when using FlexPrintJob, after calling start(), a OS system print interface will appear, and at the same time Flex code execution will be paused, and it will remain paused until user finished interaction with the OS print dialog. the problem is I do have data from server, and the connection will time out within certain period, so is there any walk around to not pause the Flex code execution while OS print dialog is popped up. Thanks.
From the doc for FlexPrintJob:
You use the FlexPrintJob class to print a dynamically rendered document that you format specifically for printing.
This makes me wonder if you couldn't (essentially) fork off a second page from the browser that contains your print job and do the printing from there. This would leave your original page still running. In my flex apps I do this via PHP (create additional pages for printing and such). Example here.
Otherwise: you should finish all the server data d/l before starting the print job to avoid this issue.
Flex is only just recently starting to add multi-threading. It's adding worker threads of a sort but this won't help what you're asking for.
Related
So I have a long-running python notebook.
As long as it's open in my browser's tab, it's autosaving every 2 minutes, and life is good.
Is it possible to keep it auto-saving even if I close the browser tab?
The kernel already keeps running when I close the tab, which is great.
This is kind of like "screen", but in jupyter
EDIT: Even if I leave the tab open in my browser, I noticed that after 24 hours, the "kernel status" in the top right becomes "disconnected", even though the running cell still has output being piped to it from the server websocket connection
No, you can't (for now), and their will be no point in doing it.
The reason is, as soon as you close your tab, some critical information is lost because it is in the memory of the Javascript VM that run the page.
Any update sent by the kernel after you've closed your page are lost.For example try the following.
create a cell with sleep(10);print('Hello')
Execute the cell
Quickly close and reopen the tab.
the "Hello" will never be printed.
The mapping between the "Execution request" and the "Execution reply" have been lost, and can't be recovered.
The Jupyter team is aware of that. The fixes are not that hard, but require a lot of careful refactor and API design. There was a long in person discussion in NYC at the end of August 2017. Right now the focus is to polish JupyterLab, and once this is done it will be one of the area of focus. It will go hand in hand with real-time collaboration.
In more detail, the fix requires to "move" the notebook model from the client (your browser) to a server side (what is serverside is handwaved for now, but here is not the place to expand it), there are technical questions about that, like what to do with widgets, and when collaborating what state is shared by everyone and what state is per-client. Like if you fold some code, should this be stored ? or not ?
If you are interested in that, I would suggest getting involved with JupyterLab, there will be soon a number of low hanging fruits to contribute that should quickly fix 80% of the usecases.
My Qt 4 application can only update the log box area (actually the whole GUI) until a function finishes execution. Is there any way to update the GUI/log box during the execution? Like adding something like QWidget::repaint() or QWidget::update() in the for loop, so the user can see that the GUI is processing, rather than wait until the function finishes and print out the log at once.
You need to occasionally call QCoreApplication::processEvents() during the execution of your function. This will keep the GUI alive and responsive by letting the event loop run.
An alternative is to execute your function in a separate thread. More information on threads in Qt can be found here: http://qt-project.org/doc/qt-4.8/threads.html.
I have a servlet program for counting numbers, I want to control it through an html interface.
by pressing the start button the program must start running and by pressing pause button the servlet program must be paused and by clicking on the restart button it must restart again. by the way i used thread. My problem is that each time I should click one button and send its value to the servlet, and when I'm getting the buttons values inside the servlet a NullPointerException is occur... any help ??
I wouldn't use a Thread for that purpose and in general is not usually a good idea to create threads in servlets.
Say we count one number per millisecond meaning: it will give me the time between one click and another in milliseconds.
One work around could be:
Click on start = save the start time in the session.
click on stop = to get the count we do currentTime-StartTime (saved in session)
Now if you really must use Threads be sure then to create it using another class.
One suggestion might be create a ThreadManager class and store it in the session (use a listener for this) and then start it in that session object.
Even better store the ThreadManager inside the servletContext and have a way to create your thread per session.
To create Threads favor the Executor classes instead of the Thread classes.
Also make sure you stop your threads since having threads created by us inside a web container may prevent it from stoping entirely.
If you provide some code I can help you further.
Good luck, have fun.
