Re: WorkerThread + ProgressDlg - C / C++ / MFC Discussion Boards

StuartHall10-Mar-02 18:10

10-Mar-02 18:10

Hi,

I want to teach myself COM, I'm an experience Visual C++/MFC progammer, can anyone recommend a book?

Thanks,
Stuart OMG | :OMG:

Re: COM

Paul M Watt10-Mar-02 18:15

Paul M Watt

10-Mar-02 18:15

Well there are two approaches:

Theorietical

Practical

COM is a model or a paradigm, and the developers that I have met that have read and understand the theory, go alot farther, and are able to do alot more with COM. Therefore I would recommend Don Box's book on Essential COM for theory.

You are notreally going to absorb it until you practice it. I do not have any books that explain COM in MFC, except Jeff Prosise's Programming Windows with MFC, however, it only glosses over the topics.

If you are interested in ATL, which I think is a cleaner way of programming with COM since that is what it was conceived to do, then I would recommend Brett Rector's and Chris Sells' ATL Internals.

With these two books and all of the examples in MSDN, I have had no problem learning anything that I wanted to do in COM.

unexpected results

Mohe10-Mar-02 18:04

Mohe

10-Mar-02 18:04

Hi guys
when i execute this code
void main ()
{
float x=3/2;
cout<

Re: unexpected results

Paul M Watt10-Mar-02 18:23

Paul M Watt

10-Mar-02 18:23

Mohe wrote:
float x=3/2;

A computer is only smart enough to operate on two items at a time. If you break your statement in question down into its simplest parts, 3 is an integer, and 2 is an integer. When the compiler performs an operation on these two numbers, it does integer division which results in 1.

In order to fix this, make one or both of the parameters floats like this:

float x=3.0 / 2;
float x=3 / 2.0;
float x=3.0 / 2.0;

Then you will get the result that you expect.

Modifying Environment Variables

v_krishnan10-Mar-02 17:36

v_krishnan

10-Mar-02 17:36

How can I modify an environment variable such that the changes are made to the registry, so that they are propagated to others when system restarts or some new application starts? The SetEnvironmentVariable API updates the environment for the current process only.

Thanks,
Krishnan

Re: Modifying Environment Variables

Lim Bio Liong10-Mar-02 20:48

Lim Bio Liong

10-Mar-02 20:48

Hello Krishnan,

I have a suggestion for you : on a Windows NT machine, you can try modifying the following registry entry :

"HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment"

Search for the environment variable you want to modify and make the necessary changes.

Best Regards,
Bio.

WorkerThread + ProgressDlg

Peter Molnar10-Mar-02 13:55

Peter Molnar

10-Mar-02 13:55

Hi,

I have a worker thread for some file processing, the status of which I wanna display on a Progress dialog.
I took advantage of the built in progress dialog in Add To Project/Components and Controls.
I create and manipulate the Progress dlg in the worker thread using the pointer to CProgressDlg passed from AfxBeginThread's 2 parameter to the worker thread.

Problem: the Progress dialog has very slow responsiveness to buttonclicks as if there were no threads involved at all.

What's wrong?

Thanks

Bunburry

Re: WorkerThread + ProgressDlg

Todd Smith10-Mar-02 14:00

Todd Smith

10-Mar-02 14:00

Each thread should have it's own message loop. Maybe your implementation does not?

Todd Smith
CPUA 0x007 ... shaken not stirred

Re: WorkerThread + ProgressDlg

Peter Molnar10-Mar-02 14:04

Peter Molnar

10-Mar-02 14:04

the built-in progress dialog has its own message pump which is automatically called by every StepIt or SetPos.

ASSERT(m_hWnd!=NULL);

MSG msg;
// Handle dialog messages
while(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
  if(!IsDialogMessage(&msg))
  {
    TranslateMessage(&msg);
    DispatchMessage(&msg);
  }
}

This is meant...

Bunburry

Re: WorkerThread + ProgressDlg

Peter Molnar10-Mar-02 15:00

Peter Molnar

10-Mar-02 15:00

Case solved.

I will always remember to call

if (pProgressDlg->CheckCancelButton)
    pProgressDlg->DestroyWindow();

in the loop of my worker thread.
Thanks anyway for your help.

Bunburry

Thread ........need help

10-Mar-02 12:30

Hi,

I'm beginner for thread process. Does anyone know any good and easy tutorial about thread (or multi-thread???).

Actually, I need to do write a program to simulate the Locking System in DBMS. Just simulate and no SQL or DBMS required. And I think i need to use thread to implement it. But I know nothing about thread....

Can anyone help me???? Big Grin | :-D

THANKS A LOT!!!!!!!!!!!!!!!!

Smile | :)

Re: Thread ........need help

Ravi Bhavnani10-Mar-02 12:39

Ravi Bhavnani

10-Mar-02 12:39

This CP article may help.

/ravi

"There is always one more bug..."
http://www.ravib.com
ravib@ravib.com

Re: Thread ........need help

Joaquín M López Muñoz10-Mar-02 12:45

Joaquín M López Muñoz

10-Mar-02 12:45

As a starter, you might want to take a look at CP Threads, Processes & IPC section. There are a couple of tutorials on multithreading there.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Heap Allocation error when use MSVCRT.DLL (6.00.8797)

Hoang Le10-Mar-02 11:46

Hoang Le

10-Mar-02 11:46

Hi everyone:

My C++ application ran perfetly when complied with Visual Studio 5.00 and MSVCRT.DLL version (5.00.7022).

