scrolling logic - C / C++ / MFC Discussion Boards

RChin2-Dec-03 22:32

2-Dec-03 22:32

Best Friend wrote:
button

What button? Your button, my button, everyone's button?

Best Friend wrote:
program @ file

What's program @ file? Is this a new computer term I've yet to grasp?

---
Your question is not quite coherent, my Best Friend, but are you by any chance
talking about using the ::ShellExecute() API to launch the windows program associated with the given filename?

If so then your question has been answered. Smile | :)

I Dream of Absolute Zero

Simple dialo app, memory leak

J.B.2-Dec-03 21:13

J.B.

2-Dec-03 21:13

Hi guys,
I have just learned how to create a dialog-based application with mutiple child dialogs. So far it works fine, however, in Debug window, I always received memory leak warning upon the app exit :

Detected memory leaks!
Dumping objects ->
childdlg.cpp ........

I am just wondering what could cause this?
Basically, say, I have a parent dialog class, say CMyDlg and a child dialog class called CChildDlg. The child class was included on the top of MyDlg.cpp file

#include <ChildDlg.h>

CChildDlg *vChildDlg;

I embedded the child dialog into parent by putting the following codes in OnInitDialog() of the parent's cpp file, MyDlg.cpp.

vChildDlg = CChildDlg();
vChildDlg->Create(IDD_CHILD_DIALOG, this);
vChildDlg->SetWindowPos(this, 20, 20, 50, 50);
vChildDlg->ShowWindow(SW_SHOW);

That looks pretty straight forward. But why on the app's exit, it causes memory leak? Is there something I need to do perhaps in the parent and child class' destructor?

Thanks

Re: Simple dialo app, memory leak

Anonymous2-Dec-03 21:22

Anonymous

2-Dec-03 21:22

the line
vChildDlg = CChildDlg();
creates an instance of CChildDlg.
You need to delete this instance of vChildDlg when the app exits.

Re: Simple dialo app, memory leak

J.B.2-Dec-03 21:43

J.B.

2-Dec-03 21:43

Thank you guys.

I realise I originally placed "delete vChildDlg" in the parent's destructor, which however, was never called. Because the program exit with exit() associated to the exit button in the child dialog.

Re: Simple dialo app, memory leak

Marek Grzenkowicz2-Dec-03 21:23

Marek Grzenkowicz

2-Dec-03 21:23

Don't you use new without delete?

"Gods die, when their believers are gone." --from Sandman by Neil Gaiman

how to get the message for window show?

zecodela2-Dec-03 20:57

zecodela

2-Dec-03 20:57

hi,
i want to know how to get the message after window has been shown. i have checked out with OnShowWindow, WindowPosChanged ... seems that all can report me the Window is about to be shown. that's not ok... as i want to do sth after the window already being seen by the user.
any help?
thanks,
jim

Re: how to get the message for window show?

BaldwinMartin2-Dec-03 22:50

BaldwinMartin

2-Dec-03 22:50

OnDestroy()

Best Wishes and Happy Holiday's,
ez_way

scrolling logic

R. Thomas2-Dec-03 20:48

R. Thomas

2-Dec-03 20:48

hi..

void CEditorView::OnInitialUpdate()<br />
{<br />
	CScrollView::OnInitialUpdate();<br />
<br />
	//CSize sizeTotal;<br />
	// TODO: calculate the total size of this view<br />
	//sizeTotal.cx = sizeTotal.cy = 100;<br />
	//SetScrollSizes(MM_TEXT, sizeTotal);<br />
	SetScrollSizes(MM_LOENGLISH, CSize(2020, 1020));<br />
}<br />

in the above code..i wanna know when i set the mapping mode to MM_LOENGLISH, the param that i supply...are they depicted in mapping mode as i entered??or are they changed to mapping mode params and then entered??
for eg..above is the mapping mode taken in, is it exacly 2020 and 1020 in MM_LOENGLISH???
or is it converted to LOENGLISH and the value has changed to LOENGLISH and is no longer 2020 by 1020???
i gues its a more of my understanding prob...can someone pls help???tks.... Smile | :)

Have a Super Blessed Day!
-------------------------
For God has not given us a spirit of fear, but of power and of love and of a sound mind.
2 Timothy 1:7
"For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life."
John 3:16
"Therefore you also be ready, for the Son of Man is coming at an hour you do not expet."
Luke 12:40

mapping mode prob?

