Add the code for the - - operators as well.
• Take off the int parameter on the postfix
  operations and see what kind of error you get
  (compile, link, name)
• Make the or -- friend functions rather than
  methods.

9
Building using components

• Components can mean different things
• Subprogram
• Class
• DLL (Dynamic Link Library)
• COM (Common Object Model)
• CORBA (Common Object Request Broker Architecture)
• First two imply source code as components
• Last three utilize binary code as components

10
Source Binary Components

• Class (source-based) approach
• Build source code in individual components
• Link these components together
• Must rebuild the entire system every time a
  component is changed/modified
• Binary components are treated as separate units
  at the executable (system) level
• Example DLL files
• The application links to appropriate DLLs as
  needed during execution (at run-time)

11
Benefits to Binary Components

• Applications can share components
• Less disk space required for applications
• Components can be reused in applications
• Upgrades to a component do not require
  recompilation of the applications
• Can upgrade applications by simply upgrading
  individual components, but be careful!
• Upgrading an implementation of a DLL is fine
• Upgrading the interface can be dangerous
• Why?

12
Consider an example with DLLs

• Simple windows painting program
• Left click draws randomly colored/sized rectangle
• Right click draws randomly colored/sized ellipse
• OnPaint redraws as needed
• Define a new data type to store information about
  each shape
• Need location, size, color, ellipse or rectangle
• Use a vector of this data type in our application

13
Build this application with DLLs

• 1st Build the DLL (the new data type)
• Built in its own MFC project
• Need to create a .lib file
• Need to create a .dll file
• 2nd Build the application
• A different (second) MFC project
• Must link in references to DLL object
• Include header file for compilation
• Include .lib file for linking state

14
Building the DLL

• In VC, select
• New
• Project
• Win32 Dynamic Link Library
• Create header file
• images.h
• Note the extra stanza that must be added to the
  header file
• Two underscores at the start of declspec

• include ltafxwin.hgt
• class __declspec(dllexport) Images
• publicImages()COLORREF GetColor( )int
  GetShape( )int GetSize( )CPoint GetPoint(
  )void SetColor(COLORREF)void
  SetShape(int)void SetSize(int)void
  SetPoint(CPoint)
• privateCOLORREF mColorint mShape,
  mSizeCPoint mPoint

15
Building the DLL (continued)

• include "images.h"
• ImagesImages()
• COLORREF ImagesGetColor() return mColor
• CPoint ImagesGetPoint() return mPoint
• int ImagesGetShape() return mShape
• int ImagesGetSize() return mSize
• void ImagesSetColor(COLORREF c) mColor
  c
• void ImagesSetPoint(CPoint p) mPoint p
  
• void ImagesSetShape(int s) mShape s
• void ImagesSetSize(int s) mSize s

• The body of the class simply contains the code
  needed to implement all the various methods in
  the class

16
Building the DLL (last steps)

• Under Build menu, select build xxx.dll
• This should generate two files of interest
• xxx.dll, the binary component we are interested
  in, located in the Debug directory
• xxx.lib, library information that tells where the
  component code exists (a link to the DLL), also
  located in the Debug directory
• Can now use this class in other applications

17
Building our Application

• In VC
• New
• Project
• Win32 application
• Header
• Include the header for DLL class
• Keep vector of images

• include "..\ImagesDLL\images.h"
• include ltafxwin.hgt
• include ltvectorgt
• using namespace std
• class CPaintWin public CFrameWnd
• publicCPaintWin()afx_msg void
  OnLButtonDown(UINT, CPoint)afx_msg void
  OnRButtonDown(UINT, CPoint)afx_msg void
  OnPaint()
• privatevectorltImagesgt dataDECLARE_MESSAGE_MAP(
  )

18
Building our application (cont)

• OnLButtonDown and OnRButtonDown are similar in
  nature
• Get a random size
• Get a random color
• Declare a new Images object and then sets
• Color
• Size
• Shape (1rect, 2circle)
• Location
• Push this object onto our vector of Images

• //this is main.cpp
• afx_msg void CPaintWinOnLButtonDown (UINT
  flags, CPoint point)
• int size, r, g, bsize rand()50 10r
  rand()255g rand()255b
  rand()255COLORREF c RGB(r,g,b)Images
  pp.SetColor(c)p.SetSize(size)p.SetShape(1)/
  /2 w/right buttonp.SetPoint(point)data.push_bac
  k(p)InvalidateRect(NULL)

19
Building our application (cont)

• OnPaint routine runs thru the vector of Images
  and draws each of them
• What is bad about this?

• afx_msg void CPaintWinOnPaint( ) CPaintDC
  dc(this)if ( data.empty( ) ) return // handles
  initial windowvectorltImagesgtiterator afor
  (adata.begin() altdata.end() a) // print
  all Images CPoint p a-gtGetPoint( ) int s
  a-gtGetSize( ) CBrush pBrush new CBrush(
  ) pBrush-gtCreateSolidBrush(a-gtGetColor( ))
  if (a-gtGetShape( )1) // rectangle
  dc.FillRect(CRect(p.x-s/2,p.y-s/2,p.xs/2,p.ys/2)
  ,pBrush) else // ellipse CPen pPen
  new CPen() pPen-gtCreatePen(PS_SOLID, 1,
  a-gtGetColor()) dc.SelectObject(pPen)
  dc.SelectObject(pBrush) dc.Ellipse(CRect(p.x-s/
  2, p.y-s/2, p.xs/2, p.ys/2))

20
Compiling our application

• Project / Settings
• General Using MFC in a Shared DLL
• Link Object/Library Modules
• Must add location of DLL library file
• Example ..\ImagesDLL\Debug\ImagesDLL.lib
• If you name your dll project something else, the
  names wont be the same as this example
• This should allow application to compile
• To run executable, need access to the DLL file
• Must be in a known location
• Would normally want it in the system path
• Copy it to the application directory (in the
  DEBUG folder)

21
Class Exercises

• The files needed to generate an MFC application
  using DLLs are out on the web
• DLL part
• Snippita contains Images.h
• Snippitb contains Images.cpp
• Front End
• Snippitc contains PaintWin.h
• Snippitd contains PaintWin.cpp
• Build this application (using DLLs)