WIN32 SDK : GetWindowDC works, GetDCEx doesn't - C / C++ / MFC Discussion Boards

George230-Jan-03 23:16

30-Jan-03 23:16

Hi, everyone!

I do not understand what is the function of new operator
in the following example. Especially this statement,

--------
(void)new (pint) Elem(10);
--------

Another question, when compiling, a warning jumps out like the
following, I want to know how to avoid the warning.

Thanks in advance,
George

--------
c:\program files\microsoft visual studio\myprojects\testnew\testnew.cpp(25) : warning C4291: 'void *__cdecl operator new(unsigned int,void *)' : no matching operator delete found; memory will not be freed if initialization throws an exception
--------

#include <iostream.h>

inline void* operator new(size_t, void* ptr) { return ptr;}

class Elem{
public:
Elem(int a)
{
data = a;
}

public:
int getData()
{
return data;
}

private:
int data;
};

void main()
{
int* pint = new int[2 + sizeof(Elem)];
(void)new (pint) Elem(10);
Elem* elem = (Elem*)pint;
cout << elem->getData() << endl;
delete pint;
}

Re: Question about new operator.

Hans Ruck31-Jan-03 1:00

Hans Ruck

31-Jan-03 1:00

(void)new (pint) Elem(10);

Constructs a new Elem object at the address pint. Run it step by step with a breakpoint in new's body and you'll see what is all about.

rechi

Re: Question about new operator.

George231-Jan-03 3:16

George2

31-Jan-03 3:16

Hi, Bogdan buddies!

I do not understand why we add a "(void)" before
the statement?

Thanks in advance,
George

Re: Question about new operator.

Hans Ruck31-Jan-03 3:35

Hans Ruck

31-Jan-03 3:35

George2 wrote:
I do not understand...

Neither do i. The call has right value so the conversion appears to be useless since there's no variable to receive it.

rechi

Re: Question about new operator.

George231-Jan-03 4:28

George2

31-Jan-03 4:28

Hi, Bogdan pal!

The return type of new operator is void*, so
I think we should use

--------
(void*) ...
--------

other than
--------
(void) ...
--------

Since void* is a C++ data type and void is not a C++ data type. What is your opinion?

Thanks in advance,
George

Re: Question about new operator.

Anonymous31-Jan-03 5:18

Anonymous

31-Jan-03 5:18

Perhaps it's to get it rid of a compile warning. Leave it out and see if there is one.

Re: Question about new operator.

George231-Jan-03 17:52

George2

31-Jan-03 17:52

Thanks, Anonymous buddies.

I have tried and you are right. Can you tell
me why?

George

WIN32 SDK : GetWindowDC works, GetDCEx doesn't

30-Jan-03 23:11

I am implementing a skin based tool kit.
When repainting the frame of a window,
i catch WM_NCPAINT message then get window's
device context :

case WM_NCPAINT:
{
  HDC hdc = NULL;
  if( wparam==1 )
    // it returns a valid DC
    hdc = GetWindowDC( hwnd );
  else
    // it always returns NULL !!!
    hdc = GetDCEx( hwnd, (HRGN)(wparam), DCX_WINDOW|DCX_INTERSECTRGN );

  // custom frame painting
  paintFrame( hdc );

  ReleaseDC( hwnd, hdc );  
}

The 'GetDCEx line' is taken from MSDN.

I use MSVC++7 under winXP
Thanks for your help

Replacing and resizing of the controls in formview to bestfit of Monitor on change system resolution

sulaxan30-Jan-03 22:11

sulaxan

30-Jan-03 22:11

REQUIREMENT:: Application shud be sized to full monitor irrespective of the monitor size and current system resolution.
My APPLICATION:: Application is having four formviews in tabcontrol with many controls(AcitveX Lables and Buttons) on each forma view. My application is developed for best view in 15 inch and 800*600 resolution.

MY PROBLEM: i have written code to catch when resolution ic changed.and accorind to the new resolution m changing the each contols's client rect and moving the corresponding control to new client react. but reafreshing si becoming problem and some controls are painting over other controls.

Adi Narayana

Any good references?

dsuratman30-Jan-03 20:57

dsuratman

30-Jan-03 20:57

Hi All,
I'm currently a firmware engineering and trying to get into software programming (using C++ for right now). I've decided to create a simple text editor as my first project.

Does anybody know any good references out there on this topic in particular and Windows programming in general?

Any suggestion on better projects for beginners?

Thanks y'all

Dody

Re: Any good references?

LittleYellowBird30-Jan-03 23:51

LittleYellowBird

30-Jan-03 23:51

onezerocode wrote:
I'm currently a firmware engineer

Snap! I moved from firmware to software too, so I thought I would answer your question. I'm still a novice really so others may have something more usefull to say.

I started with the book 'SAMS Teach Yourself Visual C++' and I found it very poor, it didn't expain much just took you through some examples (very briefly).

Next I got the book 'Practical Visual C++' by Bates & Tompkins, this was much better, it assumes that you know very little and explains a fair ammount.

Lastly, I am currently reading 'Programming Windows with MFC' by Jeff Prosise, this is an excelent book it talks alot about what is actually going on - I like that, coming from a firmware/hardware background I want to know what is 'under the hood', but you need to understand C++ first as it does not explain this.

Hope that helps, good luck Smile | :)

,

Ali

Re: Any good references?

