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• Hp Pavilion dv6000 wont boot right and freezes

  - by MalwareManiac

  I have an hp pavilion dv6000 that was having windows issues recently including randomly freezing. I eventually concluded that the hard drive was bad (And I was correct as the bad drive started making funny noises and quit working soon after). So I replaced it with a known good drive and put windows on it and it worked for a few hours. After a few restarts startup didn't even make it to the login screen. It just stays at a lighted black screen until I restarted. After another restart it made it to windows but then froze after a few minutes. A few more restarts yielded one of these two results. Like I mentioned earlier I have a know good drive in it and I also replaced the memory that was in it with a know good stick along with running memtest with no errors. So What does that leave? a corrupted windows installation? Motherboard? CPU? Any ideas?

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• Memory Usage by Mapped Files (Win7 64Bit)

  - by Dexter

  When copying files from/to my external USB3 HDD memory usage in Win7 goes up to 100% and remains there. I'm not sure whether this is a problem caused by faulty drivers or not, but I already have the current version of them (Etron USB3 controller on a Gigabyte 990fxa board).. Using RAMMap it becomes obvious that the files, that are to be copied, are mapped into memory. Clicking on Empty > Empty System Working Set seems to temporarily fix the problem (without causing any trouble with the file copy process), but it needs to be done every few seconds. Is there any way to schedule this operation to happen ever 10 or so seconds on its own? What underlying system command is RAMMap using? Or, alternatively, is there any way to limit how much RAM mapped files may use in Windows 7? I know mapped files would usually be removed from memory if other programs need the memmory, but while memmory usage is at 100% the system starts freezing up for half a second or so everytime I click anything .. thus the automatic removal of unused memory contents seems to be failing here.

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• Plymouth and GRUB do not show at all

  - by WarriorIng64

  I am using Ubuntu 11.04 64-bit as my only OS on my desktop computer, which used to only run Ubuntu 10.04 LTS until I had the time to upgrade it with a fresh install. It uses integrated NVIDIA graphics (listed as a GeForce 6150SE nForce 430 by the NVIDIA X Server Settings utility) with the current proprietary driver as provided by the Additional Drivers utility, and has a VGA connection to a 1680x1050 Acer monitor. I used to get the (ugly-looking version of) Plymouth graphical boot screen while under 10.04. It didn't look that great, but I was fine with it. Now, it doesn't show on 11.04 at all during boot (I just get an error message in a moving gray box from the monitor saying "Input Not Supported"), and only rarely it will show on shutdown, all garbled up. I could not get GRUB to show during boot while holding down Shift, either (same error message), but pressing Enter while it should be up starts the system normally. A picture of the error message I was getting: Once fully booted, the system still shows the login screen and desktop just fine. Any information on how to troubleshoot this would be appreciated. If there's any hardware-specific stuff I forgot to include here, let me know the relevant commands to run in a comment below. Things that I've tried: Running plymouth in a framebuffer: no effect Booting with nomodeset as my grub boot: option no effect Booting with nomodeset and plymouth in a framebuffer: no effect other than Plymouth showing during shutdown only Following the Softpedia instructions for fixing Plymouth's resolution: Problem mostly solved, except logo does not show in Plymouth during boot, and both grub and Plymouth are slightly off-center #4 above, but with nomodeset removed as a grub boot option: same effect as #4 #5 above, but with vt.handoff=7 added as a grub boot option: same effect as #4 I have added the current contents of /etc/default/grub as requested in the comments: # If you change this file, run 'update-grub' afterwards to update # /boot/grub/grub.cfg. # For full documentation of the options in this file, see: # info -f grub -n 'Simple configuration' GRUB_DEFAULT=0 GRUB_HIDDEN_TIMEOUT=0 GRUB_HIDDEN_TIMEOUT_QUIET=true GRUB_TIMEOUT=10 GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian` GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video=uvesafb:mode_option=1280x1024-24,mtrr=3,scroll=ywrap" GRUB_CMDLINE_LINUX="" # Uncomment to enable BadRAM filtering, modify to suit your needs # This works with Linux (no patch required) and with any kernel that obtains # the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...) #GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef" # Uncomment to disable graphical terminal (grub-pc only) #GRUB_TERMINAL=console # The resolution used on graphical terminal # note that you can use only modes which your graphic card supports via VBE # you can see them in real GRUB with the command `vbeinfo' GRUB_GFXMODE=1280x1024 # Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux #GRUB_DISABLE_LINUX_UUID=true # Uncomment to disable generation of recovery mode menu entries #GRUB_DISABLE_RECOVERY="true" # Uncomment to get a beep at grub start #GRUB_INIT_TUNE="480 440 1" CURRENT STATUS: I forgot to uncomment one line as per "things that I've tried" #4, so I took care of that. I can now see GRUB during startup when I hold Shift and a normal-looking Plymouth during shutdown...but Plymouth during boot is now just a solid purple screen. In each case, it's displayed a little off-center to the left, with a thin black bar running down the right side of the monitor. The error pictured above no longer shows. I'd say this problem is about 2/3 solved now. UPDATE: After Natty started freezing up on me, I decided to dual-boot with Oneiric, which unfortunately shows the same problems. Rather than trying all these workarounds though, I decided to do what I should have done from the start and file a pair of bug reports. LAST UPDATE: Bug 850908 has been confirmed as a legitimate nouveaufb bug. I have overwritten my 11.04 partition with 12.04 LTS, and I can confirm at this time that the issue is present there, as well. I will now flag this question to be closed, yet I hope it was helpful for anyone who experienced similar issues; if you are still having the same problem as me, please go there and mark yourself as affected. Thanks!

