C / C++ / MFC

don't understand MSDN explanations. Can someone explain this?

19-Sep-07 2:57

In the sheet's OnInitDialog() method, you can move and hide any of the four buttons. For example:

CWnd *pWnd = GetDlgItem(ID_APPLY_NOW);
ASSERT(NULL != pWnd);
pWnd->ShowWindow(SW_HIDE);

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Nelek18-Sep-07 23:23

Re: don't understand MSDN explanations. Can someone explain this?

18-Sep-07 23:23

Hi all,

As I mentioned in another message, I have to connect my program with a PLC of Siemens. I have found a quite good DLL to do that. Now I'm reading the documentation and the examples that come with the DLL, but there are somethings that I don't understand very well and the help/tutorial is supposing a high level in plain C (that I don't reach Frown | :(

My programm is made in VC++ 6.0, I would like to have some explanations about the following things and to know if in VC++ 6.0 are needed these commands/prerrogatives.

In the header file
1)
#if defined( _MSC_VER ) && _MSC_VER > 600
#pragma pack( push, 1 )
#else
#pragma pack( 1 )
#endif

2)
#if defined( _MSC_VER ) && _MSC_VER > 600
#pragma pack( pop )
#else
#pragma pack()
#endif

These 2 blocks mean that depending on the version the parameters of those functions are different. I have taken a look in the help but I have not understood it well.

MSDN says:
push (optional)
Puts a specified packing alignment value, n, on the internal compiler stack, and sets the current packing alignment value to n. If n is not specified, the current packing alignment value is pushed.
pop (optional)
Removes the record from the top of the internal compiler stack. If n is not specified with pop, then the packing value associated with the resulting record on the top of the stack is the new packing alignment value. If n is specified, for example, #pragma pack(pop, 16), n becomes the new packing alignment value. If you pop with identifier, for example, #pragma pack(pop, r1), then all records on the stack are popped until the record with identifier is found, and that record is popped and the packing value associated with the resulting record on the top of is the stack the new packing alignment value. If you pop with an identifier that is not found in any record on the stack, then the pop is ignored.

But... wtf does it mean? D'Oh! | :doh:

In the *.cpp
1) #define WIN32_LEAN_AND_MEAN // we don’t need all specifications Confused | :confused:

2) __cdecl

A decent explanation will be very wellcome.

Thanks

Greetings.

--------
M.D.V.

If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?

Help me to understand what I'm saying, and I'll explain it better to you

Wink | ;)

toxcct18-Sep-07 23:35

toxcct

18-Sep-07 23:35

this 2 block will delimit every 1-Byte-aligned structs/classes/unions between the pack and the pop.

the subtlty is in the syntax understood by the compiler.

#if defined( _MSC_VER ) && _MSC_VER > 600 searches if the version of the compiler is higher that Visual C++ 6. if so, it tells to the compiler to user the 1 byte alignment with #pragma pack( push, 1 ). but it the compiler is more recent #pragma pack( 1 ) is sufficient. Same applies to the #pragma pop syntax.
you have to know that the compiler manages such alignments with a stack of integers. the current alignement is the integer at the top of the stack. but at any time, you can add a new value (push), or remove some (pop)...

[VisualCalc][Binary Guide][CommDialogs] | [Forums Guidelines]

Didn't explain myself good

Nelek19-Sep-07 0:35

Re: Didn't explain myself good

19-Sep-07 0:35

Hi toxcct,

First of all... Thanks for your answer.

But the problem was not with the version of compiler.

The things that I didn't understand are the pragma pack (...), the WIN32_LEAN_AND_MEAN and the __cdecl

Anyways thanks.

toxcct19-Sep-07 1:49

toxcct

19-Sep-07 1:49

as explained in the MSDN, "When WIN32_LEAN_AND_MEAN is defined, a large number of header files are deliberately excluded by windows.h". read here[^] for a short brief.

for the __cdecl, this is what we name a "calling convention".
a calling convention is for the compiler to which of the caller or the callee is to clean the call stack.
I explain myself. when you call a function, a call stack is implicitely created to push the parameters and some extra informations such as the execution pointer. but once the function called ended its process, the memory then allocated has to be freed. such a memory can me cleaned by either the caller or the callee, but the important point here is that BOTH must accort themselves to use the same convention (imagine the leak if none is freeing the memory, or the disaster if both are cleaning a one and only memory place).

that is, several calling convention exist such like __cdecl, __stdcall, __fastcall, __thiscall...
google/MSDN can help you more than me for sure.

