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  • Context Menu on QGraphicsWidget

    - by onurozcelik
    Hi, In my application I have two object type. One is field item, other is composite item. Composite items may contain two or more field items. Here is my composite item implementation. #include "compositeitem.h" CompositeItem::CompositeItem(QString id,QList<FieldItem *> _children) { children = _children; } CompositeItem::~CompositeItem() { } QRectF CompositeItem::boundingRect() const { //Not carefully thinked about it return QRectF(QPointF(-50,-150),QSizeF(250,250)); } void CompositeItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget ) { FieldItem *child; foreach(child,children) { child->paint(painter,option,widget); } } QSizeF CompositeItem::sizeHint(Qt::SizeHint which, const QSizeF &constraint) const { QSizeF itsSize(0,0); FieldItem *child; foreach(child,children) { // if its size empty set first child size to itsSize if(itsSize.isEmpty()) itsSize = child->sizeHint(Qt::PreferredSize); else { QSizeF childSize = child->sizeHint(Qt::PreferredSize); if(itsSize.width() < childSize.width()) itsSize.setWidth(childSize.width()); itsSize.setHeight(itsSize.height() + childSize.height()); } } return itsSize; } void CompositeItem::contextMenuEvent(QGraphicsSceneContextMenuEvent *event) { qDebug()<<"Test"; } My first question is how I can propagate context menu event to specific child. Picture on the above demonstrates one of my possible composite item. If you look on the code above you will see that I print "Test" when context menu event occurs. When I right click on the line symbol I see that "Test" message is printed. But when I right click on the signal symbol "Test" is not printed and I want it to be printed. My second question what cause this behaviour. How do I overcome this.

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  • SQL: script to create country, state tables

    - by pcampbell
    Consider writing an application that requires registration for an entity, and the schema has been defined to require the country, state/prov/county data to be normalized. This is fairly typical stuff here. Naming also is important to reflect. Each country has a different name for this entity: USA = states Australia = states + territories Canada = provinces + territories Mexico = states Brazil = states Sweden = provinces UK = counties, principalities, and perhaps more! Most times when approaching this problem, I have to scratch together a list of good countries, and the states/prov/counties of each. The app may be concerned with a few countries and not others. The process is full of pain. It typically involves one of two approaches: opening up some previous DB and creating a CREATE script based on those tables. Run that script in the context of the new system. creating a DTS package from database1 to database2, with all the DDL and data included in the transfer. My goal now is to script the creation and insert of the countries that I'd be concerned with in the app of the day. When I want to roll out Countries X/Y/Z, I'll open CountryX.sql, and load its states into the ProvState table. Question: do you have a set of scripts in your toolset to create schema and data for countries and state/province/county? If so, would you share your scripts here? (U.K. citizens, please feel free to correct me by way of a comment in the use of counties.)

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  • Converting Makefile to Visual Studio Terminology Questions (First time using VS)

    - by Ukko
    I am an old Unix guy who is converting a makefile based project over to Microsoft Visual Studio, I got tasked with this because I understand the Makefile which chokes VS's automatic import tools. I am sure there is a better way than what I am doing but we are making things fit into the customer's environment and that is driving my choices. So gmake is not a valid answer, even if it is the right one ;-) I just have a couple of questions on terminology that I think will be easy for an experienced (or junior) user to answer. Presently, a make all will generate several executables and a shared library. How should I structure this? Is it one "solution" with multiple projects? There is a body of common code (say 50%) that is shared between the various executable targets that is not in a formal library, if that matters. I thought I could just set up the first executable and then add targets for the others, but that does not seem to work. I know I am working against the tool, so what is the right way? I am also using Visual C++ 2010 Express to try and do this so that may also be a problem if support for multiple targets is not supported without using Visual C++ 2010 (insert superlative). Thanks, this is really one of those questions that should be answerable by a quick chat with the resident Windows Developer at the water cooler. So, I am asking at the virtual water cooler, I also spring for a virtual frosty beverage after work.

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  • Why does autoboxing in Java allow me to have 3 possible values for a boolean?

