C / C++ / MFC Discussion Boards

Sanjoy Sinharoy13-Dec-05 4:59

13-Dec-05 4:59

I have some doubt on DC operations in Windows.

1. When we call Invalidate() for any window, does WM_PAINT is sent to all child windows and child of child windows as well??

2. I have created a Compatible memory DC for a picture control of a dialog box. I am painting something in the memoryDC and I am using BitBlt() to copy from the MemoryDC to the DC of the pic control in a regular interval. I am seeing when I am calling Invalidate() for the dialog box, the memory DC is also getting erased, the old painting is lost and a subsequent BitBlt() paints from the beginning (of the graph what I am drawing in the Memory DC). If I dont call Invalidate() old painting is not lost- why its happening, does Invalidate() also erase memory DC.

3. Does BitBlt() not require a subsequent call to Invalidate() to display the data in the window?? (unlike SetPixel() or Lineto() which require a subsequent call to Invalidate() or WM_PAINT to display the data in the screen) !!

Please help

Sanjoy Sinharoy
Software Enggineer
HCL Technologies
India

Re: Some doubt on WM_PAINT and MemoryDC

TheGreatAndPowerfulOz13-Dec-05 12:01

TheGreatAndPowerfulOz

13-Dec-05 12:01

1. Depends on whether or not the WS_CLIPCHILDREN style is set on the owner window. Look at WS_CLIPSIBLINGS too.

2. Try calling Invalidate with the erase parameter set to false.

3. You do not want to call Invalidate afterwards. You might want to consider doing the bitblt in the WM_PAINT (OnPaint) handler.

hope this helps.

Re: Some doubt on WM_PAINT and MemoryDC

Sanjoy Sinharoy15-Dec-05 5:35

Sanjoy Sinharoy

15-Dec-05 5:35

Still answer to this uestion is not clear:

1. Does BitBlt() require a subsequent call to Invalidate() to display the data in the window?? Or it is NOT required??

2. Does Invalidate() also erase memory DC. I have tested Invalidate(true) and Invalidate(false) both erases the previous content of the display. If I dont call Invalidate() old painting is not erased.

Please help

Sanjoy Sinharoy
Software Enggineer
HCL Technologies
India

How can I create a PDF using Visual C++?

DanYELL13-Dec-05 4:39

DanYELL

13-Dec-05 4:39

Is there a way to programmatically create a PDF file in
visual c++? I can print to paper and Im hoping that
if I change a few lines somewhere that I can print an
electronic copy in PDF somehow.

Please, any response any one can give me will be greatly
appreciated.

Sincerely,
Danielle Brina (an overworked graduate student)

Re: How can I create a PDF using Visual C++?

TheGreatAndPowerfulOz13-Dec-05 9:29

TheGreatAndPowerfulOz

13-Dec-05 9:29

there are some free libraries you can get that will generate PDFs. You can google for "PDF Generation"

There also are some PDF projects here on codeproject. Search the articles.

Re: How can I create a PDF using Visual C++?

ThatsAlok13-Dec-05 22:08

ThatsAlok

13-Dec-05 22:08

DanYELL wrote:
Is there a way to programmatically create a PDF file in
visual c++? I can print to paper and Im hoping that
if I change a few lines somewhere that I can print an
electronic copy in PDF somehow

What about this :-
http://www.codeproject.com/tools/Text2PDF.asp[^]

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV

Memory leak detection

the pink jedi13-Dec-05 4:26

the pink jedi

13-Dec-05 4:26

Can someone provide me with a simple set of code to show heap memory allocation and deallocation?

