Waiting in GUI till thread ends

I have a dialog that does a certain operation in a thread. I create the thread upon pressing a button.
From the button handler I want to wait till the thread ends.
If I wait till the thread turns on a flag, the GUI is freeze.
What is the optimal way to do it ?

Thanks.

Quote:

---

Originally Posted by zvivered

I have a dialog that does a certain operation in a thread. I create the thread upon pressing a button.
From the button handler I want to wait till the thread ends.
If I wait till the thread turns on a flag, the GUI is freeze.
What is the optimal way to do it ?

---

Not sure what you really want. Without a worker thread, your GUI would wait for the operation to complete (and hence freeze). You normally introduce a worker thread so that your GUI does not have to wait. Now you say you want to wait - so why the thread? What do you mean by "waiting" without freezing? What exactly is the behaviour you are expecting?

First of all, is there a need to wait for the thread operation inside the Button handler? Normally, u create a worker thread to perform certain operations so that your GUI can continue to receive user action.

Quote:

---

Originally Posted by gstercken

Not sure what you really want. Without a worker thread, your GUI would wait for the operation to complete (and hence freeze). You normally introduce a worker thread so that your GUI does not have to wait. Now you say you want to wait - so why the thread? What do you mean by "waiting" without freezing? What exactly is the behaviour you are expecting?

---

Thank you for your answer:
This is what I'm trying to do in the button handler:

void CThreadDlg::OnButton1()
{
// TODO: Add your control notification handler code here
CreateThread (0,1024*10,Acquire,this,0,&AcquireId);
while (!ThreadEnd)
Sleep(10);
}

The while (with sleep) causes the GUI to freeze. The window can not be moved.
What should I do ?

The while loop will keep calling Sleep() until the thread is finished, so no messages are processed, that's why your application freezes. I don't understand what you'd like to happen while the thread is running

Quote:

---

Originally Posted by zvivered

This is what I'm trying to do in the button handler: The while (with sleep) causes the GUI to freeze.

---

Well, the code shows what you're currently doing, not what you want to happen. It's pretty obvious that calling Sleep() in your main thread freezes the UI.

Quote:

---

Originally Posted by zvivered

What should I do ?

---

As said above: What would you like to happen? It's still unclear how you expect your app to behave.

Quote:

---

Originally Posted by gstercken

Well, the code shows what you're currently doing, not what you want to happen. It's pretty obvious that calling Sleep() in your main thread freezes the UI.

As said above: What would you like to happen? It's still unclear how you expect your app to behave.

---

Thank you for your reply.
While the handler waits for the thread to end I want to be able to press other buttons in my dialog. This is not possible now. My main thread freezes the UI.

Quote:

---

Originally Posted by EoF

The while loop will keep calling Sleep() until the thread is finished, so no messages are processed, that's why your application freezes. I don't understand what you'd like to happen while the thread is running

---

Thank you for your reply.
While the thread is runnig I want to press other buttons in my dialog.
But at the same time I want to wait in the handler till the thread ends.
I want that messages will continue to be processed.

Quote:

---

Originally Posted by zvivered

While the handler waits for the thread to end I want to be able to press other buttons in my dialog. This is not possible now. My main thread freezes the UI.

---

Well, if that's the only requirement: Just remove the loop with the Sleep().

Quote:

---

Originally Posted by gstercken

Well, if that's the only requirement: Just remove the loop with the Sleep().

---

I can't. I want that after the thred ends, the handler will do something else.
Thanks.

Quote:

---

Originally Posted by zvivered

I can't. I want that after the thred ends, the handler will do something else.

---

The handler's purpose is to handle the button click. What else do you want it to do? Whatever that is - wouldn't it be better to put that into the thread function?

If I understand correctly (which I am not sure) you want to be able to interact with the rest of your application except for the button that launched the new thread. If this is the case, you should disable the button when you create the thread, remove the while loop and reenable the button when the thread has finished.

Give your dialog's hwnd to the thread. When the worker thread ends, have it post a message to your dialog to tell it that it's done.

Make your own message, e.g.
#define WM_MYTHREADENDED WM_USER


Then at the end of your worker thread
::PostMessage(hwndDialog, WM_MYTHREADENDED, 0, 0);

And then make a method in your dialog class called OnThreadEnded().

Then in your dialog's message map:
ON_MESSAGE(WM_MYTHREADENDED, OnThreadEnded)

And your method will get called when the thread is done. Does that help?

Quote:

---

Originally Posted by torfil

.... Does that help?

---

It should help: it's a great answer.

