Keyboard hook code explanation - C / C++ / MFC Discussion Boards

Rafael Fernández López9-Apr-06 7:32

9-Apr-06 7:32

Hi,

I am using Visual Studio .NET 2003. I'd like to know if there is some way to run a memory leak checker (like CodeGuard in Borland C++).

Thank you,
Rafael Fernández López.

Written by: Rafael Fernández López.

Visit: http://www.maestroprogramador.com

Re: HOW TO DETECT MEMORY LEAKS

sunit59-Apr-06 19:12

sunit5

9-Apr-06 19:12

install Bounds Checker

never say die

STL Qs

RalfPeter9-Apr-06 6:10

RalfPeter

9-Apr-06 6:10

Hi all,

could any one help me with an STL problem? the code below throws an assertion error [_SCL_SECURE_VALIDATE(this->_Mycont != NULL); from vector.h, line 117] when executing line #5 only after executing line #4. Line #5 works fine as long as the 'if' block is not entered. I am using MSVC 2005 and did not have this problem with the previous version. Is there any change to the way STLs are handled now? Thx everyone,
Ralf.

1 ivFKey = szvCopy.begin();
2 while (ivFKey != szvCopy.end()) {
3 if (*ivFKey == szFKey) //delete all equal; what's left are 0-catches
4 szvCopy.erase(ivFKey);
5 ++ivFKey;
6 }

ralf.riedel@usm.edu

Re: STL Qs

C^hris L^osinger9-Apr-06 7:07

C^hris L^osinger

9-Apr-06 7:07

calling erase on a sequence invalidates any iterators on that sequence.

Cleek | Image Toolkits | Thumbnail maker

Re: STL Qs

Jörgen Sigvardsson9-Apr-06 10:40

Jörgen Sigvardsson

9-Apr-06 10:40

ivfKey = szvCopy.erase(ivFKey)

CArray of CBrush and CRgn

stifmeister_ro9-Apr-06 6:10

stifmeister_ro

9-Apr-06 6:10

I am coding an application that displays a couple of CRgn objects. Each CRgn is filled using anoher brush. So I need two arrays to store the CRgn and CBrush objects.
I also need to save to a file the arrays so when I open the application again I can continue to work with those objects.

It would like to use CArray because I can use m_rgnArray.Serialize(ar) to save the array to a file... Smile | :)

But my program doesn`t work as expected and I get a lot of "assertion failed" messages.
This is how I declared the variables:

<br />
CArray <CRgn, CRgn> m_rgnArray;<br />
CArray <CBrush, CBrush> m_brushArray;

Is this the way I should use CArray with CBrush and CRgn? Is it even possible to use CArray with CBrush and CRgn?

Re: CArray of CBrush and CRgn

Michael Dunn9-Apr-06 7:15

Michael Dunn

9-Apr-06 7:15

You can't persist GDI objects like that. You'll need to store the coordinates of the regions and attributes of the brushes, and recreate the GDI objects later.

--Mike--
Visual C++ MVP Cool | :cool:

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Keyboard hook code explanation

EvScott9-Apr-06 5:42

EvScott

9-Apr-06 5:42

LRESULT CALLBACK KeybrdHook( int code,WPARAM key, LPARAM lParam)
{
if (((DWORD)lParam & 0x40000000) &&(HC_ACTION==code))(1)
{
...
GetKeyboardState(ks);(2)
...
ToAscii(key,scan,ks,&w,0);(3)
}
...
}

Could someone please put me out of my misery and explain the lines numbered 1..3. It's driving me potty. There's not a lot of useful, simple to understand explanations on the Net. Many thanks.

EvScott

Re: Keyboard hook code explanation

David Crow10-Apr-06 3:32

David Crow

10-Apr-06 3:32

EvScott wrote:
Could someone please put me out of my misery and explain the lines numbered 1..3.

1) The bits in lParam are being ANDed with 0x40000000. If that result is non-zero and code equals HC_ACTION, the next two statements are executed.

2) The function GetKeyboardState() is being called. When finished, ks is a 256-byte array that will receive the status data for each virtual key.

3) The function ToAscii() is being called. This will translate the specified virtual-key code and keyboard state to the corresponding character or characters.

EvScott wrote:
There's not a lot of useful, simple to understand explanations on the Net.

Actually, quite the opposite is true.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

stack trace

LiYS9-Apr-06 4:17

LiYS

9-Apr-06 4:17

void foo1()
{
    foo2();
}
void foo2()
{
    foo3();
}
void foo3()
{
   STACKFRAME64 frame;
   DWORD_PTR    programcounter;
   programcounter = getprogramcounter();

    // Initialize the STACKFRAME64 structure.
    memset(&frame, 0x0, sizeof(frame));
    frame.AddrPC.Offset    = programcounter;
    frame.AddrPC.Mode      = AddrModeFlat;
    frame.AddrFrame.Offset = framepointer;
    frame.AddrFrame.Mode   = AddrModeFlat;
    // use some kind of loop, till this funtion reach foo1()
    StackWalk64(, , , &frame, , NULL, , , NULL); 
}

DWORD_PTR getprogramcounter()
{
    DWORD_PTR programcounter;

    __asm mov AXREG, [BPREG + SIZEOFPTR] // Get the return address out of the current stack frame
    __asm mov [programcounter], AXREG    // Put the return address into the variable we'll return

    return programcounter;

}

My assumption about the above code snippet is that foo3 obtain the address of "getprogramcounter()(program counter?)" by calling getprogramcounter(), and it is
from there the foo3 begin to trace back. So in this case getprogramcounter()->foo3()-2()->1()? But What's the relation between foo3()'s getprogramcounter()'s address and its frame pointer, as the "frame.AddrPC.Offset" and "frame.AddrFrame.Offset" indicate.Doesn't the frame pointer alone enough to get its caller's stack frame? why use program counter? How the StackWalk64 deal with them. What exactly happened?

