C / C++ / MFC

Alvaro Mendez6-Jan-03 11:38

Alvaro Mendez

6-Jan-03 11:38

I'd like to give you an exact answer but I'm afraid my experience with member function pointers is extremely limited (thank God). If you haven't already, you may want to search the C/C++ articles here for ways of accomplishing what you need.

What I'd like to know is why? Why go through this syntactic nightmare when OO techniques such as virtual functions may provide a more elegant and maintainable solution?

Regards,
Alvaro

Well done is better than well said. -- Benjamin Franklin
(I actually prefer medium-well.)

William E. Kempf6-Jan-03 12:03

William E. Kempf

6-Jan-03 12:03

C++ is strongly typed, so you can't use member-function pointers with out a class name. Nor can you mix function pointers with member-function pointers. However, you can accomplish what you want (and a lot more) by giving up on function pointers and turning to higher level "function objects" with libraries like Loki or Boost.Function (and Boost.Bind is quite handy when using Boost.Function as well!). http://www.boost.org[^]

William E. Kempf

valikac6-Jan-03 16:07

valikac

6-Jan-03 16:07

One solution is static declaration. Given assignFuncs points to a class member function, then that class member function must be static if you want to call it anytime and anywhere. Otherwise, you must call it via object.

Kuphryn

tilli again7-Jan-03 8:43

tilli again

7-Jan-03 8:43

Great! Making them static is working. To answer the question about "why the hassle": I'm writing on an Win32 API OOP Wrapper, and I wanted the user to be able to overwrite a function (assignFunc in this case) which is called by the class during the initialization process. What it does then is returning a list of Window Messages with their corresponding callback functions. Once a message needs to be processed then, the window message loop checks if the message has a callback defined and launches it. The reason I wanna be able to use class member functions for this purpose is so the callback functions can use member variables.

tilli

Tree Control Check Boxes... ???

tilli again8-Jan-03 8:18

tilli again

8-Jan-03 8:18

Well...making them static did work for what I wanted. But I'm no more able to access non-static functions from these functions then, so the intended advantage over non-class-functions will be exactly void. So, anyone has an idea how to rewrite the original code? I'd like to keep something at least somewhat similiar to the current approach, because I found it to be quite convenient and flexible for the user!

Thanks
tilli

work_to_live6-Jan-03 9:31

work_to_live

6-Jan-03 9:31

I inserted a tree control in a dialog box, and enabled the Check Boxes property. Then I load up the control with items, allow the user (me right now) to select some of them by placing checks next to the items of interest.

All is well and good. The only problem I have is... I can't figure out how to determine which items have been checked! Any help would be greately appreciated.

Thanks,
Gary H

Re: Tree Control Check Boxes... ???

work_to_live6-Jan-03 9:51

work_to_live

6-Jan-03 9:51

I found it...

I was looking at the item state, and didn't realize there was a GetCheck member function of CTreeCtrl. I knew it was going to be simple.

Later.

Synchronization.. do I need?

Subrahmanyam6-Jan-03 9:15

Subrahmanyam

6-Jan-03 9:15

I have a dialog based application in which I have two sources of events
1) On Timer
2) On User input(such as click of button)

Now on both events I will be calling a function, which acts on a single resource.
Calling the function while it is already executing is dangerous & can corrupt all my data.

Now I want to know do I need to put any synchronization code (SingleLock etc.) in my function.

** The important point here is that I am not creating any threads explicitly.
So my assumption is that my app is single threaded. In such case my function can never be called (from anywhere else) while it is running.

Am I correct? Am I missing anything here?

Please help me.

Re: Synchronization.. do I need?

Tim Smith6-Jan-03 10:17

Tim Smith

6-Jan-03 10:17

Since you only have one thread, you need not worry.

Tim Smith

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

Re: Synchronization.. do I need?

C^hris L^osinger6-Jan-03 10:59

C^hris L^osinger

6-Jan-03 10:59

you might not need SingleLock, etc.. but if there's a chance you could end up going through the same function twice at the same time (especially if you're doing message pumping) you might need to use a flag at the top of any functions where this could be dangerous.

bool g_alreadyInFuncA = false;

void funcA()
{
  if (g_alreadyInFuncA)
  {
    error? return early? crash?
  }

  g_alreadyInFuncA = true;

  blah 
  blah
  MessagePump...
  blah
  g_alreadyInFuncA = false;
}

void OnMyMessage()
{
 funcA()
}

-c

I'm not the droid you're looking for.

ThumbNailer

Debugging Mutexes?

clintsinger6-Jan-03 8:09

clintsinger

6-Jan-03 8:09

Hi All,

I was wondering where I would find information on the techniques for debugging mutexes, semaphores, critical sections etc. I have a place in my code that blocks and locks the application. It appears to be happening randomly on a CSingleLock(&mymutex). How do I takle it and find out what the real problem is?

Cheers,
Clint

Tim Smith6-Jan-03 8:39

Tim Smith

6-Jan-03 8:39

1. Are you 100% positive you are always unlocking your locks?
2. Do you have any deadly embraces in your locks. (i.e. thread #1 locks lock A then lock B while thread #2 locks lock B then lock A.)

Tim Smith

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

clintsinger6-Jan-03 8:47

clintsinger

6-Jan-03 8:47

As far as I know I don't have these problems. Would either problem cause random mutex lockups? I can see where #2 could potentially be the culprit as there looks like a race condition there.

Cheers,
Clint

Tim Smith6-Jan-03 10:16

Tim Smith

6-Jan-03 10:16

Both examples cause lockups. The first because some thread never released the mutex. The second for the race condition you saw.

Tim Smith

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

clintsinger9-Jan-03 7:42

clintsinger

9-Jan-03 7:42

It was a deadly embrace.

Thanks for you help.

Cheers,
Clint

Localization issue

Nish Nishant6-Jan-03 7:30

Nish Nishant

6-Jan-03 7:30

hey guys

I have run into this problem now. In my application, I use FindWindow to search for a window with a specific title text. This is all fine as long as the language is english. But what do I do for non-english versions of Windows? One solution is to have a string table with the text for the title in various languages. But is there some easier simpler way to do this that I am not aware of?

Regards,
Nish

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

Maximilien6-Jan-03 7:34

Maximilien

6-Jan-03 7:34

Couldn't you ID the windows with an internal hard-coded (in english ) string ?

Max.

Nish Nishant6-Jan-03 7:47

Nish Nishant

6-Jan-03 7:47

Maximilien wrote:
Couldn't you ID the windows with an internal hard-coded (in english ) string ?

Not a window created my me unfortunately. This is the IE save-as window. I am using a browser control in my dialog and using IE to save the html and all the reqd images. problem is I wanna automate this and I find the save as window, find the save button and send a click to it.

Nish

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

nde_plume6-Jan-03 8:32

nde_plume

6-Jan-03 8:32

The IE Save As box does not save the page with images, it just saves the source HTML.

To save with images is quite an involved process, but basically what you have to do is this:

1. Open the page in your Web Browser control
2. Get the IHTMLDocument2 handle (using GetHtmlDocument)
3. Get a list of images from the IHTMLDocument2 (get_images)
4. iterate through each image:
a. Download the image to a file.
b. iterate through each IMG tag on the page, and if the
image is referenced in the HREF tag, modify the HREF
tag to point to your newly save file. (This comparison
is non trivial, because you have to connonicize both
filenames first.)
5. When you have rewritten the images, get the HTML text
from the IHTMLDocument2 and save it.