Abbas_Riazi31-Jan-03 0:13

Abbas_Riazi

31-Jan-03 0:13

Programming MFC (written by Jeff Prosise) is a good reference.
A. Riazi

Re: Any good references?

Lhenno Ferrari31-Jan-03 0:22

Lhenno Ferrari

31-Jan-03 0:22

Looking for a good C++ reference book ??? "Thinking in C++" rocks, take a look at http://www.mindview.net/Books/TICPP/ThinkingInCPP2e.html.

Also, for M$ Development, MSDN provide exelent references e documentation.

Hope it Helps !!!

?

Re: Any good references?

Lhenno Ferrari31-Jan-03 1:01

Lhenno Ferrari

31-Jan-03 1:01

WORDPAD and SUPERPAD are applications included with Windows OSs that are part of VS 6 samples Wink | ;)

, so you can download it from http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vcsample98/html/_sample_mfc_wordpad.asp

They were written using the Microsoft Foundation Class Library (MFC), so i think you can use them as a reference for your project.

Regards.

Toolbar

satyavasu30-Jan-03 19:52

satyavasu

30-Jan-03 19:52

How to create a toolbar of more than one row in which bitmap is used to create buttons?

Re: Toolbar

dsuratman30-Jan-03 20:59

dsuratman

30-Jan-03 20:59

Try CreateToolbarEx.

Dody

sdi app starts minimized

bryce30-Jan-03 19:00

bryce

30-Jan-03 19:00

hey my sdi ap starts off by mimising itself and i can't see why (i even so a showwindow sw_maximixed in by view's oninitialupdate)
anyone got any thoguhts?
Cheerypip
Bryce

Re: sdi app starts minimized

ROK_RShadow30-Jan-03 19:17

ROK_RShadow

30-Jan-03 19:17

I am no expert, but I belive that you would need to overide the showwindow function in your MainFrame class.. not the views..

Re: sdi app starts minimized

sulaxan31-Jan-03 20:07

sulaxan

31-Jan-03 20:07

hey get the Mainframe pointer in InitInstance() of AppClass and do as follow
pMainFrame->ShowWindow(m_nCmdShow|SW_SHOWMAXIMIZED);

it shud work now

nice time
Adi narayana

Re: sdi app starts minimized

bryce1-Feb-03 13:28

bryce

1-Feb-03 13:28

duuuh of course *feels like a plonker*
cheers for that

Bryce

const help

ROK_RShadow30-Jan-03 18:03

ROK_RShadow

30-Jan-03 18:03

Hello. This is a general C++ question. Can somebody please shed some light on the const modifier? I have been programming for about a year.. and I never use const because I really don't understand it... so I am trying to gain some ground, and I just can't understand this.

Please look at the class declaration below, and can somebody explain to me why the functions draw(), and getx() allow me to modify the private data members. they are declared const, so they shouldn't allow me to modify those variables.. but they do.

according to MSDN help library, you declare a member function const by placing the keyword after the parameter list.. this is what I did.. but it still lets me modify them.

I know if I declare the variables const it will work.. but shouldn't I be able to declare a function const so the compiler won't let me modify?

class cRectangle
{
public:

// constructors
cRectangle();
cRectangle(int nL, int nW);

// Destructor
~cRectangle();

// public accesors
void SetLength(int nL);
void SetWidth(int nW);
int GetLength() const { return *nLength;}
int GetWidth() const { return *nWidth;}

// public methods
void Draw() const;

private:

// Data Members
int* nLength; // pointers because they will be stored on the heap
int* nWidth;

};

// implementation file
// striped but draw() function
// Drawing functions
void cRectangle::Draw() const
{
// try and change a variable
*nWidth = 42; // why its this allowed????
// function is const? should not let me change
// the object.
}

If anybody could explain this to me. It would be greatly appreciated. Thank you.

Re: const help

C^hris L^osinger30-Jan-03 18:11

C^hris L^osinger

30-Jan-03 18:11

because nWidth is a pointer to an int, not an int. your Draw code is changing the value that nWidth points to, not nWidth itself. and it will probably give you an access violation, since nWidth isn't initialized.

if you change the Draw code to "nWidth = 42", it will not compile.

-c

A | B - it's not a choice.

ThumbNailer

Re: const help

Christian Graus30-Jan-03 18:13

Christian Graus

30-Jan-03 18:13

Damn - looks like you can type faster than me. Smile | :)

Christian

No offense, but I don't really want to encourage the creation of another VB developer.
- Larry Antram 22 Oct 2002

C# will attract all comers, where VB is for IT Journalists and managers - Michael
P Butler 05-12-2002

It'd probably be fairly easy to make a bot that'd post random stupid VB questions, and nobody would probably ever notice - benjymous - 21-Jan-2003

Re: const help

C^hris L^osinger30-Jan-03 18:17

C^hris L^osinger

30-Jan-03 18:17

i even made a quick project to test it out, just to be sure! Smile | :)

-c

A | B - it's not a choice.

ThumbNailer

Re: const help

Christian Graus30-Jan-03 18:22

Christian Graus

30-Jan-03 18:22

You're a machine, I stand in awe.... All I did was type.

Christian

No offense, but I don't really want to encourage the creation of another VB developer.
- Larry Antram 22 Oct 2002

C# will attract all comers, where VB is for IT Journalists and managers - Michael
P Butler 05-12-2002

It'd probably be fairly easy to make a bot that'd post random stupid VB questions, and nobody would probably ever notice - benjymous - 21-Jan-2003

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