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• Red Gate's on the road in 2012 - Will you catch us?

  - by RedAndTheCommunity

  Annabel Bradford, our Communities and Events Manager, tells all about her experience of our 1st SQL Saturday of the year. The first stop this year was SQL Saturday #104 Colorado Springs, back in early January. I made the trip across from the UK just for this SQL Saturday event, and I'm so glad I did. I picked up Max from Red Gate's Pasadena office and we flew into Colorado Springs airport late on Friday evening to be greeted by freezing temperatures, which was quite a shock after the California sunshine. Rising before the sun, we arrived at Mr Biggs, the venue for the event, in the darkness. It was great to see so many smiling attendees so bright and early on a Saturday morning. Everyone was eager to learn more about SQL Server, and hundreds of people came and chatted with us at the table, saw demos and learnt more about Red Gate tools. The event highlights for the attendees were definitely the unlimited lazer quest, bowling and pool available during the break times. For Max, Grant Fritchey and I on the Red Gate table, the highlights have to be meeting customers and getting the opportunity to meet attendees who'd heard of, but wanted to know more about, Red Gate. We were delighted to hear lots of valuable feedback that we took back to share with the team. As a thank you for sharing insights about their work lives and how they use SQL Server and Red Gate tools, attendees are able to take away Red Gate SQL Server books. We aim to have a range of titles available when we exhibit, so that attendees can choose a book that's going to be most interesting to them, and that they can use as a reference back at the office. Every time I meet a Red Gate user or a member of the SQL community, I'm always overwhelmed by the enthusiasm they have for their industry. Everyone who gives up their time to learn more about their job should be rewarded, and at Red Gate we like to do just that. Red Gate has long supported the SQL community through sponsorship to facilitate user group meetings and community events, but it's only though face-to-face contact that we really get a chance to see the impact of our support. I hope we'll have the chance to see you on the road at some point this year. We'll be at a range of events, including free SQL Saturdays, one day free events 'the Red Gate way', two-day Rallys, and full-week conferences. Next stop is SQL Saturday #109 Silicon Valley on March 3rd where you'll meet Jeff and Arneh, two of our US-based SQL team members. Be sure to ask them any questions you've got about the Red Gate tools, as these guys will be delighted to hear your questions, show you the options, and will make a note of your feedback to send through to the development team. Until the next time. Happy learning! Annabel                         Grant, Max and Annabel at SQL Saturday #104 Colorado Springs

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• Why would Copying a Large Image to the Clipboard Freeze a Computer?

  - by Akemi Iwaya

  Sometimes, something really odd happens when using our computers that makes no sense at all…such as copying a simple image to the clipboard and the computer freezing up because of it. An image is an image, right? Today’s SuperUser post has the answer to a puzzled reader’s dilemna. Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites. Original image courtesy of Wikimedia. The Question SuperUser reader Joban Dhillon wants to know why copying an image to the clipboard on his computer freezes it up: I was messing around with some height map images and found this one: (http://upload.wikimedia.org/wikipedia/commons/1/15/Srtm_ramp2.world.21600×10800.jpg) The image is 21,600*10,800 pixels in size. When I right click and select “Copy Image” in my browser (I am using Google Chrome), it slows down my computer until it freezes. After that I must restart. I am curious about why this happens. I presume it is the size of the image, although it is only about 6 MB when saved to my computer. I am also using Windows 8.1 Why would a simple image freeze Joban’s computer up after copying it to the clipboard? The Answer SuperUser contributor Mokubai has the answer for us: “Copy Image” is copying the raw image data, rather than the image file itself, to your clipboard. The raw image data will be 21,600 x 10,800 x 3 (24 bit image) = 699,840,000 bytes of data. That is approximately 700 MB of data your browser is trying to copy to the clipboard. JPEG compresses the raw data using a lossy algorithm and can get pretty good compression. Hence the compressed file is only 6 MB. The reason it makes your computer slow is that it is probably filling your memory up with at least the 700 MB of image data that your browser is using to show you the image, another 700 MB (along with whatever overhead the clipboard incurs) to store it on the clipboard, and a not insignificant amount of processing power to convert the image into a format that can be stored on the clipboard. Chances are that if you have less than 4 GB of physical RAM, then those copies of the image data are forcing your computer to page memory out to the swap file in an attempt to fulfil both memory demands at the same time. This will cause programs and disk access to be sluggish as they use the disk and try to use the data that may have just been paged out. In short: Do not use the clipboard for huge images unless you have a lot of memory and a bit of time to spare. Like pretty graphs? This is what happens when I load that image in Google Chrome, then copy it to the clipboard on my machine with 12 GB of RAM: It starts off at the lower point using 2.8 GB of RAM, loading the image punches it up to 3.6 GB (approximately the 700 MB), then copying it to the clipboard spikes way up there at 6.3 GB of RAM before settling back down at the 4.5-ish you would expect to see for a program and two copies of a rather large image. That is a whopping 3.7 GB of image data being worked on at the peak, which is probably the initial image, a reserved quantity for the clipboard, and perhaps a couple of conversion buffers. That is enough to bring any machine with less than 8 GB of RAM to its knees. Strangely, doing the same thing in Firefox just copies the image file rather than the image data (without the scary memory surge). Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

