Re: using New Opperator for object pointers ( Polymorphism ) - C / C++ / MFC Discussion Boards

Mark Salsbery6-Mar-08 5:14

6-Mar-08 5:14

An MFC DLL is a Win32 DLL. Getting it to compile has nothing to do with
the type of DLL.

The MFC header file(s) and/or Windows SDK header files need to be included
in a certain order.

Again, if you need to know for sure how to order the includes correctly,
create a temporary MFC project with the wizard and copy the way
stdafx.h is layed out. It's better than trying to guess.

Mark

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

Service or Singleton COM exe or DLL

act_x5-Mar-08 11:13

act_x

5-Mar-08 11:13

Hi ,
I have a requirement , where I want one entity to be persistent in the computer.
I am struggling to decide on what this entity will be .

My model is such that I want to be able to intercept USB device notifications utilizing the WM_DEVICE_CHANGE messages by creating a hidden window in this entity and then update the elements of a system tray icon ( which exposes a Menu ) .

So my requirement does not fit the Client Server model , yet I am leaning towards COM to provide one EXE that does it all . So in other words , this entity will not provide any APIs for other clients to use . Am I unnecessarily using COM ?

So finally I need to finalize the form that this need to take .

Service - actually the Visual Studio 6 gives the option to create a COM Object as a Service.

COM DLL

COM EXE

Standalone EXE ?

Your inputs are really appreciated

Engineering is the effort !

Re: Service or Singleton COM exe or DLL

Matthew Faithfull5-Mar-08 12:23

Matthew Faithfull

5-Mar-08 12:23

I think a stand alone exe will do the trick. You can prevent more than one instance running at a time easily enough with a named mutex. You can have the main window as your hidden window which keeps things simple, perhaps one DLL to encapsulate the system tray icon stuff, I've seen that done well although it's not easy unless you're targetting only XP or only Server 200?, and another to encapsulate the USB WM_DEVICE_CHANGE stuff, I've written one like that but it's closed source Frown | :(

. I can tell you that you may need to download a DDK to get the correct headers for the defines you might need, again if you use any XP and upward only defines it won't work on earlier system. Win2K in the earliest that has usably reliable USB device stuff although some things work a bit on Win98.
Do you need COM? You might need a little to get the System tray stuff to work, It's been too long since I looked at it, but nothing more complex than emulating a VB enumeration type if that.
A Service? No as long as you can start your app on or near startup and automatically I can't see the need for it being a service. A service shouldn't interact with the UI anyway so not if it's going to have an icon. Remember to scan for already plugged in USB devices on startup and also that they can be reported as fixed or removable, sometimes depending on the chipset revision on the removable media in the removable drive!
Enjoy Smile | :)

Nothing is exactly what it seems but everything with seems can be unpicked.

using New Opperator for object pointers ( Polymorphism )

ScotDolan5-Mar-08 10:07

ScotDolan

5-Mar-08 10:07

I have two different object CLX_MITSUBISHI_POLLING and CLX_LENZE_POLLING. These two classes both inherit four other classes that are similar but not identical. The functions names and parameter of the different inherited classes are identical but the code is not.

I am have difficultly finding a way to create a generic class object pointer and then useing the new operator. I am finding it difficult because, i don't have a way to create a generic base class because of the four other objects inherited(CLX_LENZE_LIFT_INVERTOR,etc.) I was thinking may i could do something with templates or null pointer( void *inverter; inverter = new CLX_MITSUBISHI_POLLING();) Unfortunately, the null pointer did not work. Any recommendations would be greatly a appreciated.

