Re: Hiding mouse ? - C / C++ / MFC Discussion Boards

Blaq18-Feb-08 7:31

18-Feb-08 7:31

Hi!
I have to implement in my app a selection tool which lets users to select region of any shape in raster image (in graphics aplication it is called "free shape selection tool" or lasso). Anybody knows some free libraries or examples with source code which can be usefull? I will postpone choosing the image processing library till I get some answers from programers community Smile | :)

Not necessarily C++, may be also .Net classes.

import library

George_George18-Feb-08 2:55

George_George

18-Feb-08 2:55

Hello everyone,

http://msdn2.microsoft.com/en-us/library/aa271769(VS.60).aspx[^]

My current confusion is, what is the content and format of import library, especially, how magic the import library is -- so that the linker could utilize it to generate the two forms of call statement,

1. using JMP indirection, one additional indirection level;
2. smarter way, no additional indirection level.

Also, how import library referred to the IAT of the EXE during link phase, so that the loader could resolve the IAT during loading time.

The content seems too abstract and high level, and if there could be a sample, it will be great! Smile | :)

Any referred reading or description to my question.

thanks in advance,
George

Re: import library

Randor 18-Feb-08 5:15

Randor

18-Feb-08 5:15

Hello George,

The article in question is referring to functions imported from a DLL. When you call a function which resides in a DLL the linker generates an address pointer which will point to a thunk. A thunk is a function which accesses a table containing address translations. By default the linker will generate a 'call instruction' or JMP instruction to the thunk. This takes additional cpu cycles.

The article describes using __declspec(dllimport) which will instruct the linker that the function resides in an external DLL. Once the linker knows this, it can generate better performing code. Rather than generating a 'call instruction' the linker will generate an indirect call through the IAT entry. Essentially the linker is inlining the thunk.

For Example:

__declspec(dllimport) void Myfunction(void);
int main()
{
	Myfunction();
}

generates an indirect call such as:

ff 15 00 00 00 00 call DWORD PTR __imp__Myfunction

So now the linker has generated optimized code with a single indirect call instruction. In addition to what the article mentions... if all DLL calls from the application are hinted with __declspec(dllimport) this will cause the linker to not generate thunk code which will save 6 bytes plus 1 byte per call site on the final PE image.

Hope this helps,
-Randor (David Delaune)

Re: import library

George_George18-Feb-08 15:44

George_George

18-Feb-08 15:44

Thanks Randor!

Your reply is great! One more question, why the address of the import function (or say, the function exported by the DLL) can not be known by the linker? Because of until load time, the address of the function in the DLL is not decided? Like DLL Rebase or something?

regards,
George

Re: import library

Mike Dimmick18-Feb-08 7:51

Mike Dimmick

18-Feb-08 7:51

Randor's correct in the overall behaviour but not some of the details. The compiler normally generates direct CALL instructions to call code not in the current translation unit. It leaves a direction to the linker to fill in the necessary value with the address of the corresponding symbol at link time.

The import library that you link with is what contains the JMP instructions, which look like:

MyFunc:
    JMP __imp__MyFunc

That's the 'import thunk'. There's one thunk per routine in the DLL that this is the import library for.

If you specify __declspec(dllimport), the compiler instead generates an indirect call instruction and the instruction to the linker references __imp__MyFunc rather than MyFunc. When the call is made, instead of the instruction pointer going first to the thunk, then to the function itself, it goes directly to the function.

The symbol __imp__MyFunc itself actually points to a pointer-sized value in the Import Address Table which the loader (part of the OS) writes the actual address of the function to at load time.

Also included in the import library is the full Import Address Table for the DLL, which contributes to building up the IAT in the executable itself.

For more, see http://msdn.microsoft.com/msdnmag/issues/02/03/PE2/[^].

DoEvents: Generating unexpected recursion since 1991

Re: import library

George_George18-Feb-08 15:42

George_George

18-Feb-08 15:42

Thanks Mike,

Two more comments,

1.

For the less-optimized form (if user does not specify dllimport),

jmp DWORD PTR __imp_func1

is treated as implementation function func1?