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• Software Center seems to freeze system when installing, syslog has "blocked for more than 120 seconds" errors

  - by nbm

  12.04 (precise) 64-bit Kernel Linux 3.2.0-39 3.6GB memory Intel Core 2 Duo CPU @ 2.40GHz x2 WUBI-installed Ubuntu running on a MacBook Pro 7.1 with OSX running Vista via Boot Camp (hey, I like lots of OS's m'kay?) When installing from Ubuntu software center my system very frequently freezes. This has happened 4 of the last 5 installs. Most recently I was installing the Google Earth .deb from Google's website: clicking the .deb file automatically opens Software Center (otherwise I would have used Synaptic, as I've grown to expect Software Center to freeze my system and I'm rather tired of it.) By "freeze" I mean nothing works: no dash, no launcher, no mouse movement, no alt-tab, can't open terminal (keyboard does not work). Software center does show the "installing" icon but after that it greys out and I can't click anything. REISUB has no effect but a cold power-down and restart is possible. Occasionally, after 5-10 minutes, I'll be able to move the mouse / use the keyboard and run a launcher command or two, although other open apps (Chrome and Software Center) will still be greyed-out/frozen. (I've never waited longer than that - if still unresponsive after 15 minutes I just power down and restart.) Most recently, which is why I am finally posting a question, I waited about 15 minutes and was finally able to open System Monitor while this was going on. Processes tells me that System Monitor is using about 20% of CPU, and nothing else is using much (zeros mostly). In fact I didn't even see Software Center listed? However at this point the system finally partially unfroze, the installation completed, and while I wasn't about to close Software Center I was able to do a system shutdown and fresh restart and I went and took a look at the syslog. In /var/log/syslog I see a lot of ":blocked for more than 120 seconds" messages. Similar to ubuntu hang out with this message :blocked for more than 120 seconds Which has not been answered, and I'm not running a virtual machine. My full syslog with stack traces looks very, very similar to this: Why do tasks on Amazon Xen instance block for over 120 seconds causing server to hang? Note that that question was solved, but that's because the problem was being caused by Amazon and Amazon fixed the bug. I'm not running anything Amazon-related. My syslog does look very similar, however. My question is also similar to this: Troubleshooting server hang But the referenced "duplicate" in that question is about how to kill processes/restart when the system freezes. I know how to kill processes and restart. I want to figure out what is causing the problem so I can try to fix it. I realize that I could just use Synaptic instead of Ubuntu Software Center, but I'd like to try to solve the problem if possible. I'm thinking I should perhaps submit a bug report, but I wanted to first see if anyone else was having any similar problems, and if so what you all did to fix it. I see a number of questions about Software Center freezing and others, including those I linked, about the "blocked for more than 120 seconds" log error, but I didn't see any question that links the two. I did save a copy of the syslog report if anyone wants to see it, but as mentioned it's quite similar to the one posted in the Amazon-related question...and I didn't want to take up even more space unnecessarily as, my apologies - this question has already become extremely verbose!

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• Getting web page after calling DownloadStringAsync()?

