Hey Guys,
I've another question I couldn't find an answer on the internet. I hope you can help me.
I'm writing an Cocoa Application which runs in background and does several tasks for me. If I quit the application, I show a NSAlert. That all works great. But here comes my problem. This Alert is presented from inside the applicationShouldTerminate: Method. So if I Logout, this method is triggered and the alert is shown. But OSX quits the application and logs out without waiting for a response even if I return NSTerminateCancel.
How can I force the OS to stop logging out/shutting down from within my application, so that the user (myself :-D) can decide what to do. (It just a dialog which asks if the done work shall be saved or not.)
I hope you can help me...
Sandro
Mac OS X is based on UNIX. When a system shuts down, the SIGKILL signal is send that terminates all the processes. But before that, the SIGTERM signal is sent that informs the processes that a shutdown is going to take place.
I think the solution lies in handling of the signals, i.e. detecting and blocking them. Regarding this, you may find guidance in GNU C Library: Signal Handling: Blocking Signals.
The examples there maybe about BSD, but you may know that the OS X core is derived from BSD and therefore OS X supports it. Moreover, C is supported in Objective-C.
Related
I am working with the QuickTime API and need to perform a few lengthy (as in hours) operations in the background. Unfortunately, it is not multi-thread friendly, so I am falling back to perform the tasks in a separate process, so all QuickTime related calls can happen in its main thread.
After launching it, I need a way of getting feedback on its progress, since the operations can take very long.
I am unsure of how to do this, specifically:
Should the separate process be compiled as another cocoa app or a command line tool?
How to launch it from the main cocoa app?
How to periodically get an object from it to get status information?
How to determine when it finished?
How to avoid showing a window/console when called?
How to have it part of the .app bundle so that it does not appear as a separate executable to the user?
These are really 6+ questions, but they are very related and very specific, and I think anyone needing to launch external processes (instead of spawning worker threads) can benefit from their answers. Generic code examples would be very helpful.
If it is possible, then implement the functionality in a command line tool, or another form of GUI-less application. For Cocoa applications it is possible to prevent them appearing on the Dock or in the Force Quit dialog, however a command line tool is a single binary file which does that anyway, so that would probably be a better way.
In terms of launching the tool, NSTask & NSPipe are your friends in this endeavour. The tool can definitely be kept inside your main Application's bundle, inside the Resources directory or some such, and then launched when needed. You can use the pipe to communicate back and forth.
I don't have any example code to hand, and its been a long while since I've had occasion to use either of these classes so the information I can give is limited, but it should be enough to point you in the right direction.
I'm working on porting an app from iOS to WinRT/8 Metro/8 Immersive/Whatever the current name is.
On iOS, we have the ability to set Application does not run in background to YES to cause the app to actually quit whenever the user leaves the app.
I would like to figure out how to replicate this behavior in WinRT.
Yes, I understand that this is abnormal behavior.
Yes, I have thought this through.
Yes, I have an extremely good reason for doing this.
I'm assuming that during the userLeavingApp event, I would just call Application.Current.Exit(), but I can't seem to find the userLeavingApp event. I thought about using OnSuspending (Handles Me.Suspending) in App.xaml.vb, but that doesn't seem to be called quickly enough for me.
Is there a .NET equivalent of viewWillDisappear or something?
Any ideas? This is an important security characteristic of my app, and I'd hate to have such difficulty in an entire platform due to such a small issue.
Thanks!
I'm not actually seeing Application.Current.Exit() working in OnSuspending; although as you mention the suspending isn't happening fast enough for you (which is by design). Throwing an exception there didn't work for me either.
There is Window.VisibilityChanged and if I issue Exit/exception there, it does shutdown the app when another app takes over. That said, VisibilityChanged will fire under other circumstances too so not sure if you could cover all the scenarios or rely on them not changing. See here for a bit more context.