Thank you very much

Re: Memory leak detection

kdehairy13-Dec-05 6:35

kdehairy

13-Dec-05 6:35

to allocate memory for an object of type OBJECT

<br />
OBJECT* obj = new OBJECT;<br />

to allocate memory for an array of objects of type OBJECT

<br />
OBJECT* obj = new OBJECT[array_size];<br />

to deallocate memory for an object of type OBJECT

<br />
delete obj;<br />

to deallocate memory for an array of objects of type OBJECT

<br />
delete [] obj;<br />

k_dehairy

Re: Memory leak detection

ThatsAlok13-Dec-05 22:11

ThatsAlok

13-Dec-05 22:11

the pink jedi wrote:
Memory leak detection

Here what MSDN say about this :-
To detect a memory leak

Create a CMemoryState object and call the Checkpoint member function. This creates the first memory snapshot.
After your program performs its memory allocation and deallocation operations, create another CMemoryState object and call Checkpoint for that object. This gets a second snapshot of memory usage.
Create a third CMemoryState object and call its Difference member function, supplying as arguments the two previous CMemoryState objects. If there is a difference between the two memory states, the Difference function returns a nonzero value. This indicates that some memory blocks have not been deallocated.
This example shows what the code looks like:

// Declare the variables needed
#ifdef _DEBUG
CMemoryState oldMemState, newMemState, diffMemState;
oldMemState.Checkpoint();
#endif

// Do your memory allocations and deallocations.
CString s = "This is a frame variable";
// The next object is a heap object.
CPerson* p = new CPerson( "Smith", "Alan", "581-0215" );

#ifdef _DEBUG
newMemState.Checkpoint();
if( diffMemState.Difference( oldMemState, newMemState ) )
{
TRACE( "Memory leaked!\n" );
}
#endif
Notice that the memory-checking statements are bracketed by #ifdef _DEBUG / #endif blocks so that they are compiled only in Win32 Debug versions of your program.

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV

How to get size of file ???????

VikramDelhi13-Dec-05 4:01

VikramDelhi

13-Dec-05 4:01

Hi Do anyone know how to get the size of any file in win32 system using APIs. Confused | :confused:

thanks

Re: How to get size of file ???????

Graham Bradshaw13-Dec-05 4:15

Graham Bradshaw

13-Dec-05 4:15

Use _stat64

Re: How to get size of file ???????

Tim Smith13-Dec-05 4:26

Tim Smith

13-Dec-05 4:26

GetFileSize if you want to stick to Win32.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

Re: How to get size of file ???????

ThatsAlok13-Dec-05 19:39

ThatsAlok

13-Dec-05 19:39

vikramdelhi wrote:
Do anyone know how to get the size of any file in win32 system using APIs.

if you tring to open Big file, try GetFileSizeEx

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV

Thanks a lot guys

VikramDelhi14-Dec-05 3:39

VikramDelhi

14-Dec-05 3:39

hi
thanks a lot guys.
you all are really nice guys.

Replacing open/save dialogs

Krishnan V13-Dec-05 3:42

Krishnan V

13-Dec-05 3:42

I want to prevent access to windows explorer when the user is using my app. Therefore, I have created a new desktop to run my app on. This way even though he can run explorer, he cannot practically use it. However, if from my app's open/save dialogs the user right-clicks and selects the explore option, he gets a new instance of explorer running on my desktop. Sniff | :^)

My question therefore is how do I prevent this? As far as my app goes, I can think of replacing the standard open/save and browse for folder dialogs with custom made ones. However, my app uses certain third-party resources for which I cannot do the same. Can I then somehow "hook" these dialog boxes, and prevent the user from running explorer.

Any other ideas on achieving my end result are welcome.

Thanks! Smile | :)

Re: Replacing open/save dialogs

David Crow13-Dec-05 3:57

David Crow

13-Dec-05 3:57

Krishnan V wrote:
I want to prevent access to windows explorer when the user is using my app.

Why? What is it that you are ultimately trying to prevent access to?

"Take only what you need and leave the land as you found it." - Native American Proverb

Re: Replacing open/save dialogs

Krishnan V13-Dec-05 18:26

Krishnan V

13-Dec-05 18:26

My application is used in critical applications. Therefore, normal users are not allowed to use anything outside of my app. Not even calculator! To get access to other applications, I might provide a password-protected option to them.