  - by OverTheRainbow

  Hello I don't know enough about VB.Net yet to use the richer HttpWebRequest class, so I figured I'd use the simpler WebClient class to download web pages asynchronously (to avoid freezing the UI). However, how can the asynchronous event handler actually return the web page to the calling routine? Imports System.Net Public Class Form1 Private Shared Sub DownloadStringCallback2(ByVal sender As Object, ByVal e As DownloadStringCompletedEventArgs) If e.Cancelled = False AndAlso e.Error Is Nothing Then Dim textString As String = CStr(e.Result) 'HERE : How to return textString to the calling routine? End If End Sub Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim client As WebClient = New WebClient() AddHandler client.DownloadStringCompleted, AddressOf DownloadStringCallback2 Dim uri As Uri = New Uri("http://www.google.com") client.DownloadStringAsync(uri) 'HERE : how to get web page back from callback function? End Sub End Class Thank you. Edit: I added a global, shared variable and a While/DoEvents/EndWhile, but there's got to be a cleaner way to do this :-/ Public Class Form1 Shared page As String Public Shared Sub AlertStringDownloaded(ByVal sender As Object, ByVal e As DownloadStringCompletedEventArgs) ' If the string request went as planned and wasn't cancelled: If e.Cancelled = False AndAlso e.Error Is Nothing Then page = CStr(e.Result) End If End Sub Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim wc As New WebClient AddHandler wc.DownloadStringCompleted, AddressOf AlertStringDownloaded page = Nothing wc.DownloadStringAsync(New Uri("http://www.google.com")) 'Better way to wait until page has been filled? While page Is Nothing Application.DoEvents() End While RichTextBox1.Text = page End Sub End Class

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• UIScrollView notifications

  - by ryyst

  Hi, I'm coding an app that works much like Apple's Weather.app: There's a UIPageControl at the bottom and a UIScrollView in the middle of the screen. In my code, I implemented the - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView method to figure out when the user did move to a new page. If they move to a new page, I load the adjacent pages' data, as to make further page-switching faster. (In one of Apple's examples, the - (void)scrollViewDidScroll:(UIScrollView *)sender is used, but that causes my app to shortly hang when loading a new page, so it's not suitable.) That code works very well. I'm using scrollRectToVisible:: to programmatically scroll inside the scrollview when the user clicks the UIPageControl. The problem is that the scrollRectToVisible: doesn't post a notification to the UIScrollViewDelegate when it's done scrolling - so the code responsible for loading adjacent pages never get's called when using the UIPageControl. Is there any way to make the UIScrollView notify its delegate when it gets called by the scrollRectToVisible: method? Or will I have to use threads in order to prevent my app from freezing? Thanks! -- Ry

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• DirectShow Filter I wrote dies after 10-24 seconds in Skype video call

  - by Robert Oschler

  I've written a DirectShow push filter for use with Skype using Delphi Pro 6 and the DSPACK DirectShow library. In preview mode, when you test a video input device in the Skype client Video Settings window, my filter works flawlessly. I can leave it up and running for many minutes without an error. However when I start a video call after 10 to 24 seconds, never longer, the video feed freezes. The call continues fine with the call duration counter clicking away the seconds, but the video feed is dead, stuck on whatever frame the freeze happened (although after a long while it turns black which I believe means Skype has given up on the filter). I tried attaching to the process from my debugger with a breakpoint literally set on every method call and none of them are hit once the freeze takes place. It's as if the thread that makes the DirectShow FillBuffer() call to my filter on behalf of Skype is dead or has been shutdown. I can't trace my filter in the debugger because during a Skype call I get weird int 1 and int 3 debugger hard interrupt calls when a Skype video call is in progress. This behavior happens even with my standard web cam input device selected and my DirectShow filter completely unregistered as a ActiveX server. I suspect it might be some "anti-debugging" code since it doesn't happen in video input preview mode. Either way, that is why I had to attach to the process after the fact to see if my FillBuffer() called was still being called and instead discovered that appears to be dead. Note, my plain vanilla USB web cam's DirectShow filter does not exhibit the freezing behavior and works fine for many minutes. There's something about my filter that Skype doesn't like. I've tried Sleep() statements of varying intervals, no Sleep statements, doing virtually nothing in the FillBuffer() call. Nothing helps. If anyone has any ideas on what might be the culprit here, I'd like to know. Thanks, Robert

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• Django-South introspection rule doesn't work.

  - by Ory Band

  I'm using Django 1.2.3 and South 0.7.3. I am trying to convert my app (named core) to use Django-South. I have a custom model/field that I'm using, named ImageWithThumbsField. It's basically just the ol' django.db.models.ImageField with some attributes such as height, weight, etc. While trying to ./manage.py convert_to_auth core I receieve South's freezing errors. I have no idea why, I'm Probably missing something... I am using a simple custom Model: from django.db.models import ImageField class ImageWithThumbsField(ImageField): def __init__(self, verbose_name=None, name=None, width_field=None, height_field=None, sizes=None, **kwargs): self.verbose_name=verbose_name self.name=name self.width_field=width_field self.height_field=height_field self.sizes = sizes super(ImageField, self).__init__(**kwargs) And this is my introspection rule, which I add to the top of my models.py: from south.modelsinspector import add_introspection_rules from lib.thumbs import ImageWithThumbsField add_introspection_rules( [ ( (ImageWithThumbsField, ), [], { "verbose_name": ["verbose_name", {"default": None}], "name": ["name", {"default": None}], "width_field": ["width_field", {"default": None}], "height_field": ["height_field", {"default": None}], "sizes": ["sizes", {"default": None}], }, ), ], ["^core/.fields/.ImageWithThumbsField",]) This is the errors I receieve: ! Cannot freeze field 'core.additionalmaterialphoto.photo' ! (this field has class lib.thumbs.ImageWithThumbsField) ! Cannot freeze field 'core.material.photo' ! (this field has class lib.thumbs.ImageWithThumbsField) ! Cannot freeze field 'core.material.formulaimage' ! (this field has class lib.thumbs.ImageWithThumbsField) ! South cannot introspect some fields; this is probably because they are custom ! fields. If they worked in 0.6 or below, this is because we have removed the ! models parser (it often broke things). ! To fix this, read http://south.aeracode.org/wiki/MyFieldsDontWork Does anybody know why? What am I doing wrong?

