C / C++ / MFC Discussion Boards

dynamically create controls and attaching listeners to them?

misterbear25-Jul-04 20:23

25-Jul-04 20:23

Hello, I don't know if this is super-easy to accomplish,
I am pretty new to VC++/MFC..

I need to create a dialog which must contain a different number
of CButton controls depending on certain state parameters of the
applications. So I need to dynamically create a number of those
controls and attach a message handler for them ( they all share
the same message handler code ).

How do I attach this listener function to the controls once
I've created them?
(I destroy all buttons and create a bunch of new ones when the layout changes)

thankful for any help.

GDI Objects

0v3rloader25-Jul-04 13:25

0v3rloader

25-Jul-04 13:25

Hello,

Can a GDI object be created once (say when the class is constructed) and be used as many times as the programmer is pleased?

Example:

Class::Class()
{
	myPen = CPen(....);
}

void Class::DrawThis()
{
	pDC = new CDC();
	pDC -> Attach(GetDC() -> GetSafeHdc());
	pDC -> SelectObject(&myPen);
}

Is this valid and recommended?

dNimrod#X
________________________

Re: GDI Objects

Ravi Bhavnani25-Jul-04 14:54

Ravi Bhavnani

25-Jul-04 14:54

Yes, but I don't recommend it because it can be hard(er) to maintain code that shares GDI objects. The only time I'd keep a GDI object around for the lifetime of my app is when it's very expensive to create one on the fly.

One other thing - DrawThis() should unselect myPen when it's done using it. For example:

void Class::DrawThis()
{
  CPen* pOldPen = pDC->SelectObject (&myPen);
  ...
  pDC->SelectObject (pOldPen);
}

/ravi

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Re: GDI Objects

Michael Dunn25-Jul-04 18:21

Michael Dunn

25-Jul-04 18:21

I disagree with Ravi, if you are going to use a GDI object a lot, I say create it once and just keep using it. The exception is device contexts (CDC and related classes) - DCs are a shared and scarce system resource, and CDCs should exist for only as long as you need them.

Your sample code is wrong, however, in the way it's using CDC. You need to match GetDC() and ReleaseDC() calls, as well as select the pen out of the DC before releasing it.

--Mike--
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----
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Re: GDI Objects

Antony M Kancidrowski26-Jul-04 2:06

Antony M Kancidrowski

26-Jul-04 2:06

... Additionally to the other comments. If you are using multiple threads to access GDI objects then take a look at the following MSDN article.

MTGDI Sample: Demonstrates Sharing GDI Resources Across Multiple Threads of Execution[^]

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fruity and sweet.
I'm jelly, what am I? Muse on it further, I shall return! - David Williams (Little Britain)

Readfile from *.txt

71cwill25-Jul-04 8:39

71cwill

25-Jul-04 8:39

I have been trying to create a tokeninzer/scanner for my school project. But I have a hard time dealing with spaces between words. rather than it would separates the words after spaces, it will keep on adding the characters to one big word. If I inputed "print codes", it will make the variables as one 'printcodes' rather than "print" as one keyword and "codes" as identifier.
Could anyone help me solve this problem?
Here is the c++ codes I created:
while(!read.eof()) //(read>>letter)
{
//catching symbols
if(letter == '*'||'/'||'+'||'-'||'='||'('||')') {
checkid.checktokenop(letter); }
char gotit2 = letter;
//catching letters
if(gotit2 != '*')
if(gotit2 != '/')
if(gotit2 != '+')
if(gotit2 != '-')
if(gotit2 != '=')
if(gotit2 != '(')
if(gotit2 != ')')
{
int result = 1;
codes+= gotit2;
if(gotit2 == ' ')
{
result = checkid.checktokenword(codes);
codes.erase();
}
if(result == 0)//if Reserved word and,or,print,not
{
codes.erase();
}
}//end of catching letter
}

Please help!!!

