C / C++ / MFC Discussion Boards

Re: using New Opperator for object pointers ( Polymorphism )

led mike5-Mar-08 11:34

5-Mar-08 11:34

Are you sure you provided the smallest amount of code required to understand your problem?

From "How to get an answer to your question":

#4 Keep the question as brief as possible. If you have to include code, include the smallest snippet of code you can.

led mike

Re: using New Opperator for object pointers ( Polymorphism )

ScotDolan5-Mar-08 12:18

ScotDolan

5-Mar-08 12:18

It's not a easy simple C++ Question.

Scott

Scott Dolan
Jernie Corporation
Engineering & Manufacturing
Software, Hardware, & Enclosures

Re: using New Opperator for object pointers ( Polymorphism )

Randor 5-Mar-08 13:06

Randor

5-Mar-08 13:06

You really should have thought all of this through in the design phase of the project. It can be quite difficult and confusing to fix these things midway through the project. At any rate you may be able to solve it with virtual inheritance. But I doubt anyone here at codeproject will be able to solve it just by looking at code snippits.

See if the following ariticles give you some ideas.

http://www.parashift.com/c++-faq-lite/multiple-inheritance.html#faq-25.11[^]
http://www.phpcompiler.org/doc/virtualinheritance.html[^]
http://www.informit.com/guides/content.aspx?g=cplusplus&seqNum=168[^]

Best Wishes,
-Randor (David Delaune)

Re: using New Opperator for object pointers ( Polymorphism )

Mark Salsbery5-Mar-08 14:16

Mark Salsbery

5-Mar-08 14:16

A shorter smaple of code would certainly make it easier for those of us not familiar
with it to study Smile | :)

I get the feeling that the CLX_xxxx_POLLING classes should have a common interface base class
(a class with just the common methods pure virtual).

These polling classes should only derive from this common polling base class.

Instead of being derived from the thread and four invertor classes, the polling classes
should contain objects of these classes.

Ack maybe pseudo-code makes more sense...I just think you're over-naming yourself right out of
object oriented potential here Wink | ;)

...

// classes shortened for brevity...

class CLX_COMMON_INVERTER
{
   //Common inverter data
   ClxSafeQue<char> m_sqCmdQue;
   CRITICAL_SECTION m_csLock; 

   // Common inverter methods
   virtual bool IsConnected( void ) = 0;
   virtual bool IsInhibited( void ) = 0;
   virtual bool IsActiveFault( void ) = 0;
   virtual bool IsBootMode( void ) = 0;
};


class CLX_COMMON_POLLING
{
   // Common data
   CLX_COMMON_INVERTER *pPitchInverter;
   CLX_COMMON_INVERTER *pRollInverter;
   CLX_COMMON_INVERTER *pLiftInverter;
   CLX_COMMON_INVERTER *pCounterweightInverter;
   unsigned short m_BaudRate;
   int m_CommPort;
   int m_SerialPortHandlePolling;

   // Common methods
   virtual bool mvInitComm( int comm_port, int baud_rate ) = 0;
   virtual bool mvCloseComm( void ) = 0;
   virtual bool mvRestartComm( void ) = 0;
   virtual void mvSetBaudRate(int value) = 0;
   virtual unsigned short mvGetBaudRate(void) = 0;

}


class CLX_MITSUBISHI_POLLING : public CLX_COMMON_POLLING
{
   // Data specific to this derived class

   // Implement Common methods
   virtual bool mvInitComm( int comm_port, int baud_rate );
   virtual bool mvCloseComm( void );
   virtual bool mvRestartComm( void );
   virtual void mvSetBaudRate(int value);
   virtual unsigned short mvGetBaudRate(void);
}


class CLX_LENZE_POLLING : public CLX_COMMON_POLLING
{
   // Data specific to this derived class

   // Implement Common methods
   virtual bool mvInitComm( int comm_port, int baud_rate );
   virtual bool mvCloseComm( void );
   virtual bool mvRestartComm( void );
   virtual void mvSetBaudRate(int value);
   virtual unsigned short mvGetBaudRate(void);
}



// example usage...

