Re: ways to write code for a class - C / C++ / MFC Discussion Boards

Re: Static OwnerDraw SS_OWNERDRAW DrawItem not being called

Victor Nijegorodov7-Feb-22 22:49

7-Feb-22 22:49

No Richard. The OP tries to use/override the virtual method of the MFC CStatic class: CStatic Class | Microsoft Docs
I have no idea why he has any problem here. I tried his DrawItem implementation and it works (however, I had to fix some bugs in his sample)

Re: Static OwnerDraw SS_OWNERDRAW DrawItem not being called

Richard MacCutchan7-Feb-22 23:39

Richard MacCutchan

7-Feb-22 23:39

Thanks, it's too many years since I used MFC.

Re: Static OwnerDraw SS_OWNERDRAW DrawItem not being called

Victor Nijegorodov7-Feb-22 22:42

Victor Nijegorodov

7-Feb-22 22:42

I added an owner draw static to my MFC dialog application, added your code for DrawItem, fixed some bugs in your CMyStatic class, and I have to say: it works.

Re: Static OwnerDraw SS_OWNERDRAW DrawItem not being called

ForNow8-Feb-22 1:23

ForNow

8-Feb-22 1:23

Thank you let me re-visit

Re: It gets called at the end of the OnInitDialog

ForNow8-Feb-22 11:25

ForNow

8-Feb-22 11:25

Hi
When posted I was under the impression that Drawitem runs after window Creation which in my case is the DDX_Control however it runs after the return of the OnInitDialog

Sorry and thanks

ways to write code for a class

Calin Negru6-Feb-22 7:43

Calin Negru

6-Feb-22 7:43

This subject is a foggy topic in my head could you help me clarify things a little.
basically there are two ways to write a class in c++
-declare a class and add in the class body only class member variables and function declarations and then layout the code for function bodies somewhere outside (in the same cpp file or in a different cpp file if the class declaration was made in a header file)
-declare a class and add in the class body class member variables and function bodies (not just the declarations), the later solution resembling how things are done in C#. The former approach can be used in the main cpp file but also in a c++ header file. The later approach can only be used in the main cpp file is that correct? could you place for instance a class declaration containing function bodies (not just declarations) in a another cpp file belonging to the same project or in a header file?
Is it that the h and cpp file of the same name are compiled into a single binary file which is then used by the binary form of the main cpp file? and that the header file is there just as an index/entry point to the class functions

Re: ways to write code for a class

Mircea Neacsu6-Feb-22 9:15

Mircea Neacsu

6-Feb-22 9:15

Let's talk first about C where the C++ came from. From the compiler's point of view there is not difference between .h and .cpp files. They are both source files and it treats them identically. By convention (and only by convention) we place declarations in the .h file and code in .cpp one. Also we have to make sure that the compiler sees the code generating lines only once. For instance if you place a function definition:

C++

int my_function () {return 3;}

in a .h file and that file is included by two different .cpp files, the compiler will happily compile them but the linker will complain that it has two instances of the same function and it doesn't know which one to pick.

What we do in this case is to place a function declaration in the .h file:

C++

int my_func ();

Now we can put the function definition in one of the .cpp files and everyone will be happy: the compiler has a declaration for the function so it can check all calls against the function prototype and the linker has only one body for the function.

Now we move to C++. Assume you place this:

C++

class A {
public:
  int func1 ();
  int func2 () {return 2;}
};

in a header file. The member func1 is only declared while the member func2 is also defined. Here the compiler performs a little trick: because the definition of func1 is within the body of a class it tells the linker to use only one instance of the generated code.

If we add a definition for func1 inside the same header file:

C++

class A {
public:
  int func1 ();
  int func2 () {return 2;}
};

int A::func1 () {return 1;}

the compiler will treat it as a regular function and again, if the header is included by two different .cpp file, the linker will complain that the function is doubly defined.

We can do two things now. One is to place an inline specifier in front of the function:

C++

class A {
public:
  int func1 ();
  int func2 () {return 2;}
};

inline int A::func1 () {return 1;}

The compiler will use the same trick as if the function would have been defined inside the body of the class and tell linker to use only one instance.

The other is to simply place the function definition in a .cpp file and in that case the linker will see it only once.

So in the end you have 3 alternatives:
1. place the function definition in the class body.
2. place it in the header file and make it inline.
3. place it in one .cpp file

Which solution you choose depends on your teste and what you want to achieve. The difference between 1 and 2 is purely a question of style (I prefer 2, but that's just me). Number 3 used to be by far the most popular choice until recently when header only libraries have proliferated. It's up to you to decide.