2.

How did the linker know the address of IAT table itself? It is some hard coded value or always have the same value in every PE file?

regards,
George

Hiding mouse ?

kk.tvm18-Feb-08 2:17

kk.tvm

18-Feb-08 2:17

Hi friends

How to hide mouse pointer in MFC

thanks in advance

-RisKhan-

Re: Hiding mouse ?

Iain Clarke, Warrior Programmer18-Feb-08 2:41

Iain Clarke, Warrior Programmer

18-Feb-08 2:41

Nothing to do with MFC, but still correct:

SetCursor (NULL);

Be warned though - this is prone to problems. If your message pump is still working, then you may get messages like WM_SETCURSOR, which could cause another part of your program to put the cursor back to something useful again.

And if you can cure that, you can't stop other programs setting the cursor when you go over them. And it would be a TERRIBLE thing if you could.

But if you're full screen, and well written. you can get rid of the cursor. Or if you have no mouse, and therefore no mouse movement!

Iain.

Iain Clarke appearing in spite of being begged not to by ^CPallini.

Re: Hiding mouse ?

Rajkumar R18-Feb-08 2:46

Rajkumar R

18-Feb-08 2:46

int ShowCursor(
BOOL bShow
);

Question about connection with FTP server ( What wrong with my code .... ? ) [modified]

Yanshof18-Feb-08 1:33

Yanshof

18-Feb-08 1:33

I connect to some FTP server and put on him some file.
I see that the return code of the PutFile is 1 ( that mean that all OK ) but when i try to catch the "StatusCallback" i never get the dwInternetStatus that say INTERNET_STATUS_REQUEST_COMPLETE.

When i check the FTP Server i see that my file is store fine and its look like everything is fine.
But i still except from the server to return me the flag INTERNET_STATUS_REQUEST_COMPLETE.

Beside this - i also don't understand why the call of the function OnStatusCallback is not asynchronous call.

My code:

<br />
class CMyInternetSession : public CInternetSession<br />
{<br />
public:<br />
	CMyInternetSession(LPCTSTR pstrAgent = NULL, DWORD dwContext = 1, DWORD dwAccessType = INTERNET_OPEN_TYPE_PRECONFIG, LPCTSTR pstrProxyName = NULL, LPCTSTR pstrProxyBypass = NULL, DWORD dwFlags = 0);<br />
	void OnStatusCallback( DWORD dwContext, DWORD dwInternetStatus, LPVOID lpvStatusInformation, DWORD dwStatusInformationLength );<br />
};<br />

<br />
void CTempCheckingProgDlg::OnOK() <br />
{<br />
        CMyInternetSession* pInetSession;<br />
	<br />
	pInetSession = new CMyInternetSession("Test1", 1, INTERNET_OPEN_TYPE_DIRECT,NULL, NULL)<br />
	<br />
	pInetSession->EnableStatusCallback(TRUE);	<br />
<br />
	CFtpConnection* ftpConnection = pInetSession->GetFtpConnection("10.11.12.13"), "XXX", "YYY" , INTERNET_DEFAULT_FTP_PORT);	<br />
	<br />
	BOOL bVal = ftpConnection->PutFile("SomeFile", "SomeFile_X");<br />
<br />
	DWORD Err = GetLastError();<br />
}<br />
<br />
void CMyInternetSession::OnStatusCallback( DWORD dwContext, DWORD dwInternetStatus, LPVOID lpvStatusInformation, DWORD dwStatusInformationLength )<br />
{<br />
	 AFX_MANAGE_STATE(AfxGetAppModuleState());<br />
<br />
	switch( dwInternetStatus )<br />
	{<br />
                 case(INTERNET_STATUS_REQUEST_COMPLETE):<br />
                       AfxMessageBox("INTERNET_STATUS_REQUEST_COMPLETE");<br />
                 Break;<br />
<br />

modified on Monday, February 18, 2008 7:52 AM

Re: Question about connection with FTP server ( What wrong with my code .... ? )

Rajkumar R18-Feb-08 1:54

Rajkumar R

18-Feb-08 1:54

OnStatusCallBack() is called if enabled and the operation is pending completion.

since ftpConnection->PutFile() returns successfully, i think it is not pending for completion, so no status callback.

