C / C++ / MFC Discussion Boards

Re: the function CWnd::CreateControl succeeds, but m_hWnd is NULL

Sivaraman Dhamodharan25-Oct-12 23:05

25-Oct-12 23:05

Delete(Take a backup if you want) the .tli and .tlh from the debug folder and rebuild the project. Make sure the delete files are created again.

Then check the CreateControl function. Use the GetLastError() to examine what went wrong.

Programming Article

Re: the function CWnd::CreateControl succeeds, but m_hWnd is NULL

Falconapollo25-Oct-12 23:07

Falconapollo

25-Oct-12 23:07

Thanks for your reply. CreateControl succeeded with a return value:

C++

TRUE

;

What my question is: why the handle of

C++

wnd

is still

C++

NULL

Re: the function CWnd::CreateControl succeeds, but m_hWnd is NULL

David Crow26-Oct-12 4:58

David Crow

26-Oct-12 4:58

Falconapollo wrote:
I run the code wich VC++ 6.0, everything is OK. But when run the same code under Visual C++ 2010, the handle of
C++
wnd
(namely
C++
m_hWnd
) is always NULL.

Maybe something was fixed in subsequent versions of VS.

Have you tried making wnd a global variable or class member?

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Assigning Pointer To Object (Both of Same Class)

AmbiguousName24-Oct-12 21:41

AmbiguousName

24-Oct-12 21:41

Hello. I have a pointer which I want to assign to one of my member variables of class. Both the pointer and the object are of same type. How do I assign this pointer to this object. Here is what I mean

class ABC
{
  ClassName obj1; // object of a class

  void AssignValue(ClassName* ptrValue)
  {
    obj1 = ptrValue; // here I want to assign pointer to my object
  }
};

But I am getting this error saying No operator "=" matches the operands. What do I do? Thanks for any input.

This world is going to explode due to international politics, SOON.

Re: Assigning Pointer To Object (Both of Same Class)

Richard MacCutchan24-Oct-12 22:01

Richard MacCutchan

24-Oct-12 22:01

obj1 is an object, not a pointer. You need to change your definition to:

C++

ClassName* obj1; // pointer to object of a class

One of these days I'm going to think of a really clever signature.

Re: Assigning Pointer To Object (Both of Same Class)

AmbiguousName24-Oct-12 22:21

AmbiguousName

24-Oct-12 22:21

This is what I was talking about. Is there no way ( like: I could cast it somehow ) to assign this pointer to the object? I don't wan to change it.

This world is going to explode due to international politics, SOON.

Re: Assigning Pointer To Object (Both of Same Class)

Richard MacCutchan24-Oct-12 23:09

Richard MacCutchan

24-Oct-12 23:09

AmbiguousName wrote:
I don't wan to change it.

You have no choice; an object is not a pointer and cannot be cast as such. You also have the problem that obj1 will already have been instantiated in the constructor when your object is first created.

One of these days I'm going to think of a really clever signature.

Re: Assigning Pointer To Object (Both of Same Class)

Stefan_Lang25-Oct-12 0:33

Stefan_Lang

25-Oct-12 0:33

Well, you can cast a pointer to an object - in the same way that you can eat poisonous mushrooms: only once. Wink | ;)

(provided you manage to get past the compiler that is trying to save you from that embarassement)

Re: Assigning Pointer To Object (Both of Same Class)

Richard MacCutchan25-Oct-12 1:19

Richard MacCutchan

25-Oct-12 1:19

Well, yes you can do anything you like ... Wink | ;)

One of these days I'm going to think of a really clever signature.

Re: Assigning Pointer To Object (Both of Same Class)

Santhosh G_25-Oct-12 1:24

Santhosh G_

25-Oct-12 1:24

Please check this.

void AssignValue(ClassName* ptrValue)
  {
    ClassName& localObject = *ptrValue;// Here local object is created with same members of ptrValue
    obj1 = localObject; // here = operator will work, and copy all members to your new instance obj1.
  }

Re: Assigning Pointer To Object (Both of Same Class)

Stefan_Lang25-Oct-12 1:33

Stefan_Lang

25-Oct-12 1:33

~~Yes, I was about to suggest this, but~~ there is an error in this code: you cannot define a reference that is not const - it has to be

C++

const ClassName& localObject = *ptrValue;

[edit]forget what I wrote next...