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• Swing: what to do when a JTree update takes too long and freezes other GUI elements?

  - by java.is.for.desktop

  Hello, everyone! I know that GUI code in Java Swing must be put inside SwingUtilities.invokeAndWait or SwingUtilities.invokeLater. This way threading works fine. Sadly, in my situation, the GUI update it that thing which takes much longer than background thread(s). More specific: I update a JTree with about just 400 entries, nesting depth is maximum 4, so should be nothing scary, right? But it takes sometimes one second! I need to ensure that the user is able to type in a JTextPane without delays. Well, guess what, the slow JTree updates do cause delays for JTextPane during input. It refreshes only as soon as the tree gets updated. I am using Netbeans and know empirically that a Java app can update lots of information without freezing the rest of the UI. How can it be done? NOTE 1: All those DefaultMutableTreeNodes are prepared outside the invokeAndWait. NOTE 2: When I replace invokeAndWait with invokeLater the tree doesn't get updated. NOTE 3: Fond out that recursive tree expansion takes far the most time. NOTE 4: I'm using custom tree cell renderer, will try without and report. NOTE 4a: My tree cell renderer uses a map to cache and reuse created JTextComponents, depending on tree node (as a key). CLUE 1: Wow! Without setting custom cell renderer it's 10 times faster. I think, I'll need few good tutorials on writing custom tree cell renderers.

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• [iPhone] UIScrollView notifications

  - by ryyst

  Hi, I'm coding an app that works much like Apple's Weather.app: There's a UIPageControl at the bottom and a UIScrollView in the middle of the screen. In my code, I implemented the - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView method to figure out when the user did move to a new page. If they move to a new page, I load the adjacent pages' data, as to make further page-switching faster. (In one of Apple's examples, the - (void)scrollViewDidScroll:(UIScrollView *)sender is used, but that causes my app to shortly hang when loading a new page, so it's not suitable.) That code works very well. I'm using scrollRectToVisible:: to programmatically scroll inside the scrollview when the user clicks the UIPageControl. The problem is that the scrollRectToVisible: doesn't post a notification to the UIScrollViewDelegate when it's done scrolling - so the code responsible for loading adjacent pages never get's called when using the UIPageControl. Is there any way to make the UIScrollView notify its delegate when it gets called by the scrollRectToVisible: method? Or will I have to use threads in order to prevent my app from freezing? Thanks! -- Ry

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• Qt - QWebView Problem

  - by user547057

  Hi, I have a PyQt gui script which consists of a QWebView widget. I'm trying to send a GET request, i.e go to a page, fill a form and hit click using the code at the bottom of this question. Since i'm dealing with the documentElement(a QWebElement) of the webview, I need to place all DOM actions in a separate function(which I have named fillForm) and connect the loadFinished() signal into the function. Without connecting the signal, the document will not have loaded and I won't be able to get the elements I want. I'm able to submit the form correctly and get the proper response from the webpage. The problem i'm having is that, the above leads to a sort of infinite loop. This is because the webpage gets reloaded each time a new page is loaded, so the form gets filled each and every single time without stopping. I'd like to know if there's some way of finding out whether the WebView's page has loaded fully, non-asynchronously or maybe pause execution of the script(without freezing the gui) until the whole document has loaded. I'm unable to come up with a satisfactory solution(my idea consisted of keeping a global variable to track clicks) to this problem. I would appreciate it if someone could help me out with a better way to tackle this. Thanks! Here's the code i'm using import sys from PyQt4.QtCore import * from PyQt4.QtGui import * from PyQt4.QtWebKit import * from PyQt4 import QtCore app = QApplication(sys.argv) web = QWebView() web.load(QUrl("http://mywebsite.com")) def fillForm(): doc = web.page().mainFrame().documentElement() searchform = doc.findFirst("input[type=text]") searchform.setAttribute("value", "hello") button = doc.findFirst("input[type=submit]") button.evaluateJavaScript("click()") QtCore.QObject.connect(web, QtCore.SIGNAL("loadFinished"), fillForm) web.show() sys.exit(app.exec_())

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• How should I avoid memoization causing bugs in Ruby?