To echo #Filip, whose response just popped in, it's highly unlikely you'll pass certification. An Exit() call is tantamount to an exception.
I don't think your app will pass certification if you call Application.Current.Exit(). If you are really confident this is what you want - I guess it is worth a shot to try. You could though simply unload anything that uses memory/CPU when you exit.
An interesting feature in the new iTunes is it's inability to accept debugger processes that are attached to it (crippling tools like F-Script) Not only would this involve a detection method, but it would require some kind of process that was either checking for the debugger attaching itself mid-run, or an entry-point method that the debugger would emit when it attempts to attach itself. In addition, it would need a way to tell the debugger to go away (as it were) without terminating the process. The question is: How? Clearly, polling for a debugger every X number of seconds is inefficient, and not allowing it to attach to a given process (sans override like ptrace()) seems intensely private.
iTunes is calling ptrace(PT_DENY_ATTACH) which sets the P_LNOATTACH flag which stops debuggers (and other processes, e.g. F-Script and DTrace) from attaching to the process.
See Is it possible to conceal a OS X app from DTrace? for more information.
I wouldn't be surprised if iTunes is also actively using detection methods to identify debuggers. Apple have gone to great lengths to try to protect the DRM in iTunes.
There are a number of books that have methods of securing Cocoa applications, including detecting debuggers. Some potential titles that spring to mind (I haven't double checked the contents of these so don't assume they have detection methods): "Mac Hacker's Handbook", "Hacking and Securing iOS Applications", "Professional Cocoa Application Security" and
"Secure Programming Cookbook for C & C++".
"Mac OS X Internals" and "Mac OS X and iOS Internals" might have something on PT_DENY_ATTACH.
I am using an Olimex sam7s256 board. I tried to get it up and running in linux (Ubuntu). I was able to successfully install GCC and binutils. I installed SAM-BA for linux from the atmel site. I was able to get the USB port for connection as specified in the SAM-BA manual (.dev/ttyUSB0).
But when I try to use the GUI and 'connect' there is no response.
I though that there is a connection failure, so when I presses the reset button in the board, I get a message "Failed to initialize FLASH accesses".
No matter how long I wait before pressing the reset button, I am not getting any SAM-BA window as given by other tutorials as below
can any one one help me out in this?
I did the 'tst' jumper set, reconnect the board for 10 s, disconnect and 'tst' jumper reset, reconnect before opening SAM-BA.
Any help will be greatly appreciated.
I am stuck.
It is the same for both SAM-BA 2.9 and 2.8.
By this point you are already connected. If you specified the at91sam7256-ek even if you arent using that board it will not put this gui up if it didnt talk to the chip/board. I recently went through this exercise with an olimex sam7s-256 header board. (with ubuntu linux). If I didnt specify the board type then the window came up but it wasnt really connected.
Notice how the code at 0x00200000 is valid instructions (most start with a 0xE and the vector table starts with a bunch of 0xEAs which are branches out of the vector table) that is ram it didnt make those up it read that from somewhere. Load a binary file into ram in the 0x00200000 range and the refresh the memory (assuming your binary is different from what is there) and see it change.
When ready/comfortable you can erase the flash and see in the memory window that the flash (0x0010000 or something like that) changes to all 0xFFFFFFFFs. Now remember it wont boot when you do that. With the board I have there is a jumper you move then power the board to get the built in bootloader re-loaded into the flash so that you can use sam-ba again, I am sure there is a way to do that with your board but read the users guide first.
Please do not close this person out for asking about using a software tool. There are countless numbers of how do I use my iphone simulator or why is my android simulator slower than my iphone simulator questions that dont get touched. this question is as relevant as any of the programming questions about how to use gcc or some web thing or how to start up my phone simulator or java vm. I wouldnt want to have to start a campaign to close all of the gcc or iphone tagged questions because they are not programming questions.
