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• USB interface barcode scanners

  - by Nimbuz

  Not exactly a programming question, but close. I'll try my luck anyway. The keyboard wedge barcode scanner inserts the translation device between the reader and the keyboard. Data sent through a wedge appears as if it was typed into the computer, while the keyboard itself remains fully functional. Because a computer using a keyboard wedge can't tell the difference between data that is entered by a scanning device, or data that is entered by keyboard typing, a wedge can be used to easily add barcode reading capability to an existing computer without modifying software applications. I'd like to know if all USB interface barcode scanners automatically translate digital signals from a barcode reader into keyboard strokes for a applications just like wedge or is USB different from wedge? Many thanks

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• AS3 - Event listener that only fires once

  - by Zed-K

  I'm looking for a way to add an EventListener which will automatically removes itself after the first time it fires, but I can't figure a way of doing this the way I want to. I found this function (here) : public class EventUtil { public static function addOnceEventListener(dispatcher:IEventDispatcher,eventType:String,listener:Function):void { var f:Function = function(e:Event):void { dispatcher.removeEventListener(eventType,f); listener(e); } dispatcher.addEventListener(eventType,f); } } But instead of having to write : EventUtil.addOnceEventListener( dispatcher, eventType, listener ); I would like to use it the usual way : dispatcher.addOnceEventListener( eventType, listener ); Has anybody got an idea of how this could be done? Any help would be greatly apprecitated. (I know that Robert Penner's Signals can do this, but I can't use them since it would mean a lot of code rewriting that I can't afford for my current project)

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• QWidget keyPressEvent override

  - by eaigner

  Hi there, I'm trying for half an eternity now overriding QWidgets keyPressEvent function in QT but it just won't work. I've to say i am new to CPP, but I know ObjC and standard C. My problem looks like this: class QSGameBoard : public QWidget { Q_OBJECT public: QSGameBoard(QWidget *p, int w, int h, QGraphicsScene *s); signals: void keyCaught(QKeyEvent *e); protected: virtual void keyPressEvent(QKeyEvent *event); }; QSGameBoard is my QWidget subclass and i need to override the keyPressEvent and fire a SIGNAL on each event to notify some registered objects. My overridden keyPressEvent in QSGameBoard.cpp looks like this: void QSGameBoard::keyPressEvent(QKeyEvent *event) { printf("\nkey event in board: %i", event->key()); //emit keyCaught(event); } When i change QSGameBoard:: to QWidget:: it receives the events, but i cant emit the signal because the compiler complains about the scope. And if i write it like this the function doesn't get called at all. What's the problem here?

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• How to handle a C# console application terminating?

  - by Nick R

  If I have a console application, is there any way I can handle the following: Ctrl-C (I know the answer to this. Using Console.TreatControlCAsInput and Console.CancelKeyPress) Session termination, such as when someone logs off Process exit, such as when someone uses the task manager to close the application. I know that if I was writing a unix application, I would handle various signals to catch the request to close (SIGTERM from memory), but I also know I need to handle these messages pretty quickly and exit before the system does a kill -9 (SIGKILL). But for a C# console application, I'm not sure how to do this.

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• built-in schema datatype for html / xhtml

  - by John Clements

  Is there a built-in schema datatype for xhtml data? Suppose I want to specify a "boozle" element that contains two "woozles", each of which is arbitrary xhtml. I want to write something like this, using the relax NG compact syntax: namespace nifty = "http://brinckerhoff.org/nifty/" start = element nifty:boozle {woozle, woozle} woozle = element nifty:woozle {xhtml} Unfortunately, xmllint then signals this error: ./lab.rng:43: element ref: Relax-NG parser error : Reference xhtml has no matching definition ./lab.rng:43: element ref: Relax-NG parser error : Internal found no define for ref xhtml So my question is this: is there something sensible that I should put in place of "xhtml" above?

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• django authentication .htaccess static

  - by Uszy Wieloryba

  In my app users can upload files for other users. To make the uploaded files accesible only for the addresse I need some kind of static files authentication system. My idea, is to create the apache hosted directory for each user and to limit access to this derectory using .htaccess. This means that each time new django user is created, I need to create a directory and the appropriate .htaccess file in it. I know I should do it using post_save signals on User model but I don't know how to create the .htaccess in the user's directory from python level. Can you help me with that? Or perhaps you have better solution to my problem?

