C / C++ / MFC

22-Mar-07 2:32

If I call AddString() to add a string to a listbox,how can I get it in the structure lpDrawItemStruct in DrawItem?Is the string saved in lpDrawItemStruct->itemData?
And what is difference between calling AddString and SetItemData?

Thanks~

prasad_som22-Mar-07 2:45

prasad_som

22-Mar-07 2:45

IT_DOER wrote:
Is the string saved in lpDrawItemStruct->itemData?

Yes.

IT_DOER wrote:
And what is difference between calling AddString and SetItemData?

Doesn't MSDN satisfy your query ?

Prasad
Notifier using ATL | Operator new[],delete[][^]

Chen-XuNuo22-Mar-07 3:41

22-Mar-07 3:41

I am refering to a example about ListBox,and it creates a function AddItem like this:
void CListBoxEx::AddItem(UINT IconID, LPCTSTR lpszText)
{
//Adds a string ans assigns nIndex the index of the current item
int nIndex=AddString(lpszText);
//If no error, associates the index with the bitmap ID
if (nIndex!=LB_ERR && nIndex!=LB_ERRSPACE)
SetItemData(nIndex, IconID);
}
It calls AddString and after it calls SetItemData,whether the data of string and the bitmap both are save in lpDrawItemStruct->itemData?I am puzzled~

And I call the AddString("1");
and get the string and in DrawItem like this:

CString* pt_str=(CString*)lpDrawItemStruct->itemData;
dc.TextOut(lpDrawItemStruct->rcItem.left+4,lpDrawItemStruct->rcItem.top+2,
*pt_str);
is it correct?

CPallini22-Mar-07 2:46

CPallini

22-Mar-07 2:46

IT_DOER wrote:
Is the string saved in lpDrawItemStruct->itemData

Yes, it is passed as lpDrawItemStruct->itemData in DrawItem, see the folowing excerpt from MSDN:

...
void CMyListBox::DrawItem(LPDRAWITEMSTRUCT lpDrawItemStruct) 
{
   ASSERT(lpDrawItemStruct->CtlType == ODT_LISTBOX);
   LPCTSTR lpszText = (LPCTSTR) lpDrawItemStruct->itemData;
...

IT_DOER wrote:
And what is difference between calling AddString and SetItemData?

with SetItemData, you can associate e 32-bit integer to each item of the list (it is a value completely independent from the item text). Again, see the following sample from MSDN:

// The pointer to my list box.
extern CListBox* pmyListBox;

// Set the data of each item to be equal to its index.
for (int i=0;i < pmyListBox->GetCount();i++)
{
   pmyListBox->SetItemData(i, i);
}

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

Chen-XuNuo22-Mar-07 3:13

22-Mar-07 3:13

CPallini22-Mar-07 3:38

CPallini

22-Mar-07 3:38

IT_DOER wrote:
It calls AddString and after it calls SetItemData,whether the data of string and the bitmap both are save in lpDrawItemStruct->itemData?

NO.
As I stated before, the text of the item is different (independent) from it's data (that is a 32-bit integer you can use as you like). The lpDrawItemStruct->itemData has nothing to do with SetItemData second argument.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

Chen-XuNuo22-Mar-07 3:44

22-Mar-07 3:44

Mmm,in other words,I can call different function to get the string and the data I set in SetItemData~?

Thanks a lot~~ Smile | :)

Chen-XuNuo22-Mar-07 3:24

22-Mar-07 3:24

<blockquote class="FQ"><div class="FQA">CPallini wrote:</div>LPCTSTR lpszText = (LPCTSTR) lpDrawItemStruct->itemData;</blockquote>

For calling TextOut to output the string,I get the string from lpDrawItemStruct like this:

CString* pt_str=(CString*)lpDrawItemStruct->itemData;
dc.TextOut(lpDrawItemStruct->rcItem.left+4,lpDrawItemStruct->rcItem.top+2,
*pt_str);

and I called the AddString("1") before it.

Is it correct?If it is,why there is nothing in the ListBox when I run the program?I have set the style to "Has Strings"....

