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  • How does Qt implement signals and slots?

    - by anton
    Can someone explain to me the basic idea of Qt signals&slots mechanism IMPLEMENTATION? I want to know what all those Q_OBJECT macros do "in plain C++". This question is NOT about signals&slots usage. added: I know that Qt uses moc compiler to transform Qt-C++ in plain C++. But what does moc do? I tried to read "moc_filename.cpp" files but I have no idea what can something like this mean void *Widget::qt_metacast(const char *_clname) { if (!_clname) return 0; if (!strcmp(_clname, qt_meta_stringdata_Widget)) return static_cast<void*>(const_cast< Widget*>(this)); return QDialog::qt_metacast(_clname); } Thanks in Advance, anton

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  • External config file to be used by multiple DLLs.

    - by vikp
    Hi, I have multiple DLLs that are used to read/write data into my database. There is a presentation layer DLL and a data access layer DLL. I want these DLLs to share a set of the connection strings. My idea is to store the connection string in a seperate DLL in the external configuration file. I'm not sure whether it's a good idea and whether I can reference that external DLL in both presentation and data access layers. The other question is whether I should write a helper class to read the data from the external config file or whether I should be using built in .Net methods? Thank you

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  • Firefox doesn't show my CSS

    - by vtortola
    Hi, I have a strange problem, Firefox doesn't show the CSS of the page I'm doing, but Internet Explorer does. I have tried at home and at one of my friend's home, and it happens in both. But, if I go to the Firefox Web Developer toolbar (i have it installed) and select CSS=Edit CSS, then the styles appears appears in the page and in the editor! As soon I close it, they disappears again. I have no idea what the problem is :( Do you have any idea about what could be the problem? thanks in advance.

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  • jQuery: Checking for length of ul and removing an li element?

    - by Legend
    I am trying to remove the last <li> element from a <ul> element only if it exceeds a particular length. For this, I am doing something like this: var selector = "#ulelement" if($(selector).children().length > threshold) { $(selector + " >:last").remove(); } I don't like the fact that I have to use the selector twice. Is there a shorter way to do this? Something like a "remove-if-length-greater-than-threshold" idea. I was thinking that maybe there is a way to do this using the live() function but I have no idea how.

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  • Silverlight TabControl - Finding and selecting a TabItem from a given Control in the TabItem.

    - by David Gray Wright
    I am building a LOB application that has a main section and a TabControl with various TabItems in it. On hitting save the idea is that any fields in error are highlighted and the first field in error gets the focus. If the first, and only, field in error is on an Unselected tab the tab should then become selected and the field in error should become highlighted and have focus. But I can not get this to work. What appears to be happening is that the Unselected tab is not in the visual tree so you can't navigate back to the owning TabItem and make it the currently selected TabItem in the TabControl. Has anyone got an idea on how this can be done\achieved?

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  • NHibernate custom connection string configuration

    - by user177883
    I have a c# library project, that i configured using nhibernate, and I like people to be able to import this project and use the project. This project has FrontController that does all the work. I have a connection string in hibernate config file and in app.config file of another project. it would be nice for anyone to be able to set the connection string into this library project and use it. such as through a method which will take the connectiong string as parameter. or when creating a new instance of FrontController to pass the connection string to constructor. or if you have a better idea. How to do this? I d like this class library to use the same database of the project that s imported. How to set hibernate connection string programatically? same idea for log4net.

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  • Catching java.lang.OutOfMemoryError

    - by dotsid
    Documentation for java.lang.Error says: An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch But as java.lang.Error is subclass of java.lang.Throwable I can catch this type of throwable. I understand why this is not good idea to catch this sort of exceptions. As far as I understand, if we decide to caught it, the catch handler should not allocate any memory by itself. Otherwise OutOfMemoryError will be thrown again. So, my question is: is there any real word scenarios when catching java.lang.OutOfMemoryError may be a good idea? if we catching java.lang.OutOfMemoryError how can we sure that catch handler doesn't allocate any memory by itself (any tools or best practicies)? Thanks a lot.

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  • Interpolation of scattered data: What could I do?

    - by Simon
    Hi! I need your help. I'm working on a 3D chart in Java using Java 3D. It should be able to display a bunch of measured values. As measured, the data I get is scattered. This means I will have to interpolate the missing points in order to get my surface plotted nicely. I didn't study all that 3D-Geometry stuff yet and I don't know where to start. My idea is to triangulate the points to a surface and then, based on the triangulation, interpolate the missing points. (see this to have a rough idea of what I want to achieve) Does someone have experiences with the interpolation of scattered data? Is my approach the right one? If yes, what kind of data structures and algorithms will I need in order to triangulate my points cloud?