    - by John
    Reference: http://java.sun.com/j2se/1.5.0/docs/guide/language/autoboxing.html If your program tries to autounbox null, it will throw a NullPointerException. javac will give you a compile-time error if you try to assign null to a boolean. makes sense. assigning null to a Boolean is a-ok though. also makes sense, i guess. but let's think about the fact that you'll get a NPE when trying to autounbox null. what this means is that you can't safely perform boolean operations on Booleans without null-checking or exception handling. same goes for doing math operations on an Integer. for a long time, i was a fan of autoboxing in java1.5+ because I thought it got java closer to be truly object-oriented. but, after running into this problem last night, i gotta say that i think this sucks. the compiler giving me an error when I'm trying to do stuff with an uninitialized primitive is a good thing. I think I may be misunderstanding the point of autoboxing, but at the same time I will never accept that a boolean should be able to have 3 values. can anyone explain this? what am i not getting?

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  • Which single IoC/DI container would you recommend using and why?

    - by Rob G
    I'm asking this question because it's a good way to gauge how the community at large feels about the various containers/frameworks and why. Also, whilst my expertise may lie in .Net development, I am very interested in which frameworks are popular (and why) in other languages. If I feel the need to start digging into Java for instance, then I'd like to hit the ground running with good (comfortable) knowledge that I'm starting in the right direction. Does Ruby even need one with all its magnificent dynamicism? I have my own opinions on the .Net front, and will probably add my own personal favourite in an answer below, but I'm interested in all languages and opinions here. With all that in mind, could you please state only one IoC/DI framework that you use and recommend with the language of choice (Java/Ruby/.Net/Smalltalk etc.) and your reasoning for your choice, and if someone has already answered your particular flavour, then you can just vote it up and add comments to it so that anyone looking for advice in future and see which frameworks are more than likely to work for them once they read your reasoning. I'm hoping that over time, the best ones will bubble up to the top. I realise that this question doesn't have only one correct answer, so I won't be choosing one - the community will decide which framework gets the most votes and why. Of course, if you really feel strongly opposed to a particular brand, you could take the reputation hit and vote it down too, and this question can serve as a true wiki-style entry for research into this field. Remember, only one IoC per answer you write please - if you feel the need to promote two frameworks, then write two answers with your reasoning inside for each choice - then others in the community can agree or disagree with you.

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  • How to Use Calculated Color Values with ColorMatrix?

    - by Otaku
    I am changing color values of each pixel in an image based on a calculation. The problem is that this takes over 5 seconds on my machine with a 1000x1333 image and I'm looking for a way to optimize it to be much faster. I think ColorMatrix may be an option, but I'm having a difficult time figure out how I would get a set of pixel RGB values, use that to calculate and then set the new pixel value. I can see how this can be done if I was just modifying (multiplying, subtracting, etc.) the original value with ColorMatrix, but now how I can use the pixels returned value to use it to calculate and new value. For example: Sub DarkenPicture() Dim clrTestFolderPath = "C:\Users\Me\Desktop\ColorTest\" Dim originalPicture = "original.jpg" Dim Luminance As Single Dim bitmapOriginal As Bitmap = Image.FromFile(clrTestFolderPath + originalPicture) Dim Clr As Color Dim newR As Byte Dim newG As Byte Dim newB As Byte For x = 0 To bitmapOriginal.Width - 1 For y = 0 To bitmapOriginal.Height - 1 Clr = bitmapOriginal.GetPixel(x, y) Luminance = ((0.21 * (Clr.R) + (0.72 * (Clr.G)) + (0.07 * (Clr.B))/ 255 newR = Clr.R * Luminance newG = Clr.G * Luminance newB = Clr.B * Luminance bitmapOriginal.SetPixel(x, y, Color.FromArgb(newR, newG, newB)) Next Next bitmapOriginal.Save(clrTestFolderPath + "colorized.jpg", ImageFormat.Jpeg) End Sub The Luminance value is the calculated one. I know I can set ColorMatrix's M00, M11, M22 to 0, 0, 0 respectively and then put a new value in M40, M41, M42, but that new value is calculated based of a value multiplication and addition of that pixel's components (((0.21 * (Clr.R) + (0.72 * (Clr.G)) + (0.07 * (Clr.B)) and the result of that - Luminance - is multiplied by the color component). Is this even possible with ColorMatrix?

