I need help how to unfreeze my dialog box. I'm using MFC and I have an infinite loop I want to execute when a button is pressed. However, the dialog box freezes when the infinite loop starts. Now I looked at this thread where someone was having a similar problem.
Unfortunately I tried multithreading but I found out that It can't work for me because I'm using an api that uses OLE automation and I'm getting an unhandled memory exception. I think this is because program uses the serial port and i read somewhere you can only use the handle to the serial port in one thread.
My program is simply to see if someone has dialed in to my modem and wait for them to send me a file, then hangup. Here is my loop.
while(1)
{
//get rid of input buffer
ts->_this->m_pHAScript->haReleaseRemoteInput();
ts-> _this->textBox->SetWindowTextA("thread Commence");
//wait for connected
if(success = ts->_this->m_pHAScript->haWaitForString("CONNECT",timeout))
{
//getFile
if(success = ts->_this->m_pHAScript->haWaitForXfer(5000))
{
//hangup
ts->_this->haTypeText("+++ath\r");
}
}
}
Is there a way to unfreeze the dialog box?
Add this code inside while loop:
MSG msg;
while(PeekMessage(&msg, GetSafeHwnd(), 0, 0, PM_REMOVE))
{
DispatchMessage(&msg);
}
The GUI in Windows relies on a message loop - somewhere in your code, either explicitly or hidden in a framework, there's a loop that checks for a message in a queue and processes it. If anything blocks the code from returning to that loop, the GUI gets frozen.
There are a few ways around this. One was given by David Brabant, essentially duplicating the loop. Another is to start a new "worker" thread that runs the blocking operation independently. If your message loop has a function that it calls when it is idle, i.e. no more messages are in the queue, you can do some processing there; that's not possible in your example however.
Related
I am making a program for a robot in a competition, and need to multithread.
When I make a second task (task two()) and try to start (startTask) it with a button press from a controller, it just executes the first statement of the task and only as long as the button is pressed, instead of the whole block. I've tried many things including putting a loop in the second task also, using a function instead of a task and sleeping for 200 milliseconds before, and after the startTask(two); function, but the same thing happens every time.
I can't post my program because I don't want other people to steal it, sorry.
What edits will make it run the whole block?
Any help would be appreciated.
Since this is Controller Mode, I'm assuming that you are setting the motors to stop when the corresponding button is not pressed.
if([...])
[...]
else
{
setMotorSpeed(motor10, 0);
}
This is the cause for the stopping of the motors when you release. All of the other methods that you tried had nothing to do with this, so they shouldn't have worked.
You need to put something like this:
int Motor10Speed;
[...]
if([...])
[...]
else
{
setMotorSpeed(motor10, Motor10Speed);
}
This will control an individual motor. Repeat this for all other motors being used.
After that is done, make the function look something like this:
task mini_function();
task main()
{
[...]
}
task mini_function()
{
Motor10Speed = 50;
sleep(1000);
Motor10Speed = 0;
}
Expand the above program so it matches your current function, while using the MotorSpeed variables as setMotorSpeed variables.
This should make you able to drive and run a function at the same time without them interrupting each other.
I am making a simulation tool, that runs simulation (in a separate thread) over user defined number of iterations, which can be entered in an Edit control on the Ribbon Bar. I would like to reuse it to show current iteration during simulation. I also also put CMFCRibbonProgressBar to show the progress. The Ribbon Bar is created with resource editor.
The question is what is the what to get the progress bar and iteration counter to get timely updated without causing the GUI to become unresponsive?
The conventional way over ON_UPDATE_COMMAND_UI routines requires activity in the window, like moving the mouse.
So I probably need a thread that would update this controls. Things like simply creating a thread and trying to update the controls from or using concurrency::parallel_invoke are not suitable.The former simply doesn't work, the latter works, but causes GUI to freeze.
I store pointers in my document to simplify access to the controls. https://stackoverflow.com/a/25429446?noredirect=1
My general idea is (pseudocode)
beginUpdatingThread()
{
while(simulating)
{
updateEditControl();
updateProgressBar();
sleep_40_ms();//conserves the resorces as there is no sense to update more frequent than 25 times per second
}
}
What is correct way of implementing this?