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  • All my UIButtons and UITableRowViews are now gray

    - by Greg Maletic
    Not sure how this happened, but all of the UITableRowViews and roundrect-style UIButtons in my app—spanning a dozen or so views—are now all gray instead of white. Unfortunately, I have no idea how this happened. (In fact, I had no idea it was possible to do this.) Explicitly setting the button's or tableRowView's background color to white gets it back to normal. But it'll be a lot of work to do that to every one of my views...and I'd rather not have to do it since there's obviously something simple that caused it in the first place. How did I break this? Thanks very much.

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  • MessageBox if Recordset Update is Successful

    - by Paolo Bernasconi
    In Access 2007, I have a form to add a new contact to a table: RecSet.AddNew RecSet![Code_Personal] = Me.txtCodePersonal.Value RecSet![FName] = Me.TxtFName.Value RecSet![LName] = Me.txtLName.Value RecSet![Tel Natel] = Me.txtNatTel.Value RecSet![Tel Home] = Me.txtHomeTel.Value RecSet![Email] = Me.txtEmail.Value RecSet.Update This has worked so far, and the contact has successfully been aded. But I'm having two problems: I want to display a messagebox to tell the user the contact was successfully added If the contact was not successfully added because A contact with this name already exists A different issue Then display a message box "Contact already exists" or "error occured" respectively. My idea of doing this is: If recSet.Update = true Then MsgBox "Paolo Bernasconi was successfully added" Else if RecSet![FName] & RecSet![LName] 'already exist in table MsgBox "Contact already exists" Else MsgBox "An unknown error occured" I know this code is wrong, and obviously doesn't work, but it's just to give you an idea of what I'm trying to achieve. Thanks for all your help in advance.

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  • Rush Hour - Solving the game

    - by Rubys
    Rush Hour if you're not familiar with it, the game consists of a collection of cars of varying sizes, set either horizontally or vertically, on a NxM grid that has a single exit. Each car can move forward/backward in the directions it's set in, as long as another car is not blocking it. You can never change the direction of a car. There is one special car, usually it's the red one. It's set in the same row that the exit is in, and the objective of the game is to find a series of moves (a move - moving a car N steps back or forward) that will allow the red car to drive out of the maze. I've been trying to think how to solve this problem computationally, and I can really not think of any good solution. I came up with a few: Backtracking. This is pretty simple - Recursion and some more recursion until you find the answer. However, each car can be moved a few different ways, and in each game state a few cars can be moved, and the resulting game tree will be HUGE. Some sort of constraint algorithm that will take into account what needs to be moved, and work recursively somehow. This is a very rough idea, but it is an idea. Graphs? Model the game states as a graph and apply some sort of variation on a coloring algorithm, to resolve dependencies? Again, this is a very rough idea. A friend suggested genetic algorithms. This is sort of possible but not easily. I can't think of a good way to make an evaluation function, and without that we've got nothing. So the question is - How to create a program that takes a grid and the vehicle layout, and outputs a series of steps needed to get the red car out? Sub-issues: Finding some solution. Finding an optimal solution (minimal number of moves) Evaluating how good a current state is Example: How can you move the cars in this setting, so that the red car can "exit" the maze through the exit on the right?

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  • TDD and encapsulation priority conflict

    - by Hanseh
    Hi, I just started practicing TDD in my projects. I'm developing a project now using php/zend/mysql and phpunit/dbunit for testing. I'm just a bit distracted on the idea of encapsulation and the test driven approach. My idea behind encapsulation is to hide access to several object functionalities. To make it more clear, private and protected functions are not directly testable(unless you will create a public function to call it). So I end up converting some private and protected functions to public functions just to be able to test them. I'm really violating the principles of encapsulation to give way to micro function testability. Is this the correct way of doing it?

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  • Can I make clojure macro that will allow me to get a list of all functions created by the macro?

    - by Rob Lachlan
    I would like to have a macro which I'll call def-foo. Def-foo will create a function, and then will add this function to a set. So I could call (def-foo bar ...) (def-foo baz ...) And then there would be some set, e.g. all-foos, which I could call: all-foos => #{bar, baz} Essentially, I'm just trying to avoid repeating myself. I could of course define the functions in the normal way, (defn bar ...) and then write the set manually. A better alternative, and simpler than the macro idea, would be to do: (def foos #{(defn bar ...) (defn baz ...)} ) But I'm still curious as to whether there is a good way for the macro idea to work.

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  • Why is it still so hard to write software?

