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  • Is true multithreading really necessary?

    - by Jonathan Graef
    So yeah, I'm creating a programming language. And the language allows multiple threads. But, all threads are synchronized with a global interpreter lock, which means only one thread is allowed to execute at a time. The only way to get the threads to switch off is to explicitly tell the current thread to wait, which allows another thread to execute. Parallel processing is of course possible by spawning multiple processes, but the variables and objects in one process cannot be accessed from another. However the language does have a fairly efficient IPC interface for communicating between processes. My question is: Would there ever be a reason to have multiple, unsynchronized threads within a single process (thus circumventing the GIL)? Why not just put thread.wait() statements in key positions in the program logic (presuming thread.wait() isn't a CPU hog, of course)? I understand that certain other languages that use a GIL have processor scheduling issues (cough Python), but they have all been resolved.

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  • What if we run out of stack space in C# or Python?

    - by dotneteer
    Supposing we are running a recursive algorithm on a very large data set that requires, say, 1 million recursive calls. Normally, one would solve such a large problem by converting recursion to a loop and a stack, but what if we do not want to or cannot rewrite the algorithm? Python has the sys.setrecursionlimit(int) method to set the number of recursions. However, this is only part of the story; the program can still run our of stack space. C# does not have a equivalent method. Fortunately, both C# and Python have option to set the stack space when creating a thread. In C#, there is an overloaded constructor for the Thread class that accepts a parameter for the stack size: Thread t = new Thread(work, stackSize); In Python, we can set the stack size by calling: threading.stack_size(67108864) We can then run our work under a new thread with increased stack size.

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  • Multithreading synchronization interview question: Find n words given m threads

    - by rplusg
    I came across this question: You are given a paragraph , which contain n number of words, you are given m threads. What you need to do is , each thread should print one word and give the control to next thread, this way each thread will keep on printing one word , in case last thread come, it should invoke the first thread. Printing will repeat until all the words are printed in paragraph. Finally all threads should exit gracefully. What kind of synchronization will use? I strongly feel we cannot take any advantage of threads here but interviewer is trying to understand my synchronization skills? No need of code, just put some thoughts. I will implement by myself.

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  • usage of setPropertyListener and setActionListener

    - by Vijay Mohan
    The incorrect usage could lead to hard-to-debug problems so better to understand the fundamentals behind it's working.setpropertyListener queues an event on the server side, so if for a command component you have a showPopup behavior/actionListner as well as setPropertyListener then fwk does the queuing correctly and raises further event on the component. While, the setactionListener simply raises an event on the server side instead of queueing it, so any further event on command component gets cancelled.Also, if you use an ActionListener and showPopup behavior together on a command component, then the order of their invocation is undetermined and also one of event gets cancelled on the component. So, either use only actionListner and do the popup invocation stuff progrmmatically in your bean or use the declarative stuff logically so that no clash of event happens.

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  • Data Binding to Attached Properties

