C / C++ / MFC

Re: Adding a new button to and existing CMFCRibbonBar "tab"

6-Dec-15 23:25

I now have a simple MFC example which demonstrates my issue.
Is it possible for me to upload this somewhere hoping that someone can pinpoint where I’ve gone wrong and help correct it.
Thanks.
Steve.

-- modified 7-Dec-15 5:49am.

S.T.K10-Dec-15 2:37

Re: Adding a new button to and existing CMFCRibbonBar "tab"

10-Dec-15 2:37

Can anyone help me?
I am still unable to add to a ribbonbar “tab”.
Here is an example bit of code, which when added to a new MFC MDI basing ribbon example generated from the wizard works correctly until I add the bit at the bottom.

Add to MainFrm.h

C++

// Implementation
public:
    void CMainFrame::CreateAddtoTabs();
    void CMainFrame::AddToExistingTab();
    void CMainFrame::DoIWork(UINT ID);
public:
    CMFCRibbonButton  *pQuickMenu;
	CMFCRibbonBar     m_wndRibbonBar;

Add to MainFrm.cpp

BEGIN_MESSAGE_MAP(CMainFrame, CMDIFrameWndEx)
    ON_COMMAND(2000,&CMainFrame::AddToExistingTab)
    ON_COMMAND_RANGE(1000,1001,&CMainFrame::DoIWork)
END_MESSAGE_MAP()

//Replace the existing InitializeRibbon routine.

C++

void CMainFrame::InitializeRibbon()
{
	BOOL bNameValid;

	CString strTemp;
	bNameValid = strTemp.LoadString(IDS_RIBBON_FILE);
	ASSERT(bNameValid);

	// Load panel images:
	m_PanelImages.SetImageSize(CSize(16, 16));
	m_PanelImages.Load(IDB_BUTTONS);

	// Init main button:
	m_MainButton.SetImage(IDB_MAIN);
	m_MainButton.SetText(_T("\nf"));
	m_MainButton.SetToolTipText(strTemp);

	m_wndRibbonBar.SetApplicationButton(&m_MainButton, CSize (45, 45));
	CMFCRibbonMainPanel* pMainPanel = m_wndRibbonBar.AddMainCategory(strTemp, IDB_FILESMALL, IDB_FILELARGE);

	CreateAddtoTabs();
}

//Include new routines in MainFrm.cpp

void CMainFrame::CreateAddtoTabs()
{
    pQuickMenu = new CMFCRibbonButton(1000,TEXT("QuickMenu"),NULL,0,0,0,0);
    AddToExistingTab();
    m_wndRibbonBar.AddToTabs(pQuickMenu);
}

void CMainFrame::AddToExistingTab()
{
    pQuickMenu->AddSubItem(new CMFCRibbonButton(1001,TEXT("Do I work?"),NULL,0,0,0,0),-1);
}
void CMainFrame::DoIWork(UINT ID)
{
    MessageBox(TEXT ("Yes I Do!"),TEXT("Do I Work?"), MB_ICONWARNING) ;
}

If I add the above strucutre to a ribbon based MDI MFC application, a new “QuicMenu” tab appears on the menu system. It works. If I click the “Do I work?” menu entry then it pops up a panel saying “yes I do!”

If I now add a button to the ribbonbar at time of initialisation, which when clicked will adds a new button to the “QuickMenu” menu then all is good. The additional button turns up and is selectable.

void CMainFrame::InitializeRibbon()
…
…
…
…

    CMFCRibbonCategory *pCat = m_wndRibbonBar.AddCategory(TEXT("Update AddToTabs"),0,0,CSize(16,16),CSize(32,32),-1,0);
    CMFCRibbonPanel *pPan = pCat->AddPanel(TEXT("Single Button"),0,0);
    pPan->Add(new CMFCRibbonButton(2000,TEXT("Click to add to quickmenu"),0,0,0,0,0));

    CreateAddtoTabs();
}

But when I select this new menu entry from the “quickmenu”, the click is registered but in the lower MFC code it fails to recognise a valid ribbonbar handle and exists without processing the message (see my first post for more info).

Can anyone help?
I am realy stuck and may have to scrap the ribbon and revert to basic menus only if I can not dynamicaly add to my quickmenu as rquired.

What am I missing or overlooking when I'm adding to my QuickMenu structure?

Any help would be appreciated.
Thanks.
Steve.

S.T.K17-Dec-15 23:55

C++ - Accessibility of object after deletion. (illegal still working), why this is happening?

17-Dec-15 23:55

Here is a link to a visual studio project which demonstrates my issue. If anyone can explain why the clicking of the button on the ribbon generates a new menu entry which does not get acted upon I would be very grateful.

https://onedrive.live.com/redir?resid=96603E24528956FC!133&authkey=!AAopnvy2aTNr1tY&ithint=file%2czip[^]

Thanks

Steve.