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  • How is a relative JMP (x86) implemented in an Assembler?

    - by Pindatjuh
    While building my assembler for the x86 platform I encountered some problems with encoding the JMP instruction: enc inst size in bytes EB cb JMP rel8 2 E9 cw JMP rel16 4 (because of 0x66 16-bit prefix) E9 cd JMP rel32 5 ... (from my favourite x86 instruction website, http://siyobik.info/index.php?module=x86&id=147) All are relative jumps, where the size of each encoding (operation + operand) is in the third column. Now my original (and thus fault because of this) design reserved the maximum (5 bytes) space for each instruction. The operand is not yet known, because it's a jump to a yet unknown location. So I've implemented a "rewrite" mechanism, that rewrites the operands in the correct location in memory, if the location of the jump is known, and fills the rest with NOPs. This is a somewhat serious concern in tight-loops. Now my problem is with the following situation: b: XXX c: JMP a e: XXX ... XXX d: JMP b a: XXX (where XXX is any instruction, depending on the to-be assembled program) The problem is that I want the smallest possible encoding for a JMP instruction (and no NOP filling). I have to know the size of the instruction at c before I can calculate the relative distance between a and b for the operand at d. The same applies for the JMP at c: it needs to know the size of d before it can calculate the relative distance between e and a. How do existing assemblers implement this, or how would you implement this? This is what I am thinking which solves the problem: First encode all the instructions to opcodes between the JMP and it's target, and if this region contains a variable-sized opcode, use the maximum size, i.e. 5 for JMP. Then in some conditions, the JMP is oversized (because it may fit in a smaller encoding): so another pass will search for oversized JMPs, shrink them, and move all instructions ahead), and set absolute branching instructions (i.e. external CALLs) after this pass is completed. I wonder, perhaps this is an over-engineered solution, that's why I ask this question.

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  • SQL Alchemy MVC and cross controller joins

    - by Khorkrak
    When using SQL Alchemy for abstracting your data access layer and using controllers as the way to access objects from that abstraction layer, how should joins be handled? So for example, say you have an Orders controller class that manages Order objects such that it provides getOrder, saveOrder, etc methods and likewise a similar controller for User objects. First of all do you even need these controllers? Should you instead just treat SQL Alchemy as "the" thing for handling data access. Why bother with object oriented controller stuff there when you instead have a clean declarative way to obtain and persist objects without having to write SQL directly either. Well one reason could be that perhaps you may want to replace SQL Alchemy with direct SQL or Storm or whatever else. So having controller classes there to act as an intermediate layer helps limit what would need to change then. Anyway - back to the main question - so assuming you have these two controllers, now lets say you want the list of orders for a certain set of users meeting some criteria. How do you go about doing this? Generally you don't want the controllers crossing domains - the Orders controllers knows only about Orders and the User controller just about Users - they don't mess with each other. You also don't want to go fetch all the Users that match and then feed a big list of user ids to the Orders controller to go find the matching Orders. What's needed is a join. Here's where I'm stuck - that seems to mean either the controllers must cross domains or perhaps they should be done away with altogether and you simply do the join via SQL Alchemy directly and get the resulting User and / or Order objects as needed. Thoughts?

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  • How to convert a printer driver to a stand-alone console application which can generate a printer fi

    - by Thorbjørn Ravn Andersen
    I have a situation where the only way to generate a certain datafile is to print it manually to FILE: under Windows and save it in a file for further processing. I would really like to have a small stand-alone program which embeds this binary printer driver so I can run it from a batch file and have it generate that binary file for me, as we can then fully automate the "save file in Visio, 'print' it and upload it to the final destination and trigger a remote test". Is this possible with a suitable Windows SDK? I am a Java programmer, so I do not know Visual Studio and the possibilities with MSDN - yet! - but I'd appreciate pointers. EDIT: I have the installation files for that printer driver, both 32 and 64 bit. Older versions may include a 16 bit driver. EDIT: The "print to FILE:" functionality is just what was recommended by the documentation. I have played a little bit with using the LPR-protocol to see what it can do. I'd still prefer the "invoke small binary" approach.