    - by Chris Gardner
    Originally posted on: http://geekswithblogs.net/freestylecoding/archive/2013/06/14/data-binding-to-attached-properties.aspx When I was working on my C#/XAML game framework, I discovered I wanted to try to data bind my sprites to background objects. That way, I could update my objects and the draw functionality would take care of the work for me. After a little experimenting and web searching, it appeared this concept was an impossible dream. Of course, when has that ever stopped me? In my typical way, I started to massively dive down the rabbit hole. I created a sprite on a canvas, and I bound it to a background object. <Canvas Name="GameField" Background="Black"> <Image Name="PlayerStrite" Source="Assets/Ship.png" Width="50" Height="50" Canvas.Left="{Binding X}" Canvas.Top="{Binding Y}"/> </Canvas> Now, we wire the UI item to the background item. public MainPage() { this.InitializeComponent(); this.Loaded += StartGame; }   void StartGame( object sender, RoutedEventArgs e ) { BindingPlayer _Player = new BindingPlayer(); _Player.X = Window.Current.Bounds.Height - PlayerSprite.Height; _Player.X = ( Window.Current.Bounds.Width - PlayerSprite.Width ) / 2.0; } Of course, now we need to actually have our background object. public class BindingPlayer : INotifyPropertyChanged { private double m_X; public double X { get { return m_X; } set { m_X = value; NotifyPropertyChanged(); } }   private double m_Y; public double Y { get { return m_Y; } set { m_Y = value; NotifyPropertyChanged(); } }   public event PropertyChangedEventHandler PropertyChanged; protected void NotifyPropertyChanged( [CallerMemberName] string p_PropertyName = null ) { if( PropertyChanged != null ) PropertyChanged( this, new PropertyChangedEventArgs( p_PropertyName ) ); } } I fired this baby up, and my sprite was correctly positioned on the screen. Maybe the sky wasn't falling after all. Wouldn't it be great if that was the case? I created some code to allow me to move the sprite, but nothing happened. This seems odd. So, I start debugging the application and stepping through code. Everything appears to be working. Time to dig a little deeper. After much profanity was spewed, I stumbled upon a breakthrough. The code only looked like it was working. What was really happening is that there was an exception being thrown in the background thread that I never saw. Apparently, the key call was the one to PropertyChanged. If PropertyChanged is not called on the UI thread, the UI thread ignores the call. Actually, it throws an exception and the background thread silently crashes. Of course, you'll never see this unless you're looking REALLY carefully. This seemed to be a simple problem. I just need to marshal this to the UI thread. Unfortunately, this object has no knowledge of this mythical UI Thread in which we speak. So, I had to pull the UI Thread out of thin air. Let's change our PropertyChanged call to look this. public event PropertyChangedEventHandler PropertyChanged; protected void NotifyPropertyChanged( [CallerMemberName] string p_PropertyName = null ) { if( PropertyChanged != null ) Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync( Windows.UI.Core.CoreDispatcherPriority.Normal, new Windows.UI.Core.DispatchedHandler( () => { PropertyChanged( this, new PropertyChangedEventArgs( p_PropertyName ) ); } ) ); } Now, we raised our notification on the UI thread. Everything is fine, people are happy, and the world moves on. You may have noticed that I didn't await my call to the dispatcher. This was intentional. If I am trying to update a slew of sprites, I don't want thread being hung while I wait my turn. Thus, I send the message and move on. It is worth nothing that this is NOT the most efficient way to do this for game programming. We'll get to that in another blog post. However, it is perfectly acceptable for a business app that is running a background task that would like to notify the UI thread of progress on a periodic basis. It is worth noting that this code was written for a Windows Store App. You can do the same thing with WP8 and WPF. The call to the marshaler changes, but it is the same idea.

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  • Area of testing

    - by ?????? ??????????
    I'm trying to understand which part of my code I should to test. I have some code. Below is example of this code, just to understand the idea. Depends of some parametrs I put one or another currency to "Event" and return his serialization in the controller. Which part of code I should to test? Just the final serialization, or only "Event" or every method: getJson, getRows, fillCurrency, setCurrency? class Controller { public function getJson() { $rows = $eventManager->getRows(); return new JsonResponse($rows); } } class EventManager { public function getRows() { //some code here if ($parameter == true) { $this->fillCurrency($event, $currency); } } public function fillCurrency($event, $currency) { //some code here if ($parameters == true) { $event->setCurrency($currency); } } } class Event { public function setCurrency($currency) { $this->updatedAt = new Datetime(); $this->currency = $currency; } }

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  • Corona sdk events dispatched with dispatchEvent() are handled directly upon call. Why so?

    - by Amoxus
    I noticed to my surprise that an event created with dispatchEvent(event) gets handled directly when called, and not together with other events at a specific phase of the frame loop. Two main reasons of having an event system are: so that you can call code B from code A, but still want to prioritize code A. to make sure there are no freaky loopedy loops where code A calls code B calls code A ... I wonder what Ansca's rationale behind having events being handled directly this way is. And does Corona handle loopedy loops and other such pitfalls gracefully? The following code demonstrates dispatchEvent(): T= {} Z = display.newRect(100,100,100,100) function T.doSomething() print("T.doSomething: begun") local event = { name="myEventType", target=T } Z:dispatchEvent( event ) print("T.doSomething: ended") end function Z.sayHello(event) print("Z.sayHello: begun and ended") end Z:addEventListener("myEventType", Z.sayHello) print("Main: begun") T.doSomething() print("Main: ended") However Ansca claims the contrary at http://developer.coronalabs.com/reference/index/objectdispatchevent Can anyone clear this up a little? ( Using Corona simulator V 2012.840 )

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  • How to write specs with MSpec for code that changes Thread.CurrentPrincipal?