Re: Readfile from *.txt

Michael Dunn25-Jul-04 11:33

Michael Dunn

25-Jul-04 11:33

71cwill wrote:
if(letter == '*'||'/'||'+'||'-'||'='||'('||')')

The first problem is that's not how you test for multiple vaules. You need to do:

if ( letter == '*' || letter == '/' || /*and so on...*/ )

--Mike--
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Disabling/enabling menu/toolbar items...

0v3rloader25-Jul-04 7:14

0v3rloader

25-Jul-04 7:14

Hello,

How does one do about disabling/enabling a menu and toolbar item that share the same ID?

Thanks a million,

David

Re: Disabling/enabling menu/toolbar items...

Ivan Cachicatari25-Jul-04 11:44

Ivan Cachicatari

25-Jul-04 11:44

Hi,

You can to obtain it adds an event to UPDATE_COMMAND_UI message, associated to this ID, with ClassWizard.

<br />
void CMainFrame::OnYourEvent(CCmdUI* pCmdUI) <br />
{<br />
   pCmdUI->Enable(m_bFlag);<br />
}<br />

the m_bFlag is a bool variable to manage the enabing/disabling.

Ivan Cachicatari
www.latindevelopers.com

Re: Disabling/enabling menu/toolbar items...

0v3rloader25-Jul-04 11:57

0v3rloader

25-Jul-04 11:57

Hi, thanks for the reply!

Can you tell me how to enable/disable an item without having to wait for the event to fire?

I mean, what is the way to do it manually?

Re: Disabling/enabling menu/toolbar items...

Ravi Bhavnani25-Jul-04 13:33

Ravi Bhavnani

25-Jul-04 13:33

dNimrod#X wrote:
without having to wait for the event to fire?

The event is sent during the app's idle processing. You don't have to do anything special - just set the appropriate bool variable to false and query it in the UI update handler. Try it - you'll like it!

/ravi

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Solution for globally listening to keys pressed

0v3rloader25-Jul-04 6:59

0v3rloader

25-Jul-04 6:59

Hi there,

I have this application which opens different modeless dialog boxes and has some accelerators defined.

My question is assuming a window/control/... has the focus at the time, how can the C[...]App know the user pressed a key? Basically, what I am trying to do is make the app process certain accelerators, independently of the window that has the focus.

Re: Solution for globally listening to keys pressed

PJ Arends25-Jul-04 10:13

PJ Arends

25-Jul-04 10:13

The easiest way is to use a "hot key". See RegisterHotKey.

"You're obviously a superstar." - Christian Graus about me - 12 Feb '03

"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04

Within you lies the power for good - Use it!

how to pass a simple char* to a unicode binary text??

youpiyoyo25-Jul-04 5:45

youpiyoyo

25-Jul-04 5:45

My purpose is to pass an icon to the resource of a file or dll. If you have any sugestions..

for that I have to use UpdateResource

so I did that

hUpdateRes = BeginUpdateResource("D:\\Bureau\\ressource\\test resource\\test resource.exe", FALSE); <br />
if (hUpdateRes == NULL) <br />
{ <br />
    MessageBox(0,"Could not open file for writing.",0,0); <br />
} <br />
 <br />
// Add the dialog box resource to the update list. <br />
result = UpdateResource(hUpdateRes,RT_ICON,szTitre,MAKELANGID(LANG_NEUTRAL,SUBLANG_NEUTRAL),ico,1384); // size of resource info. <br />
if (result == FALSE) <br />
{ <br />
    MessageBox(0,"Could not add resource.",0,0); <br />
} <br />
 <br />
<br />
if (!EndUpdateResource(hUpdateRes, FALSE)) <br />
{ <br />
    MessageBox(0,"Could not write changes to file.",0,0); <br />
}