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  • C# reference collection for storing reference types

    - by ivo s
    I like to implement a collection (something like List<T>) which would hold all my objects that I have created in the entire life span of my application as if its an array of pointers in C++. The idea is that when my process starts I can use a central factory to create all objects and then periodically validate/invalidate their state. Basically I want to make sure that my process only deals with valid instances and I don't re-fetch information I already fetched from the database. So all my objects will basically be in one place - my collection. A cool thing I can do with this is avoid database calls to get data from the database if I already got it (even if I updated it after retrieval its still up-to-date if of course some other process didn't update it but that a different concern). I don't want to be calling new Customer("James Thomas"); again if I initted James Thomas already sometime in the past. Currently I will end up with multiple copies of the same object across the appdomain - some out of sync other in sync and even though I deal with this using timestamp field on the MSSQL server I'd like to keep only one copy per customer in my appdomain (if possible process would be better). I can't use regular collections like List or ArrayList for example because I cannot pass parameters by their real local reference to the their existing Add() methods where I'm creating them using ref so that's not to good I think. So how can this be implemented/can it be implemented at all ? A 'linked list' type of class with all methods working with ref & out params is what I'm thinking now but it may get ugly pretty quickly. Is there another way to implement such collection like RefList<T>.Add(ref T obj)? So bottom line is: I don't want re-create an object if I've already created it before during the entire application life unless I decide to re-create it explicitly (maybe its out-of-date or something so I have to fetch it again from the db). Is there alternatives maybe ?

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  • What is faster- Java or C# (Or good old C)?

    - by Rexsung
    I'm currently deciding on a platform to build a scientific computational product on, and am deciding on either C#, Java, or plain C with Intels compiler on Core2 Quad CPU's. It's mostly integer arithmetic. My benchmarks so far show Java and C are about on par with each other, and dotNET/C# trails by about 5%- however a number of my coworkers are claiming that dotNET with the right optimizations will beat both of these given enough time for the JIT to do its work. I always assume that the JIT would have done it's job within a few minutes of the app starting (Probably a few seconds in my case, as it's mostly tight loops), so I'm not sure whether to believe them Can anyone shed any light on the situation? Would dotNET beat Java? (Or am I best just sticking with C at this point?). The code is highly multithreaded and data sets are several terabytes in size. Haskell/erlang etc are not options in this case as there is a significant quantity of existing legacy C code that will be ported to the new system, and porting C to Java/C# is a lot simpler than to Haskell or Erlang. (Unless of course these provide a significant speedup). Edit: We are considering moving to C# or Java because they may, in theory, be faster. Every percent we can shave off our processing time saves us tens of thousands of dollars per year. At this point we are just trying to evaluate whether C, Java, or c# would be faster.

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  • Cache consistency & spawning a thread

    - by Dave Keck
    Background I've been reading through various books and articles to learn about processor caches, cache consistency, and memory barriers in the context of concurrent execution. So far though, I have been unable to determine whether a common coding practice of mine is safe in the strictest sense. Assumptions The following pseudo-code is executed on a two-processor machine: int sharedVar = 0; myThread() { print(sharedVar); } main() { sharedVar = 1; spawnThread(myThread); sleep(-1); } main() executes on processor 1 (P1), while myThread() executes on P2. Initially, sharedVar exists in the caches of both P1 and P2 with the initial value of 0 (due to some "warm-up code" that isn't shown above.) Question Strictly speaking – preferably without assuming any particular CPU – is myThread() guaranteed to print 1? With my newfound knowledge of processor caches, it seems entirely possible that at the time of the print() statement, P2 may not have received the invalidation request for sharedVar caused by P1's assignment in main(). Therefore, it seems possible that myThread() could print 0. References These are the related articles and books I've been reading. (It wouldn't allow me to format these as links because I'm a new user - sorry.) Shared Memory Consistency Models: A Tutorial hpl.hp.com/techreports/Compaq-DEC/WRL-95-7.pdf Memory Barriers: a Hardware View for Software Hackers rdrop.com/users/paulmck/scalability/paper/whymb.2009.04.05a.pdf Linux Kernel Memory Barriers kernel.org/doc/Documentation/memory-barriers.txt Computer Architecture: A Quantitative Approach amazon.com/Computer-Architecture-Quantitative-Approach-4th/dp/0123704901/ref=dp_ob_title_bk