Access Synchronization in VC++

zinc_z13-Dec-05 2:35

zinc_z

13-Dec-05 2:35

Hi ,

I m having problem updating my temporary Access databse , I get messages from socket every 1 sec , and I have to update Access tables . My application is a multithreaded , so there are times when multiple threads are trying to reand/ write same table.

Now my problem is I have tried to open Access table through CRecordset class , and when I debug it locally it run fine in multithread environment , like same table is opened by thread 1 and thread 2 is reading it , thread 3 is updating it etc.

But when I go live , I get errors like :
"Could not update; currently locked by user 'admin' on machine 'XXX"

how to catch this bug ? n how to fix it ?

plz can any body help ? If I use MS SQL SERVER can it resolve problem ?

Thx,
Zinc

HELLO

Re: Access Synchronization in VC++

kakan13-Dec-05 3:30

kakan

13-Dec-05 3:30

Hello

One way is to use a Mutex (and keep Access).
You could create a special function (or class) that handles all reads from, and writes to, the Access DB.
In that function (or class), use a Mutex.

Or, if reads are allowed at all times, just block the writes with a Mutex.

Kakan

Re: Access Synchronization in VC++

Sheng Jiang 蒋晟13-Dec-05 9:57

Sheng Jiang 蒋晟

13-Dec-05 9:57

Let SQL Server or MSDE(http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnacc2k2/html/odc_msdeintro.asp[^]) do the job for you.

My blogs:

http://blog.joycode.com/jiangsheng
http://blog.csdn.net/jiangsheng
http://bloglines.com/public/jiangsheng

Command what is yours
Conquer what is not
---Kane

Exporting a function from an .exe??

Gunn31713-Dec-05 2:34

Gunn317

13-Dec-05 2:34

Just as in that you can call LoadLibrary() on a DLL and then use GetProcAddress() to call a function within that DLL, is it possible to export a function from an exe? I know you can call LoadLibrary() and pass it an .exe and it will return a valid handle...

My end result is that I'd like to load an executable by another program (NOT run it) and determine what specific version it is...without using a version info resource within it. If I could set a function to export to return the version, that would be *perfect*.

Any other suggestions on getting at my end result would be appreciated.

Thanks,

Re: Exporting a function from an .exe??

David Crow13-Dec-05 3:58

David Crow

13-Dec-05 3:58

Gunn317 wrote:
...is it possible to export a function from an exe?

Not that I am aware of.

"Take only what you need and leave the land as you found it." - Native American Proverb

Re: Exporting a function from an .exe??

Gunn31713-Dec-05 4:35

Gunn317

13-Dec-05 4:35

It IS possible! In searching the internet, I came across this article:

http://www.codeguru.com/Cpp/W-P/dll/article.php/c3649/

In trying to solve this problem yesterday, I had created a Win32 DLL using the VS.NET wizard with one function I was exporting. So, I just copy/pasted the code into a new header file which I included in one of my .exe source files, then linked. That was it and it worked.

I was able to call LoadLibrary() on the exe, then GetProcAddress() for the function. Here's the complete .h needed (VERSION_EXPORTS was defined in the project properties):

<br />
#ifdef VERSION_EXPORTS<br />
#define VERSION_API __declspec(dllexport)<br />
#else<br />
#define VERSION_API __declspec(dllimport)<br />
#endif<br />
<br />
VERSION_API int fnVersion(void)<br />
{<br />
return 6030;<br />
}<br />

Re: Exporting a function from an .exe??

toxcct13-Dec-05 5:22

toxcct

13-Dec-05 5:22

but you are using some dll methods to came across this : dllexport and dllimport
i never seen an application (.exe) defining some symbols that are to be exported... !!
this is done in dll generally.

TOXCCT >>> GEII power
[toxcct][VisualCalc 2.20][VisualCalc 3.0]

Re: Exporting a function from an .exe??

Gunn31713-Dec-05 5:36

Gunn317

13-Dec-05 5:36

I sure am...I'm sure in most cases this may not be appropriate or needed. But it fits my case perfectly. And since LoadLibrary() and GetProcAddress() both work with .exe's, there's no reason why it can't be done.

Thanks,

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