Cheers Scott

<br />
CLX_POLLING *Invertors;<br />
<br />
if( inverter_type == MITSUBISHI  )<br />
   Invertors = new CLX_MITSUBISHI_POLLING;<br />
else <br />
   Invertors = new CLX_LENZE_POLLING;<br />

My CLX_MITSUBISHI_POLLING clases

<br />
#pragma once<br />
#include "windows.h"<br />
#include "ClxThread.h"<br />
#include "ClxSafeQue.h"<br />
#include "ClxMitsubishiParameters.h"<br />
#include "ClxMitsubishiLiftInvertor.h"<br />
#include "ClxMitsubishiPitchInvertor.h"<br />
#include "ClxMitsubishiRollInvertor.h"<br />
#include "ClxMitsubishiCounterWeightInvertor.h"<br />
<br />
class CLX_MITSUBISHI_POLLING : <br />
	public  ClxThread,<br />
		public CLX_MITSUBISHI_PITCH_INVERTOR,<br />
			public CLX_MITSUBISHI_ROLL_INVERTOR,<br />
				public	CLX_MITSUBISHI_LIFT_INVERTOR,<br />
					public	CLX_MITSUBISHI_COUNTERWEIGHT_INVERTOR<br />
{<br />
	public:<br />
		CLX_MITSUBISHI_POLLING(void);<br />
		~CLX_MITSUBISHI_POLLING(void);<br />
		bool					mStartPolling(void){ return CreateNewThread(); }	<br />
<br />
<br />
	private:		// Serial Port Specific Commands and Data<br />
		unsigned short			m_BaudRate;<br />
		int						m_CommPort;<br />
		int						m_SerialPortHandlePolling;	<br />
	public:	<br />
		bool					mvInitComm( int comm_port, int baud_rate );<br />
		bool					mvCloseComm( void );<br />
		bool					mvRestartComm( void );	<br />
		void					mvSetBaudRate(int value);<br />
		unsigned short			mvGetBaudRate(void);<br />
		void					mvSetCommPort(int value);<br />
		unsigned short			mvGetCommPort(void);<br />
		int						mvGetSerialPortHandle( void );<br />
		void					mvSetSerialPortHandle( int );<br />
	private:<br />
		int						mvPutByte( char txdata );<br />
		int						mvPutPacket( int lenght, char txdata[] );	<br />
		int						mvGetBytes( void );<br />
		int						mvFlushRxBuf( void );<br />
		int						mvFlushTxBuf( void );<br />
		int						mvGetRxBuf(void);<br />
		int						mvGetTxBuf(void);	<br />
		bool					mvIsOverrunErrors(void);<br />
		bool					mvIsParityErrors(void);<br />
		bool					mvIsRxBufferEmpty(void);<br />
		bool					mvIsTxBufferEmpty(void);<br />
		int						mvGetRxBufferSize(void);<br />
		int						mvGetTxBufferSize(void);<br />
	private:   <br />
		void					ThreadRun(void);<br />
		CRITICAL_SECTION		m_csMitsubishiPolling;<br />
};

My CLX_LENZE_POLLING clases

#pragma once<br />
#include "windows.h"<br />
#include "ClxThread.h"<br />
#include "ClxSafeQue.h"<br />
#include "ClxLenzeRollInvertor.h"<br />
#include "ClxLenzeLiftInvertor.h"<br />
#include "ClxLenzePitchInvertor.h"<br />
#include "ClxLenzeCounterWeightInvertor.h"<br />
<br />
<br />
<br />
class CLX_LENZE_POLLING : <br />
	public  ClxThread,<br />
		public CLX_LENZE_PITCH_INVERTOR,<br />
			public CLX_LENZE_ROLL_INVERTOR,<br />
				public CLX_LENZE_LIFT_INVERTOR,<br />
					public CLX_LENZE_COUNTERWEIGHT_INVERTOR<br />
{<br />
	public:<br />
		CLX_LENZE_POLLING(void);<br />
		~CLX_LENZE_POLLING(void);<br />
			bool				mStartPolling(void){ return CreateNewThread(); }	<br />
<br />
	private:   <br />
		void					ThreadRun(void);<br />
		CRITICAL_SECTION		m_csLenzePolling;<br />
<br />
	private:		// Serial Port Specific Commands and Data<br />
		unsigned short			m_BaudRate;<br />
		int						m_CommPort;<br />
		int						m_AllSerialPortHandle;	<br />
	public:	<br />
		bool					mvInitComm( int comm_port, int baud_rate );<br />
		bool					mvCloseComm( void );<br />
		bool					mvRestartComm( void );	<br />
		void					mvSetBaudRate(int value);<br />
		unsigned short			mvGetBaudRate(void);<br />
		void					mvSetCommPort(int value);<br />
		unsigned short			mvGetCommPort(void);<br />
		int						mvGetSerialPortHandle( void );<br />
		void					mvSetSerialPortHandle( int );<br />
	private:<br />
		int						mvPutByte( char txdata );<br />
		int						mvPutPacket( int lenght, char txdata[] );	<br />
		int						mvGetBytes( void );<br />
		int						mvFlushRxBuf( void );<br />
		int						mvFlushTxBuf( void );<br />
		int						mvGetRxBuf(void);<br />
		int						mvGetTxBuf(void);	<br />
		bool					mvIsOverrunErrors(void);<br />
		bool					mvIsParityErrors(void);<br />
		bool					mvIsRxBufferEmpty(void);<br />
		bool					mvIsTxBufferEmpty(void);<br />
		int						mvGetRxBufferSize(void);<br />
		int						mvGetTxBufferSize(void);<br />
	<br />
<br />
<br />
<br />
	<br />
<br />
		<br />
};