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  • [Python] name 'OptionGroup' is not defined

    - by Cawas
    Ok, so I made this rookie mistake below, but in my defense I was led to it thanks to how the help about this subject is on python docs, which states how to use optparse. It is actually an error under the gigantic tutorial section. In contrast and to my offense, I may be one of the very few stupid people who can't read very well and pay close attention on what I do. But since this took me so long to discover, I wanted to "document" it here: Python 2.6.1 (r261:67515, Feb 11 2010, 00:51:29) >>> from optparse import OptionParser >>> outputGroup = OptionGroup(parser, 'Output handling') Traceback (most recent call last): File "<stdin>", line 1, in <module> NameError: name 'OptionGroup' is not defined This is strictly done with examples found on the docs, and you can't find anything about it anywhere, be it that long long docs page, google or stackoverflow. Plus, reading optparse.py shows OptionGroup is there, so that adds to the confusion. I bet it will take less than 1 minute for someone to spot my error. For that I'll only add proper tags and / or modify the title later on. :)

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  • How do I simulate the usage of a sequence of web pages?

    - by Rory Becker
    I have a simple sequence of web pages written in ASP.Net 3.5 SP1. Page1 - A Logon Form.... txtUsername, txtPassword and cmdLogon Page2 - A Menu (created using DevExpress ASP.Net controls) Page3 - The page redirected to by the server in the event that the user picks the right menu option in Page2 I would like to create a threaded program to simulate many users trying to use this sequence of pages. I have managed to create a host Winforms app which Launches a new thread for each "User" I have further managed to work out the basics of WebRequest enough to perform a request which retrieves the Logon page itself. Dim Request As HttpWebRequest = TryCast(WebRequest.Create("http://MyURL/Logon.aspx"), HttpWebRequest) Dim Response As HttpWebResponse = TryCast(Request.GetResponse(), HttpWebResponse) Dim ResponseStream As StreamReader = New StreamReader(Response.GetResponseStream(), Encoding.GetEncoding(1252)) Dim HTMLResponse As String = ResponseStream.ReadToEnd() Response.Close() ResponseStream.Close() Next I need to simulate the user having entered information into the 2 TextBoxes and pressing logon.... I have a hunch this requires me to add the right sort of "PostData" to the request. before submitting. However I'm also concerned that "ViewState" may be an issue. Am I correct regarding the PostData? How do I add the postData to the request? Do I need to be concerned about Viewstate? Update: While I appreciate that Selenium or similar products are useful for acceptance testing , I find that they are rather clumsy for what amounts to load testing. I would prefer not to load 100 instances of Firefox or IE in order to simulate 100 users hitting my site. This was the reason I was hoping to take the ASPNet HttpWebRequest route.

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  • Javascript not showing up on Facebook Application's Profile Tab

    - by prateekdayal
    Hi, This may sound very noobish but I have tried to read the forum posts and docs on javascript behavior on Facebook's profile tabs. I understand that profile tabs don't support referencing external javascript but even my inline tags are not showing up on profile pages. In fact I am trying the fbjs-swf bridge and the code needed to instantiate the swf does not show up on the page <fb:fbjs_bridge/> <div id="swfContainer"></div> <script> var swf = document.createElement('fb:swf'); swf.setId('my_swf_id'); swf.setWidth('630'); swf.setHeight('520'); swf.setSWFSrc('http://www.muziboo.com/swf/player4-2.swf'); document.getElementById('swfContainer').appendChild(swf); document.getElementById('my_swf_id').callSWF('asMethod', 'one', 'two'); </script> I see a swf embedded (the one for the fbjs bridge) but I don't see any script tag containing the above javascript code. What am I missing? I can see the javascript code on canvas page though Thanks

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  • getting expat to use .dtd for entity replacement in python