R. Thomas2-Dec-03 20:40

R. Thomas

2-Dec-03 20:40

hi...i am facing a small prob..

void CEditorView::OnDraw(CDC* pDC)<br />
{<br />
	CEditorDoc* pDoc = GetDocument();<br />
	ASSERT_VALID(pDoc);<br />
	<br />
	//<br />
	//Set the mapping mode to LOENGLISH<br />
	//<br />
	pDC->SetMapMode(MM_LOENGLISH);<br />
<br />
	//<br />
	//Convert arguments to coordinates to MM_LOENGLISH units.<br />
	//<br />
	CPoint pos;<br />
	pos.x = pDoc->GetGridWidth()*100;<br />
	pos.y = pDoc->GetGridHeight();<br />
	pDC->DPtoLP(&pos);<br />
<br />
	//<br />
	//Draw the square the has to bound the grid<br />
	//<br />
//	CRect rect(10, -10, pos.x, pos.y);//getting wrong rect in this way..WHY?<br />
	CRect rect(10, -10, 2000, -1000);<br />
	pDC->Rectangle(rect);//rectangle drawn ok..,

when i do this
CRect rect(10, -10, pos.x, pos.y);
the rectangle that is drawn isboundless...i.e no mater how long i put the scroll bars..i still cant see the end of therect..wherea as if i do this
CRect rect(10, -10, 2000, 1000);
i can see the rectangle...
why is that???why cant i see the rect when iuse the first method??
tks for any help...

Have a Super Blessed Day!
-------------------------
For God has not given us a spirit of fear, but of power and of love and of a sound mind.
2 Timothy 1:7
"For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life."
John 3:16
"Therefore you also be ready, for the Son of Man is coming at an hour you do not expet."
Luke 12:40

How do I make wrapper funtion such as "sprintf" without using "va_arg"?

dowa2-Dec-03 19:53

dowa

2-Dec-03 19:53

Hi, all

I want to make wrapper member function

like this,

class A
{
int Xsprintf (char * pszDest,const char * pszFormat, ...)
{
// this might not right, but I want like this...
sprintf( pszDest, pszFormat, ... );
}
};

How do I can this?
thanks!

Re: How do I make wrapper funtion such as "sprintf" without using "va_arg"?

Anonymous2-Dec-03 21:33

Anonymous

2-Dec-03 21:33

Only way to avoid using va-arg, is to avoid variable number of arguments.

If you have some specific setups, you could say

XSprintf(char * output, char * format, int I1, int I2){
sprintf(output, format, I1, I2);
}

and

XSprintf(char * output, char * format, int I1, int I2, int I3){
sprintf(output, format, I1, I2, I3);
}

but this is not very flexible. For every kind of argument, you need new Xsprintf definition. May be good enough, tho.

Re: How do I make wrapper funtion such as "sprintf" without using "va_arg"?

BaldwinMartin2-Dec-03 23:01

BaldwinMartin

2-Dec-03 23:01

Create an ovcerload for sprintf in your project.
In stdio.h sprintf has only one prototype so

int CYourAppSDI::sprintf(CString str)
{

}

would work or
int CYourAppSDI::sprintf(int nVar)
{

}
would work or

int CYourAppSDI::sprintf(CString str,int nVar)
{

}
would work right?

Now their are some good replacements for sprintf on this site and others.
So all you have to do is write or copy the code inside your overload.

Best Wishes and Happy Holiday's,
ez_way

Re: How do I make wrapper funtion such as "sprintf" without using "va_arg"?

David Crow3-Dec-03 3:39

David Crow

3-Dec-03 3:39

This was talked about (unsuccessfully) here.

Five birds are sitting on a fence.
Three of them decide to fly off.
How many are left?

Re: How do I make wrapper funtion such as "sprintf" without using "va_arg"?

Tim Smith3-Dec-03 4:24

Tim Smith

3-Dec-03 4:24

Review your design constraints. By excluding the use of va_arg, you are making the problem very hard if not impossible (excluding the use of hacks and kludges).