    - by nornagon
    Writing software, I find, is composed of two parts: the Idea, and the Implementation. The Idea is about thinking: "I have this problem; how do I solve it?" and further, "how do I solve it elegantly?" The answers to these questions are obtainable by thinking about algorithms and architecture. The ideas come partially through analysis and partially through insight and intuition. The Idea is usually the easy part. You talk to your friends and co-workers and you nut it out in a meeting or over coffee. It takes an hour or two, plus revisions as you implement and find new problems. The Implementation phase of software development is so difficult that we joke about it. "Oh," we say, "the rest is a Simple Matter of Code." Because it should be simple, but it never is. We used to write our code on punch cards, and that was hard: mistakes were very difficult to spot, so we had to spend extra effort making sure every line was perfect. Then we had serial terminals: we could see all our code at once, search through it, organise it hierarchically and create things abstracted from raw machine code. First we had assemblers, one level up from machine code. Mnemonics freed us from remembering the machine code. Then we had compilers, which freed us from remembering the instructions. We had virtual machines, which let us step away from machine-specific details. And now we have advanced tools like Eclipse and Xcode that perform analysis on our code to help us write code faster and avoid common pitfalls. But writing code is still hard. Writing code is about understanding large, complex systems, and tools we have today simply don't go very far to help us with that. When I click "find all references" in Eclipse, I get a list of them at the bottom of the window. I click on one, and I'm torn away from what I was looking at, forced to context switch. Java architecture is usually several levels deep, so I have to switch and switch and switch until I find what I'm really looking for -- by which time I've forgotten where I came from. And I do that all day until I've understood a system. It's taxing mentally, and Eclipse doesn't do much that couldn't be done in 1985 with grep, except eat hundreds of megs of RAM. Writing code has barely changed since we were staring at amber on black. We have the theoretical groundwork for much more advanced tools, tools that actually work to help us comprehend and extend the complex systems we work with every day. So why is writing code still so hard?

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  • Zend Framework: Flash Messenger, add a message from the model

    - by Dan
    Any idea on how best to add a message to flash messenger from the model? As FlashMessenger is an action helper, this seems not to be possible, so the obvious solution is to create an internal message object in the model, and return that to the controller from where you can use addMessage(). But if you want to return something else as well, this falls down. Another idea is an additional session namespace for these internal messages, which is then merged in with the Flash Messenger namespace messages at output time? Anyone have any thoughts or experience on this? Cheers.

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  • (Google AppEngine) Memcache Lock Entry

    - by Friedrich
    Hi, i need a locking in memcache. Since all operations are atomic that should be an easy task. My idea is to use a basic spin-lock mechanism. So every object that needs locking in memcache gets a lock object, which will be polled for access. // pseudo code // try to get a lock int lock; do { lock = Memcache.increment("lock", 1); } while(lock != 1) // ok we got the lock // do something here // and finally unlock Memcache.put("lock", 0); How does such a solution perform? Do you have a better idea how to lock a memcache object? Best regards, Friedrich Schick

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  • Coding guidelines + Best Practices?

    - by Chathuranga Chandrasekara
    I couldn't find any question that directly applies to my query so I am posting this as a new question. If there is any existing discussion that may help me, please point it out and close the question. Question: I am going to do a presentation on C# coding guidelines but it is not supposed to limit to coding standards. So I have a rough idea but I think I need to address good programing practices. So the contents will be something like this. Basic coding standards - Casing, Formatting etc. Good practices - Usage of Hashset over other data structures, String vs String Builder, String's immutability and using them effectively etc Really I would like to add more good practices (Especially to improve the performance.) So like to hear some more good practices to be used with C#. Any suggestions??? (No need of large descriptions :) Just the idea is sufficient.)

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  • Implementing a Stack using Test-Driven Development

    - by devoured elysium
    I am doing my first steps with TDD. The problem is (as probably with everyone starting with TDD), I never know very well what kind of unit tests to do when I start working in my projects. Let's assume I want to write a Stack class with the following methods(I choose it as it's an easy example): Stack<T> - Push(element : T) - Pop() : T - Seek() : T - Count : int - IsEmpty : boolean How would you approch this? I never understood if the idea is to test a few corner cases for each method of the Stack class or start by doing a few "use cases" with the class, like adding 10 elements and removing them. What is the idea? To make code that uses the Stack as close as possible to what I'll use in my real code? Or just make simple "add one element" unit tests where I test if IsEmpty and Count were changed by adding that element? How am I supposed to start with this?

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  • Coding guidelines + Best Practises?

    - by Chathuranga Chandrasekara
    I couldn't find any question that directly applies to my query so I am posting this as a new question. If there is any existing discussion that may help me, please point it out and close the question. Question: I am going to do a presentation on C# coding guidelines but it is not supposed to limit to coding standards. So I have a rough idea but I think I need to address good programing practices. So the contents will be something like this. Basic coding standards - Casing, Formatting etc. Good practices - Usage of Hashset over other data structures, String vs String Builder, String's immutability and using them effectively etc Really I would like to add more good practices (Especially to improve the performance.) So like to hear some more good practices to be used with C#. Any suggestions??? (No need of large descriptions :) Just the idea is sufficient.)

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