  - by Andrew Grimm

  Is there a consensus on how to avoid memoization causing bugs due to mutable state? In this example, a cached result had its state mutated, and therefore gave the wrong result the second time it was called. class Greeter def initialize @greeting_cache = {} end def expensive_greeting_calculation(formality) case formality when :casual then "Hi" when :formal then "Hello" end end def greeting(formality) unless @greeting_cache.has_key?(formality) @greeting_cache[formality] = expensive_greeting_calculation(formality) end @greeting_cache[formality] end end def memoization_mutator greeter = Greeter.new first_person = "Bob" # Mildly contrived in this case, # but you could encounter this in more complex scenarios puts(greeter.greeting(:casual) << " " << first_person) # => Hi Bob second_person = "Sue" puts(greeter.greeting(:casual) << " " << second_person) # => Hi Bob Sue end memoization_mutator Approaches I can see to avoid this are: greeting could return a dup or clone of @greeting_cache[formality] greeting could freeze the result of @greeting_cache[formality]. That'd cause an exception to be raised when memoization_mutator appends strings to it. Check all code that uses the result of greeting to ensure none of it does any mutating of the string. Is there a consensus on the best approach? Is the only disadvantage of doing (1) or (2) decreased performance? (I also suspect freezing an object may not work fully if it has references to other objects) Side note: this problem doesn't affect the main application of memoization: as Fixnums are immutable, calculating Fibonacci sequences doesn't have problems with mutable state. :)

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• Windows service hangs

  - by Ram

  Hi, I have a webdav client-server application. I'm using Cassini webserver to host the webdav server. One important thing here is that I start and Stop my webserver using a windows service. Now, I start my windows service and I attach my webdav server application's debugger to the windows service. Everything used to go fine, that is I could connect to the server using my webdav client, debug the server code. However, a couple of days back, when I tried to debug my webdav server application, which in turn is attached to a windows service, my computer freezes while I'm in the midst of debugging the server app. The freeze does not occur at the same line every time and is therefore not predictable. Every time this happens, I would not be able to do anything at all with my computer except to reboot the system using the power button. What could be the problem? Could it be the service that is freezing or something else? Any help? Thanks, Ram

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• C# WinForms MultiThreading in Loop

  - by Goober

  Scenario I have a background worker in my application that runs off and does a bunch of processing. I specifically used this implementation so as to keep my User Interface fluid and prevent it from freezing up. I want to keep the background worker, but inside that thread, spawn off ONLY 3 MORE threads - making them share the processing (currently the worker thread just loops through and processes each asset one-by-one. However I would like to speed this up but using only a limited number of threads. Question Given the code below, how can I get the loop to choose a thread that is free, and then essentially wait if there isn't one free before it continues. CODE foreach (KeyValuePair<int, LiveAsset> kvp in laToHaganise) { Haganise h = new Haganise(kvp.Value, busDate, inputMktSet, outputMktSet, prodType, noOfAssets, bulkSaving); h.DoWork(); } Thoughts I'm guessing that I would have to start off by creating 3 new threads, but my concern is that if I'm instantiating a new Haganise object each time - how can I pass the correct "h" object to the correct thread..... Thread firstThread = new Thread(new ThreadStart(h.DoWork)); Thread secondThread =new Thread(new ThreadStart(h.DoWork)); Thread thirdThread = new Thread(new ThreadStart(h.DoWork)); Help greatly appreciated.

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• Facebook JS API: users_getInfo() inside ifUserConnected() deadlock.

  - by serg555

  I am trying to put Facebook connect button on the site and once connected display connected username. But for some reason following code goes into some infinite loop during first connection, and then works fine unless I delete this app from my facebook profile which causes freezing again. Here is a code on FB connect button click: FB.Connect.requireSession(); Here is code directly on the page: <script src="http://static.ak.connect.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php/en_US" type="text/javascript"></script> <script type="text/javascript"> FB.init("123", "/xd_receiver.htm"); FB.ensureInit(function() { FB.Connect.ifUserConnected(function() { FB.Facebook.apiClient.users_getInfo(new Array(FB.Connect.get_loggedInUser()),new Array("name"), function(user, exec) { console.log("logged in:"+user[0].name); }); }, function(){ console.log("guest"); }); }); </script> If I remove FB.Facebook.apiClient.users_getInfo() it works fine, but I need to get username somehow. Any tips? Thanks.