All the below classes are identical except for function name which will be Lift, Roll, Pitch, or CounterWeight accordingly. The inherited PARAMETERS contains function to send and recieve packets. It also has a some virtual function such as mvGetByte, mvPutByte. mvSetCommPort. This virtual function are overrided in CLX_MITSUBISHI_POLLING and CLX_LENZE_POLLING so the all the inherited classes use the same serial port. The only differents in LENZE or MITSUBISHI is in the individual functions.
CLX_LENZE_PITCH_INVERTOR
CLX_LENZE_ROLL_INVERTOR
CLX_LENZE_LIFT_INVERTOR
CLX_LENZE_COUNTERWEIGHT_INVERTOR
CLX_MITSUBISHI_PITCH_INVERTOR
CLX_MITSUBISHI_ROLL_INVERTOR
CLX_MITSUBISHI_LIFT_INVERTOR
CLX_MITSUBISHI_COUNTERWEIGHT_INVERTOR

<br />
#pragma once<br />
#include "Windows.h"<br />
#include "ClxSafeQue.h"<br />
#include "ClxMitsubishiParameters.h"<br />
<br />
<br />
class CLX_MITSUBISHI_LIFT_INVERTOR : <br />
	public CLX_MITSUBISHI_PARAMETERS<br />
{<br />
public:<br />
	CLX_MITSUBISHI_LIFT_INVERTOR(void);<br />
	~CLX_MITSUBISHI_LIFT_INVERTOR(void);<br />
<br />
	void   LiftSetAddress( char address );		<br />
	char   LiftGetAddress( void );	<br />
<br />
	void   LiftSetJogFrequency( double value );<br />
	double LiftGetJogFrequency( void );<br />
<br />
	void   LiftSetConfigurationVoltage( int volts );	<br />
	int    LiftGetConfigurationVoltage( void );	<br />
	<br />
	bool   LiftisConnected( void );<br />
	bool   LiftisInhibited( void );<br />
	bool   LiftisActiveFault( void );<br />
	bool   LiftisBootMode( void );<br />
	bool   LiftisSerialMode( void );<br />
	bool   LiftisAnalogMode( void );<br />
	bool   LiftisUnknownMode( void ); <br />
		<br />
	bool   LiftGetBusVoltage( double *dTemp);<br />
	bool   LiftGetOutputVoltage( double *dTemp);			<br />
	bool   LiftGetOutputCurrent( double *dTemp);			<br />
	bool   LiftGetOutputFrequencey( double *dTemp);	<br />
	bool   LiftGetOutputTemperature( double *dTemp );<br />
	bool   LiftGetPoweronTime( double *dTemp);				<br />
	bool   LiftGetOperatingTime( double *dTemp);	<br />
		<br />
	bool   LiftGetActiveFault( int *iTemp );			<br />
	bool   LiftGetLastFault( int *iTemp);			<br />
	bool   LiftGetLastFault2( int *iTemp);				<br />
	bool   LiftGetLastFault3( int *iTemp);				<br />
<br />
	bool   LiftInitDefaultsCmd(void);				<br />
	bool   LiftDriveStateCmd(void);				<br />
	bool   LiftAutotuneCmd(void);		<br />
	bool   LiftEnableCmd( void );				<br />
 	bool   LiftDisableCmd( void );					<br />
 	bool   LiftAnalogModeCmd( void );				<br />
	bool   LiftAnalogBrakeNormalCmd( void );	<br />
	bool   LiftAnalogBrakeInvertedCmd( void );<br />
	bool   LiftSerialModeCmd( void );		  <br />
	bool   LiftSerialBrakeNormalCmd( void );		<br />
	bool   LiftSerialBrakeInvertedCmd( void );		<br />
	bool   LiftResetFaultsCmd( void );					<br />
	bool   LiftJogCwCmd( void );			 	<br />