1384 reprsente the exact size of the ico, I will chage it with sizeof or somethingelse

my problem is ico

acording to msdn ico, so the LPVOID lpData must be in "raw binary data" and the "text must be in Unicode format"

so I try that

char* ico;<br />
wchar_t *wchar=(wchar_t *)malloc( sizeof( wchar_t ) );<br />
<br />
_setmode( _fileno( stdin ), _O_BINARY ); <br />
FILE* file=fopen(szFile,"rb");<br />
FILE* filedest=fopen("dest.ico","w");<br />
fpos_t pos;<br />
if(fseek(file, 0,SEEK_END)!=0)MessageBox(0,"fseek erreur",0,0);<br />
else<br />
{<br />
	if( fgetpos( file, &pos ) == 0 )<br />
	{<br />
<br />
		ico=(char*) malloc((size_t)pos);<br />
		fseek(file, 0,SEEK_SET);<br />
		fread(ico, sizeof( char ), (int)pos, file );<br />
		//wctomb(&ico,wchar);<br />
		mbtowc( wchar ,ico,MB_CUR_MAX );<br />
	}<br />
}<br />
fclose(file);<br />
fclose(filedest);

I'm not sure about the mbtowc, ...

If have no clue to pass ico in "raw binary data and in Unicode format"

Pleazeeeeeeee help me!!

Re: how to pass a simple char* to a unicode binary text??

bikram singh26-Jul-04 7:53

bikram singh

26-Jul-04 7:53

If the "lpType" parameter is a string resource, it must be in UNICODE format. That is what MSDN says.
But since your "lpType" is RT_ICON, you do not need to do anything, since a icon contains no text, just binary data.

But if you wanted to update a resource type of RT_STRING for example, *that* string(pointed to by lpData) would need to be made into UNICODE.

Bikram Singh

ODBC Database Metadata (All Table names)

omair shafiq25-Jul-04 5:34

omair shafiq

25-Jul-04 5:34

Dear All,
I am trying to reterieve all the table names of a data bases selected through ODBC Data Source. The Language is MS Visual C++ 6.0 and OS is Windows 2000.
Still i am unable to do it.
I have written a code for it which is given below and is not working Frown | :-(

Please help me in this regard.

Anxiosuly Waiting for some Help

//Code
/*******************************
SQLHENV henv;
SQLHDBC hdbc;
SQLHSTMT hstmt;
SQLRETURN retcode;
char * szdatabase = "a";

SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &henv);
SQLSetEnvAttr(henv, SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3, 0);
SQLAllocHandle(SQL_HANDLE_DBC, henv, &hdbc);
SQLDriverConnect(hdbc, NULL, (SQLCHAR*)szdatabase, (short)(strlen(szdatabase)+1),
NULL, 0, NULL, SQL_DRIVER_NOPROMPT);
SQLAllocHandle(SQL_HANDLE_STMT, hdbc, &hstmt);
retcode = SQLTables(hstmt, (SQLCHAR*) "%", SQL_NTS, NULL, 0, NULL, 0, NULL,0);

omair

Re: ODBC Database Metadata (All Table names)

David Crow26-Jul-04 4:05

David Crow

26-Jul-04 4:05

Does CDaoDatabase::GetTableDefCount() help?

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

C reateProcess

Member 75213725-Jul-04 4:04

Member 752137

25-Jul-04 4:04

Somebody know how to get the Handle window of the child window created with the Instruction CreateProcess, to relocate, resize, etc. this new window..

Thanks for your help.

Re: C reateProcess

PJ Arends25-Jul-04 10:06

PJ Arends

25-Jul-04 10:06

This probably a hack, and someone else will come along and say "Don't do that, use function so-and-so". But I don't know of any function that does this directly. So what I came up with is to use EnumWindows() to enumerate all the top level windows. In the EnumWindowsProc() use GetWindowThreadProcessId() to compare the window process ID with the one you got from CreateProcess(). Just be sure to leave enough time between the CreateProcess call and the EnumWindows call for the window to be actually created.

Works like a charm.