    - by nicolas78
    I'm trying to read in an xml file which looks like this <?xml version="1.0" encoding="ISO-8859-1"?> <!DOCTYPE dblp SYSTEM "dblp.dtd"> <dblp> <incollection> <author>Jos&eacute; A. Blakeley</author> </incollection> </dblp> The point that creates the problem looks is the Jos&eacute; A. Blakeley part: The parser calls its character handler twice, once with "Jos", once with " A. Blakeley". Now I understand this may be the correct behaviour if it doesn't know the eacute entity. However, this is defined in the dblp.dtd, which I have. I don't seem to be able to convince expat to use this file, though. All I can say is p = xml.parsers.expat.ParserCreate() # tried with and without following line p.SetParamEntityParsing(xml.parsers.expat.XML_PARAM_ENTITY_PARSING_ALWAYS) p.UseForeignDTD(True) f = open(dblp_file, "r") p.ParseFile(f) but expat still doesn't recognize my entity. Why is there no way to tell expat which DTD to use? I've tried putting the file into the same directory as the XML putting the file into the program's working directory replacing the reference in the xml file by an absolute path What am I missing? Thx.

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  • If attacker has original data and encrypted data, can they determine the passphrase?

    - by Brad Cupit
    If an attacker has several distinct items (for example: e-mail addresses) and knows the encrypted value of each item, can the attacker more easily determine the secret passphrase used to encrypt those items? Meaning, can they determine the passphrase without resorting to brute force? This question may sound strange, so let me provide a use-case: User signs up to a site with their e-mail address Server sends that e-mail address a confirmation URL (for example: https://my.app.com/confirmEmailAddress/bill%40yahoo.com) Attacker can guess the confirmation URL and therefore can sign up with someone else's e-mail address, and 'confirm' it without ever having to sign in to that person's e-mail account and see the confirmation URL. This is a problem. Instead of sending the e-mail address plain text in the URL, we'll send it encrypted by a secret passphrase. (I know the attacker could still intercept the e-mail sent by the server, since e-mail are plain text, but bear with me here.) If an attacker then signs up with multiple free e-mail accounts and sees multiple URLs, each with the corresponding encrypted e-mail address, could the attacker more easily determine the passphrase used for encryption? Alternative Solution I could instead send a random number or one-way hash of their e-mail address (plus random salt). This eliminates storing the secret passphrase, but it means I need to store that random number/hash in the database. The original approach above does not require storage in the database. I'm leaning towards the the one-way-hash-stored-in-the-db, but I still would like to know the answer: does having multiple unencrypted e-mail addresses and their encrypted counterparts make it easier to determine the passphrase used?

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  • Templates, and C++ operator for logic: B contained by set A

    - by James Morris
    In C++, I'm looking to implement an operator for selecting items in a list (of type B) based upon B being contained entirely within A. In the book "the logical design of digital computers" by Montgomery Phister jr (published 1958), p54, it says: F11 = A + ~B has two interesting and useful associations, neither of them having much to do with computer design. The first is the logical notation of implication... The second is notation of inclusion... This may be expressed by a familiar looking relation, B < A; or by the statement "B is included in A"; or by the boolean equation F11= A + ~B = 1. My initial implementation was in C. Callbacks were given to the list to use for such operations. An example being a list of ints, and a struct containting two ints, min and max, for selection purposes. There, selection would be based upon B = A-min && B <= A-max. Using C++ and templates, how would you approach this after having implemented a generic list in C using void pointers and callbacks? Is using < as an over-ridden operator for such purposes... <ugh> evil? </ugh> (or by using a class B for the selection criteria, implementing the comparison by overloading ?)

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  • Can't empty JS array....

    - by solefald
    Yes, I am having issues with this very basic (or so it seems) thing. I am pretty new to JS and still trying to get my head around it, but I am pretty familiar with PHP and have never experienced anything like this. I just can not empty this damn array, and stuff keeps getting added to the end every time i run this. I have no idea why, and i am starting to think that it is somehow related to the way chekbox id's are named, but i may be mistaking.... id="alias[1321-213]", id="alias[1128-397]", id="alias[77-5467]" and so on. I have tried sticking checkboxes = []; and checkboxes.length = 0; In every place possible. Right after the beginning of the function, at the end of the function, even outside, right before the function, but it does not help, and the only way to empty this array is to reload the page. Please tell me what I am doing wrong, or at least point me to a place where i can RTFM. I am completely out of ideas here. function() { var checkboxes = new Array(); checkboxes = $(':input[name="checkbox"]'); $.each(checkboxes, function(key, value) { console.log(value.id); alert(value.id); } ); checkboxes.length = 0; } I have also read Mastering Javascript Arrays 3 times to make sure I am not doing something wrong, but still can't figure it out....