Instead of your suggestion, you could just do the assignment directly:

C++

obj = *ptrValue;

Assuming that you have a valid implementation of the assignment operator, this should work.
[/edit]

modified 25-Oct-12 7:41am.

Re: Assigning Pointer To Object (Both of Same Class)

Richard MacCutchan25-Oct-12 1:38

Richard MacCutchan

25-Oct-12 1:38

According to the compiler this will not work because obj1 is not a modifiable lvalue; it is an existing object, and cannot be set to something else.

One of these days I'm going to think of a really clever signature.

Re: Assigning Pointer To Object (Both of Same Class)

Stefan_Lang25-Oct-12 1:52

Stefan_Lang

25-Oct-12 1:52

That is not my understanding, unless you are using a compiler where ClassName has a very specific predefined meaning. I was assuming that was just meant as a synonym for the actual class rather than a keyword. E. g. this should work:

C++

class foo {
int val;
public:
   foo(int v) : val(v) {}
   int get() const { return val;}
};
class ABC {
   foo obj1;
public:
   void AssignValue(foo* ptr) {
      obj1 = *ptr;
   }
};

At least my compiler accepts it.

Re: Assigning Pointer To Object (Both of Same Class)

Richard MacCutchan25-Oct-12 2:52

Richard MacCutchan

25-Oct-12 2:52

You are correct; I had to add default constructors (MS C++), but it then did what was required.

One of these days I'm going to think of a really clever signature.

Re: Assigning Pointer To Object (Both of Same Class)

Orjan Westin25-Oct-12 3:06

Orjan Westin

25-Oct-12 3:06

Yes, but this changes obj1, which may or may not be what the original question didn't want (if the object is expensive to copy, making it a pointer rather than object, as previously suggested, might be the better solution).

If AmbiguousName has worked more with C# or Java, where the references are implicit, working with pointers might be confusing.

Re: Assigning Pointer To Object (Both of Same Class)

Stefan_Lang25-Oct-12 3:30

Stefan_Lang

25-Oct-12 3:30

Well, not only his name is Ambigous, his inquiry is, too: it isn't clear whether his problem is that he cannot assign to obj1, or that he cannot assign it from a pointer. Anyway, the solutions have been pointed out, he just needs to pick the right one.

Re: Assigning Pointer To Object (Both of Same Class)

Chris Meech25-Oct-12 2:14

Chris Meech

25-Oct-12 2:14

Have you tried to change that line of code to this

obj1 = *ptrValue;

This will make your obj1 member variable be a copy of the object that is pointed to by ptrValue. Smile | :)

Chris Meech
I am Canadian. [heard in a local bar]

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Re: Assigning Pointer To Object (Both of Same Class)

David Crow25-Oct-12 2:40

David Crow

25-Oct-12 2:40

So have you tried creating an assignment operator in the ClassName class?

Re: Assigning Pointer To Object (Both of Same Class)

CPallini25-Oct-12 10:37

CPallini

25-Oct-12 10:37

AssignValue is a clear hint of what you intend to do: assign to the object obj1 the value held by the object pointed by ptrValue, hence

C++

void AssignValue(ClassName* ptrValue)
{
  obj1 = *ptrValue; // here obj1 value gets a copy of the object pointed by ptrValue.
}

Note you should define the ClassName assignment operator in order to make such code work.

Veni, vidi, vici.

Re: Assigning Pointer To Object (Both of Same Class)

Chris Meech26-Oct-12 2:44

Chris Meech

26-Oct-12 2:44

Much clearer answer, I think. Smile | :)

MenuItems' Icons are not Displaying properly in MFC

002comp24-Oct-12 18:56

002comp

24-Oct-12 18:56

Hello Friends

I was using code

C++

void CMainFrame::OnInitMenuPopup(CMenu* a, UINT b, BOOL c)
{
    FrameWnd::OnInitMenuPopUp( a,b,c);
}

And this one displaying MenuItems correctly.

