45 Day Series: Codeproject VC++ Forum Q&A - VII

MFC

WINDOW32

GENERAL

FUNNY

Answer

MFC

• Set the size when you call Create() on the dialog.
• Change the size using SetWindowPos()
• Change the size using MoveWindow() 

TCITEM tcItem;
tcItem.mask = TCIF_TEXT;
m_ReportTabCtrl.GetItem(ID_PANE_FOUND, &tcItem);
CString csText = tcItem.pszText;

In your Button Event handler on the PropertyPage, just call the parent PropertySheet "RemovePage()" function, for example, "RemovePage(this)". Be careful that if you are removing the active page, which you most likely are, you should use the PropertySheet function "SetActivePage()" to have some other page become active, like your welcome page.

I also use the CTreePropSheet class, or one of its derivations, and I remember that there was some issue with deleting pages and having the tree redrawn properly. I would test this with the standard CPropertySheet first, watching the tabs appear and disappear properly first, then move back to the CTreePropSheet class.

void MyClass::reset(ErrorType)
{
}
OR
void MyClass::reset(ErrorType error)
{
error;
}

void MyClass::reset(ErrorType error)
{
UNREFERENCED_PARAMETER(error);
}

When MFC controls exhibit strange behavior I always take a look at the source code for the control located in the \VC\atlmfc\src\mfc installation path.

If you look at the Microsoft implementation within afxmaskededit.cpp you will find that the CMFCMaskedEdit class handles the WM_GETTEXTLENGTH, WM_GETTEXT and WM_SETTEXT messages overriding the default CWnd behavior.

The CMFCMaskedEdit class is actually returning the length of an internal CString buffer in response to the WM_GETTEXTLENGTH message. Therefore the Microsoft documentation that states: 'EN_CHANGE notification code is sent when the user has taken an action that may have altered text in an edit control. Unlike the EN_UPDATE notification code, this notification code is sent after the system updates the screen.' would not apply to this particular window class. Unfortunately you will have to implement something outside the box here. A couple of ideas:

Option [1] Highlight all of the code in afxmaskededit.cpp and afxmaskededit.h and copy/paste into DavidCrowsMaskedEdit new class and change/improve the behavior.

Option [2] You could override PreTranslateMessage and check for the WM_KEYUP message belonging to the CMFCMaskedEdit control. Once the control has recieved this message... the CMFCMaskedEdit should have updated its internal buffer because it does its filtering in response to the WM_CHAR message. Note that this method will not handle copy/cut/paste from the clipboard so your mileage may vary.

BOOL YourMaskDlg::PreTranslateMessage(MSG* pMsg)
{
if(WM_KEYUP == pMsg->message)
{
if(::GetDlgCtrlID(pMsg->hwnd) == m_YourMaskEdit.GetDlgCtrlID())
{
int iLength = m_YourMaskEdit.GetWindowTextLength();
	
if(iLength)
{
	CString str;
	m_YourMaskEdit.EnableGetMaskedCharsOnly(TRUE);
	m_YourMaskEdit.GetWindowText(str);
	str.Remove(_T('_'));
 
	BOOL UserAddedText = str.GetLength();
}
}
}
return CDialog::PreTranslateMessage(pMsg);
}

HBRUSH YourMaskDlg::OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor)
{
HBRUSH hbr = CDialog::OnCtlColor(pDC, pWnd, nCtlColor);
 
if(pWnd->GetDlgCtrlID() == m_YourMaskEdit.GetDlgCtrlID())
{
//Check to see if user added some text
}
return hbr;
}

WINDOW32

#include
<winioctl.h>
BOOL DeviceSupportsDVDMedia(TCHAR *szDrive)
{
BOOL bRet = FALSE;
if(NULL != szDrive && DRIVE_CDROM == GetDriveType(szDrive))
{
GET_MEDIA_TYPES media[CHAR_MAX];
TCHAR szVol[MAX_PATH] = {0};
DWORD dwBytesRet =0;
int iSize = CHAR_MAX * sizeof(GET_MEDIA_TYPES);
_stprintf(szVol,_T("\\\\.\\%c:"),szDrive[0]);
HANDLE hDevice = CreateFile(szVol,GENERIC_READ,FILE_SHARE_READ|FILE_SHARE_WRITE,NULL,OPEN_EXISTING,0,0);
if(INVALID_HANDLE_VALUE != hDevice)
{
if(DeviceIoControl(hDevice,IOCTL_STORAGE_GET_MEDIA_TYPES_EX,NULL,0,media,iSize,&dwBytesRet,FALSE))
{
	bRet = FILE_DEVICE_DVD == media->DeviceType;
}
}
}
return bRet;
}