[VisualCalc][Binary Guide][CommDialogs] | [Forums Guidelines]

Re: Didn't explain myself good

Nelek19-Sep-07 2:08

Re: don't understand MSDN explanations. Can someone explain this?

19-Sep-07 2:08

I already was tin MSDN and didn't understand it well. With your explanation I can now imagine some things. I will make my own try-errors to check if I have got it. Thanks

David Crow19-Sep-07 3:04

Re: don't understand MSDN explanations. Can someone explain this?

19-Sep-07 3:04

Are you not understanding stacks (e.g., pushing and popping), or byte alignments?

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Nelek19-Sep-07 20:28

Re: don't understand MSDN explanations. Can someone explain this?

19-Sep-07 20:28

Also...

In a simple mode with a comparison: The stack is a box with two doors, where the allocation of the memory are packets incoming through the "push" side, then the cpu use the info that is inside (like toxcct said, the pointer to an application that is running to have access or communication). Once the information is not needed anymore, then the box is discharged through the "pop" side to let the box containing new usefull things. If the box is overloaded, an error comes and the things doesn't work fine anymore.

about the bytes alignment... Maybe is a problem of language, but I can not relate the term with anything logical.

For me is like:

----Byte----
----Byte---- They are aligned

-Byte-------
------Byte-- They are not aligned

David Crow20-Sep-07 2:42

Re: don't understand MSDN explanations. Can someone explain this?

20-Sep-07 2:42

Using your analogy, a stack would only have one door, whereas a queue would have two doors. A stack gets items pushed and popped from the same end. A queue gets items pushed onto one end and popped from the other end.

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Nelek20-Sep-07 4:12

Re: don't understand MSDN explanations. Can someone explain this?

20-Sep-07 4:12

Ahmm, ok

then it can happen like in the step7. If one programmer opens/calls a lot of different functions/processes, without closing the previous ones... there must be a moment where the stack overflows and then the programm/cpu crashes.

What about the bytes alignment? Was I right?

What I still don't understand (sorry if I ask a lot) is what a relation has the alignment of the Bytes with the question of the stack.

If the Bytes of a stack are pushed and popped through the same entry... with what should to be aligned?

David Crow20-Sep-07 4:30

Re: don't understand MSDN explanations. Can someone explain this?

20-Sep-07 4:30

You seem to be confusing structure alignment (the byte packing stuff) with stack operations.

The #pragma pack(n) preprocessor directive specifies packing alignment for structure and union members. For example, for n having a value of 1, 2, 4, 8, or 16, each structure member after the first is stored on the smaller member type or n-byte boundaries.

Each occurrence of #pragma pack (push) stores the current packing alignment on an internal compiler stack. Each occurrence of #pragma pack (pop) retrieves the value at the top of an internal compiler stack and makes that value the new packing alignment.

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Nelek21-Sep-07 1:47

EM_GETSELTEXT Message Doesn't retrive the Text

21-Sep-07 1:47

Yes I was mixing concepts.

Thanks, I don't understand it perfect, but more than before. This is in a level higher than mine. But at least I can now read the info without thinking is written in japanese Wink | ;)

:P

Thank you both

Fonts

Waldermort18-Sep-07 22:57

Waldermort

18-Sep-07 22:57

I have created a custom control which contains two buttons. I want these buttons to display the same arraows which are displayed on a scrollbars buttons. So, I create a font using the Marlett face name and instruct the button to use this font via WM_SETFONT. I also set the buttons text to "3" 4, 5 or 6 ( which maps to the arrows ). But the button still displays the number instead of the arrow. The marlett font doesn't contain any ASCII characters, it's all pictographs!

I have verified that the button is using the font via WM_GETFONT. Everything appears to be correct except that the arrows are not being displayed. Any clue as to what's gone wrong?