	bool   LiftJogCcwCmd( void );				<br />
	bool   LiftJogStopCmd( void );					<br />
<br />
	void   LiftDisableParity( void )			{	DisableParity();	}<br />
	void   LiftEnableParity( void )				{	EnableParity();		}<br />
	bool   LiftGetParity( void )				{   GetParity();		}<br />
	void   LiftSetRxTimeout( unsigned long value )		{	SetReceiveTimeout(value); }<br />
	int    LiftGetRxTimeout( void )				{   return GetReceiveTimeout(); }<br />
	void   LiftSetRxRetryNum( int value );			<br />
	int    LiftGetRxRetryNum( void );<br />
<br />
	void   LiftRun( void );<br />
<br />
private:<br />
	bool   LiftActivateCmd( char incmd );<br />
	<br />
	ClxSafeQue<char>	m_sqCmdQue;<br />
	CRITICAL_SECTION	m_csLock;	<br />
<br />
	char	m_cAddress;// This is the address of the lift inverter. This value should never change<br />
	double	m_dJogFrequency;	// Jog 		<br />
	int	m_cConfigurationVoltage;	<br />
	bool	m_bActiveFault;	// Indicates if there is a active fault<br />
	bool	m_bConnected;	// Indicates if there drive or software is problems<br />
	bool	m_bInhibited;				// Indicates if the drive is inhibited<br />
	bool	m_bIsBootMode;				// Boot<br />
	bool	m_bIsSerialMode;			// Serial<br />
	bool	m_bIsAnalogMode;			// Analog<br />
	bool	m_bIsUnknownMode;			// Unknown<br />
	bool	m_bValidDriveState;	<br />
	double	m_dBusVoltage;				// Holds the current drive bus voltage<br />
	bool	m_bValidBusVoltage;		<br />
	double	m_dOutputVoltage;	// Holds the current drive output voltage<br />
	bool	m_bValidOutputVoltage;		<br />
	double	m_dOutputCurrent;			<br />
	bool	m_bValidOutputCurrent;			<br />
	double	m_dOutputFrequencey;	<br />
	bool	m_bValidOutputFrequencey;	<br />
	double	m_dOutputTemperature;	<br />
	bool	m_bValidOutputTemperature;	<br />
	double	m_dOperatingTime;			<br />
	bool	m_bValidOperatingTime;		<br />
	double	m_dPowerOnTime;				// Holds the drives Power On Time <br />
	bool	m_bValidPowerOnTime;		<br />
	int	m_iActiveFault;				// Holds the most recent fault<br />
	bool	m_bValidActiveFault;			<br />
	int	m_iLastFault;				<br />
	bool	m_bValidLastFault;		<br />
<br />
	int	m_iLastFault2;				// Holds the thrid most recent fault<br />
	bool	m_bValidLastFault2;			<br />
<br />
	int	m_iLastFault3;				// Holds the Fourth most recent fault<br />
	bool	m_bValidLastFault3;				<br />
<br />
	<br />
	unsigned long		m_lCurrentNumTxPktFailed;	<br />
	unsigned long		m_iMaxinumNumTxPktFailures;	<br />
	unsigned long		m_lTotalNumTxPktFailed;	<br />
	unsigned long		m_lTotalNumTxPktCount;	<br />
	char			m_cPollingCommandIndex;<br />
<br />
<br />
};<br />
<br />

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

Re: using New Opperator for object pointers ( Polymorphism )

led mike5-Mar-08 11:34

led mike

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

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