ASSERT(m_hWnd!=NULL);
MSG msg;
while (simulating)
{
// Handle dialog messages
while(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
if(!IsDialogMessage(&msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
}
I solved this by adding a method to the main window that performs the update. now the thread updating from above continually post messages to the main window to perform the update:
auto h = static_cast<CMainFrame*>(AfxGetMainWnd())->m_hWnd;
//here code for starting simulation in a separate thread
std::thread updating([this,h]{
while (simulating)
{
::PostMessage(h, WM_UPDATE_VISUALS, sumulator.getCurrentIteration(), 0);
std::this_thread::sleep_for(std::chrono::milliseconds(40));
}
::PostMessage(h, WM_UPDATE_VISUALS, num_iterations, 0);
});
updating.detach()
I made a subtle mistake at first by capturing h by reference, which quickly expires
But in the end, the above code does exactly what I wanted to achieve
I know there has been a few of these, but a lot of the answers always to have a lot of buts, ifs, and you shouldn't do that.
What I'm trying to do is have a background program that can monitor the keyboard events from X11. This is on an embedded device, and it will have a main app basically running in something like a kiosk mode. We want to have a background app that manages a few things, and probably a back doors hook. But this app generally will not have focus.
I can't use the main app, because its partially there for a fail safe if the main app ever fails, or to do some dev type things to bypass the main app.
The best question I found is a few years old, so I'm not sure how up to date it is. This was extremely easy to do with windows.
X KeyPress/Release events capturing irrespective of Window in focus
The correct way for doing that is using Xlib. Using this library you can write code like this:
while (1) {
XNextEvent(display, &report);
switch (report.type) {
case KeyPress:
if (XLookupKeysym(&report.xkey, 0) == XK_space) {
fprintf (stdout, "The space bar was pressed.\n");
}
break;
}
}
// This event loop is rather simple. It only checks for an expose event.
// XNextEvent waits for an event to occur. You can use other methods to get events,
// which are documented in the manual page for XNextEvent.
// Now you will learn how to check if an event is a certain key being pressed.
// The first step is to put case KeyPress: in your switch for report.type.
// Place it in a similar manner as case Expose.
Also you could use poll or select on the special device file that is mapped to your keyboard. In my case is /dev/input/event1.
If you have doubts about what's the special file mapped to your keyborad, read the file /var/log/Xorg.0.log (search for the word keyboard).
Here you have another link of interest: Linux keyboard event capturing /dev/inputX
In my project I have created some network calls to the servlets in separate Thread where before that thread starts I show a spinner as wait progress. Until that network Thread finishes the waitprogress is displayed on to the screen and when I receive response from the server I have to explicitly call progress bar's dispose() method to dispose that progress bar. So, This is bit complicated whenever I make calls establishing GPRS connection while network strength goes down there I found sometimes it takes about 2-3 minutes to throw an IO Exception or receive response from server where I dispose waitprogress, show error message and proceed. I dont add any cancel command to waitprogress as network calls are made using separate thread so disposing waitprogress will allow user to make another call where the user is needed to wait until he gets response.
The above scenario is complicated because the user will not be waiting for this long to get response. There must be some way that whenever I call network Thread and show progress bar the user should be able to cancel all the operations including network thread, go back to previous state and make another call if there is no or poor connectivity.
Here, I am using Lwuit.
In NetworkManager class you can add this function and actived at from your class
only if lwuit is at open code in your application , you can add this function:
public void killAll() {
for (int i = 0; i < pending.size(); i++) {
((ConnectionRequest) pending.elementAt(i)).kill();
}
pending.removeAllElements();
for (int i = 0; i < networkThreads.length; i++) {
networkThreads[i].currentRequest.kill();
}
}
after or before this you need call dispose() method.
Background: I am using OmniThreadLibrary to load batch mode ADO stored procedures in the background. I am doing some slightly dodgy stuff by swapping the connection after opening the SP but that seems to be quite reliable. I'm using PostMessage to send messages back to the calling form and that works in my test applications. Primoz' comms channels work for me, I'm using those for inter-thread comms but for our main application I'm trying to avoid that dependency by using standard PostMessage calls as we do elsewhere in the app.
Problem: Unfortunately when I put this into our main application the PostMessage calls in the thread start failing with 1400:invalid window handle.