 
HMODULE hModule  = ::LoadLibrary("GameLogicWZQ.dll");
typedef GameObject* (*CreateObjProc)();
CreateObjProc pCreateProc = (CreateObjProc)::GetProcAddress(hModule,"CreateGameObject");
m_pGameObject = pCreateProc();
::FreeLibrary(hModule);

• http://msdn.microsoft.com/en-us/library/ms632679%28v=vs.85%29.aspx
• http://msdn.microsoft.com/en-us/library/ms632680%28v=vs.85%29.aspx

To start with, run:

mountvol /?
mountvol /L

• http://msdn.microsoft.com/en-us/library/dd541832%28PROT.10%29.aspx
• http://msdn.microsoft.com/en-us/library/cc225342%28v=PROT.10%29.aspx 
• http://msdn.microsoft.com/en-us/library/dd303455%28v=PROT.10%29.aspx

/* CAUTION: ONLY WIN32
* get the threadId of the main thread of a target process
*
* params:
*     DWORD pId    processId of the target process
*
* return:
*     Success      threadId
*     Error        NULL
*/
DWORD GetMainThreadId(DWORD pId)
{
LPVOID lpThId;
 
_asm
{
mov eax, fs:[18h]
add eax, 36
mov [lpThId], eax
}
 
HANDLE hProcess = OpenProcess(PROCESS_VM_READ, FALSE, pId);
if(hProcess == NULL)
return NULL;
 
DWORD tId;
if(ReadProcessMemory(hProcess, lpThId, &tId, sizeof(tId), NULL) == FALSE)
{
CloseHandle(hProcess);
return NULL;
}
 
CloseHandle(hProcess);
 
return tId;
}

DWORD GetSizeOfImage(HMODULE hModule))
{
DWORD dwSize = 0;
PIMAGE_DOS_HEADER pDOSHeader = (PIMAGE_DOS_HEADER)hModule;
PIMAGE_NT_HEADERS pNTHeader = (PIMAGE_NT_HEADERS)((PBYTE)hModule + pDOSHeader->e_lfanew);
if(IMAGE_NT_SIGNATURE == pNTHeader->Signature)
{
PIMAGE_FILE_HEADER pFileHeader = (PIMAGE_FILE_HEADER)((PBYTE)&pNTHeader->FileHeader);
PIMAGE_OPTIONAL_HEADER pOptionalHeader = (PIMAGE_OPTIONAL_HEADER)((PBYTE)&pNTHeader->OptionalHeader);
if(IMAGE_NT_OPTIONAL_HDR32_MAGIC ==  pNTHeader->OptionalHeader.Magic)
{
dwSize = pNTHeader->OptionalHeader.SizeOfImage;
}
}
return dwSize;
}

Check out the /FIXED (Fixed Base Address) linker option.

I consider fixed base addresses to be an insecure option... I highly recommend that all software engineers support a dynamic base address.

PE images with support for ASLR will have the IMAGE_DLL_CHARACTERISTICS_DYNAMIC_BASE bit set in the PE image characteristics. These modules are essentially saying 'put me anywhere you want... I don't care' and the kernel pseudo-randomly chooses an address to map the image.

PE images without support for ASLR... the NT kernel will make an attempt to load the image at its preferred address at pNTHeader->OptionalHeader.ImageBase. If the address is already allocated the kernel will make an attempt to map the image at another address and apply its fixups.

The GetClipBox Function will return a NULLREGION if the window is completely obscured. Unfortunately this will not work if DWM/Aero is enabled and you will probably need to calculates the intersections.

Dynamic linking: your code is built to use functions in a shared library; your code runs, the OS finds the shared lib and gives you access to the functions you need.

Dynamic loading: your code can discover, load and execute code from shared libraries. but the shared libraries might not even exist at run time. your code explicitly loads the shared library. best example of this is plugins.

Method for XP or earlier is slightly different from Vista/Win7 from my experience.

For XP or earlier, return 0 for WM_QUERYENDSESSION and this should be enough.

For Vista/Win7, I haven't found a way to entirely stop logging off. But temporarily blocking logging off is possible. I would return 1 for WM_QUERYENDSESSION and register a blocking reason during WM_ENDSESSION, by calling ShutdownBlockReasonCreate. Then call ShutdownBlockReasonDestroy when your application is finished running.

You should obey the description mentioned in WM_ENDSESSION Message and WM_QUERYENDSESSION to make sure both user and Windows system are happy.