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• Cleanest way to tell if 3 times are within half an hour of each other

  - by niggles

  I have 3 date / time input boxes on a form and the user cannot select any times within half an hour of each other. I've converted all values to epoch format using a Javascript implementation of strtotime, but not sure how to recursively check that any of the times are actually half an hour apart. I can hand code all checks, but it would be cleaner to write a recursive function (especially if there were theoretically more than 3 time slots). Did some Google research but no luck. Any suggestions on implementing this in Javascript or Jquery. Thanks.

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• PyQt: How to Know Progress of a Process Running background

  - by krishnanunni

  Hello there. Im in real confusion with the ProgressBar mechanisms. However now i need help on this "Can we know the percentage completion or time remaining of completion of a Process, that has been initiated from a Qt interface like this ` self.process = QProcess() self.connect(self.process, SIGNAL("readyReadStdout()"), self.readOutput) self.connect(self.process, SIGNAL("readyReadStderr()"), self.readErrors) tarsourcepath="sudo tar xvpf "+ self.path1 self.process.setArguments(QStringList.split(" ",tarsourcepath)) self.textLabel3.setText(self.__tr("Extracting.....")) self.process.start()` slots readOUtput just implements the collection of data fron stdout and transferring it to a text browser. I need to know is there any way we could monitor the ongoing process, making to knowpercentage completion, so that i can manage a progressbar for this. Thanks Experts

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• integrating django-paypal

  - by ramdaz

  Hi I am trying to integrate Django-Paypal onto a site, where once the customer makes a payment I need to send a dynamic URL from which the user can download some specific information. I am registering all users to a URL which allows them to buy the document. The URL which can only be accessed by a registered user with a verified email ids using django-registration, allows the user to connect to paypal and make payment. How do I capture the signal and verify which user has made the payment for which product he/she is purchased, based on this information 1) I need to know two information, which user made the payment, and for which product did he or she make the payment? 2) Only if I have these information can I send the right UR:L by email. Any help appreciated. I am not very sure how django-signals work. What all details does payment_was_successful signal return? I am using IPN

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• Creating a QLineEdit search field for items displayed in a QListView

  - by krunk

  I want to create a search field that filters the items shown in a QListView. Basically the user could type in "foo" and only items with "foo" in the DisplayRole are shown. I already have a few ideas on how to do this, but thought I'd ask those more experienced than I. My idea would be to use some signals and slots to set a filter in the QAbstractItem model and trigger an update() in the QListView. Are there any helper methods in QListView for filtering I may have missed? Is there a canonical way of handling this I haven't run across?

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• Accurate Timings with Oscilloscopes on PC

  - by Paul Bullough

  In the world of embedded software (firmware) it is fairly common to observe the order of events, take timings and optimise a program by getting it to waggle PIO lines and capturing their behavior on an oscilloscope. In days gone by it was possible to toggle pins on the serial and parallel ports to achieve much the same thing on PC-based software. This made it possible to capture host PC-based software events and firmware events on the same trace and examine host software/firmware interactions. Now, my new laptop ... no serial or parallel ports! This is increasingly the case. So, does anyone have any suggestions as to go about emitting accurate timing signals off a "modern" PC? It strikes me that we don't have any immediately programmable, lag-free output pins left. The solution needs to run off a laptop, so using add-on cards that only plug into desktops are not permitted.

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• Mysql eliminate user based on conditions

  - by Dustin

  I asked this last week over the weekend and it got buried in the archives before anyone could answer. So forgive me if you've already seen this. I teach classes and want to be able to select those students who have taken one class, but not another class. I have two tables: lessons_slots which is the table for every class such as: -------------------- -ID name slots- -1 basics 10 - -2 advanced 10 - -3 basics 10 - --------------------- The other table is class_roll, which holds enrollment info, such as: -------------------- -sID classid firstname lastname- -1 1 Jo Schmo -2 1 Person Two ... -13 2 Jo Schmo --------------------- What I want to do, I select everyone who has not had the advanced class (for example). I've tried doing SELECT * FROM lessons_slots LEFT JOIN class_roll ON lessons_slots.ID = class_roll.classid WHERE lessons_slots.name != 'advanced' But that doesn't work...All it does is eliminate that row, without eliminating the user. I want Jo Schmo, for example, to not show up in the results. Any ideas?

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• Hash Table: Should I increase the element count on collisions?

  - by Nazgulled

  Hi, Right now my hash tables count the number of every element inserted into the hash table. I use this count, with the total hash table size, to calculate the load factor and when it reaches like 70%, I rehash it. I was thinking that maybe I should only count the inserted elements with fills an empty slot instead of all of them. Cause the collision method I'm using is separate chaining. The factor load keeps increasing but if there can be a few collisions leaving lots of empty slots on the hash table. You are probably thinking that if I have that many collisions, maybe I'm not using the best hashing method. But that's not the point, I'm using one of the know hashing algorithms out there, I tested 3 of them on my sample data and selected the one who produced less collisions. My question still remains. Should I keep counting every element inserted, or just the ones that fill an empty slot in the Hash Table?