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  • Java method keyword "final" and its use

    - by Lukas Eder
    When I create complex type hierarchies (several levels, several types per level), I like to use the final keyword on methods implementing some interface declaration. An example: interface Garble { int zork(); } interface Gnarf extends Garble { /** * This is the same as calling {@link #zblah(0)} */ int zblah(); int zblah(int defaultZblah); } And then abstract class AbstractGarble implements Garble { @Override public final int zork() { ... } } abstract class AbstractGnarf extends AbstractGarble implements Gnarf { // Here I absolutely want to fix the default behaviour of zblah // No Gnarf shouldn't be allowed to set 1 as the default, for instance @Override public final int zblah() { return zblah(0); } // This method is not implemented here, but in a subclass @Override public abstract int zblah(int defaultZblah); } I do this for several reasons: It helps me develop the type hierarchy. When I add a class to the hierarchy, it is very clear, what methods I have to implement, and what methods I may not override (in case I forgot the details about the hierarchy) I think overriding concrete stuff is bad according to design principles and patterns, such as the template method pattern. I don't want other developers or my users do it. So the final keyword works perfectly for me. My question is: Why is it used so rarely in the wild? Can you show me some examples / reasons where final (in a similar case to mine) would be very bad?

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  • Hierarchical object model with property inheritance and event bubbling?

    - by Winston Fassett
    I'm writing a document-based client application and I need a DOM or WPF-like, but non-visual model that: Is a tree composed of elements Can accept an unlimited number of custom properties that get/set any CLR type, including collections. Can inherit their values from their parent Can inherit their default values from an ancestor Can be derived/calculated from other properties, ancestors, or descendants Support event bubbling / tunneling There will be a core set of properties but other plugins may add their own or even create custom documents Supports full inspection by the owning document in order to persist the tree and attributes in an XML format. I realize that's a tall order but I was really hoping there would be something out there to help me get started. Unfortunately WPF DependencyObjects are too closed, proprietary, and coupled to WPF to be of any use as a document model. My needs also have a strong resemblance to the HTML DOM but I haven't been able to find any clean DOM implementations that could be decoupled from HTML or ported to .NET. My current platform is .NET/C# but if anyone knows of anything that might be useful for inspiration or embedding, regardless of the platform, I'd love to know.

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  • Silverlight - how to render image from non-visible data bound user control?

    - by MagicMax
    Hello! I have such situation - I'd like to build timeline control. So I have UserControl and ItemsControl on it (every row represents some person). The ItemsControl contains another ItemsControl as ItemsControl.ItemTemplate - it shows e.g. events for the person arranged by event's date. So it looks as some kind of grid with dates as a column headers and e.g. peoples as row headers. ........................|.2010.01.01.....2010.01.02.....2010.01.03 Adam Smith....|......[some event#1].....[some event#2]...... John Dow.......|...[some event#3].....[some event#4]......... I can have a lot of persons (ItemsControl #1 - 100-200 items) and a lot of events occured by some day (1-10-30 events per person in one day) the problem is that when user scrolls ItemsControl #1/#2 it happened toooo sloooooowwww due to a lot of elements should be rendered in one time (as I have e.g. a bit of text boxes and other elements in description of particular event) Question #1 - how can I improve it? May be somebody knows better way to build such user control? I have to mention that I'm using custom Virtual panel, based on some custom Virtual panel implementation found somewhere in internet... Question #2 - I'd like to make image with help of WriteableBitmap and render data bound control to image and to show image instead of a lot of elements. Problem is that I'm trying to render invisible data bound control (created in code behind) and it has actualWidth/Height equals to zero (so nothing rendered). How can I solve it? Thank you very much for you help!