GENERAL

class CInterface
{
virtual ~CInterface()=0{}
virtual void SomeAction()=0;
}
 
class DerivedA:public CInterface
{
DerivedA(){}
~DerivedA(){}
void SomeAction()
{
cout<<"Action from Derived class A ."<<endl;
}
}
But what make me confused is that it works well after I change CInterface,like below:

class CInterface
{
//virtual ~CInterface()=0{}
virtual void SomeAction()=0;
}

class CInterface
{
public:
virtual ~CInterface() = 0 {};
virtual void SomeAction()=0;
};
class DerivedA:public CInterface
{
public:
DerivedA(){}
~DerivedA(){cout<<"In Deriveda"<<endl;}
void SomeAction()
{
cout<<"Action from Derived class A ."<<endl;
}
};
int main()
{
CInterface* A = new DerivedA;
delete A;
return 0;
}

• If you implement a destructor in a derived type, this destructor will be called in any case.
• If you don't need a destructor in your inherited classes, this will not hurt.

Here this might help

#include <windows.h>
#include <iostream>

using namespace std;
 
union MyUnion
{
ULONGLONG ull;
BYTE b[8];
};
 
int main()
{
ULONGLONG v = 0x0123456789ABCDEF;
MyUnion mu;
mu.ull = v;
for (int i=0; i<6; i++)
{
// assuming you need the least significative bytes
cout << hex << (INT) mu.b[i] << endl;
}
}

You can read what the inventor of the language, Bjarne Stroustrup, thinks about this right here[^]. No-one can give you a better explanation than him.

What you need is a Deskband.There are 4 types of deskband objects. 3 of them reside inside internet explorer. The last one is on the desktop.Look at the second image in the article Implementing Shell Desk Band and Internet Explorer Bars

From MSDN blogs: How to detect the presence of Visual C++ 2010 redistributable package.

What You need can be found at : http://msdn.microsoft.com/en-us/library/aa366216(VS.85).aspx all necessary interfaces are there ..

You can use DosBox under Windows XP. It should probably work under Windows 7 too.

I would say the return type should be an Angle (or Bearing, ..). Create a class Angle to use. Internally it can use a floating point member for the decimal value. Then add a string formating member function to get the desired string when needed.

Advantages: Easy to perform calculations, and you can reduce the risk of mixing units, such as degrees and radians. I use the following if it helps you in any way

class angle
{
public:
enum unit
{
rad = 0,
deg = 1
};
angle() : r(0.) {}
explicit angle(double a, unit u = rad) {
if (u == rad) r = a; else r = a*M_PI/180;
}
angle(const angle& fi) : r(fi.r) {}
double radians() const { return r; }
double degrees() const { return r*180/M_PI; }
 
// -pi <= a < pi
void normalize() {
while(r<-M_PI)r+=2*M_PI;while(r>=M_PI)r-=2*M_PI;
}
// 0 <= a < 2pi
void normalize_positive() {
while(r<0.)r+=2*M_PI;while(r>=2*M_PI)r-=2*M_PI;
}
 
angle& operator=  (const angle &fi) { if (&fi != this) r = fi.r; return *this; }
angle& operator+= (const angle &fi) { r += fi.r; return *this; }
angle& operator-= (const angle &fi) { r -= fi.r; return *this; }
bool   operator== (const angle &fi) { return r == fi.r; }
bool   operator>  (const angle &fi) { return r > fi.r; }
bool   operator<  (const angle &fi) { return r < fi.r; }
bool   operator>= (const angle &fi) { return r >= fi.r; }
bool   operator<= (const angle &fi) { return r <= fi.r; }
angle  operator-  () { return angle(-r); }
angle  operator-  (const angle& fi) { return angle(r-fi.r); }
protected:
double r;
};

Nowadays, when copying text to the clipboard, is it any better to SetClipboardData as CF_UNICODETEXT instead of CF_TEXT ? Will it make a difference for the pasting entity ?

Answer#1
According to MSDN: The system implicitly converts data between certain clipboard formats: if a window requests data in a format that is not on the clipboard, the system converts an available format to the requested format. The system can convert data as indicated in the following table.

Clipboard Format | Conversion Format | Platform Support 
 
CF_OEMTEXT       | CF_TEXT           | Windows NT/Windows 2000, Windows 95/Windows 98/Windows Me 
CF_OEMTEXT       | CF_UNICODETEXT    | Windows NT/Windows 2000 
CF_TEXT          | CF_OEMTEXT        | Windows NT/Windows 2000, Windows 95/Windows 98/Windows Me 
CF_TEXT          | CF_UNICODETEXT    | Windows NT/Windows 2000 
CF_UNICODETEXT   | CF_OEMTEXT        | Windows NT/Windows 2000 
CF_UNICODETEXT   | CF_TEXT           | Windows NT/Windows 2000 

SetClipboardData(/*an ansi string*/, CF_TEXT);
// then
IsClipboardFormatAvailable(CF_TEXT); // success
IsClipboardFormatAvailable(CF_UNICODETEXT); // success
GetClipboardData(CF_TEXT); // success and read right string
GetClipboardData(CF_UNICODETEXT); // success and read right string
// unicode string also can test passed

One way can be declaring a

private:
operator new(size_t);

OBEX is used to send files. For sending simple text, SerialPortServiceClass_UUID.