This is only my guess, try sending larger file.

Re: Question about connection with FTP server ( What wrong with my code .... ? )

Yanshof18-Feb-08 2:08

Yanshof

18-Feb-08 2:08

Thanks .... But

But i did Enable the callback - and the function OnStatusCallBack() is call - but I'm not sure that this call is really Callback call ( i except that this call will be from other thread and i see that this call is from the same thread.

Can someone help here.... ?

Re: Question about connection with FTP server ( What wrong with my code .... ? )

David Crow18-Feb-08 2:54

David Crow

18-Feb-08 2:54

Yanshof wrote:
pInetSession = new CMyInternetSession("Test1", 1, INTERNET_OPEN_TYPE_DIRECT,NULL, NULL)

Why have you not specified INTERNET_FLAG_ASYNC? There is also a missing semicolon.

"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

Re: Question about connection with FTP server ( What wrong with my code .... ? )

Yanshof18-Feb-08 3:06

Yanshof

18-Feb-08 3:06

The flag INTERNET_FLAG_ASYNC is not relevant -

When i add this flag i getting ASSERT ( on the constructor ( first line of the constructor ) ) of the function "CInternetSession" (in my case the function "CMyInternetSession").

So i remove this flag - and from what i see - this flag is not relevant ( Maybe i wrong ... )

Re: Question about connection with FTP server ( What wrong with my code .... ? )

David Crow18-Feb-08 3:15

David Crow

18-Feb-08 3:15

Yanshof wrote:
When i add this flag i getting ASSERT...

I see that now. Have you considered that to handle any operations asynchronously, you must either create your own thread or use the WinInet functions without MFC.

Re: Question about connection with FTP server ( What wrong with my code .... ? ) [modified]

Yanshof18-Feb-08 3:21

Yanshof

18-Feb-08 3:21

I try to use WinInet also ( i try to avoid of using thread Frown | :(

) here is the code

[ The problem is that the CALLBACK function does not call at all ]

<br />
<br />
	HINTERNET hInternetSession;          // handle to Internet connection<br />
	HINTERNET hFTPSession;               // handle to FTP session<br />
	HINTERNET hFileConnection;           // handle to file enumeration<br />
<br />
	INTERNET_STATUS_CALLBACK iscCallback;<br />
<br />
	//create the root HINTERNET handle using the systems default settings.<br />
	hInternetSession  = InternetOpen("Test1", INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, INTERNET_FLAG_ASYNC);<br />
<br />
	//sets the callback function<br />
	iscCallback = InternetSetStatusCallback(hInternetSession, (INTERNET_STATUS_CALLBACK)_OnStatusCallBack);<br />
<br />
	// Make connection to ftp server.<br />
	hFTPSession = ::InternetConnect(hInternetSession,							// Handle from a previous call to InternetOpen.<br />
									"10.11.10.11",								// Server we want to connect to<br />
									INTERNET_INVALID_PORT_NUMBER,				// Use appropriate port.<br />
									"XXX",										// Use anonymous for userName.<br />
									"YYY",										// Use e-mail name for password<br />
									INTERNET_SERVICE_FTP,						// Flag to use FTP services<br />
									INTERNET_SERVICE_FTP,						// Flags (see SDK docs)<br />
									0);											// Synchronous mode<br />
<br />
<br />
	<br />
	::FtpGetFile(hFTPSession,<br />
				 "File",<br />
			     "File_X",<br />
				 FALSE,<br />
				 FILE_ATTRIBUTE_NORMAL,<br />
				 FTP_TRANSFER_TYPE_BINARY,<br />
				 0);<br />
<br />
<br />

modified on Monday, February 18, 2008 9:29 AM

Re: Question about connection with FTP server ( What wrong with my code .... ? )

David Crow18-Feb-08 4:43

David Crow

18-Feb-08 4:43

Yanshof wrote:
0); // Synchronous mode

This would appear to conflict with INTERNET_FLAG_ASYNC. Confused | :confused:

Re: Question about connection with FTP server ( What wrong with my code .... ? )

Yanshof18-Feb-08 4:57

Yanshof

18-Feb-08 4:57

No,

This param is Specifies the application-defined value that is used to identify the application context for the returned handle in callbacks.
If/When i add the flag INTERNET_FLAG_ASYNC - nothing happand Frown | :(

How can I check the exsistence of a Registry Key?