CLX_COMMON_POLLING *Invertors;

if( inverter_type == MITSUBISHI )
   Invertors = new CLX_MITSUBISHI_POLLING;
else
   Invertors = new CLX_LENZE_POLLING;

See what I've done here?

You can use the common inverter class to make any specific inverter
subclass. Note I changed the method names and removed the class-specific part of
the name (lift, pitch, roll, counterweight).

You can make any polling class from the common polling class.

Any given polling class can have any type of inverter objects for the four inverters.

Also note how the object names read well when you use the inverter objects
from the polling class. eg if (pPitchInverter->IsConnected())...

If not a solution, hopefully at least adifferent way to look at the issue Smile | :)

Mark

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

Re: using New Opperator for object pointers ( Polymorphism )

led mike6-Mar-08 6:09

led mike

6-Mar-08 6:09

Mark Salsbery wrote:
See what I've done here?

No, but I can picture you flopping all around inside his boat. Poke tongue | ;-P

led mike

Re: using New Opperator for object pointers ( Polymorphism )

Mark Salsbery6-Mar-08 6:12

Mark Salsbery

6-Mar-08 6:12

....gills flaring...gasping for any water to extract some O2 from...it's a sad sight... Sigh | :sigh:

We need a fish smiley! Laugh | :laugh:

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

Re: using New Opperator for object pointers ( Polymorphism )

led mike6-Mar-08 6:31

led mike

6-Mar-08 6:31

Mark Salsbery wrote:
We need a fish smiley!

That would be so great, I'd ask Chris for one if I thought there was any chance of getting it.

led mike

Knowing if the Application is already beeing executed (Previnstance)

marcio kovags5-Mar-08 7:44

marcio kovags

5-Mar-08 7:44

Hello. there is the variable app.previnstance in visualbasic 6 to know if the application is already open. How can i do that using Win32 API?
i saw there's a variable in the winmain() function called hPrevInstance, but i do not know how to use it.

Any help would be welcome.

thanks Smile | :)

Re: Knowing if the Application is already beeing executed (Previnstance)

Randor 5-Mar-08 7:57

Randor

5-Mar-08 7:57

I use a semaphore to detect if there is already an instance of the application running.

Heres what I use:

CString szGuid;
szGuid= _T("Create your own unique GUID here, I used guidgen.exe");
m_hSem=CreateSemaphore(NULL, 1, 1, szGuid);
if (GetLastError() == ERROR_ALREADY_EXISTS)
{
	TCHAR szCaption[_MAX_FNAME];
	LoadString(m_hInstance,AFX_IDS_APP_TITLE,szCaption,_MAX_FNAME);
	
	CWnd* pwndFirst = CWnd::FindWindow(NULL,szCaption);
	if (pwndFirst)
	{
		CWnd* pwndPopup = pwndFirst->GetLastActivePopup();								   
		pwndFirst->SetForegroundWindow();
		if (pwndFirst->IsIconic())
		{
			pwndFirst->ShowWindow(SW_SHOWNORMAL);
			pwndFirst->PostMessage(WM_SYSCOMMAND, SC_MAXIMIZE);
		}
		if (pwndFirst != pwndPopup)
		{
			pwndPopup->SetForegroundWindow();
			pwndPopup->PostMessage(WM_SYSCOMMAND, SC_MAXIMIZE);
		}
	}
	CloseHandle(m_hSem);
	return FALSE;
}

Note that this code will bring the previous instance to the foreground.
Don't forget to CloseHandle(m_hSem) when your application exits.

-Randor (David Delaune)

Re: Knowing if the Application is already beeing executed (Previnstance)

Joan M5-Mar-08 7:59

Joan M

5-Mar-08 7:59

You can do it in several different ways:

http://www.codeproject.com/KB/cpp/csingleinst.aspx[^]

There are plenty of solutions out there just search for "single instance c++" in google and you'll see...

