C / C++ / MFC

Re: Getting access to a variable.

24-Jul-01 13:31

I need access to a CListBox variable which is in View.h, m_ctrlMyListBox, from various of my other classes. How can I get that?

Christian Graus24-Jul-01 14:13

Christian Graus

24-Jul-01 14:13

You can access your view from anywhere like this:

CFrameWnd *pFrameWnd = (CFrameWnd *)AfxGetMainWnd();
ASSERT (pFrameWnd != NULL && pFrameWnd->IsKindOf(RUNTIME_CLASS(CMDIFrameWnd)));
pFrameWnd = ((CMDIFrameWnd *)pFrameWnd)->GetActiveFrame();
CMyView * pView = (CMyView*)pFrameWnd->GetActiveView();

Christian

#include "std_disclaimer.h"

The careful application of terror is also a form of communication.

Eagles may soar, but weasels don't get sucked into jet engines.

How to populate a tree control

nulldreamer24-Jul-01 13:03

nulldreamer

24-Jul-01 13:03

Hi,
I have a dialog box, I've placed a tree control in it.
How can I populate that tree?I need to place items from a .dat file into that tree? I just don't know the basic syntax of doing it...
How do you add items?
Thanks!
P.S.
I'm new at this. Tried to use a sample from msdn, but the only thing that it does is gives me a tree with only "united states" in it.
Thanks again
// Gain a pointer to our tree control

CTreeCtrl* pCtrl = (CTreeCtrl*) GetDlgItem(IDC_TREE1);
ASSERT(pCtrl != NULL);

// Insert a root item using the structure. We must
// initialize a TVINSERTSTRUCT structure and pass its
// address to the call.

TVINSERTSTRUCT tvInsert;
tvInsert.hParent = NULL;
tvInsert.hInsertAfter = NULL;
tvInsert.item.mask = TVIF_TEXT;
tvInsert.item.pszText = _T("United States");

HTREEITEM hCountry = pCtrl->InsertItem(&tvInsert);

// Insert subitems of that root. Pennsylvania is
// a state in the United States, so its item will be a child
// of the United States item. We won't set any image or states,
// so we supply only the TVIF_TEXT mask flag. This
// override provides nearly complete control over the
// insertion operation without the tedium of initializing
// a structure. If you're going to add lots of items
// to a tree, you might prefer the structure override
// as it affords you a performance win by allowing you
// to initialize some fields of the structure only once,
// outside of your insertion loop.

HTREEITEM hPA = pCtrl->InsertItem(TVIF_TEXT,
_T("Pennsylvania"), 0, 0, 0, 0, 0, hCountry, NULL);

// Insert the "Washington" item and assure that it is
// inserted after the "Pennsylvania" item. This override is
// more appropriate for conveniently inserting items with
// images.

HTREEITEM hWA = pCtrl->InsertItem(_T("Washington"),
0, 0, hCountry, hPA);

// We'll add some cities under each of the states.
// The override used here is most appropriate
// for inserting text-only items.

pCtrl->InsertItem(_T("Pittsburgh"), hPA, TVI_SORT);
pCtrl->InsertItem(_T("Harrisburg"), hPA, TVI_SORT);
pCtrl->InsertItem(_T("Altoona"), hPA, TVI_SORT);

pCtrl->InsertItem(_T("Seattle"), hWA, TVI_SORT);
pCtrl->InsertItem(_T("Kalaloch"), hWA, TVI_SORT);
pCtrl->InsertItem(_T("Yakima"), hWA, TVI_SORT);

Re: How to populate a tree control

Doug Garno24-Jul-01 23:43

Doug Garno

24-Jul-01 23:43

Ah, the basic problem of the parent doesn't know that it has any children attached. Change your tvInsert.mask to include TVIF_CHILDREN and set the tvInsert.cChildren either true or false depending on if the parent has any children.

Another way is to create parents with no children, then when you add children to a parent, tell the parent that it now has children. When you add a child to a parent, call a function like UpdateParentItem( HTREEITEM hParent );

void UpdateParentItem( HTREEITEM hParent )
{
// Can't use ItemHasChildren() because it will always return
// the value of the item.cChildren variable.
// Need to get the first child and update the parent as needed.

// Getting the first child of a parent will always return either
// NULL if no children exist or the handle to the first child
// regardless of the item.cChildren variable.
HTREEITEM hChild = m_pTree->GetChildItem( hParent );

// Set up the item structure
TV_ITEM item;
ZeroMemory( &item, sizeof(TV_ITEM) );
item.hItem = hParent;
item.mask = TVIF_CHILDREN;
item.cChildren = hChild != NULL;

// Update the parent node to reflect the children state.
m_pTree->SetItem( &item );
}

Also make sure that when the tree control is created you set the TVS_HASBUTTONS or you will not see the plus/minus button on the parent. You would have to double click the parent to see if there is any children.