I think my question was misunderstood. The GUI window which I have posted is NOT what I get. I just posted it to say that I am not getting such a window at all. That window pops up only when I select 'no board'. When I select SAM7S256-EK there is no response. No window opens. As given in your blog sam7stuff.blogspot.com, I downloaded SAM-BA. The onlydifference as u have posted and in the response also id that u are using a 'h' board.
Right now I am using a custom made SAMBA alternative from this website,
http://claymore.engineer.gvsu.edu/~steriana/Software/
It is also a python based boot loader. It is command line though.
I would love to use the SAM-BA GUI. I am sure that the board is OK and samba is communicating with the board b'cos if I select any other board type other than ARM7S256-EK option it is giving me 'communication failure'.
If you have any suggestions please do let me know. Also many thanks for backing me up. I had some real good insights from this forum about embedded field and I felt it is a good place to discuss embedded programming doubts and never thought of 'programming' or 'non-programming' b'cos for SAM-BA user guide itself talks a lot about customizing the SAM-BA for a custom made board involving TCL scripts but I couldnot get hold of the concepts. So I thought someone would have had the same problem and would have found a TCL or C 'programming' solutions in this forum.
Thank you.
I have a college assignment due quite soon, and I need to be able to call a C++ dll that takes a long time (possibly infinte, it relies on user input)to execute. Im calling this through VB. My VB GUI freezes up when this happens, and I would like to keep the GUI responsive, so that the user can stop this possibly infinte loop.
Can anyone suggest the best/fastest way of doing this?
A bit of background, the C++ is trying to keep score on a snooker table using a webcam, and while the VB scoreboard updates easily, I would like to script it so that the analysis is almost continuous, while still allowing the user to interact. Currently the project requires the user to press a button to start the shot analysis, but it would be preferable if the program scripted itself. I have only realised this problem now and the deadline is very soon.
Update: Our lecturer suggested an option to solve the problem, but it would appear that most options here and the one he suggested will not work for us as the processing time required for the webcam image capture is too great to handle due to hardware constraints. Thanks for taking the time to help, it was much appreciated!
The best way to handle threading in VB.NET is via the System.Threading namespace.
You might also look into Application.DoEvents()
Try the system.Threading as Mark said, also try looking at Background Worker Process which is a bit simpler in VB.NET. Readup here
I would definitely use the Background Worker process. You can drag it onto your form and use the DoWork sub routine to actually do the work that is freezing your GUI thread. You can also use the ReportProgress event to actually provide progress back to your form.
As for your question regarding two separate threads, If both steps take a long time to complete I would run them in the same thread one after the other.
The one thing that could bite you with using the thread is cross-threading. In the context of your problem this means not having your second thread update form controls.
A really good resource for how to implement this code along with dealing with cross-threading is this PDF.
I also should point out that if you are using .net 1.0/1.1 you can still do the multi-threading, but don't have the luxary of having a background worker control. You'd just have to create a new thread from the System.Threading Namespace.
Just as an alternative, you could have your C++ actually processing in the background all the time. When called from VB, it would just be retrieving data from it or sending it a command (start, quit, ???) all of which would return instantly.
This could also give you more reliability since C++ would never miss video frames while VB was collecting the garbage or doing the dishes or whatever VB does in the background--C++ is going to let you be closer to a real time system.
RE: the comment about how.
What I'd probably do is have my VB programs send "Messages" to the C++ (As I said). A message is just a way to think of a function/method call--but generally they return quickly.
The "Start" message would tell the C++ code to start it's thread running and return. This is a Linux C++ thread howto, I'm not sure if you need to do something different in windows (I'd hope not, but I haven't used C++ as my main dev. language in decades).
If that doesn't work, just google "C++ Threads"
Sending a "Stop" message would stop the thread (and probably free resources).
A "Get Data" call would go to the location that the C++ thread used to store data, grab it and return.
Sorry to be so general, I'm pretty heavily Java these days.
I'm surprised nobody has suggested using a BackgroundWorker yet.