Satish Shankar Jagtap3-Dec-15 23:54

Satish Shankar Jagtap

3-Dec-15 23:54

In my project I created object for class using new operator. After use I deleted that object and set that to NULL. But even after deletion, I could able to access and able to run other functions using that (deleted)object.

Please go through example:

CTemp *objTemp = new CTemp;

objTemp->Fun1();

delete objTemp;
objTemp = NULL;

objTemp->Fun2(); // It is illegal still works, why?

Why this is happening?

modified 4-Dec-15 6:09am.

Re: C++ - Accessibility of object after deletion. (illegal still working), why this is happening?

CPallini4-Dec-15 0:17

CPallini

4-Dec-15 0:17

Because the method is generated for the class, not for the instance of the class (that is you don't delete code).

Re: C++ - Accessibility of object after deletion. (illegal still working), why this is happening?

Jochen Arndt4-Dec-15 1:45

Jochen Arndt

4-Dec-15 1:45

In addition to the answer by CPallini:

It will only work when your CTemp::Fun2() function does not access non-static member variables or call other member functions that would do so. Then the implicit this pointer will be used which is NULL generating an access violation.

Re: C++ - Accessibility of object after deletion. (illegal still working), why this is happening?

CPallini4-Dec-15 9:18

CPallini

4-Dec-15 9:18

Of course. Thumbs Up | :thumbsup:

Floating point conversion

Still learning how to code3-Dec-15 22:19

Still learning how to code

3-Dec-15 22:19

I am in the process of trying to code the transmission of floating point data over an ethernet cable. I decided to send two bytes, the first with the "whole" part and the second with the "fractional" part (but as an unsigned char). The first byte works fine, but the second (trivial) part is giving me a strange (to me) problem which is driving me nuts - I can't see WHAT I'm getting wrong. Here is the test code:-

float flTest = 0.04;
float flResult;
flResult = flTest * 100;
unsigned char ucResult;
ucResult = (unsigned char)flResult;

flResult ends up as 4.00000 which is correct, but ucResult gives 3 !!
If I change flTest to 0.05, ucResult is 4 !!

There is clearly a decrementation involved here, but I can't understand why !

I'm sure that when some kind soul explains it, I shall be kicking myself - HARD !!

Doug

Michael_Davies3-Dec-15 22:29

Michael_Davies

3-Dec-15 22:29

Hate float, try decimal. every time I have used float, the results are unpredictable for what seems like straight forward math, decimal behaves itself.

Richard MacCutchan3-Dec-15 22:40

3-Dec-15 22:40

Float (and double) do exactly what they are supposed to do. The problem is that too many users do not understand how to use it.

Michael_Davies4-Dec-15 21:08

Michael_Davies

4-Dec-15 21:08

Granted. In this case he is not getting the results he is seeking float may be the problem...

Richard MacCutchan4-Dec-15 22:12

4-Dec-15 22:12

Michael_Davies wrote:
float may be the problem.

No, the problem is he does not understand how float values are represented in computers.

Richard MacCutchan3-Dec-15 22:39

3-Dec-15 22:39

There is no decrementation, you just need to understand What Every Computer Scientist Should Know About Floating-Point Arithmetic[^].

What you should do to transfer the data (via serial or internet) is to transfer the exact bytes of the data, rather than trying to convert them to something else. So take the address of the number, cast that to an unsigned char* and send the four bytes thus pointed at. This will ensure that your receiver will get the exact data that you send.

Jochen Arndt3-Dec-15 23:10

Jochen Arndt

3-Dec-15 23:10

Still learning how to code wrote:
flResult ends up as 4.00000 which is correct

That is not correct. The problem occurs when assigning 0.04 because the binary representation of floating point values can be slightly inexact. In your case flTest will be set to the value 0.0399999991. The following multiplication by 100 will not add another error so that flResult becomes 3.99999991.

Because there is no rounding when casting floating point values to integers, the result is 3. To avoid this, you can add 0.5 before casting:

ucResult = (unsigned char)(flResult + 0.5f);

Note that the above is for positive numbers only. With negative numbers, 0.5 must be subtracted.

Still learning how to code

Still learning how to code5-Dec-15 0:29

5-Dec-15 0:29

First of all, apologies for not replying earlier !
WOW, I didn't think that a few lines of code could provoke so much discussion !!!

The technique that I am trying to employ is between a PC and an Arduino (via Com port - actually USB). I used it a few years ago to transfer floating point numbers, but in the OPPOSITE direction and it worked perfectly.

Anyway, thank you all for your comments - I am amazed that the "error" is actually in the assignment as pointed out by Jochen. In this particular application, the floating point numbers will be quite small, so I think that I'll have to go for the 4 byte transfer method to maintain accuracy - but I'll be doing a lot of testing !! Thank you all once again !

Doug

CPallini3-Dec-15 23:30

CPallini

3-Dec-15 23:30

If you need to transmit a float value on the net then do transmit it, that is send its binary representation (e.g 4 bytes for a float, 8 for a double).

k50544-Dec-15 4:21

k5054

4-Dec-15 4:21

That's assuming that you have similar processors at both ends of the connection. While big-endian systems are rare these days, they're not non existent. Furthermore, be careful when going between 32-bit and 64-bit systems. On my x86 linux boxes, a long is 4 bytes, whereas on a x86_64 they're 8 bytes, x86 long-double is 12 bytes and x86_64 its 16.

