C / C++ / MFC

19-Mar-08 2:49

In my opinion, a design would be better if it can guide the using of it, for example, it should prevent coders from overriding the functions that should not be overridden.

modified on Wednesday, March 19, 2008 8:57 AM

George_George19-Mar-08 3:16

George_George

19-Mar-08 3:16

Thanks followait,

I think your points and answers to this question are, if code are common in both base and derived class, and derived class has no need to override it, do not make it virtual?

regards,
George

followait19-Mar-08 3:37

19-Mar-08 3:37

Simply, virtual function is invented for polymorphism.

In essence, a virtual function is an indirect call to a non-virtual function, so it can always replace a non-virtual function, with more flexibility and less efficiency.

George_George19-Mar-08 17:22

George_George

19-Mar-08 17:22

Thanks followait,

1.

followait wrote:
a virtual function is an indirect call to a non-virtual function

You mean through vtable?

2.

followait wrote:
so it can always replace a non-virtual function

You mean virtual function has all the functions of a non-virtual function?

regards,
George

followait19-Mar-08 18:00

19-Mar-08 18:00

1. Yes.
2.
Yes, but more.

Is it not safe to use RectF::Equals? (float comparison problem) [modified]

George_George19-Mar-08 18:30

George_George

19-Mar-08 18:30

Thanks followait,

Question answered.

regards,
George

followait18-Mar-08 19:10

Re: Is it not safe to use RectF::Equals? (float comparison problem)

18-Mar-08 19:10

Here is its implementation. Simply compared with ==. It seems not very useful in practical, doesn't it?

BOOL Equals(IN const RectF & rect) const
{
    return X == rect.X &&
           Y == rect.Y &&
           Width == rect.Width &&
           Height == rect.Height;
}

modified on Wednesday, March 19, 2008 2:00 AM

Mark Salsbery18-Mar-08 20:05

Mark Salsbery

18-Mar-08 20:05

Ouch!

It may be fine if you use integers/whole numbers Roll eyes | :rolleyes:

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

not installaing visual studio .Net 2003 in vista?

rowdy_vc++18-Mar-08 18:55

rowdy_vc++

18-Mar-08 18:55

Hi 2 All!!!

When I install visual studio .Net 2003 in Windows Vista it does not installed why?

*****THANKS N ADVANCE****
Mathen.K
(I WILL TRY MY LEVEL BEST )

Re: not installaing visual studio .Net 2003 in vista?

Naveen18-Mar-08 19:18

Naveen

18-Mar-08 19:18

Google[^]

nave

[OpenedFileFinder]

Re: not installaing visual studio .Net 2003 in vista?

Rajesh R Subramanian18-Mar-08 22:05

Rajesh R Subramanian

18-Mar-08 22:05

Probably because you suck at asking questions. It's been a long time, I am seeing you ask two different questions over and over. One is that your program will work in XP, but not on Vista. And the other is that you fail to install VS 2003 on Vista. And you won't ever give us a remotest clue to solve the problem.

Nobody can give you wiser advice than yourself. - Cicero
.·´¯`·->Rajesh<-·´¯`·.
Codeproject.com: Visual C++ MVP

Re: not installaing visual studio .Net 2003 in vista?

David Crow19-Mar-08 4:23

David Crow

19-Mar-08 4:23

rowdy_vc++ wrote:
why?

Maybe because it failed. Other than that, I'm unsure.

"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Structure array initialization error

LiYS18-Mar-08 18:53

LiYS

18-Mar-08 18:53

Hi all,

I have something like this in one of the header file:

VAL Val1[1];

where VAL is defined as:

struct VAL
{
    LPWSTR      pszVal;
    LPWSTR      pszEmailAdrVal;
    ULONG       ulVal;
    SYSTEMTIME  stVal;
    BOOL        fVal;
};

when I doing something like this in CPP file:

Val1[0] = {L"Jack",      L"Jack@somewhere.com",      256,     {2006, 3, 4, 9, 0, 0, 0, 0},   TRUE};

I got "missing ';' before '{'" compilation errors. What's the reason behind this?