However, when I re-compiled the application with Visual Studio 6.00 and ran with MSVCRT.DLL ver 6.00.8797, it oftenly had set-sbh-threashold problem when allocate memory and bad node in heap. Eventually, it threw Dr Watson. (Switching back to MSVCRT.DLL v. 5.00.7022 at RUN-TIME seemed to fixed this heap problem.)

Do you know why my application has this problem ? And should I re-compile the application with different option if using MSVCRT.DLL version 6.00 ???

(I am currently compling with -WIN32, WIN32 options)

Thanks a lot.

Hoang Le

Re: Heap Allocation error when use MSVCRT.DLL (6.00.8797)

Joaquín M López Muñoz10-Mar-02 11:55

Joaquín M López Muñoz

10-Mar-02 11:55

Are you using some DLL (apart from those of the system)? If so, is your program by chance allocating/freeing memory freed/allocated by some of these DLLs?

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Re: Heap Allocation error when use MSVCRT.DLL (6.00.8797)

Hoang Le10-Mar-02 12:20

Hoang Le

10-Mar-02 12:20

Thanks for your reply.

My application is CORBA based application, sure it uses CORBA DLLs (Expersoft) and Rogue DLLs, which also use to MSVCRT.DLL to allocate/free memory.

When the application crashed, the Dr Watson dump showed access violation or exception un-handling in a CORBA dll (e.g mtcor.dll).

However, when I used heapchk() function to check for heap status, the "bad node in heap" indicator showed the problem had begun initially somewhere in my own code.

Thanks again.

(i am using option -WINT32, WIN32,...)

Hoang Le

Re: Heap Allocation error when use MSVCRT.DLL (6.00.8797)

Joaquín M López Muñoz10-Mar-02 12:36

Joaquín M López Muñoz

10-Mar-02 12:36

Take a look at this MS article about an update to MSVCRT.DLL as shipped with VC++ 6.0 to prevent some heap compatibility problems of the C run-time library. Maybe this could fix your problem.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

QUESTION ABOUT TIFFS WITH MFC

jafrazee10-Mar-02 11:48

jafrazee

10-Mar-02 11:48

i am working with tiffs and need help on one part.
i can get the pointer to the header.

ImageHdr = (LPSTR)::GlobalLock((HGLOBAL) hTif2);

my problem is getting the pointer to the raw image.

the following works if i know what the bytesoffset should be.
i can access it using tif tags (273) the first time. but after the image is manipulated (dialated, rotated, etc) i can not find the pointer to the raw image(the image offset changes).

pImage=(unsigned char*)ImageHdr+BytesOffset;

is there a function that can give me the pointer to the raw image without using tif tags?

thank you.

MAPI and AOL 7.0

Dave_10-Mar-02 10:11

Dave_

10-Mar-02 10:11

It looks like AOL 7.0 supports some MAPI functionality in AOL 7.0.
Does anyone know if it is possible to write a subject, and the message text? It looks like these fields are being ignored, and only the recipients email is being accepted.
If not, does anyone know of a different way (other than MAPI) to create an email in a C++ program for AOL? I don't need it to actually send, just set an email up with the recipient addr, subject, and message text.

Thank you.

XP Style progress dialog

10-Mar-02 9:35

Hi.
Anyone knows how to implement Xp style progress dialog which runs from one side to the other (i.e. in the find files dialog) ?

Re: XP Style progress dialog

Joaquín M López Muñoz10-Mar-02 11:52

Joaquín M López Muñoz

10-Mar-02 11:52

I haven't tried it myself, but maybe playing with extended styles WS_EX_LAYOUTRTL or WS_EX_RTLREADING for the progress bar control one manages to have the bar drawn in right-to-left direction. From this and with a little code it's not hard to replicate the "Knight Rider car" effect you're after.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Re: XP Style progress dialog

Ravi Bhavnani10-Mar-02 12:33

Ravi Bhavnani

10-Mar-02 12:33

I haven't seen the XP progress dialog, but if you're looking for a progress control that works like Netscape's "infinite" progress bar, check out:

/ravi

"There is always one more bug..."
http://www.ravib.com
ravib@ravib.com

design pattern problem

10-Mar-02 9:33

Who can offer a design pattern to solve the following problem:
1. I have a class which is a singleton
2. this class manages a collection (map) of objects.
3. each object is a subject
4. I have another class who uses the singleton from step 1 which is an observer of the objects from step 2
5. in some point of the flow, an object from step two decided it is finished. it notifies it's observer from step 4.
6. the observer from step 4 performs some action based on the recieved notification and now it needs to delete the object that notified him that it was finished doing it's work, BUT (and here's the problem): it cannot delete it since the object from step 2 is in the middle of it's notification loop. the class from step 4 doesn't know if there are other observers and need not care about it. How can I break the notification loop and delete the object which sent the notification safly ?
Now, please don;t offer me to use a message loop or a message queue and a timer since it is out of the question for my current design.
Thanks.

Shoval Lior.

Re: design pattern problem

Paul M Watt10-Mar-02 9:53

Paul M Watt

10-Mar-02 9:53

Do you have multiple observers that are trying to delete the object from step two, or do the other observers simply react to the notification?

If you have multiple observers, I would add reference counting to the managed object of step two, and each observer that observes this object will increment the count. Then when it gets the notification to stop observing, it will 'release' its reference count.

In your managed object of step two, when all of the references are released, then it will delete itself with delete this, or what ever other mechanism you have set up.

Re: design pattern problem

10-Mar-02 18:07

Currently there are no other observers, but some day they might be.
The main problem is not deleting the object, but breaking the notification loop.
How do I accomplish that ?

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