"You're obviously a superstar." - Christian Graus about me - 12 Feb '03

"Obviously ??? You're definitely a superstar!!!" mYkel - 21 Jun '04

Within you lies the power for good - Use it!

bandwidth monitoring

Paolo Ponzano25-Jul-04 2:38

Paolo Ponzano

25-Jul-04 2:38

hello,
I have always asked myself, how a program as flashget knows download speed? is there any library that those that job? anyone can give me some info about? thanks a lot!
Paolo

Jumping out of a heavily-nested looping noy by using "goto" statement?

Link260024-Jul-04 17:24

Link2600

24-Jul-04 17:24

Is there a way to jump of out a heavily-nested loop not by using goto statement? Since most people would agree that goto statement is evil, and it will easily destory a program's structure, so, I want to stay away from it. However, to my surprise, there is really no easy and effective way to jump out of a heavily-nested loop not by using it.

Well, I thought I should consult those experts on codeproject.com, so I could learn from them -- you.

Thanks

-----------------------------
C++ without virtual functions is not OO. Programming with classes but without dynamic binding is called "object based", but not "object oriented".

Re: Jumping out of a heavily-nested looping noy by using "goto" statement?

Ravi Bhavnani24-Jul-04 17:52

Ravi Bhavnani

24-Jul-04 17:52

Alex Ngai wrote:
goto statement is evil,

It is not evil to use a goto statement when it transfers control to the end of the containing block. The C language even supplies you a couple of built-in constructs to make this easy to do - continue and break, the latter being nothing more than a continue followed by a loop terminator.

If you can't get yourself to use a goto for fear that someone will throw things at you in a code review (because they "learned in school that a goto is bad, bad, very bad"), you could instead throw an exception when you want to break out of a nested block, and take appropriate action in the catch.

Whatever you do, be sure to write a nice comment explaining what you've done. The person who ends up maintaining your code (usually yourself) will thank you for this while debugging at 3am on a winter's night. Smile | :)

/ravi

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Re: Jumping out of a heavily-nested looping noy by using "goto" statement?

Mike Dimmick25-Jul-04 5:30

Mike Dimmick

25-Jul-04 5:30

I recently saw a horrible code structure (thankfully that I didn't have to maintain) that looked like:

while ( TRUE )
{
   /* actions */

   if ( condition1 )
   {
      /* actions */
      break;
   }

   /* actions */

   if ( condition2 )
   {
      break;
   }

   /* actions */

   break;
}

Note the break at the bottom of the while block.

That's right: the while block isn't actually a loop at all - it's simply a device to get break to skip to the bottom of the block.

I'M NOT RECOMMENDING THIS. I think it's a horrible practice. It took me a good two hours to actually realise that it was, in fact, a goto.

When Dijkstra originally wrote his 'goto considered harmful' paper, he was pointing out the benefits of block control structures for those programmers using languages without them, or die-hard programmers not using those structures in the new languages. Uncontrolled, poorly-designed use of gotos is simply confusing - it's hard for a maintainer to know what's going on - but so is the misuse of any control structure. I don't recommend misusing exceptions in the way you suggest, either.

For more, see Gotos Considered Harmful and Other Programmers' Taboos[^].

Stability. What an interesting concept. -- Chris Maunder

Re: Jumping out of a heavily-nested looping noy by using "goto" statement?

peterchen25-Jul-04 6:13

peterchen

25-Jul-04 6:13

how about

do { // while 0, block to exit with break
  // same pain as above
} while(0);

we are here to help each other get through this thing, whatever it is Vonnegut jr.

sighist || Agile Programming | doxygen

Re: Jumping out of a heavily-nested looping noy by using "goto" statement?

Ravi Bhavnani25-Jul-04 12:01

Ravi Bhavnani

25-Jul-04 12:01

Mike Dimmick wrote:
horrible code structure
Yikes! Three nested if-elses would have sufficed, since that it in fact the programmer's intent.

Mike Dimmick wrote:
I don't recommend misusing exceptions in the way you suggest, either.
Neither do I, as I'm sure you'd surmise if you re-read the "if" preceding the "suggestion". Smile | :)

/ravi

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