Thanks,

Re: Structure array initialization error

Naveen18-Mar-08 19:08

Naveen

18-Mar-08 19:08

LiYS wrote:
Val1[0] = {L"Jack", L"Jack@somewhere.com", 256, {2006, 3, 4, 9, 0, 0, 0, 0}, TRUE};

You cannot do like this after the object has been constructed. The object gets contructed at the statement

VAL Val1[1];

So the only option is to do as follows

VAL Val1[1] = {L"Jack",      L"Jack@somewhere.com",      256,     {2006, 3, 4, 9, 0, 0, 0, 0},   TRUE};

nave

[OpenedFileFinder]

Re: Structure array initialization error

ThatsAlok18-Mar-08 20:00

ThatsAlok

18-Mar-08 20:00

LiYS wrote:
VAL Val1[1];

HI, if you need only one object, why not you declare VAL Val1; instead of VAL Val1[1];

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
Never mind - my own stupidity is the source of every "problem" - Mixture

cheers,
Alok Gupta
VC Forum Q&A :- I/IV
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How to show a bitmap in a CStatic control?

fantasy121518-Mar-08 17:55

fantasy1215

18-Mar-08 17:55

In the default CAboutDlg, I just erase all controls. And I add a CStatic control. I just want to show a bitmap in the CStatic control.
And I also import a bitmap file to the resource.
my codes:

The header file

class CAboutDlg : public CDialog
{
  CBitmap m_bitmap;
  CStatic m_ctlPic;
}

The cpp file:

CAboutDlg::CAboutDlg()
{
  m_bitmap.LoadBitmap(IDB_BITMAP1);
}
CAboutDlg::~CAboutDlg()
{
  if (m_bitmap.GetSafeHandle())
    m_bitmap.DeleteObject();
}

BEGIN_MESSAGE_MAP()
  ON_WM_PAINT()
END_MESSAGE_MAP()

void CAboutDlg::OnPaint()
{
CPaintDC dc(this);
CRect rcWnd;
m_ctlPic.GetWindowRect(&rcWnd);
this->ScreenToClient(&rcWnd);
BITMAP bm = {0};
m_bitmap.SelectObject(&bm);
CDC dcMem;
dcMem.CreateCompatibleDC(&dc);
dcMem.SelectObject(&m_bitmap);
dc.StretchBlt(rcWnd.left, rcWnd.top, rcWnd.Width(), rcWnd.Height(), &dcMem, 0, 0, bm.bmWidth, bm.bmHeight, SRCCOPY);
}

But when I open the CAboutDlg, the bitmap shows flash, and vanish immediately, Please tell me what's wrong in my mind?

Naveen18-Mar-08 18:31

Naveen

18-Mar-08 18:31

fantasy1215 wrote:
How to show a bitmap in a CStatic control?

Why dont you use a Picture control?

nave

[OpenedFileFinder]

MANISH RASTOGI18-Mar-08 18:35

MANISH RASTOGI

18-Mar-08 18:35

Use SetBitmap() method of static control.

fantasy121518-Mar-08 19:11

fantasy1215

18-Mar-08 19:11

I just want to try GDI, Please tell me what wrong with my code. When I first show the CAboutDlg I see the bitmap show as a flash in the right place.

Mark Salsbery18-Mar-08 20:14

Mark Salsbery

18-Mar-08 20:14

fantasy1215 wrote:
Please tell me what wrong with my code

You're drawing on the dialog window.

The static control, being higher in the z-order, is then drawn on top of your drawing.

You need to subclass the static control and paint on it instead.

With MFC, simply derive a class from CStatic and handle WM_PAINT just like you did on
the dialog, except you don't have to convert coordinates.

In the dialog class, use an object of your CStatic-derived class instead of a CStatic object.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

fantasy121518-Mar-08 20:26

fantasy1215

18-Mar-08 20:26

Mark Salsbery
Thanks very much for reply. You just unlock my mind. Before you give me the answer, I am so confused.
BTW, Except for subclassing a CStatic class, Can I draw the bitmap in the CStatic control just in the CAboutDlg class? And how?

Mark Salsbery18-Mar-08 20:35

Mark Salsbery

18-Mar-08 20:35

fantasy1215 wrote:
Can I draw the bitmap in the CStatic control just in the CAboutDlg class? And how?

You can, but there's a slight problem.

Getting a dc to the client or window area of the control is no problem.
That makes drawing simple.

The problem is when to draw.

You can draw any time you want to, but you also need to draw in response to WM_PAINT,
to refresh windows overdrawn in instances like when the user drags another window over
the top of yours then moves it away.

From the dialog (parent) window's WM_PAINT handler, there's no reliable way I know of to
know when the child windows are finished drawing themselves, at which time it would be safe
to draw on top of them.

MFC does subclassing for you, and makes handling the messages consistent regardless of
window/control class, so it's definitely IMO the easier way to go.

Besides, painting from the window class itself instead of from a window's parent class
just makes for a better object-oriented implementation.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]