Mircea

Re: ways to write code for a class

Greg Utas6-Feb-22 10:16

Greg Utas

6-Feb-22 10:16

To add to what Mircea said, function definitions (implementations) usually go in a .cpp for two reasons:

By default, a header is recompiled each time that a .cpp #includes it, so defining large functions in headers can really slow down a compile. Some compilers optimize this, but it isn't guaranteed.
A header should be an interface, with implementation details going in a .cpp rather than cluttering the header.

However, there are two situations when function definitions go in a header:

If a function is simple, usually just a single line, it's expedient to just define it in the header.
A function template, or a function in a class template, is defined in a header.

As far as where to define functions is concerned, I prefer to define each class in its own header (Class.h) and implement its functions in Class.cpp. This isn't mandatory, because the .h and .cpp are not compiled into a single binary. Each .cpp, along with all the headers that it #includes, is compiled into its own binary, after which the linker merges them all.

Some C++ gurus say there is no rationale for putting each class in its own .h and .cpp. They're wrong, but there are exceptions:

A "helper" class (used only to implement another one) can be defined in the same .cpp as the only class that uses it.
Small, related classes can be defined in a common .h and implemented in a common .cpp.

However, each important class gets its own .h and .cpp. This makes code easy to find, even outside the IDE. Besides, anything else is arbitrary; no one would suggest that one big .cpp is good for a project with 10,000+ lines of code. Some kind of organization is needed, and the approach that I've described is the obvious one.

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Re: ways to write code for a class

Calin Negru6-Feb-22 23:28

Calin Negru

6-Feb-22 23:28

thanks Greg that`s very descriptive

C++

Naveenkumarreddy Ramireddy6-Feb-22 6:44

Naveenkumarreddy Ramireddy

6-Feb-22 6:44

 you are a tax calculator in company, and you should calculate the tax based on staff’s salary as follows:
-the salary is less than 600, the tax is 0.
-the salary is greater than 600 and less than 800, the tax is 10% of the salary.
-the salary is greater than 800 and less than 1000, the tax is 13% of the salary.
-the salary is greater than 1000 and less than 1500, the tax is 18% of the salary.
-the salary is greater than 1500, tax is 20% of the salary.
Write a program in C++ to ask the user to enter the salary then calculate the tax using:
If-Only structure, If-Else structure, Switch-Case structure.

Re: C++

trønderen6-Feb-22 8:00

trønderen

6-Feb-22 8:00

So do it! Write that program! It won't write itself ...

Re: C++

Victor Nijegorodov6-Feb-22 8:50

Victor Nijegorodov

6-Feb-22 8:50

It looks like a good start to develop a working program! Thumbs Up | :thumbsup:

Re: C++

Artem Moroz8-Feb-22 9:19

Artem Moroz

8-Feb-22 9:19

Hi there!
I have started this Tax software program for you:

#include <iostream>

using namespace std;

int main()
{
    cout<< "Tax software developed by https://iq.direct" << endl;
    cout<< "Enter Salary:";
    
    double s = 0, t = 0;
    cin >> s;
    
    cout<<"you entered: " << s << endl;
    
    if (s < 600)
    {
        t = 0;
    }
    if (s >= 600 && s < 800 )
    {
        t = s * 0.1;
    }
    if (s >= 800 && s < 1000 )
    {
        t = s * 0.13;
    }
    
    cout<< "The tax will be :" << t;

    
    return 0;
}

RichEdit Streamin SF_TEXT not appearing

ForNow30-Jan-22 14:58

ForNow

30-Jan-22 14:58

Hi
I have done this many times streamin text, this time however the text just doesn't appear I do a SW_SHOW on both the rich edit and the dialog

So I decided just to do a simple test copy "this is a test\r\n": info the pBuff *pcb = 16 for the next call I have *pcb = 0 to tell rich edit no more

The Dialog box and rich edit appear with no test however When I press any character on my keyboard e.g type D The text This is a text magically appears in front of D

Any ideas are appreciated

Re: RichEdit Streamin SF_TEXT not appearing

Victor Nijegorodov30-Jan-22 20:43

Victor Nijegorodov

30-Jan-22 20:43

No idea until we will see your actual code.

Re: RichEdit Streamin SF_TEXT not appearing

ForNow30-Jan-22 20:48

ForNow

30-Jan-22 20:48

I’ll post it about 7 am thank you

Re: RichEdit Streamin SF_TEXT not appearing CODE POSTED !!!!!