I have an application which makes use of 20 different classes. The program execution starts in mainwindow. I start a progress dialog. I will make use of different classes for different purposes. After each function call which the execution goes to the particular class and does the required and come back to the mainwindow class, I will update the progress dialog. Now, the issue is the progress dialog freezes when the execution goes away from the mainwindow class. The cancel button is unable to accessed and so, the execution could not be stopped at the required time.
mainclass::mainclass()
{
ProgressDialog->exec();
x->add();
updateProgressDialog();
y->do();
updateProgressDialog();
zz->bring();
updateProgressDialog();
}
// x, y, z are three different classes.
This is how the execution goes. As soon as I enter the function in the main class, I will start the progress dialog. and call functions from different classes. The functions take considerable amount of time. I have invoked a thread to do the execution part, but I am unable to cancel the progress diaolog. I want the program execution to be stopped as and when the cancel button is pressed on the proggress dialog.
Please let me know how to get away with this issue. Hope I am clear here.
Without knowing exactly what calculations are being preformed in your threads its hard to isolate the problem. Maybe this can help: Keeping the GUI Responsive
Excerpt from: Performing Long Operations (by: Witold Wysota)
During long calculations (regardless of any usage of signals and slots) all event processing gets halted. As a result, the GUI is not refreshed, user input is not processed, network activity stops and timers don't fire—the application looks like it's frozen and, in fact, the part of it not related to the time-intensive task is frozen.
The functions you are calling are not processing the Qt events loop. You are using a modal progress bar, since you are calling exec(). This means that Qt only gets control at the times where you update the dialog.
The only way that I know of to work around this is to code the dialog as modeless, but you will also have to provide an opportunity for the events loop to process.
This is explained in a fair amount of detail in the Qt docs: QProgressDialog
I have been involved in building a custum QGIS application in which live data is to be shown on the viewer of the application.
The IPC being used is unix message queues.
The data is to be refreshed at a specified interval say, 3 seconds.
Now the problem that i am facing is that the processing of the data which is to be shown is taking more than 3 seconds,so what i have done is that before the app starts to process data for the next update,the refresh QTimer is stopped and after the data is processed i again restart the QTimer.The app should work in such a way that after an update/refresh(during this refresh the app goes unresponsive) the user should get ample time to continue to work on the app apart from seeing the data being updated.I am able to get acceptable pauses for the user to work-- in one scenario.
But on different OS(RHEL 5.0 to RHEL 5.2) the situation is something different.The timer goes wild and continues to fire without giving any pauses b/w the successive updates thus going into an infinite loop.Handling this update data definitely takes longer than 3 sec,but for that very reason i have stopped-restarted the timer while processing..and the same logic works in one scenario while in other it doesnt.. The other fact that i have observed is that when this quick firing of the timer happens the time taken by the refreshing function to exit is very small abt 300ms so the start-stop of the timer that i have placed at the start-and-end of this function happens in that small time..so before the actual processing of the data finishes,there are 3-4 starts of the timer in queue waiting to be executed and thus the infinite looping problem gets worse from that point for every successive update.
The important thing to note here is that for the same code in one OS the refresh time is shown to be as around 4000ms(the actual processing time taken for the same amount of data) while for the other OS its 300ms.
Maybe this has something to do with newer libs on the updated OS..but I dont know how to debug it because i am not able to get any clues why its happening as such... maybe something related to pthreads has changed b/w the OSs??
So, my query is that is there any way that will assure that some processing in my app is timerised(and which is independent of the OS) without using QTimer as i think that QTimer is not a good option to achieve what i want??
What option can be there?? pthreads or Boost threads? which one would be better if i am to use threads as an alternate??But how can i make sure atleast a 3 second gap b/w successive updates no matter how long the update processing takes?
Kindly help.
Thanks.
If I was trying to get an acceptable, longer-term solution, I would investigate updating your display in a separate thread. In that thread, you could paint the display to an image, updating as often as you desire... although you might want to throttle the thread so it doesn't take all of the processing time available. Then in the UI thread, you could read that image and draw it to screen. That could improve your responsiveness to panning, since you could be displaying different parts of the image. You could update the image every 3 seconds based on a timer (just redraw from the source), or you could have the other thread emit a signal whenever the new data is completely refreshed.