Multiple Inheritence and MFC

Stan Shannon24-Jul-01 10:24

24-Jul-01 10:24

What are the issues involved with using multiple inheritence on MFC classes such as CDocument?

if I wanted to do this:

class CMyDocument : public CDocument, public iSomeAbstractClass
{
...
};

where iSomeAbstractClass is just a pure virtual class.

Should that work? What problems might I expect? Currently, when I try this I get compile errors out of my ON_MESSAGE handlers in the CMyDocument Message Map. The issue seems to be that it cannot convert from CMyDocument* to CWnd*.

Tomasz Sowinski24-Jul-01 10:46

Tomasz Sowinski

24-Jul-01 10:46

ON_MESSAGE handler is for CWnd-derived objects only. CDocument is derived from CCmdTarget and can only have ON_COMMAND and friends in its message map.

The message handler macros in VC6 are not type safe, making CYourDoc a class with multiple bases only helps this error to surface at compile time.

Tomasz Sowinski -- http://www.shooltz.com

Stan Shannon24-Jul-01 11:52

24-Jul-01 11:52

Hmmm, thats very interesting. I actually inherited all this crap, er, I mean code when I took this job last year. I had never paid much attention to what the message maps they had in the document classes were doing. Now that you mention that, it makes perfect sense. Thanks.

Stan Shannon25-Jul-01 3:21

25-Jul-01 3:21

Tomasz, on further investigation I find that allowing a CDocument derived class to contain an ON_MESSAGE handler for another window appears to work fine, type safe or not. What our code does is this (I didn't write it!):

// In a seperate thread:
::PostMessage( hOurMainFrameWnd,AMessageID, NULL, NULL );

// Primary thread...
// COurDocument MESSAGE MAP...
ON_MESSAGE( AMessageID,OnMessage )

COurDocument ::OnMessage( .... )
{
// This is reached just fine.
}

We have worked our way around this issue, but I am just curious to know what your opinion is of this methodology? My input to my boss is that the CDocument/CMainFrame interaction here was bad design - but it does seem to work.

Tomasz Sowinski25-Jul-01 3:42

Tomasz Sowinski

25-Jul-01 3:42

1) I can't reproduce the behavior you've described. I've added ON_MESSAGE macro to CDocument-derived messagemap. It doesn't get called when I'm sending/posting the message. Could you have a look at the stack when breakpoint is hit inside CYourDoc::OnMessage?

2) Here's how ON_MESSAGE is defined in VC 6:

#define ON_MESSAGE(message, memberFxn) \
	{ message, 0, 0, 0, AfxSig_lwl, \
		(AFX_PMSG)(AFX_PMSGW)(LRESULT (AFX_MSG_CALL CWnd::*)(WPARAM, LPARAM))&memberFxn },
<pre>
The function should be a member of CWnd-derived class; I've heard that VC7 uses static_cast instead of old-style casting, your code may not compile under VC7.

3) There's a topic called "Message Categories" in VC help that explicitly says that non-CWnd objects derived from CCmdTarget can't handle messages other than WM_COMMAND. My understanding was that only WM_COMMAND is routed to document and app, but your experience denies that. I'd really like to see who's calling CYourDoc::OnMessage :-D

Tomasz Sowinski -- <a href="http://www.shooltz.com">http://www.shooltz.com</a>

Stan Shannon25-Jul-01 4:06

25-Jul-01 4:06

Very curious indeed. I'm actually surprised, and concerned, that ours is working (although my boss isn't). We have a work around for the original problem, so its no longer an issue (until VC7 I suppose!). But if I get time I am going to look into this, just to satisfy my curiosity.

Thanks much, Stan.

Fazlul Kabir24-Jul-01 11:19

Fazlul Kabir

24-Jul-01 11:19

Look at the MSDN tech note #16 on MI in MFC
Hope this helps.

_________________________________
Get RadVC today. Play RAD in VC++
http://www.capitolsoft.com

Stan Shannon24-Jul-01 11:54

Problem with child Wnd(dialogBox) Please HELP !!!! it is very URGENT !!!

24-Jul-01 11:54

Thanks. That's pretty much exactly what I was hoping to find.

24-Jul-01 10:17

This is my code:
-----------------------------------
void CMainDlg::OnButtonData()
{
CDemo dlg;
dlg.DoModal();

}
----------------------------------
and all is right.(not warnings or errors by compailer)
but when I press on cancle in run time in the Demo dialog I gets error message:
"illegal operation..." and all the program shut down .