Hope this helps...

Re: Knowing if the Application is already beeing executed (Previnstance)

CPallini5-Mar-08 8:04

CPallini

5-Mar-08 8:04

You cannot use hPrevInstance, the reason why is here.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

Re: Knowing if the Application is already beeing executed (Previnstance)

Roger Stoltz5-Mar-08 21:12

Roger Stoltz

5-Mar-08 21:12

There's only one way I know of that is bullet proof:
http://www.flounder.com/nomultiples.htm[^]

The other ways may fail if certain conditions are not satisfied. You can the reasons why in the article above.

"It's supposed to be hard, otherwise anybody could do it!" - selfquote
"High speed never compensates for wrong direction!" - unknown

Windows Service

act_x5-Mar-08 6:59

act_x

5-Mar-08 6:59

I am a total stranger to windows service development.

I needed to understand the limitations .

1. Is it possible to have MFC support in Service code?
2. Can I create a hidden window in a Service ?

My basic requirement is to intercept WM_DEVICE_CHANGE notifications to process this message.

Engineering is the effort !

Re: Windows Service

Joan M5-Mar-08 7:19

Joan M

5-Mar-08 7:19

Yes, you can (1 and 2), you must set the service to be able to interact with the desktop.

Moreover you can use XYNTService (you can easily find it here) in order to use any app as a service.

Hope this helps.

Re: Windows Service

Mark Salsbery5-Mar-08 11:53

Mark Salsbery

5-Mar-08 11:53

No need to interact with the desktop for hidden windows.

That's only if you want a user to see the windows, which is really frowned upon
from services going forward with Vista+.

Mark

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

Re: Windows Service

Randor 5-Mar-08 8:13

Randor

5-Mar-08 8:13

RegisterDeviceNotification may be what you are looking for if developing a service to monitor a specific device.

http://msdn2.microsoft.com/en-us/library/aa363431.aspx[^]

Not sure if you are the author of the device driver but perhaps this document will help:

http://www.microsoft.com/whdc/driver/kernel/KM-UMGuide.mspx[^]

It describes WM_DEVICE_CHANGE notifications and other techniques of device change notification.

Best Wishes,
-David Delaune

Self-registered edit control class crashes because of wrong GetWindowTextLength return value

Skarrin5-Mar-08 6:50

Skarrin

5-Mar-08 6:50

Hello,

long title, short story: a rather old third-party library uses the following code to register its own edit control class:

static const TCHAR BASED_CODE szEdit[] = _T("GXEDIT");<br />
WNDCLASS wcls;<br />
// check to see if class already registered<br />
	if (!::GetClassInfo(hResource, szEdit, &wcls))<br />
	{<br />
		// Use standard "edit" control as a template.<br />
		VERIFY(::GetClassInfo(NULL, _T("edit"), &wcls));<br />
<br />
		// set new values<br />
		wcls.style |= GX_GLOBALCLASS;<br />
		wcls.hInstance = hResource;<br />
		wcls.lpszClassName = szEdit;<br />
<br />
		AfxRegisterClass(&wcls);

This works fine unless XP themes are enabled.
If they are and I use GetWindowText(CString-variable) with this edit control, the CString destructor causes a heap corruption because ::GetWindowTextLength reports less bytes than ::GetWindowText actually receives, and thus CString::GetBufferSetLength allocates not enough memory.

Is there a simple solution to change the above code so that this GXEDIT works with XP themes?
I already tried rewriting it using WNDCLASSEX instead, but that didn't help.

adTHANKSvance, Jens

Re: Self-registered edit control class crashes because of wrong GetWindowTextLength return value

CPallini5-Mar-08 8:27

CPallini

5-Mar-08 8:27

Are you sure there is such a bug affecting GetWindowTextLength? I cannot find related info.