Don't shoot yourself in the foot by using silly design constraints.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

GetUserName() fails in ATL COM object

bryces2-Dec-03 19:47

bryces

2-Dec-03 19:47

Hi All,

Does anyone know why I would get a first chance exception occur when I try to get the current Username in a COM object I have? the error message is as follows:

First-chance exception in app.exe (SECUR32.DLL): 0xC0000005: Access Violation.
The program 'C:\app.exe' has exited with code 0 (0x0).

when all I am trying to do is

LPTSTR username;
DWORD cchBuff = 1024;
BOOL result = GetUserName(username, &cchBuff);

thanks for your help

cheers
Bryce

Re: GetUserName() fails in ATL COM object

Michael P Butler2-Dec-03 20:20

Michael P Butler

2-Dec-03 20:20

bryces wrote:
LPTSTR username;
DWORD cchBuff = 1024;
BOOL result = GetUserName(username, &cchBuff);

Well off the top of my head,

Doesn't GetUserName require the buffer to have the memory allocated for the username string?

I'd double check on MSDN.

Michael

Blue canary in the outlet by the light switch
Who watches over you
Make a little birdhouse in your soul - They Might Be Giants

Re: GetUserName() fails in ATL COM object

bryces2-Dec-03 21:09

bryces

2-Dec-03 21:09

Hi Michael,

Thanks, you are indeed correct.

below is what is needed to be done:

<br />
LPTSTR username;<br />
DWORD cchBuff = 1024;<br />
TCHAR tchBuffer[1024];   <br />
<br />
username = tchBuffer; //this is what I was missing... <br />
BOOL result = GetUserName(username, &cchBuff);<br />

cheers
Bryce

Re: GetUserName() fails in ATL COM object

BaldwinMartin2-Dec-03 23:21

BaldwinMartin

2-Dec-03 23:21

#define MAX_LEN 255
CString str;
char ch[MAX_LEN];
DWORD dwNameSize = MAX_LEN;
GetUserName(ch, &dwNameSize);

Best Wishes and Happy Holiday's,
ez_way

gripper in top left corner of resiable combo box

Suneet Chandok2-Dec-03 19:08

Suneet Chandok

2-Dec-03 19:08

Hi Guys
I have made my custom resizable combo box. I want to display a gripper in top right corner but windows don't has any in built style for that.
Can anyone guide me how to bring a gripper in top right corner.
can we rotate it some how using the funtion : SetWorldTransform
or is there some other possible way out

Display a MessageBox in CDialog::OnActivate()

Chris Ormerod2-Dec-03 18:16

Chris Ormerod

2-Dec-03 18:16

First of all I am new to C++ and in particular MFC, but I am making some minor changes to a project that I downloaded from here and the final change I need to make is to ask the user a question right after the dialog has loaded. In Visual FoxPro I would put this in the Activate of the Dialog, but in MFC this causes a multitude of issues such as:

1. The dialog doesn't actually display, so there is just a MessageBox in the middle of the screen. - The dialog displays after I click OK on the message which is understandable.
2. The Activate runs many times while the dialog is loading which causes any code I put in there to run many times (I put a flag in there to make it run only once.)

My OnActivate is shown bellow:

<br />
afx_msg void CdotNetInstallerDlg::OnActivate(UINT nState, CWnd* pWndOther, BOOL bMinimised)<br />
{<br />
	CDialog::OnActivate(nState, pWndOther, bMinimised);<br />
<br />
	// Chris Ormerod 3/Dec/2003<br />
	if (m_bRunFromReboot)<br />
	{<br />
                // Make sure it doesn't run again.<br />
		m_bRunFromReboot = false;<br />
		if (MessageBox("Continue with installation?", "Requirements Checker", MB_YESNO | MB_ICONQUESTION) == IDYES)<br />
			ResumeInstall();<br />
	}<br />
	return;<br />
}<br />

Can somebody please tell me where I should put this code? I have figured that putting it in OnActivate is probably wrong.