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• Why can't I reclaim my dynamically allocated memory using the "delete" keyword?

  - by synaptik

  I have the following class: class Patient { public: Patient(int x); ~Patient(); private: int* RP; }; Patient::Patient(int x) { RP = new int [x]; } Patient::~Patient() { delete [] RP; } I create an instance of this class on the stack as follows: void f() { Patient p(10); } Now, when f() returns, I get a "double free or corruption" error, which signals to me that something is attempted to be deleted more than once. But I don't understand why that would be so. The space for the array is created on the heap, and just because the function from inside which the space was allocated returns, I wouldn't expect the space to be reclaimed. I thought that if I allocate space on the heap (using the new keyword), then the only way to reclaim that space is to use the delete keyword. Help! :)

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• MIDI on Android: Java and/or AIR libraries

  - by yar

  I've been contemplating (re)building an app on iPad for some time, where I would use objective-C and DSMI to send MIDI signals to a host computer. This is not bad (I mean, except for actually writing the app). Now I'm contemplating perhaps developing the app for Android tablets (TBA). In Java, what options are available for MIDI message communication? I'm quite familiar with javax.sound.midi, but then I would need a virtual MIDI port to send messages to the host. On the other hand, if the app were done in Adobe AIR, what options would I have available for communicating with MIDI? Obviously another option is to send/receive messages over a TCP/IP socket to a Java host, and talk that way, but it sounds a tad cumbersome... or perhaps not? DSMI does use a host program, after all.

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• Java: Best practices for turning foreign horror-code into clean API...?

  - by java.is.for.desktop

  Hello, everyone! I have a project (related to graph algorithms). It is written by someone else. The code is horrible: public fields, no getters/setters huge methods, all public some classes have over 20 fields some classes have over 5 constructors (which are also huge) some of those constructors just left many fields null (so I can't make some fields final, because then every second constructor signals errors) methods and classes rely on each other in both directions I have to rewrite this into a clean and understandable API. Problem is: I myself don't understand anything in this code. Please give me hints on analyzing and understanding such code. I was thinking, perhaps, there are tools which perform static code analysis and give me call graphs and things like this.

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• QT clicked signal dosnt work on QStandardItemModel with tree view

  - by user63898

  Hello i have this code in QT and all i want to to catch the clicked event when some one clicking in one of the treeview rows without success here is my code: (parant is the qMmainwindow) m_model = new QStandardItemModel(0, 5, parent); // then later in the code i have proxyModel = new QSortFilterProxyModel; proxyModel->setDynamicSortFilter(true); setSourceModel(createMailModel(parent)); ui.treeView->setModel(proxyModel); ui.treeView->setSortingEnabled(true); ui.treeView->sortByColumn(4, Qt::DescendingOrder); // and my signal/slot looks like this but its not working //and im not getting eny clicked event fired connect(ui.treeView,SIGNAL(Clicked(const QModelIndex& ) ), this,SLOT( treeViewSelectedRow(const QModelIndex& ) ) ); also how can i debug QT signal/slots so i can see some debug massages printing when something is wrong ?

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• MIDI on Android: Libs and So Forth

  - by yar

  I've been contemplating (re)building an app on iPad for some time, where I would use objective-C and DSMI to send MIDI signals to a host computer. This is not bad (I mean, except for actually writing the app). Now I'm contemplating perhaps developing the app for Android tablets (TBA). In Java, what options are available for MIDI message communication? I'm quite familiar with javax.sound.midi, but then I would need a virtual MIDI port to send messages to the host. On the other hand, if the app were done in Adobe AIR, what options would I have available for communicating with MIDI? Obviously another option is to send/receive messages over a TCP/IP socket to a Java host, and talk that way, but it sounds a tad cumbersome... or perhaps not? DSMI does use a host program, after all.

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• How to use QMetaMethod with QObject::connect

  - by VestniK

  I have two instances of QObject subclasses and two QMetaMethod instances of signal in one of objects and slot in another object. I want to connect this signal and slot with each other. I've looked through the qobject.h file and find that SIGNAL() and SLOT() macro are just add "1" or "2" character to the beginning of method signature so it looks like it should be possible to add the same character to the beginning of string returned by QMetaMethod::signature() but this approach depends on some undocumented internals of toolkit and may be broken at any time by a new version of Qt. Does anybody know reliable way to connect signals and slots through their QMetaMethod reflection representation?