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  • Who architected / designed C++'s IOStreams, and would it still be considered well-designed by today'

    - by stakx
    First off, it may seem that I'm asking for subjective opinions, but that's not what I'm after. I'd love to hear some well-grounded arguments on this topic. In the hope of getting some insight into how a modern streams / serialization framework ought to be designed, I recently got myself a copy of the book Standard C++ IOStreams and Locales by Angelika Langer and Klaus Kreft. I figured that if IOStreams wasn't well-designed, it wouldn't have made it into the C++ standard library in the first place. After having read various parts of this book, I am starting to have doubts if IOStreams can compare to e.g. the STL from an overall architectural point-of-view. Read e.g. this interview with Alexander Stepanov (the STL's "inventor") to learn about some design decisions that went into the STL. What surprises me in particular: It seems to be unknown who was responsible for IOStreams' overall design (I'd love to read some background information about this — does anyone know good resources?); Once you delve beneath the immediate surface of IOStreams, e.g. if you want to extend IOStreams with your own classes, you get to an interface with fairly cryptic and confusing member function names, e.g. getloc/imbue, uflow/underflow, snextc/sbumpc/sgetc/sgetn, pbase/pptr/epptr (and there's probably even worse examples). This makes it so much harder to understand the overall design and how the single parts co-operate. Even the book I mentioned above doesn't help that much (IMHO). Thus my question: If you had to judge by today's software engineering standards (if there actually is any general agreement on these), would C++'s IOStreams still be considered well-designed? (I wouldn't want to improve my software design skills from something that's generally considered outdated.)

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  • Communication between EJB3 Instances (JEE inter-bean communication) possible?

    - by Hank
    I'm designing a part of a JEE6 application, consisting of EJB3 beans. Part of the requirements are multiple parallel (say a few hundred) long running (over days) database hunts. Individual hunts have different search parameters (start time, end time, query filter). Parameters may get changed over time. Currently I'm thinking of the following: SearchController (Stateless Session Bean) formulates a set of search parameters, sends it off to a SearchListener via JMS SearchListener (Message Driven Bean) receives search parameters, instantiates a SearchWorker with the parameters SearchWorker (SLSB) hunts repeatedly through the database; when it finds something, the result is sent off via JMS, and the search continues; when the given 'end-time' has reached, it ends What I'm wondering now: Is there a problem, with EJB3 instances running for days? (Other than that I need to be able to deal with container restarts...) How do I know how many and which EJB instances of SearchWorker are currently running? Is it possible to communicate with them individually (similar to sending a System V signal to a unix process), e.g. to send new parameters, to end an instance, etc..

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  • Colour manipulation of custom tags in niceEdit HTML editor ( JS / DOM )

    - by Chris
    Hi, I would like to be able to highlight, during typing and in real time, certain custom tags in the format #tag_name# within the text of a nicEdit instance ( http://nicedit.com/ ). My current attempt to implement as close to this as possible revolves around using the blur event of the editor to highlight the tags once the editor loses focus. I then use the following logic to wrap the tags in a span with a highlight class.. htmlEditor.addEvent( "blur", function( ) { str = nicEditors.findEditor( "html_content" ).getContent( ); // Remove existing spans first, leaving just the tag ( this could mess up if the html has been edited directly ) str = str.replace( /(<span class=\"highlight\">)(.[^<]+)(<\/span>)/gi, "$2" ); // Then wrap all instances of a particular tag with the highlight span str = str.replace( /#tag_name#/gi, "<span class='highlight'>#tag_name#</span>" ); nicEditors.findEditor( "html_content" ).setContent( str ); }); This is not ideal as my actual text now contains unwanted spans ( I only want the highlighting for the user's input experience, not to be saved to the database ). Obviously I could remove the spans before saving the text but the whole system is currently open to errors ( If the html is directly edited then other text may get highlighted etc ). What I would like to know is.. Is there any way to directly change the colour of the tags in the editor or DOM without using a mechanism such as this? Perhaps a way of colouring the text in memory rather than changing the HTML ? Any ideas ? Regards Chris P

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