Thanks,

Chris Ormerod

Re: Display a MessageBox in CDialog::OnActivate()

Chris Ormerod2-Dec-03 18:22

Chris Ormerod

2-Dec-03 18:22

Thanks to GeMe_Hendrix about 10 posts below this one I have the answer (I should look before I post):

Try creating your own custom message ad handler for it first therefore at the top of your dialog CPP file...

#define WM_MYOWNMESSAGE WM_USER + 1001;

... Then in the header file put...

afx_msg LRESULT OnMyOwnMessage(WPARAM wParam, LPARAM lParam);

...Then the appropriate body for it...

LRESULT CMyDialog::OnMyOwnMessage(WPARAM wParam, LPARAM lParam)
{
... Show the file dialog box (I know it has to be modal)
return 0;
};

... And finally in the body put...

ON_MESSAGE(WM_MYOWNMESSAGE, OnMyOwnMessage)

... in the BEGIN_MESSAGE_MAP section...

... To call the message handler put this in the OnInitDialog function just before it returns...

PostMessage(WM_MYOWNMESSAGE, 0, 0);

And as a bonus I got an explanation of the message queue.

Chris.

Question regarding inheritance

lsanil2-Dec-03 17:24

lsanil

2-Dec-03 17:24

Hi All,

I have a question on the following code.

class ClassA<br />
{<br />
   virtual void TestA()=0;<br />
};<br />
<br />
class ClassB: public ClassA<br />
{<br />
  virtual void TestA();<br />
  ClassB();<br />
  virtual ~ClassB();<br />
  void PrintB();<br />
};<br />
<br />
void ClassB::TestA()<br />
{<br />
  cout << "TestA is Called from ClassB"<<endl;<br />
  return;<br />
}<br />
<br />
void ClassB::PrintB()<br />
{<br />
  cout << "PrintB is called" << endl;<br />
  return;<br />
}<br />
<br />
class ClassC: public ClassA<br />
{<br />
  virtual void TestA();<br />
  ClassC();<br />
  virtual ~ClassC();<br />
  void PrintC();<br />
};<br />
<br />
void ClassC::TestA()<br />
{<br />
  cout << "TestA is Called from ClassC" << endl;<br />
  return;<br />
}<br />
<br />
void ClassC::PrintC()<br />
{<br />
  cout << "PrintC is called" << endl;<br />
  return;<br />
}<br />
<br />
ClassA *pB;<br />
ClassA *pC;<br />
<br />
pB = new ClassB();<br />
pC = new ClassC();<br />
<br />
pB->TestA(); //works fine<br />
pC->TestC(); //works fine<br />
<br />
//Compilation Errors<br />
pB->PrintB();<br />
pC->PrintC();

In the above code, I am getting compilation errors as commented in the code. Is there anyway of calling methods of inherited class with a pointer to the base class?

My requirement is to call appropriate inherited class at runtime basing upon the user input with a single pointer to a base class. i.e

ClassA *pGeneric;<br />
if(user_input == 1)<br />
 pGeneric = new ClassB()<br />
else<br />
 pGeneric = new ClassC();

This works when the both inherited classes have the same methods but fails if inherited class an extra method. Is there any way to call one of the inherited classes during runtime with a SINGLE pointer to base class?

First of all, I want to know is it possible to do in C++? If it is possible, please suggest me the approach to take.
Please help me out. Please suggest me any other methods that provide the same functionality.

Thanks in Advance,
Anil

Re: Question regarding inheritance

Christian Graus2-Dec-03 17:29

Christian Graus

2-Dec-03 17:29

you can use dynamic_cast to see if the class is indeed of a particular derived type, then cast it to make the call. If you want the functionality to be available from a base class instance, the method needs to be in the base class.

Christian

I have drunk the cool-aid and found it wan and bitter. - Chris Maunder

Re: Question regarding inheritance

lsanil2-Dec-03 18:57

lsanil

2-Dec-03 18:57

Hi Chris, Thank you for your email. Could you please tell me how to declare the pointer variable for dynamic cast?

Thanks,
Anil

Re: Question regarding inheritance

lsanil2-Dec-03 19:05

lsanil

2-Dec-03 19:05

Hi Chris,

I found information about dynamic cast in MSDN. Thank you very much!!
Anil

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