    - by Dan Jensen
    I've been converting some old specs to MSpec (were using NUnit/SpecUnit). The specs are for a view model, and the view model in question does some custom security checking. We have a helper method in our specs which will setup fake security credentials for the Thread.CurrentPrincipal. This worked fine in the old unit tests, but fails in MSpec. Specifically, I'm getting this exception: "System.Runtime.Serialization.SerializationException: Type is not resolved for member" It happens when part of the SUT tries to read the app config file. If I comment out the line which sets the CurrentPrincipal (or simply call it after the part that checks the config file), the error goes away, but the tests fail due to lack of credentials. Similarly, if I set the CurrentPrincipal to null, the error goes away, but again the tests fail because the credentials aren't set. I've googled this, and found some posts about making sure the custom principal is serializable when it crosses AppDomain boundaries (usually in reference to web apps). In our case, this is not a web app, and I'm not crossing any AppDomains. Our pincipal object is also serializable. I downloaded the source for MSpec, and found that the ConsoleRunner calls a class named AppDomainRunner. I haven't debugged into it, but it looks like it's running the specs in different app domains. So does anyone have any ideas on how I can overcome this? I really like MSpec, and would love to use it exclusively. But I need to be able to supply fake security credentials while running the tests. Thanks! Update: here's the spec class: [Subject(typeof(CountryPickerViewModel))] public class When_the_user_makes_a_selection : PickerViewModelSpecsBase { protected static CountryPickerViewModel picker; Establish context = () => { SetupFakeSecurityCredentials(); CreateFactoryStubs(); StubLookupServicer<ICountryLookupServicer>() .WithData(BuildActiveItems(new [] { "USA", "UK" })); picker = new CountryPickerViewModel(ViewFactory, ViewModelFactory, BusinessLogicFactory, CacheFactory); }; Because of = () => picker.SelectedItem = picker.Items[0]; Behaves_like<Picker_that_has_a_selected_item> a_picker_with_a_selection; } We have a number of these "picker" view models, all of which exhibit some common behavior. So I'm using the Behaviors feature of MSpec. This particular class is simulating the user selecting something from the (WPF) control which is bound to this VM. The SetupFakeSecurityCredentials() method is simply setting Thread.CurrentPrincipal to an instance of our custom principal, where the prinipal has been populated will full-access rights. Here's a fake CountryPickerViewModel which is enough to cause the error: public class CountryPickerViewModel { public CountryPickerViewModel(IViewFactory viewFactory, IViewModelFactory viewModelFactory, ICoreBusinessLogicFactory businessLogicFactory, ICacheFactory cacheFactory) { Items = new Collection<int>(); var validator = ValidationFactory.CreateValidator<object>(); } public int SelectedItem { get; set; } public Collection<int> Items { get; private set; } } It's the ValidationFactory call which blows up. ValidationFactory is an Enterprise Library object, which tries to access the config.

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  • Windows 2008 R2 Task Scheduler triggered an event for unknown reasons.

    - by Mike
    Today I arrived at the office only to find that a task, which was scheduled to trigger at 5:30PM EST each Friday, had triggered on its own at 6:01AM EST this morning. I checked the event logs as well as the task schedule log and all of the evidence points to a timed trigger starting this task with the correct credentials, however the task history reports the task has not been triggered since last Friday when it ran to completion successfully. I do not have this task set to random start times or start if missed. This is the first time I have observed this happen in the Windows Task Scheduler and want to know if anyone else has come across this, why it happened and how to fix it?

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  • How to run long time process on Udev event?