SetTimer critical section problem

CPallini22-Mar-07 3:47

CPallini

22-Mar-07 3:47

IT_DOER wrote:
CString* pt_str=(CString*)lpDrawItemStruct->itemData;

The code above is wrong, you cannot cast lpDrawItemStruct->itemData to a CString *.

Please use the original code:

LPCTSTR lpszText = (LPCTSTR) lpDrawItemStruct->itemData;

and then

dc.TextOut(lpDrawItemStruct->rcItem.left+4,lpDrawItemStruct->rcItem.top+2,
                            lpszText);

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

D G McKay22-Mar-07 1:35

D G McKay

22-Mar-07 1:35

I have a class which sets a timer to fire every five minutes:

m_hTimer = ::SetTimer(NULL, NULL, 5*60*1000, MyTimerProc);

Dependent on circumstances, MyTimerProc() may need to ask for user intervention (for simplicity I'll use an AfxMessageBox()). Obviously I don't want the AfxMessageBox to pop up multiple times should the program be unattended for a period of time. I have come up with the following:

void CALLBACK MyTimerProc(HWND hWnd, UINT nMsg, UINT nIDEvent, DWORD dwTime)<br />
{<br />
   static bool locked = false;<br />
<br />
   if (!locked)<br />
   {<br />
      locked = true;<br />
      AfxMessageBox("HELLO");<br />
      locked = false;<br />
   }<br />
}

Of course, I'd rather be using something safer than the frankly dodgy static variable. But EnterCriticalSection() et al don't work (they merely increment the LockCount and RecursionCount without blocking), and the CreateMutex()/WaitForSingleObject() method seems to suffer from the same problem.

I think the problem is down to each successive SetTimer() event being seen as being in the same thread.

Anybody been here before? Any suggestions gratefully received!

James R. Twine22-Mar-07 1:46

James R. Twine

22-Mar-07 1:46

   EnterCriticalSection(...) is working correctly in this case - if the same thread tries to enter the same CS, it just increments the counters.

   I think that using the static variable may be the easiest way to make this kind of issue work, short of not throwing up a blocking interface. There is no need to take something simple that works and make it unnecessarily complex.

   If the number of times the message would have been shown is significant, I would suggest having a custom dialog where you can update a message or counter indicating multiple messages (like: "this message has occurred xxx times").

   Peace!

-=- James
Please rate this message - let me know if I helped or not!<HR>If you think it costs a lot to do it right, just wait until you find out how much it costs to do it wrong!
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kakan22-Mar-07 1:55

kakan

22-Mar-07 1:55

Just a thought:
1.
Stop the timer in the callback function.
2.
Display the message.
3.
(Re)start the timer.

Alcohol. The cause of, and the solution to, all of life's problems - Homer Simpson

James R. Twine22-Mar-07 2:09

James R. Twine

22-Mar-07 2:09

Considering that the OP wrote:

Dependent on circumstances, MyTimerProc() may need to ask for user intervention [...]

- It sounds like the timer function is doing something other than showing a message box. Because of that, stopping the time may not be such a good idea...

Peace!

kakan22-Mar-07 2:19

kakan

22-Mar-07 2:19

Then, just stop the timer when the messagebox has to be shown. The timer proc (I assume) will have to wait for a response anyway.

Else, another way could be to let the timer proc start a thread that shows the messagebox. That way, the thread can keep on working, and the thread is responsible for getting input from the message box.

Alcohol. The cause of, and the solution to, all of life's problems - Homer Simpson

D G McKay22-Mar-07 2:30

D G McKay

22-Mar-07 2:30

Killing, then re-enabling the timer looks to be the way forward. A little annoyed I didn't think of it myself!

Thanks for the input everyone!

kakan22-Mar-07 2:34

kakan

22-Mar-07 2:34

I'm glad to be able to help you out. Smile | :)

And sometimes, the simplest answers are the hardest to find.

Alcohol. The cause of, and the solution to, all of life's problems - Homer Simpson

Parthi_Appu22-Mar-07 1:57

Parthi_Appu

22-Mar-07 1:57

Show a Dialog instead of message box and kill the timer.
Then notify the parent class to start the timer, when the dialog is about to destroy.

Do your Duty and Don't expect the Result