This is the cod of OnCancle:
______________________________________
void CDemo::OnCancel()
{
// TODO: Add extra cleanup here

CDialog::OnCancel();

}
_______________________________________

Maybe it is because I need to give the constructor of Demo dlg the pointer to main CWnd ??? How do I this ???

Re: Problem with child Wnd(dialogBox) Please HELP !!!! it is very URGENT !!!

Not Active24-Jul-01 10:29

Not Active

24-Jul-01 10:29

You don't need to pass in the HWND, if NULL it just uses the desktop window.

Are there any controls on the demo dialog that may not be created or instantiated correctly?

Re: Problem with child Wnd(dialogBox) Please HELP !!!! it is very URGENT !!!

Jake Palmer24-Jul-01 10:36

Jake Palmer

24-Jul-01 10:36

This might not matter at all, but people generally call DoModal in an "if" statement, such as:

if (dlg.DoModal() == IDOK)
{
//do stuff
}
This way, when they hit cancel the program doesn't try to do anything you don't want. It seems like there might be some code that you only want executed when they click "OK", so you might try putting that inside the if block.
Jake

Blinking Static Text

John Uhlenbrock24-Jul-01 10:13

24-Jul-01 10:13

As I understand it the easiest way to get blinking static text, is to create a class who's base class is CStatic. I have overrridden the WM_TIMER message handler, and created a member function, StartBlink(). I have a boolean variable that determines whether the text is shown or not, and I try to simply use ShowWindow() to get a blinking affect. My code:

void CStaticBlink::OnTimer(UINT nIDEvent) 
{
  if(m_bVisible == TRUE)
    ShowWindow(SW_HIDE);
  else
    ShowWindow(SW_SHOW);
		
  m_bVisible = !m_bVisible;

  CStatic::OnTimer(nIDEvent);
}

void CStaticBlink::StartBlink()
{
  SetTimer(1, 500, NULL);
}

What am I missing, using the debugger, I never make it into OnTimer()

Christian Graus24-Jul-01 11:31

Christian Graus

24-Jul-01 11:31

I dunno, because I did this:

void CBlinkStatic::OnTimer(UINT nIDEvent) 
{
	if (nIDEvent == 42)
	{
		ShowWindow(m_bBlink ? SW_SHOW : SW_HIDE);
		m_bBlink = ! m_bBlink;
	}
	
	CStatic::OnTimer(nIDEvent);
}

void CBlinkStatic::StartBlink(int speed)
{
	SetTimer(42,speed,NULL);
}

and it works a treat. Are you sure your start method is called ?

Christian

#include "std_disclaimer.h"

The careful application of terror is also a form of communication.

Eagles may soar, but weasels don't get sucked into jet engines.

John Uhlenbrock24-Jul-01 12:28

24-Jul-01 12:28

Yeah, I did that exactly, and made sure I called the start function, and made sure the control variable was of the correct class.

// Dialog Data
//{{AFX_DATA(CProgressDlg)
  enum { IDD = IDD_PROGRESS_DLG };
  CStaticBlink	m_ctrlDownload;
//}}AFX_DATA

void CStaticBlink::OnTimer(UINT nIDEvent) 
{
  if(nIDEvent == 42)
  {
    ShowWindow(m_bVisible ? SW_SHOW : SW_HIDE);
    m_bVisible = ! m_bVisible;
  }
	
  CStatic::OnTimer(nIDEvent);
}

void CStaticBlink::StartBlink()
{
  SetTimer(42, 500, NULL);
}

void CProgressDlg::LoadDialog()
{
  m_ctrlErrorCheck.StartBlink();
}

Christian Graus24-Jul-01 12:45

Christian Graus

24-Jul-01 12:45

And you traced to ensure that StartBlink is called ? If so, I am at a loss ? I created the code I posted and ran it and it worked a treat, like I said. There is no reason I can see for it not to.

BTW it can be any number, I only choose 42 because it's the answer to the ultimate question. Just so I've not muddied the waters needlessly Smile | :)

Christian

#include "std_disclaimer.h"

The careful application of terror is also a form of communication.

Eagles may soar, but weasels don't get sucked into jet engines.

John Uhlenbrock25-Jul-01 6:52

25-Jul-01 6:52

Ok its a different problem than we thought. The Timer and blinking code was fine. The situation is this. My program error checks a file (which takes 5 seconds or so) and three other comparable (length) operations, before it downloads this file to a device. So, I figured a progress bar would be overboard for the 5 second operations, but do have one for the download. I thought I would just blink text when the program is doing each operation. Well if I run the program all the way through, the text starts blinking AFTER all the operations and download is complete. So it seems as though my download isn't allowing other "things" to run in side my application while it is downloading, though all other windows apps are unaffected.

Do I need to send some sort of update message or something?

Thanks for all your help.

John Uhlenbrock25-Jul-01 7:10