HFONT hFont = NULL;
    
hFont = (HFONT)SendMessage( m_hButtonUp, WM_GETFONT, 0, 0 );
if ( ! hFont )
    hFont = (HFONT)GetStockObject( DEFAULT_GUI_FONT );
if ( ! hFont )
    hFont = (HFONT)GetStockObject( ANSI_VAR_FONT );
    
if ( hFont )
{
    LOGFONT lf;
    GetObject( hFont, sizeof( LOGFONT ), &lf );
    
    _tcscpy_s( lf.lfFaceName, LF_FACESIZE, _T("Marlett") );
    
    hFont = CreateFontIndirect( &lf );
    
    SendMessage( m_hButtonUp,	WM_SETFONT, (WPARAM)hFont, TRUE );
    SendMessage( m_hButtonDown, WM_SETFONT, (WPARAM)hFont, TRUE );
    
    SendMessage( m_hButtonUp,	WM_SETTEXT, 0, (LPARAM)_T("3") );
    SendMessage( m_hButtonDown,	WM_SETTEXT, 0, (LPARAM)_T("4") );
}

Waldermort

Re: Fonts

KarstenK18-Sep-07 23:05

KarstenK

18-Sep-07 23:05

The returncodes of the SendMessage() and try an Invalidate() of the controls D'Oh! | :doh:

Greetings from Germany

Re: Fonts

nbugalia18-Sep-07 23:14

nbugalia

18-Sep-07 23:14

SendMessage( m_hButtonUp, WM_SETFONT, (WPARAM)hFont, TRUE );

Have you checked the return value ? I mean has the font got set ? If not, check using different fonts like arial etc.

Re: Fonts

Waldermort19-Sep-07 0:46

Waldermort

19-Sep-07 0:46

The WM_SETFONT does not return a value according to MSDN, also I noted in my post that I did verify that the font has been set.

The mistake was simple, I forgot to set the SYMBOL_CHARSET flag.

Thanks anyway.

Waldermort

GauranG Shah18-Sep-07 22:37

GauranG Shah

18-Sep-07 22:37

Hello Friends,

I am using the Win32 Application. In this project I am using EM_GETSELTEXT to get the selected Text From Rich Edit Control.

RichEdit Control is in another window. I have retrived its handle through FindWindowEx() Function.

But When I use the Following code it doesn't retrive the selected text

WCHAR SText[100]={};
 lr = SendMessage(hChild,EM_GETSELTEXT ,(WPARAM)0,(LPARAM)SText);
  if(lr <0)
    {
          dError = GetLastError();
    }

lr shows the Number of charcter selected. But the SText(STEXT="") is empty after SendMessage.

nbugalia18-Sep-07 23:23

nbugalia

18-Sep-07 23:23

Gaurang, I completely agree with you. It returns the length but not the value.

GauranG Shah18-Sep-07 23:30

GauranG Shah

18-Sep-07 23:30

But why ??? do u have any Idea. ?? or is there any other way I can got the Selected text. WM_GETTEXT and WM_SETTEXT working fine.

David Crow19-Sep-07 3:24

19-Sep-07 3:24

GauranG033But When I use the Following code it doesn't retrive the selected text

It fails as a result of Unicode being used. You'll find that if you use ANSI, EM_GETSELTEXT would work as expected. Is that a viable option?

If not, use this:

char sz[100] = {'\0'};
LPWSTR SText;
LRESULT lr = SendMessage(hChild, EM_GETSELTEXT, 0, (LPARAM) sz);   
USES_CONVERSION;
SText = A2W(sz);

Notice your text that I quoted above is not formatted correctly.

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

GauranG Shah19-Sep-07 21:14

GauranG Shah

19-Sep-07 21:14

I tried you code. But still facing the same problem. Empty String.

is there any other way I can get the selected Text By user.
I have tried it in MFC application Like this

CWnd *hParent = FindWindow(_T("TfrmChat"),0);
CWnd *hChild = FindWindowEx(hParent->m_hWnd,0,_T("TPanel"),0);
hParent =  FindWindowEx(hParent->m_hWnd,hChild->m_hWnd,_T("TPanel"),0);
hChild =   FindWindowEx(hParent->m_hWnd,0,_T("TExRichEdit"),0);

char sz[100] = {'\0'};
LPWSTR SText;
LRESULT lr;
lr = hChild->SendMessage(EM_GETSELTEXT, 0, (LPARAM) sz);
 USES_CONVERSION;
SText = A2W(sz);

David Crow20-Sep-07 2:27