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• IndexOutofRangeException while using WriteLine in nested Parallel.For loops

  - by Umar Asif

  I am trying to write kinect depth data to a text file using nested Parallel.For loops with the following code. However, it gives IndexOutofRangeException. The code works perfect if using simple for loops but it hangs the UI since the depth format is set to 640x480 causing the loops to write 307200 lines in the text file at 30fps. Therefore, I switched to Parallel. For scheme. If I omit the writeLine command from the nested loops, the code works fine, which indicates that the IndexOutofRangeException is arising at the writeline command. I do not know how to troubleshoot this. Please advise. Any better workarounds to avoid UI freezing? Thanks. using (DepthImageFrame depthImageframe = d.OpenDepthImageFrame()) { if (depthImageframe == null) return; depthImageframe.CopyPixelDataTo(depthPixelData); swDepth = new StreamWriter(@"E:\depthData.txt", false); int i = 0; Parallel.For(0, depthImageframe.Width, delegate(int x) { Parallel.For(0, depthImageframe.Height, delegate(int y) { p[i] = sensor.MapDepthToSkeletonPoint(depthImageframe.Format, x, y, depthPixelData[x + depthImageframe.Width * y]); swDepth.WriteLine(i + "," + p[k].X + "," + p[k].Y + "," + p[k].Z); i++; }); }); swDepth.Close(); } }

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• Any useful suggestions to figure out where memory is being free'd in a Win32 process?

  - by LeopardSkinPillBoxHat

  An application I am working with is exhibiting the following behaviour: During a particular high-memory operation, the memory usage of the process under Task Manager (Mem Usage stat) reaches a peak of approximately 2.5GB (Note: A registry key has been set to allow this, as usually there is a maximum of 2GB for a process under 32-bit Windows) After the operation is complete, the process size slowly starts decreasing at a rate of 1MB per second. I am trying to figure out the easiest way to quickly determine who is freeing this memory, and where it is being free'd. I am having trouble attaching a memory profiler to my code, and I don't particularly want to override the new/delete operators to track the allocations/deallocations (IOW, I want to do this without re-compiling my code). Can anyone offer any useful suggestions of how I could do this via the Visual Studio debugger? Update I should also mention that it's a multi-threaded application, so pausing the application and analysing the call stack through the debugger is not the most desirable option. I considered freezing different threads one at a time to see if the memory stops reducing, but I'm fairly certain this will cause the application to crash.

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• Android CursorAdapters, ListViews and background threads

  - by MattC

  This application I've been working on has databases with multiple megabytes of data to sift through. A lot of the activities are just ListViews descending through various levels of data within the databases until we reach "documents", which is just HTML to be pulled from the DB(s) and displayed on the phone. The issue I am having is that some of these activities need to have the ability to search through the databases by capturing keystrokes and re-running the query with a "like %blah%" in it. This works reasonably quickly except when the user is first loading the data and when the user first enters a keystroke. I am using a ResourceCursorAdapter and I am generating the cursor in a background thread, but in order to do a listAdapter.changeCursor(), I have to use a Handler to post it to the main UI thread. This particular call is then freezing the UI thread just long enough to bring up the dreaded ANR dialog. I'm curious how I can offload this to a background thread totally so the user interface remains responsive and we don't have ANR dialogs popping up. Just for full disclosure, I was originally returning an ArrayList of custom model objects and using an ArrayAdapter, but (understandably) the customer pointed out it was bad memory-manangement and I wasn't happy with the performance anyways. I'd really like to avoid a solution where I'm generating huge lists of objects and then doing a listAdapter.notifyDataSetChanged/Invalidated() Here is the code in question: private Runnable filterDrugListRunnable = new Runnable() { public void run() { if (filterLock.tryLock() == false) return; cur = ActivityUtils.getIndexItemCursor(DrugListActivity.this); if (cur == null || forceRefresh == true) { cur = docDb.getItemCursor(selectedIndex.getIndexId(), filter); ActivityUtils.setIndexItemCursor(DrugListActivity.this, cur); forceRefresh = false; } updateHandler.post(new Runnable() { public void run() { listAdapter.changeCursor(cur); } }); filterLock.unlock(); updateHandler.post(hideProgressRunnable); updateHandler.post(updateListRunnable); } };

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• Why does this javascript code have an infinite loop?

  - by asdas

  optionElements is a 2d array. Each element has an array of length 2. These are an integer number and an element. I have a select list called linkbox, and i want to add all of the elements to the select list. The order I want them to go in is important, and is determined by the number each element has. It should be smallest to highest. So think of it like this: optionElements is: [ [5, <option>], [3, <option], [4, <option], [1, <option], [2, <option]] and it would add them to link box in order of those numbers. BUT that is not what happens. It is an infinite loop after the first time. I added the x constraint just to stop it from freezing my browser but you can ignore it. var b; var smallest; var samllestIndex; var x = 0; while(optionElements.length > 0 && ++x < 100) { smallestIndex = 0; smallest = optionElements[0][0]; b = 0; while( ++b < optionElements.length) { if(optionElements[b][0] > smallest) { smallestIndex = b; smallest = optionElements[b][0]; } } linkbox.appendChild(optionElements[smallestIndex][1]); optionElements.unshift(optionElements[smallestIndex]); } can someone point out to me where my problem is?