Just to be clear, your button click handler should do nothing except start the thread and then exit. The thread then posts the WM_MYTHREADENDED message when it's done, and your message handler for WM_MYTHREADENDED should then perform the steps that you originally wanted to do in your original button click handler (i.e., "the handler will do something else").

If you want to prevent the user from re-clicking the button while the thread is running (for example, maybe it would be a bad thing to try to acquire again while another acquisition is in-process), then you can disable the button in the button click handler and re-enable it in the handler for WM_MYTHREADENDED. Use EnableWindow(FALSE). For example, assuming that your dialog has a member variable of type "CButton" for the button, named m_ctlButtonAcquire:

Code:

---

void CThreadDlg::OnButton1()
{
CreateThread (0,1024*10,Acquire,this,0,&AcquireId);
m_ctlButtonAcquire.EnableWindow(FALSE);
}

LRESULT CThreadDlg::OnWmThreadEnded(LPARAM lParam, WPARAM wParam)
{
// TODO: Add the steps that you wanted to do in the
// original button click handler, i.e., "the handler will do
// something else"
m_ctlButtonAcquire.EnableWindow(TRUE);
return 0L;
}

---

Mike

I solved the problem:
while (GetMessage(&msg,NULL,NULL,NULL) && !ThreadEnd)
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
//Do someting ...

This works great (I Think).

Quote:

---

Originally Posted by zvivered

I solved the problem:
This works great (I Think).

---

You should rather have listened to our suggestions. An additional message pump as you coded it was the usual way to simulate some kind of "multithreading" back in the days of 16-bit Windows. Under Win32, this approach is discouraged (for various reasons). Why don't you simply add the "something else" to the end of your thread procedure? And if that "something else" is supposed to interact with the UI (which you didn't specify): Use a user-defined message and send it to your main thread (as suggested by torfil). And if your thread can't be started multiple times in parallel, but you need to prevent the button from being clicked while the thread executes (which, again, you didn't specify, but it has only been guessed): Disable the button as suggested by EoF.

Quote:

---

Originally Posted by zvivered

I solved the problem:
while (GetMessage(&msg,NULL,NULL,NULL) && !ThreadEnd)
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
//Do someting ...

This works great (I Think).

---

If you're using multithreading, then this is a ridiculous solution. Why start the thread at all? Just do your "Acquire" function in the main thread and pump messages (as above) every once in a while during the acquisition.

The solution you have coded is like being given the keys to a Porsche, and then driving it onto a flatbed truck and driving the truck instead.

Mike

Quote:

---

Originally Posted by gstercken

You should rather have listened to our suggestions. An additional message pump as you coded it was the usual way to simulate some kind of "multithreading" back in the days of 16-bit Windows. Under Win32, this approach is discouraged (for various reasons). Why don't you simply add the "something else" to the end of your thread procedure? And if that "something else" is supposed to interact with the UI (which you didn't specify): Use a user-defined message and send it to your main thread (as suggested by torfil). And if your thread can't be started multiple times in parallel, but you need to prevent the button from being clicked while the thread executes (which, again, you didn't specify, but it has only been guessed): Disable the button as suggested by EoF.

---

Thank you for your time. I learned a lot.

Quote:

---

Originally Posted by MikeAThon

It should help: it's a great answer.

Just to be clear, your button click handler should do nothing except start the thread and then exit. The thread then posts the WM_MYTHREADENDED message when it's done, and your message handler for WM_MYTHREADENDED should then perform the steps that you originally wanted to do in your original button click handler (i.e., "the handler will do something else").

If you want to prevent the user from re-clicking the button while the thread is running (for example, maybe it would be a bad thing to try to acquire again while another acquisition is in-process), then you can disable the button in the button click handler and re-enable it in the handler for WM_MYTHREADENDED. Use EnableWindow(FALSE). For example, assuming that your dialog has a member variable of type "CButton" for the button, named m_ctlButtonAcquire:

Code:

---

void CThreadDlg::OnButton1()
{
CreateThread (0,1024*10,Acquire,this,0,&AcquireId);
m_ctlButtonAcquire.EnableWindow(FALSE);
}

LRESULT CThreadDlg::OnWmThreadEnded(LPARAM lParam, WPARAM wParam)
{
// TODO: Add the steps that you wanted to do in the
// original button click handler, i.e., "the handler will do
// something else"
m_ctlButtonAcquire.EnableWindow(TRUE);
return 0L;
}

---

Mike

---

Thank you for your help. I learned a lot.

[ moved thread ]