Now,i trying to add icons to MenuItems.So for that I am using extenal CoolMenuManager to show up Icons with menuItems.

Here is code for this :

C++

void CMainFrame::OnInitMenuPopup(CMenu* a, UINT b, BOOL c)
{
   if(m_menuManager.InitMenuPopup(a,b,c))
    FrameWnd::OnInitMenuPopUp( a,b,c);
}
Now, in this case,If i use External fn then only icons are showing up. But as now, i am calling frameWnd::OnINitMenupopup too then icons are coming and strings are not coming properly and only for some menuItems and even menuList is coming Wider covering whle screen.

Any Ideas?

Regards
Yogesh

Re: MenuItems' Icons are not Displaying properly in MFC

Richard MacCutchan24-Oct-12 21:58

Richard MacCutchan

24-Oct-12 21:58

Without knowing what CoolMenuManager does it is impossible to even hazard a guess.

One of these days I'm going to think of a really clever signature.

Re: MenuItems' Icons are not Displaying properly in MFC

002comp24-Oct-12 22:22

002comp

24-Oct-12 22:22

Hello

I found something interesting tht icons and text of menuItem is coming fine Except the menuList. As i click on any menu,menuList pops up and that list is coming wider,covering almost full screen.

I checked that OnMeasureItem which calculates ItemWidth and height is Having some Prob.As I Converted this from VC6 to VS2010.

C++

BOOL CCoolMenuManager::OnMeasureItem(LPMEASUREITEMSTRUCT lpms)
{
	ASSERT(lpms);
	CMyItemData* pmd = (CMyItemData*)lpms->itemData;
	ASSERT(pmd);
	if (lpms->CtlType != ODT_MENU || !pmd->IsMyItemData())
		return FALSE; // not handled by me

	if (pmd->fType & MFT_SEPARATOR) {
		// separator: use half system height and zero width
		lpms->itemHeight = GetSystemMetrics(SM_CYMENU)>>1;
		lpms->itemWidth  = 0;

	} else {

		// compute size of text: use DrawText with DT_CALCRECT

		CWindowDC dc(NULL);	// screen DC--I won't actually draw on it
		CRect rcText(0,0,0,0);
		CFont* pOldFont = dc.SelectObject(GetMenuFont());
		dc.DrawText(pmd->text, rcText, DT_MYSTANDARD|DT_CALCRECT);
		dc.SelectObject(pOldFont);

		// height of item is just height of a standard menu item
		lpms->itemHeight= max(GetSystemMetrics(SM_CYMENU), rcText.Height());

		// width is width of text plus a bunch of stuff
		int cx = rcText.Width();	// text width 
		cx += CXTEXTMARGIN<<1;		// L/R margin for readability
		cx += CXGAP;					// space between button and menu text
		cx += m_szButton.cx<<1;		// button width (L=button; R=empty margin)

		// whatever value I return in lpms->itemWidth, Windows will add the
		// width of a menu checkmark, so I must subtract to defeat Windows. Argh.
		//
		cx -= GetSystemMetrics(SM_CXMENUCHECK)-1;
		lpms->itemWidth = cx;		// done deal

		CMTRACE(_T("OnMeasureItem for '%s':\tw=%d h=%d\n"), (LPCTSTR)pmd->text,
			lpms->itemWidth, lpms->itemHeight);
	}
	return TRUE; // handled
}

or u can refer to this link
http://www.codeforge.com/read/89577/coolmenu.cpp__html[^]

Regards
Yogesh

Re: MenuItems' Icons are not Displaying properly in MFC

002comp25-Oct-12 0:43

002comp

25-Oct-12 0:43

I found tht Drawtext with parameter DT_CALCRECT is not returning right parameters of rectangle.

Any Ideas ?

Re: MenuItems' Icons are not Displaying properly in MFC

Richard MacCutchan25-Oct-12 6:19

Richard MacCutchan

25-Oct-12 6:19

Sorry no, what values does it return and what values do you think it should return?

One of these days I'm going to think of a really clever signature.

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