ForNow31-Jan-22 1:32

ForNow

31-Jan-22 1:32

i'LL POST THREE pieces 1) the oninitdialog of the parent Cdialog 2) the Steamin 3) resource file Tell me if you want to see more thanks you

C++

BOOL CStorge::OnInitDialog()
{
	int numolines;
	



	storagepointer = new CRichEditCtrl;
	

	CDialog::OnInitDialog();
	
	CHARFORMAT cf2 = { 0 };

	
	STREAMIN((WPARAM)storage_ptr, (LPARAM)storagelen);
	storagepointer->SetSel(0, -1);
	cf2.cbSize = sizeof(cf2);
	cf2.dwMask = CFM_FACE | CFM_PROTECTED;
	cf2.dwEffects = CFE_PROTECTED;
	memcpy(&cf2.szFaceName[0], "Courier New",12);
	storagepointer->SetSelectionCharFormat(cf2);
	storagepointer->SetSel(0, 0);
	storagepointer->ShowWindow(SW_SHOW);
	ShowWindow(SW_SHOW);
	return TRUE;
}

call to setup STREAMIN

C++

LRESULT CStorge::STREAMIN(WPARAM mywparam, LPARAM mylparam)
{
	char *sendptr;
	sendptr = (char*)mywparam + 4;
	streaminparm parms;
	parms.storpointer = (char  *)sendptr;
	parms.storlen = (int)mylparam;

	EDITSTREAM STORAGESTREAM;
	STORAGESTREAM.pfnCallback = storagestreamin;
	STORAGESTREAM.dwCookie = mywparam;
	STORAGESTREAM.dwCookie = (DWORD_PTR) &parms;

long numstream = storagepointer->StreamIn(SF_TEXT,STORAGESTREAM);

	return TRUE;

}

the Streamin function

C++

DWORD storagestreamin(DWORD_PTR dwCookie,
	LPBYTE pbBuff,
	LONG cb,
	LONG* pcb)
	
{


	static BOOL flag = 0;
	if (flag == 0)
		flag = 1;
	else
	{
		*pcb = 0;
		flag = 0;
		return 0;
	}
	int i;
	streaminparm* inparms = (streaminparm *)dwCookie;
	void* holdptr = inparms->storpointer;
	char* holdptr1 = (char*)pbBuff;
		int totalen = inparms->storlen;
		memcpy((char *)pbBuff, "This is a test\r\n",16);
		*pcb = 16;
   	return 0;

		for (i = 0; i < totalen; i += storageline)
		{
			memcpy(holdptr1, holdptr, storageline);
			holdptr = (char*)holdptr + storageline;
			holdptr1 = (char*)holdptr1 + storageline;
			*holdptr1 = '\r';
			holdptr1 = (char*)holdptr1 + 1;
			*holdptr1 = '\n';
			*pcb += 74;
		}

		return 0;


}

the Dataexchange member to create the rich edit HWND

C++

void CStorge::DoDataExchange(CDataExchange* pDX)
{
	CDialogEx::DoDataExchange(pDX);
	

	DDX_Text(pDX, IDC_ASID, asidstr);
	DDX_Text(pDX, IDC_SP, spstr);
	DDX_Text(pDX, IDC_TCB, tcbstr);
	DDX_Text(pDX, IDC_FP, fpstr);
	DDX_Control(pDX, IDC_EDIT2, (CWnd&) *storagepointer);
			
}

The resource indentfier of the cdialog with richedit

IDD_DIALOG10 DIALOGEX 0, 0, 769, 429
STYLE DS_SETFONT | DS_MODALFRAME | DS_FIXEDSYS | WS_POPUP | WS_CAPTION | WS_SYSMENU | WS_VISIBLE
CAPTION "Storage View / Change"
FONT 8, "MS Shell Dlg", 400, 0, 0x1
BEGIN
    CTEXT           "",IDC_TCB,45,30,47,8
    CTEXT           "OwnIng TCB",IDC_STATIC,41,13,58,8
    CTEXT           "",IDC_SP,164,28,43,8
    CTEXT           "Storage SubPool",IDC_STATIC,162,12,55,8
    CTEXT           "",IDC_ASID,265,26,32,8
    CTEXT           "Asid",IDC_STATIC,269,9,31,8
    CTEXT           "",IDC_FP,399,31,19,8
    CTEXT           "Fetch Protect Key",IDC_STATIC,392,15,63,8
    CONTROL         "",IDC_CUSTOM5,"PieCOntrol",WS_TABSTOP,617,99,109,109
    COMBOBOX        IDC_COMBO1,491,236,48,30,CBS_DROPDOWN | CBS_SORT | WS_VSCROLL | WS_TABSTOP
    CONTROL         "",IDC_EDIT2,"RichEdit20A",ES_MULTILINE | WS_BORDER | WS_TABSTOP | WS_VISIBLE, 45,106,494,314  THE RICH EDIT
    EDITTEXT        IDC_EDIT1,45,110,494,314,ES_AUTOHSCROLL
    COMBOBOX        IDC_COMBO2,637,244,67,16,CBS_DROPDOWN | CBS_SORT | WS_VSCROLL | WS_TABSTOP
    LISTBOX         IDC_LIST2,641,310,68,11,LBS_SORT | LBS_NOINTEGRALHEIGHT | WS_VSCROLL | WS_TABSTOP
END