    - by neclude
    (sorry for my bad english) I want run ppp connection when my usb modem is connect. so i use next udev rule: ACTION=="add", SUBSYSTEM=="tty", ATTRS{idVendor}=="16d8",\ RUN+="/usr/local/bin/newPPP.sh $env{DEVNAME}" (my modem appear in /dev as ttyACM0) newPPP.sh: #!/bin/bash /usr/bin/pon prov $1 >/dev/null 2>&1 & Problem: udev event fire, newPPP.sh running, BUT newPPP.sh process will be killed after ~4-5s. ppp not have time to connect. (in it params is timeout 10s for dial up). How can i run long time process, that will not be killed? (I was try nohup. It don't work too.) System: Arch Linux

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  • How to write onclick event for ListView in Android?

    - by Srikanth Naidu
    Hi i have the listview the sixitems in it, but when i call alet function on event it doesnt work ? let me know how to write a function on item event on click? public class PhotoListView extends ListActivity { String[] listItems = {"HeadShot", "BodyShot ", "ExtraShot", "Video Take1", "Video Take2", "Video Take3", }; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); setListAdapter(new ArrayAdapter(this,android.R.layout.simple_list_item_1, listItems)); } OnListclick ListView Shot = getListView(); protected void onListItemClick(View view) { if(view == Shot){ AlertDialog.Builder alertbox = new AlertDialog.Builder(this); // set the message to display alertbox.setMessage("Please Get Ready"); }

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  • Difference between performSelectorInBackground and NSOperation Subclass

    - by AmitSri
    I have created one testing app for running deep counter loop. I run the loop fuction in background thread using performSelectorInBackground and also NSOperation subclass separately. I am also using performSelectorOnMainThread to notify main thread within backgroundthread method and [NSNotificationCenter defaultCenter] postNotificationName within NSOperation subclass to notify main thread for updating UI. Initially both the implementation giving me same result and i am able to update UI without having any problem. The only difference i found is the Thread count between two implementations. The performSelectorInBackground implementation created one thread and got terminated after loop finished and my app thread count again goes to 1. The NSOperation subclass implementation created two new threads and keep exists in the application and i can see 3 threads after loop got finished in main() function. So, my question is why two threads created by NSOperation and why it didn't get terminated just like the first background thread implementation? I am little bit confuse and unable to decide which implementation is best in-terms of performance and memory management. Thanks

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  • How to do early binding for event handler in JavaScript? (example with jQuery)

    - by Sven Larson
    JavaScript's late binding is great. But how do I early bind when I want to? I am using jQuery to add links with event handlers in a loop to a div. The variable 'aTag ' changes in the loop. When I click the links later, all links alert the same message, which is the last value of 'aTag'. How do I bind a different alert message to all links? All links should alert with the value that aTag had when the event handler was added, not when it was clicked. for (aTag in tagList) { if (tagList.hasOwnProperty(aTag)) { nextTag = $('<a href="#"></a>'); nextTag.text(aTag); nextTag.click(function() { alert(aTag); }); $('#mydiv').append(nextTag); $('#mydiv').append(' '); } }

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  • C#, WinForms: Why aren't KeyDown events chaining up to Form? I have to add event handler to each chi

    - by blak3r
    As i understand it, when a button is pressed it should first invoke the Control which has focus' KeyDown Handler, then it call the KeyDown handler for any Parent controls, all the way up to the main form. The only thing that would stop the chain would be if somewhere along the chain one of the EventHandlers did: e.SuppressKeyPress = true; e.Handled = true; In my case, KeyDown events never get to the main form. I have Form - Panel - button for example. Panel doesn't offer a KeyDown Event, but it shouldn't stop it from reaching the main form right? Right now as a work around I set every single control to call an event handler I wrote. I'm basically trying to prevent Alt-F4 from closing the application and instead minimize it.

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  • Please help. Creating threads and wait till finsh

    - by Raj Aththanayake
    Hi I have two method calls that I want to call using two threads. Then I want them to wait till method executions get completed before continuing. My sample solution is something like below. public static void Main() { Console.WriteLine("Main thread starting."); String[] strThreads = new String[] { "one", "two" }; String ctemp = string.Empty; foreach (String c in strThreads) { ctemp = c; Thread thread = new Thread(delegate() { MethodCall(ctemp); }); thread.Start(); thread.Join(); } Console.WriteLine("Main thread ending."); Console.Read(); } public static void MethodCalls(string number) { Console.WriteLine("Method call " + number); } Is this will do the job? Or is there another better way to do the same thing?