I have liberally added extra PostMessage calls and logging code to try to locate the problem, but I'm out of ideas now. The code is boilerplate:
const WM_PW_ADLQUEUEEMPTY = WM_USER + 11;
...
if PostMessage (OwnerHandle, WM_PW_ADLPROGRESS, QueueID, 10) then
pwDebugLog ('TADLQueue.Run WM_PW_ADLPROGRESS send to ' + IntToHex (OwnerHandle, 8) + ' (IsWindow '+BoolToStr(IsWindow(OwnerHandle),true)+') OK for Queue ' + IntToStr (QueueID))
else
pwDebugLog ('TADLQueue.Run WM_PW_ADLPROGRESS send to ' + IntToHex (OwnerHandle, 8) + ' (IsWindow '+BoolToStr(IsWindow(OwnerHandle),true)+') failed for Queue ' + IntToStr (QueueID));
But the log for a series of calls is not very revealing to me. note that the four hex digits after the time is the thread id from GetCurrentThreadID.
15:41:53.221 1614 TpwAsyncDataLoader.RunQueue WM_PW_ADLPROGRESS send to 00A5110C (IsWindow True) OK for Queue -6
15:41:53.265 13B4 TADLQueue.Run WM_PW_ADLPROGRESS send to 00A5110C (IsWindow True) OK for Queue -6
15:41:53.554 13B4 TADLQueueManager.WriteSysErrorMessageToDatabase Postmessage 00A5110C (IsWindow False) failed with 1400 Invalid window handle
Can anyone shed some light on this? I'm confused at how a window handle can become invalid while I'm looking at it, but that's what it looks like to me.
The one thing I can think of is that the form I'm showing here isn't processing messages and I'm seeing a "message queue full" failure rather than the IsWindow(handle) failure that it looks like. How can I test for that?
There are cases where a handle gets recreated, most notably when you change window flags. This might be what's happening in your application.
All I found so far about recreating windows handle is this post from Allen Bauer but I'm certain reading a more detailed one written by Peter Below. Unfortunatly I can't seem to find that one.
Finally, you need to be aware of cases
where your handle may need to get
recreated. This can happen if the
surrounding form or the parent
component's handle goes through a
recreate process. Up until more recent
releases of Windows, the only way to
change some window flags was to
destroy the handle and recreate with
new flags in the CreateWindowEx()
call. There are many components that
still do this. You know if you're in a
recreate situation by checking
(csRecreating in ControlState).
Edit
Not actually the posts from Peter I had in mind but it might give you some fresh ideas.
The form will not have a handle until
you show it the first time (unless
something in the form load sequence
request the handle) but the handle is
not destroyed when you hide the form
and unless you do something that
forces the form to recreate the
handle, e.g. change its border style
or border icons, or call RecreateWnd
yourself the handle will stay the
same.
It may not be desirable but it cannot
be avoided, at least not the way
Delphi drag&dock is currently
implemented. When you dock the dragged
form to another form it becomes a
control (with WS_CHILD window style)
and that means that its window handle
has to be destroyed and recreated with
the new style. And destroying the
window handle of a container control
automatically destroys the handles for
all child controls as well.
and
There is also the fact that the forms
window handle is destroyed and
recreated when you assign to its
Parent property. This also destroys
and recreates the handles for all
controls on the form.
I had a similar issue (but in VC++2010), and I did not find the solution on any forum, so I post it here, hope this will help:
Issue:
Creating a thread,
Passing the HWnd handle
In the thread, PostMessage
throws a 1400 error (invalid handle), although the pointer was equal
with the handle as seen from UI thread (with GetSafeHWnd()).
Solution:
Do not pass the handle, but the parent CDialog(Ex) class
This class has a m_hWnd member that will do the job
Here is a (Cpp) example, sorry for the cast mess.
// In the worker thread
ThreadParam *threadParam = (ThreadParam*)param
// This is ugly because my pointer is a void *, to avoid one more forward declaration
CCoreGenDlg *dlg = static_cast<CCoreGenDlg *>(threadParam->ptr);
// Post
bool b = PostMessage(dlg->m_hWnd ,1221,0,(LPARAM)message);
Cheers'