C++ ISO Compliance

HalfWayMan9-Apr-06 4:11

HalfWayMan

9-Apr-06 4:11

Having moved back to Visual Studio 2005, it is now bombarding me with warnings about ISO C++ deprecation of certain functions (such as strdup and stricmp). Most of these warnings disappear when I tell it to mind it's own business with _CRT_SECURE_NO_DEPRECATE. However, is it advisable to actually do what Microsoft say and switch everything over to the new versions of the functions?

Re: C++ ISO Compliance

Hans9-Apr-06 7:03

Hans

9-Apr-06 7:03

Yes the annoying security warnings Wink | ;-)

There are many reasons to not use the new functions, even if MS recommends:
- your code gets much more complicated
- no cross-compiling with other compilers/operating systems possible
- every open-source lib you use will bring again these warnings

It is also widely not understood that the wrong functions were blamed by
MS. Most of them are not unsafe and never were. But they depend on correct
usage, so you as the programmer are in charge to not give them garbage.
So, my advice is to use the old functions, and check (if you must use plain C)
every buffer for long enough size, esp. if you get data from user input.

Hans

Re: C++ ISO Compliance

HalfWayMan10-Apr-06 7:34

HalfWayMan

10-Apr-06 7:34

Thankyou, Hans. I was thinking something along the same lines, although I never thought of the cross-compatibility issue. Best to check.

HWM

problem in retrieving records

swapna_signsin9-Apr-06 3:11

swapna_signsin

9-Apr-06 3:11

hi,
I actually have a very simple application,I need to retrieve 2 record from my database.Everytime I click a button then records should be displayed sequentially into my edit boxes.
So,for that I used the code while(!objrs.ISEOF()) and objrs.movenext() where objrs is the recordset object,I can get only one record.

so,pls solve my problem.
bye

swapna_signsin

Re: problem in retrieving records

thatsme_cool9-Apr-06 21:09

thatsme_cool

9-Apr-06 21:09

Good Luck

Re: problem in retrieving records

David Crow10-Apr-06 3:41

David Crow

10-Apr-06 3:41

swapna_signsin wrote:
So,for that I used the code while(!objrs.ISEOF())...

Why are you using a while loop when you are only interested in two rows? That would not be very intuitive to someone having to read through the code.

swapna_signsin wrote:
...I can get only one record.

Have you called objrs.MoveNext() a second time to advance to the next row?

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Re: problem in retrieving records

swapna_signsin10-Apr-06 21:42

swapna_signsin

10-Apr-06 21:42

yes

swapna_signsin

how can i get the main window after shellexecuteex

supertianqu9-Apr-06 1:57

supertianqu

9-Apr-06 1:57

i use ShellExecuteEx to open many other 3rd programme, then i use EnumWindows to get the main window by hProcess returned by shellexecuteex. i found that some programmes, such as notepad.exe, calc.exe, cmd.exe, work correctly. but it couldn't get the correct window of some programmes like word.exe.

Re: how can i get the main window after shellexecuteex

YaronNir9-Apr-06 2:23

YaronNir

9-Apr-06 2:23

ask yourself, what is the diffrenece between running notepad.exe and winword.exe?

one answer could be that notepad opens immediately and winword first opens a splash screen,
then initialize and only then display the main frame window....

the only way to overcome this is the hook into the creation of the process, and then find out who is the main window and use it.....

hope this helps

Ask not what your application can do for you,
Ask what you can do for your application

How to run a console application in MFC

kflrei9-Apr-06 1:50

kflrei

9-Apr-06 1:50

I want to create MFC Application to run console application
Example,when I click a button,it will run a specified console application to open another file.
Like the run command,EX : ConsoleApp Text.txt

Please help me!

Re: How to run a console application in MFC

mehrdadov9-Apr-06 1:55

mehrdadov

9-Apr-06 1:55

I think you can use CreateProcess function with parameters that show you can use Console type

Agh

Re: How to run a console application in MFC

supertianqu9-Apr-06 1:58

supertianqu

9-Apr-06 1:58

use ShellExecute or ShellexecuteEx

Re: How to run a console application in MFC

David Crow10-Apr-06 3:44

David Crow

10-Apr-06 3:44

See here.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Move Window

mehrdadov9-Apr-06 1:49

mehrdadov

9-Apr-06 1:49

Hello
I want to Create a modaless dialog that user can't move it
how can i do it?
thanks.

Agh

Re: Move Window

YaronNir9-Apr-06 2:28

YaronNir

9-Apr-06 2:28

when you drag the dialog a message is called i.e : SendMessage(WM_NCLBUTTONDOWN, HTCAPTION)

just override this message not to do its defaults...

hope this helps

Ask not what your application can do for you,
Ask what you can do for your application

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.