You can refer this article Serial ports. Enumeration and FIFO control

Answer#1
 I believe a common approach is to use a "watchdog" process that monitors the main process and re-starts it if it is terminated. Then of course the main process must monitor the watchdog. Not bullet proof but annoying enough.

Answer#2

• Windows has Job Kernel Object which can be used to monitor activities of processes, even it can be used to monitor the process which created it.
• JOB_OBJECT_MSG_EXIT_PROCESS can be used to if the process gets terminated.
• By handling the above message the terminated process can be restarted by calling CreateProcess() or spawn(). 

#include
<iostream> 
using namespace std; 
 
class A
{
public:
virtual void show()=0;
};
 
class B: public A
{
public:
virtual void show(){cout << "Hey, I'm a B" << endl;}
};
 
class C: public B
{
public:
virtual void show(){cout << "Hey, I'm a C" << endl;}
};
 
int main()
{
A * p = new C();
p->show();
}

Hey, I'm a C

How To Find String Literals?

Answer#1
Concrete regular exceptions is not something to be known to be in someone's possession. This is something to be build to the required task. No, they won't help you where a serious parser is required. Do I understand you right that you want to parse C++ code? You will need to learn this field. Start here:

• http://en.wikipedia.org/wiki/Parsing 
• http://en.wikipedia.org/wiki/Category:Parsing_algorithms 
• http://en.wikipedia.org/wiki/Parsing_expression_grammar 

1. Backup your project! I take no responsibility for the outcome.
2. Open Find and Replace menu.
3. Add the following text into the find box: {:q}
4. Add the following to the replace box: _T(\1)
5. Iterate through the matches and selectively replace your strings. I recommend avoiding the Replace All button as undo will probably not be available.

The "virtual" mechanism depends on the VTable, which will be setup by the constructor. So, the constructor itself cannot be virtual (not with C++), even though you could try something like this. The link that I've provided to you is among one of the best C++ FAQs on the internet. You may as well refer to it to read about Virtual destructors and other basic C++ stuff.

When you construct your object, you always know the type of object you want to create at that time (you always call a specific constructor, not the one from the base class). So, it doesn't make sense to have a virtual constructor. Virtual destructors make more sense: when you destroy your object, you often manipulate objects as a pointer to their base class (typical scenario where polymorphism is used). In that case, you want to call the correct version of your destructor.

Interrupt numbers are used by the hardware to signal the operating system when some external event occurs. The AX register is merely a general purpose register used by the CPU. Neither of them are specific to a mouse program (whatever that may be). Take a look here for some information on how processors work.

#include <windows.h>
#include <tchar.h>
#include <sstream>
using namespace std;
 
int main()
{
wostringstream wos;
double d = 0.57;
wos << d;
BSTR bstr = SysAllocString(wos.str().c_str());
// enjoy with bstr
// ...
SysFreeString(bstr);
}

class Animal {
public:
virtual ~Animal() {};
void talk (string sound) {
cout << " Grrrr " << (char *)&sound <<  endl;
}
};
 

class Flyer {
public:
void fly (string destination) {
cout << " Flying to " << (char *)&destination <<  endl;
}
}; 
 
class Dog:public Animal{
};
 

class Crow:public Animal, public Flyer{
};

Flyer* myAnimal = dynamic_cast<Flyer*>(pAnimal);
 
if(!myAnimal)
cout<<" my animal can't fly :( ..."<< endl;
else
cout<<" my animal can flye :) ..."<< endl;

char *var = "\nWhats Up";
var = "newval";
// or
char var[] = "\nWhats Up";
strcpy(var, "newval");

FUNNY

There are 5 pots having different amount of water and total amount of water in all the pots is 10 liters.
now we want to have 2 liters of water in each pot but in minimum no of transactions. in starting we can have an array showing the initial content of water in each of the pot or any other structure can also be used.
So please suggest me any algorithm or a way so that i can find an algorithm to solve above problem.

• Aescleal
• Alain Rist
• CPallini
• DavidCrow
• Iain Clarke
• J_E_D_I
• Jackson2010
• Mark Salsbery  
• Maxwell Chen
• Michael Dunn
• Michael Schubert
• Mike O'Neill
• Moak
• Naveen
• Nibu babu thomas
• Niklas Lindquist
• Nuri Ismail
• PJ Arends
• Rajesh R Subramanian
• Rajkumar R
• Randor
• Richard MacCutchan
• Roger Stoltz
• SandipG
• Sauro
• Stephen Hewitt
• ThatsAlok
• Thaddeus Jones
• Viti
• cmk
• cofi++
• emilio_grv
• led mike
• «_Superman_»
• వేంకటనారాయణ(venkatmakam)
• Ou Wei