J_E_D_I18-Feb-08 1:21

J_E_D_I

18-Feb-08 1:21

How can I check the exsistence of a Registry Key using C++?
I want the program to perform a certain action if the key does not exist.
Thanks

Re: How can I check the exsistence of a Registry Key?

Rajkumar R18-Feb-08 1:26

Rajkumar R

18-Feb-08 1:26

RegOpenKeyEx() API returns ERROR_SUCCESS if reg key exist

Re: How can I check the exsistence of a Registry Key?

J_E_D_I18-Feb-08 2:42

J_E_D_I

18-Feb-08 2:42

Thanks, that was a prompt reply!
How can I assign a certain value to a variable of my choice if the key does not exist?

Re: How can I check the exsistence of a Registry Key? [modified]

Rajkumar R18-Feb-08 2:54

Rajkumar R

18-Feb-08 2:54

J_E_D_I wrote:
How can I assign a certain value to a variable of my choice if the key does not exist?

MyChoiceVariableType MyChoiceVariable = MyChoiceInitialValue; :) 
if (ERROR_SUCCESS != RegOpenKeyEx( HKEY_LOCAL_MACHINE,
            "SYSTEM\\CurrentControlSet\\Control\\ProductOptions", // u can replace with ur choice key
            0, KEY_QUERY_VALUE, &hKey ))
{
  MyChoiceVariable = MY_CHOICE_VARIABLE_VALUE; :) 
}

modified on Monday, February 18, 2008 9:11 AM

Re: How can I check the exsistence of a Registry Key?

J_E_D_I18-Feb-08 7:10

J_E_D_I

18-Feb-08 7:10

I get error C2065: 'hKey' : undeclared identifier. Have I missed something? D'Oh! | :doh:

Here is my code:

int MyChoiceVariable = 1;
if (ERROR_SUCCESS != RegOpenKeyEx(HKEY_LOCAL_MACHINE, "SOFTWARE\\ProgramX\\Key", 0, KEY_QUERY_VALUE, &hKey ))

{ MyChoiceVariable = 0;
cout << MyChoiceVariable << endl;
}

Re: How can I check the exsistence of a Registry Key? [modified]

Rajkumar R18-Feb-08 7:38

Rajkumar R

18-Feb-08 7:38

J_E_D_I wrote:
error C2065: 'hKey' : undeclared identifier

so u r now in this stage, to write a registry based program. Suspicious | :suss:

I was already wondering in ur previous post asking how to assign a variable. Roll eyes | :rolleyes:

Any way let me complete the code. Cry | :((

declare hKey,
HKEY hKey = NULL;

modified on Monday, February 18, 2008 2:06 PM

Re: How can I check the exsistence of a Registry Value?

J_E_D_I18-Feb-08 10:07

J_E_D_I

18-Feb-08 10:07

That's great, now it works! I am reporting below a simplified code for who's joined the post only now.

//If you want to check if a Registry key exists:
HKEY hKey = NULL;
string MyChoiceVariable;
if (ERROR_SUCCESS != RegOpenKeyEx( HKEY_LOCAL_MACHINE, "SOFTWARE\\..", 0, KEY_QUERY_VALUE, &hKey ))

{ MyChoiceVariable = "KEY DOES NOT EXIST";
cout << MyChoiceVariable << endl;
}

if (ERROR_SUCCESS == RegOpenKeyEx( HKEY_LOCAL_MACHINE, "SOFTWARE\\..", 0, KEY_QUERY_VALUE, &hKey ))

{ MyChoiceVariable = "KEY EXISTS";
cout << MyChoiceVariable << endl;
}

Now the next (and final!) question is...what if I want instead to check if a REG_DWORD value exists?

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