Re: Self-registered edit control class crashes because of wrong GetWindowTextLength return value

Skarrin5-Mar-08 21:28

Skarrin

5-Mar-08 21:28

Part of this third-party library is a grid control, and the problems occurs when a GXEDIT control is created in-place to edit the contents of a cell.
The cell contains a 4-digit number, and the value returned by GetWindowTextLength is 12.
But only if I discard this value and reserve 25 bytes or more in CString::GetBufferSetLength, the heap doesn't get corrupted.

It's strange, but I think this is only a side effect of some error in the class registration.
If I don't use the XP visual styles for this app (no manifest file), everything works fine.
Other edit controls that are of the systems standard "edit" class type, work ok with or without styles enabled...

Regards, Jens

Re: Self-registered edit control class crashes because of wrong GetWindowTextLength return value

Randor 5-Mar-08 8:56

Randor

5-Mar-08 8:56

Maybe its a Unicode/ANSI issue.

The third party control may be using Unicode. Windows Unicode (UTF-16) uses 2 bytes to represent each character.

Try changing your GetWindowText to GetWindowTextW and see what happens, perhaps you need a CStringW.

Best Wishes,
-Randor (David Delaune)

Re: Self-registered edit control class crashes because of wrong GetWindowTextLength return value

Skarrin5-Mar-08 21:52

Skarrin

5-Mar-08 21:52

The control does not use unicode, I have checked that. As I wrote, the problem only occurs if I enable XP visual styles and themes for the application by including a manifest file in the executables directory.

I already tried to write replacements for Get/SetWindowText:

void CGXEditControl::GetWindowText(CString& s)<br />
{<br />
	if (IsThemeActive())<br />
	{<br />
		const int nLen = ::GetWindowTextLengthW(m_hWnd);<br />
		CStringW sW;<br />
		::GetWindowTextW(m_hWnd, sW.GetBufferSetLength(nLen), nLen+1);<br />
		sW.ReleaseBuffer();<br />
<br />
		s = sW;<br />
	}<br />
	else<br />
	{<br />
//CGXEditControl is derived from CEdit, CGXStatic<br />
		CEdit::GetWindowText(s);<br />
	}<br />
}<br />
<br />
void CGXEditControl::SetWindowText(const CString& s)<br />
{<br />
	if (IsThemeActive())<br />
	{<br />
		CStringW sW(s);<br />
		::SetWindowTextW(GetSafeHwnd(), sW);<br />
	}<br />
	else<br />
	{<br />
		CEdit::SetWindowText(s);<br />
	}<br />
}

This prevents the heap corruption, but then the edit control contains a lot of unreadable stuff like arabic letters OMG | :OMG:

even though the debugger shows that sW seems to contain a correct string like "1120".

The problem seems to be the registration process of the class GXEDIT.
In CGXEditControl::CreateControl, if I replace the class name "GXEDIT" with the standard "edit" class in the call to CEdit::Create, everything works!
But I don't know what side effects this will have for the rest of the library Confused | :confused:

, so I want to avoid this workaround if possible.

BTW, this library is a very antique version of Stingray's Objective Grid, dated 1997 Blush | :O

.

Regards, Jens

How to display animated gif on status bar

ptr_Electron5-Mar-08 4:56

ptr_Electron

5-Mar-08 4:56

Friends,

Do you have any smart idea to display animated gif on the status bar,

Thax

Re: How to display animated gif on status bar

toxcct5-Mar-08 5:04

toxcct

5-Mar-08 5:04

you'd better search for using AVIs rather than GIFs...

[VisualCalc][Binary Guide][CommDialogs] | [Forums Guidelines]

Re: How to display animated gif on status bar

ptr_Electron6-Mar-08 0:41

ptr_Electron

6-Mar-08 0:41

Yes Thanks you very much... here it is found

http://www.codeguru.com/cpp/controls/statusbar/article.php/c2971/[^]

Re: How to display animated gif on status bar

Mark Salsbery5-Mar-08 14:31

Mark Salsbery

5-Mar-08 14:31

Search! There's lots of samples out there for rendering animated GIFs.

For example: Adding GIF-animation using GDI+[^]

Mark

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

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