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  • Converting Asynchronous Programming Model (Begin/End methods) into event-based asynchronous model?

    - by David
    Let's say I have code that uses the Asynchronous Programming Model, i.e. it provides the following methods as a group which can be used synchronously or asynchronously: public MethodResult Operation(<method params>); public IAsyncResult BeginOperation(<method params>, AsyncCallback callback, object state); public MethodResult EndOperation(IAsyncResult ar); What I want to do is wrap this code with an additional layer that will transform it into the event-driven asynchronous model, like so: public void OperationAsync(<method params>); public event OperationCompletedEventHandler OperationCompleted; public delegate void OperationCompletedEventHandler(object sender, OperationCompletedEventArgs e); Does anyone have any guidance (or links to such guidance) on how to accomplish this?

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  • JW Player - How can I add an event listener for fullscreen toggling?

    - by Charles
    I'm using JW Player 4.5 on my site and I need to add an event listener for when fullscreen is toggled. The reason for this is to switch between a low-def version and high-def version. The default video will be the low-def version and when they switch to a fullscreen display, it will change to the high-def version. According to http://developer.longtailvideo.com/trac/wiki/Player5Events, the ViewEvent.JWPLAYER_VIEW_FULLSCREEN1 event can only be called from Actionscript. I need it to be from Javascript... Is there any way to achieve this? Can you recommend a better solution?

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  • How to cancel drop event in YUI drag & drop utility?

    - by gk
    We are using drag & drop utility between one source and multiple targets. We have a restriction that one of the target can only have one child element while the other ones can have multiple items. I have tried subscribing dragDropEvent of the proxy item and returning false in case the destination target has multiple child elements, with out much luck. var m = new YAHOO.example.DDList("dli" + j, 'documentSelection'); m.subscribe('dragDropEvent', function(e){ if (e.info == 'ulMasterDocument' && $('#ulMasterDocument').children().length > 1){ e.event.canceBubble = true; return false; } return true; }); Is this code correct? Or do i need to subscribe some other event? Thanks

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  • Why does an event handler never get called if it's added within a loop on an ienumerable?

    - by André Carvalho
    Why does an event handler never get called if it's added within a loop on an ienumerable? For instance: IEnumerable<MyType> list = someCollection.Select(i => new MyType(i)); foreach (var item in list) item.PropertyChanged += item_PropertyChanged; <-- this never gets called Bu if list is assigned like list = someCollection.Select(i => new MyType(i)).ToArray(); the event handler does get called.. Why? (I imagine it has something to do with the fact that a LINQ query is lazy, but the fact of looping through the result isn't enough?)

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  • How can I pass checkbox onclick event to parent onclick ?

    - by Kim
    I a with an onclick event and , and inside it. When I click on the checkbox then the div-onclick event doesnt fire - I would like it to fire without having to dublicate the onclick onto the checkbox. <div id="id-tag" onclick="do()"> <span>text</span> <img src="pic.jpg" /> <input type="checkbox" name="mycheck" /> </div> I know the div-idtag but ideally would like to avoid specifying it inside the checkbox. Using another function call on the checkbox onclick to call the parent is NOT what I am looking for, like onclick="run_parent_onclick()" but this is okay (untested) onclick="this.parent.click()"

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  • jQuery - draggable images on iPad / iPhone - how to integrate event.preventDefault();?