IEEE 754-1985

enhzflep4-Dec-15 5:43

enhzflep

4-Dec-15 5:43

Are you remembering to take into account the established standard for floating point numbers?
The relevant section of the standard, at wikipedia: https://en.wikipedia.org/wiki/IEEE_floating_point#Interchange_formats[^]

S.T.K8-Dec-15 3:19

Re: Comboboxx issue in MFC

8-Dec-15 3:19

I am not seeing this issue.
I get 4 for unResult.

Do you have your floating point options set correctly in the compiler?

In visual studio, select properties on your C project. Expand the projects setting out for "c/C++->Code Generation" and set the option for "Floating Point Model" to Precise(/fp:precise).

Comboboxx issue in MFC

Amrit Agr3-Dec-15 2:48

Amrit Agr

3-Dec-15 2:48

I have a combobox in a mfc application. I created it at runtime with following code -
if (!m_sortBox.Create(WS_CHILD | WS_VISIBLE | CBS_DROPDOWNLIST, rect, this, eSortBox))

return FALSE;

Now the requirements, if user is selecting an item from combobox like , if combo box have focus & user is pressing up/down arrow key, it should NOT update the data.
If user is pressing enter key after selecting a item, it should update data.

So i didn't handled OnSelchange here.

For enter key requirement, I checked enter key event in preTranslateMsg & checking if combo box have focus, it should trigger the function, who will eventually update the data.
if (pMsg->message == WM_CHAR && pMsg->wParam == VK_RETURN)
{
CWnd pActiveWnd = CWnd::FromHandle(GetFocus()->GetSafeHwnd());
CWnd pcbSortBoxWnd = CWnd::FromHandle(m_sortBox.GetSafeHwnd());

    //If sort combo box has focus and user press Enter key, it should trigger OnComboSelChange event
    //Eventually it will update the data.
    if (pcbSortBoxWnd == pActiveWnd)
        OnSortChange();

}

I also handled ON_CBN_CLOSEUP(eSortBox, OnSortChange)
So that mouse functionality will work(because with mouse, data should get update)

Now my logic is working but its crashing in some cases.
Like - If I press Alt + Down arrow key, which will expand combobox, I select an item(with help of arrow keys) and press enter.

Sometimes its getting crash.

please help me out.

Regards,
Amrit Agrawal

Richard MacCutchan3-Dec-15 3:50

Visual Studio error LNK2005: variable XXX redefined in xxx.obj

3-Dec-15 3:50

Amrit Agr wrote:
Sometimes its getting crash

Then you need to use your debugger to try and identify where the crash occurs, and why.

Javier Luis Lopez26-Nov-15 0:09

Javier Luis Lopez

26-Nov-15 0:09

I tried to isolate the problem

It appears when a global variable is declared at the .h header file and the header file is called from 2 or more cpp files, as example I tried to link the following 3 files:

C++

//==File: header.h 
#pragma once
#include <stdio.h>

int variable;
//==end header.h

//==File: main.cpp
#include "header.h"
void main()
{
	variable=0;
}
//==end main.h

//File: source2.cpp 
#include "header.h"

void change()
{
	variable=0;
}
//==end source2.cpp

Then the following LINKER error appear:
1>source2.obj : error LNK2005: redefined "int variable" (?variable@@3HA) in main.obj

The only way I could "fix" the problem is in project properties> linker>command line add:
/FORCE:MULTIPLE
Unfortunately it can hide possible problems

I think the problem is that the #pragma once does not work.
It does not work also to define a constant and use #ifndef to avoid reading 2 times.

Re: Visual Studio errYou should declare it or LNK2005: variable XXX redefined in xxx.obj

Richard MacCutchan26-Nov-15 0:24

Re: Visual Studio errYou should declare it or LNK2005: variable XXX redefined in xxx.obj

26-Nov-15 0:24

You should declare it extern in the header, and define it in only one of your .cpp
files. Something like:

C++

//==File: header.h 
#pragma once
#include <stdio.h>

extern int variable;
//==end header.h

//==File: main.cpp
#include "header.h"

int variable = 0;

void main()
{
    // the rest of your code
}

Javier Luis Lopez26-Nov-15 0:53

Javier Luis Lopez

26-Nov-15 0:53

It works!

It must be "declared" as extern in the header file one time and "defined" one time as you said in the main.cpp.
It must not be defined again at any other file (source.cpp) unless extern is added
The dafault value must be placed in the main.cpp as you wrote

I do not like the solution very much because I have to be careful when changing the name of the variable to do in both sides.

Re: Visual Studio errYou should declare it or LNK2005: variable XXX redefined in xxx.obj

Richard MacCutchan26-Nov-15 1:11