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• How-to dispose a waithandle correctly

  - by TomTom

  Hello, I'm doing some multi-threading and use AutoResetEvents and ManualResetEvents do control my main - loop. When "destryoing" the threads I also have to dispose these signals, that's clear. But I saw different ways how to dispose Waithandles, and I'm not sure which one is correct: Version 1 if (disposing) { this.threadExitEvent.SafeWaitHandle.Dispose(); this.threadExitEvent.Close(); this.threadExitEvent = null; .... } Version 2 if (disposing) { this.threadExitEvent.Close(); this.threadExitEvent = null; .... } Version 3 if (disposing) { this.threadExitEvent.Close(); .... }

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• Cannot save model due to bad transaction? Django

  - by Kenneth Love

  Trying to save a model in Django admin and I keep getting the error: Transaction managed block ended with pending COMMIT/ROLLBACK I tried restarting both the Django (1.2) and PostgreSQL (8.4) processes but nothing changed. I added "autocommit": True to my database settings but that didn't change anything either. Everything that Google has turned up has either not been answered or the answer involved not having records in the users table, which I definitely have. The model does not have a custom save method and there are no pre/post save signals tied to it. Any ideas or anything else I can provide to make answering this easier?

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• GPU Computing - # of GPUs supported

  - by TehTypoKing

  I currently have a desktop with 6 GPUs ( 3x HD 5970s ) in non-crossfire mode. Unfortunately, it seems that Windows 7 64bit only supports up to 4 GPUs. I have not been able to find a reliable source to deny or confirm this. If windows 7 has this limitation, is there a Linux flavor that supports more than 4 GPUs? In-case you are wondering, this is not for gaming but high-speed single precision computing. With this current setup ( if I can find 6gpu support ) I am looking to reach 13.8 Teraflops. Also, my motherboard does support 3 16x pci-xpress gen2 slots... and I have a 1500w powersupply plugged into a 20amp outlet. Windows is able to detect all 6 cores.. although, 2 of which displays the warning "Drivers failed to load". To recap: - Can windows support 6 GPUs? - If not, does Linux? Thank you.

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• Mean of Sampleset and powered Sampleset

  - by Milla Well

  I am working on an ICA implementation wich is based on the assumption, that all source signals are independent. So I checked on the basic concepts of Dependence vs. Correlation and tried to show this example on sample data from numpy import * from numpy.random import * k = 1000 s = 10000 mn = 0 mnPow = 0 for i in arange(1,k): a = randn(s) a = a-mean(a) mn = mn + mean(a) mnPow = mnPow + mean(a**3) print "Mean X: ", mn/k print "Mean X^3: ", mnPow/k But I couldn't produce the last step of this example E(X^3) = 0: >> Mean X: -1.11174580826e-18 >> Mean X^3: -0.00125229267144 First value I would consider to be zero, but second value is too large, isn't it? Since I subtract the mean of a, I expected the mean of a^3 to be zero as well. Does the problem lie in the random number generator, the precision of the numerical values in my misunderstanding of the concepts of mean and expected value?

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• Implementing Qt File Dialog with a Different File System Library (boost)

  - by knight

  Hi, I am writing an application which requires me to use another file system and file engine handlers and not the qt's default ones. Basically what I want to be able to do is to use qt's file dialog but have an underlying file system handler (for example built using boost file system library) of mine handling all the operations with regards to file and directory operations within that dialog. I have already written a custom file engine which handles some of the operations but I am now stuck with Qt's file system model and the file system watcher engine, as I need to have the signals transmitted for this custom file engine. Seems like I have a daunting task ahead. Am I heading in the right direction? Is there any other simpler way that I could implement this? Can anyone give me any idea on how to proceed. I was thinking of looking into proxy models but not sure if that would work. Thanks in advance for any help.

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• MySQL with Java: Open connection only if possible

  - by emempe

  I'm running a database-heavy Java application on a cluster, using Connector/J 5.1.14. Therefore, I have up to 150 concurrent tasks accessing the same MySQL database. I get the following error: Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Too many connections This happens because the server can't handle so many connections. I can't change anything on the database server. So my question is: Can I check if a connection is possible BEFORE I actually connect to the database? Something like this (pseudo code): check database for open connection slots if (slot is free) { Connection cn = DriverManager.getConnection(url, username, password); } else { wait ... } Cheers

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