    - by Tim
    Hello! I use jQuery, jQuery UI and jQuery mobile to build a web application for iPhone / iPad. Now I create images and they should be draggable, so I did this: <!DOCTYPE html> <html> <head> <meta http-equiv="Content-type" content="text/html; charset=utf-8"> <title>Drag - Test</title> <link rel="stylesheet" href="http://code.jquery.com/mobile/1.0a2/jquery.mobile-1.0a2.min.css" /> <script src="http://code.jquery.com/jquery-1.4.4.min.js"></script> <script src="http://code.jquery.com/mobile/1.0a2/jquery.mobile-1.0a2.min.js"></script> <script src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.8.7/jquery-ui.min.js"></script> </head> <body> <div> <div style="width:500px;height:500px;border:1px solid red;"> <img src="http://upload.wikimedia.org/wikipedia/en/thumb/9/9e/JQuery_logo.svg/200px-JQuery_logo.svg.png" class="draggable" alt="jQuery logo" /> <img src="http://upload.wikimedia.org/wikipedia/en/a/ab/Apple-logo.png" class="draggable" alt="Apple Inc. logo" /> </div> </div> </body> <script type="text/javascript"> $(document).ready(function() { $(".draggable").draggable(); }); </script> </html> Here you can see the live example: http://jsbin.com/igena4/ The problem is, that the whole page want to scroll. I searched in Apple's HTML5 examples and found this to prevent the scrolling of the page, so that the image is draggable: ... onDragStart: function(event) { // stop page from panning on iPhone/iPad - we're moving a note, not the page event.preventDefault(); ... } But the problem is for me, how can I include this into my jQuery? Where do I get event? Best Regards.

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  • How to make an HTTP request in a separate thread with timeout?

    - by Vitaly
    Hi, I haven't programmed in Delphi for a while and frankly didn't think I'll ever have to but... Here I am, desperately trying to find some information on the matter and it's so scarce nowadays, I can't find anything. So maybe you guys could help me out. Currently my application uses Synapse library to make HTTP calls, but it doesn't allow for setting a timeout. Usually, that's not a big problem, but now I absolutely must to have a timeout to handle any connectivity issues nicely. What I'm looking for, is a library (synchronous or not) that will allow making HTTP requests absolutely transparent for the user with no visible or hidden delays. I can't immediately kill a thread right now, and with possibility of many frequent requests to the server that is not responding, it's no good.

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  • To detect if the user is closing the IE browser apart from onunload event, as it is triggerred when

    - by AndAars
    hi, After being through numerous forums available on the net for last 5 days, I am still not able to completely track down the browser close event. My requirement is to generate a popup message, when user tries to close the browser. I have called my javascript function on body 'onbeforeunload' event. And I have hardcoded the conditions to check the mouse-coordinates for the red 'X' buton of browser, refresh, File-close or Alt-F4. My code works fine when browser window is Maximized, but fails if we shrink it after a limit. Please help me, if some body has already found the solution to a similar problem. Thank you. Aggregated Responses of OP Ok, just tell me if it is possible to detect if a user has clicked on the Refresh button of the browser. Also, Refresh can be triggered by Right-click - Refresh or Ctrl-R. My requirement is to make a variable false on Refresh. I am just able to do it on F5, but all other ways are still out of my reach. The same would be applied to Back buton. Hi ppl, Thanks for all who replied atleast. I have talked to my seniors regarding this and they have now understood and have compromised with the browser menu buttons. So now my task has become easy. Now, I am using a variable and making it true by default. As, I mentioned earlier I just have to catch the onbeforeunload and popup a message when user tries to leave. The message will not popup when user is navigating to other pages, as I have made the variable as false on all the links of my page using following piece of code: document.onclick = function() { //To check if user is navigating from the page by clicking on a hyperlink. if (event.srcElement.tagName == 'A') blnShowMsg = false; //To not popup the warning message else blnShowMsg = true; //To popup the warning message } In my case still the message is shown when user does Refresh, back or goes to any link in Favorites, etc. Thanks buddy, but I have already gone through that and didn't find much help there too. My seniors are not happy with that solution as putting a flag on evry link of my application is a complicated job and they fear of breaking the application. Any other suggestions would be appreciated. Thanks once again. Is there no one who can think of a solution here!!! where are all the experts???

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  • MovieClip.onResize event? how?

    - by Phil
    I have a an swf, called 'controls' that I created with flash cs4. I upload the controls.swf to my web server. I create an application in flex and it loads the external swf controls into itself. So far I can manipulate the controls.swf via my flex app. I created a class in my external swf, but I need to add some onResize event/check to my scroll bar. For example, if my scrollbar size increases/decreases, I want it to change variable values. Is there some movieClip.onResize event?

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