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• Thread is being killed by the OS

  - by Or.Ron

  I'm currently programming an app that extracts frames from a movie clip. I designed it so that the extraction will be done on a separate thread to prevent the application from freezing. The extraction process itself is taking a lot of resources, but works fine when used in the simulator. However, there are problems when building it for the iPad. When I perform another action (I'm telling my AV player to play while I extract frames), the thread unexpectedly stops working, and I believe it's being killed. I assume it's becauase I'm using a lot of resources, but not entirely sure. Here are my questions: 1. How can I tell if/why my thread stopping? 2. If it's really from over processing what should I do? I really need this action to be implemented. Heres some code im using: To create the thread: [NSThread detachNewThreadSelector:@selector(startReading) toTarget:self withObject:nil]; I'll post any information you need, Thanks so much! Update I'm using GCD now and it populates the threads for me. However the OS still kills the threads. I know exactly when is it happening. when i tell my [AVplayer play]; it kills the thread. This issue is only happening in the actual iPad and not on the simulator

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• jqgrid questions

  - by user508518

  Hi All- I recently posted a question on SO on freezing columns in jqgrid(http://stackoverflow.com/questions/4586924/jqgrid-freeze-columns). I got the following solution to be working in IE8, but its not all perfect: I set to use two css classes, one for header and other one for the rows like below: .jqgridbodyLock{ position:relative; left: expression(parentNode.parentNode.parentNode.parentNode.parentNode.scrollLeft); z-index: 10; } .jqgridheaderLocked{ position:relative; left: expression(parentNode.parentNode.parentNode.parentNode.parentNode.scrollLeft); /* IE5+ only */ z-index:30; } Then in colModel, I used the property classes {name:'column1', width:100, index:'column1', sorttype:"string", classes:'jqgridbodyLock'},//lock the body row and to lock the respective header I used code as below: $("#grid").setLabel("column1","column1","jqgridheaderLocked"); Though the solution works, I have the following problems: 1) The header values shake a lot when scrolling to the right though they remain frozen 2) The body values of the frozen column disappear when the cursor is taken out of the grid. 3) How to lock a normal table in firefox. I see that 'expression' is exclusive only to IE browser Thanks a lot

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• Creating a function within a loop (pointers?)

  - by user352151

  Im trying to create a simple loop that creates 50 buttons, adds them to screen and then when a button is pressed, it traces out that number. I can get it to work by doing stuff I consider hacky (such as using the buttons X/Y location to determine its value), but I'd rather just be able to hold a single value in the function. The code itself is: for (var a:int = 0; a < 5; a++) { for (var b:int = 0; b < 10; b++) { var n = (a * 10) + b + 1; var btt:SimpleButton = new BasicGameButton(); btt.x = 20 + b * 50; btt.y = 50 + a * 80; addChild(btt); btt.addEventListener(MouseEvent.CLICK, function f() { trace(n); } ); } } At the moment, whenever a button is pressed, it simply outputs "50". Is there a way of "freezing" the value of n when the function is created, for that function? (BasicGameButton is just a square button, created in the flash library) Many thanks.

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• Weird random application hang problem

  - by haridsv

  I am trying to understand an application hang problem that started up lately on my windows xp system. The system runs fine for days (sometimes) without ever shutting down or putting it to sleep, but the problem first shows up as one of the apps hanging. The application's UI stops responding or one or more background threads hang, so even though the GUI is responding, it is not doing anything (e.g., in VirtualDub's case, the UI responds fine, but the job doesn't progress and I won't even be able to abort it). The weirdness part comes from the fact that if I try to kill such an app, the program that is used to kill it goes into the same mode (i.e, that hangs instead of the original). E.g., if I use Process Explorer to kill it, the original program exits, but procexp now hangs. If I use another instance of procexp to kill the one that is hanging, this repeats, so there is always at least one program hanging in that state. This is not specific to procexp, I tried the native task manager and even the "End Process" dialog from windows explorer that shows up when you try to close a non-responsive GUI (in this case, the explorer itself hangs). The only program that didn't hang after the kill, is the command line taskkill. However, in this case, explorer hangs instead of taskkill. Also, once this problem starts manifesting, it soon ends up freezing the whole system to the extent that even a clean shutdown is not possible, so I have learned to reboot as soon as I notice this problem, however this is very inconvenient, as I often have encoding batch jobs going on which can't continue the job after the restart. The longer I leave the system running after seeing this problem, the more applications get into this state. I have tried to do a repair install but that didn't make any difference. I also uninstalled some of the newer installs, but again no difference. I tried to search online, but got inundating results for generic hang and crash related problems. Though I couldn't notice any pattern, it seems as though the problem is more frequent if I have some video encoding going on at that time. I had the system running for days when I only do browsing and internet audio/video chat before I decide to start encoding something and the problem starts to show up. I am not too sure if it is the encoding program that first hangs, though I almost always noticed that too hanging (like the VirtualDub stopping to make progress). I also had to reboot 3 times on one day when I was heavily experimenting with encoding. I would appreciate any help in narrowing down this problem and save me the trouble of reinstalling. I don't especially want to loose my gotd installs.

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