Re: RichEdit Streamin SF_TEXT not appearing CODE POSTED !!!!!

Victor Nijegorodov31-Jan-22 1:45

Victor Nijegorodov

31-Jan-22 1:45

ForNow wrote:
CDialog::OnInitDialog();
CHARFORMAT cf2 = { 0 };

STREAMIN((WPARAM)<b>storage_ptr</b>, (LPARAM)storagelen);</blockquote>
What is storage_ptr? Its type and value?

Re: RichEdit Streamin SF_TEXT not appearing CODE POSTED !!!!!

ForNow31-Jan-22 2:11

ForNow

31-Jan-22 2:11

you think thats the problem I should make it a CRicheditrl *

BTW I did Call AfxRichEditInit and I did observer that storage__ptr had a Hwnd after the DoDataExange

C++

void* storage_ptr;

Re: RichEdit Streamin SF_TEXT not appearing CODE POSTED !!!!!

Victor Nijegorodov31-Jan-22 2:17

Victor Nijegorodov

31-Jan-22 2:17

ForNow wrote:
C++Copy Code
void* storage_ptr;

You mean you pass an uninitialized pointer into your STREAMIN method?
BTW, did you debug your code (and, particularly, this STREAMIN method)?

Re: RichEdit Streamin SF_TEXT not appearing CODE POSTED !!!!!

ForNow31-Jan-22 2:31

ForNow

31-Jan-22 2:31

The Ponter I pass to the streamin is 1) the data ptr and 2) the length of it I did debug it and it passed the value back that I wanted in pBuff and *pcb

storage_ptr should be of type CrRicheditCtrl * instead of void * but it does a value and After the Call Cdialog::OnInitDialog it Called my DoDataExchage and had a valid HWND

In in fact if you look at that small test when I pass "this is a test\r\n" back to pBuff and *pcb = 16 that doesn't display

When I type any chanarcter in the rich edit for example a D this is a test follow it for example looks like this DThis is a test

thanks

Re: RichEdit Streamin SF_TEXT not appearing CODE POSTED !!!!!

Victor Nijegorodov31-Jan-22 10:34

Victor Nijegorodov

31-Jan-22 10:34

I could not test your "code" because there is a lot of problems with:
undeclared identifier
undeclared identifier
cannot convert from 'DWORD (__cdecl *)(DWORD_PTR,LPBYTE,LONG,LONG *)' to 'EDITSTREAMCALLBACK'
...
and so on.
Could you post a code (sample project) that would reproduce your problem?

Re: RichEdit Streamin SF_TEXT not appearing CODE POSTED !!!!!

ForNow31-Jan-22 10:39

ForNow

31-Jan-22 10:39

is there anywhere I could zip it if not the total project is 6 .cpp files with 6 headers and resource file

thanks you are really nice

Re: RichEdit Streamin SF_TEXT not appearing CODE POSTED !!!!!

Victor Nijegorodov31-Jan-22 10:52

Victor Nijegorodov

31-Jan-22 10:52

Sorry! I don't know.
But if you won't find a way to do that then you could repost your question in Visual C++ Programming
Or just email it to me: <my surname=""> at <onlinehome.de>

Re: RichEdit Streamin SF_TEXT not appearing CODE POSTED !!!!!

ForNow31-Jan-22 11:00

ForNow

31-Jan-22 11:00

Ill take the latter thanks but this mini project is a tcp/ip application that gets data into the RichEdit from a z z/os machine

let me see if I can somehow segregate it The rich edit portion that is causing the problems and then get a clean build and i'll send it over thanks you are very nice

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