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• How can story and gameplay be artfully merged?

  - by NauticalMile

  Let me give some context. Three of my friends and I have a pretty good game idea cooking. It's based off of a prototype I made that's evolving into a cool game mechanic. The mechanic itself is a toy that's fun on its own, but we haven't designed any puzzles around it yet. We have a design document going, and we are answering a lot of questions about what's in the game. It's become clear early on that everyone (including myself) likes the characters and the story a lot. Considering what our favorite games are, this is unsurprising. A story driven game makes sense to me. I like the emphasis that Paper Mario: The Thousand-Year-Door, Portal 2, and Tomb Raider place on story, and I imagine our game will have a similar feel (lots of dialogue, plot twists, lovable characters). However, one team member raised this point in the design doc: I am feeling like [fleshing out the story] is our biggest hurdle right now for making more design decisions - like more specific decisions about levels etc. Is this true? I am uncertain about working on the story extensively before gameplay, and my uneasiness was reinforced when I read this question about story vs. gameplay. What I want to say is: "Let's continue to work on the story, but also start brainstorming and prototyping abstract puzzles and combat sequences, and we'll creatively match them together later." Is this a reasonable approach? If so, how much of the development of these elements should be done independently? Should I try and create a whole bunch of puzzles while my other teammates focus on story and aesthetics? Then when we have a lot of story and game 'chunks' we can match them with eachother to build something meaningful. Or should we focus on iterating individual levels as distinct units where puzzles, story, etc... are designed together? Or maybe we need to put our excitement about the story on hold and just focus on gameplay. Is there another approach to design that we can take? Am I missing something crucial? I have discussed story and gameplay because they seem the most likely to be at odds with each other, but we also have to consider user interface, music, art direction, etc... Can we design these independently as well?

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• What type of interview questions should you ask for "legacy" programmers?

  - by Marcus Swope

  We have recently been receiving lots of applicants for our open developer positions from people who I like to refer to as "legacy" programmers. I don't like the term "old" because it seems a little prejudiced (especially to HR!) and it doesn't accurately reflect what I mean. We are a company that does primarily .NET development using TDD in an Agile environment, we use Git as a source control system, we make heavy use of OSS tools and projects and we contribute to them as well, we have a strong bias towards adhering to strong Object-Oriented principles, SOLID, etc, etc, etc... Now, the normal list of questions that we ask doesn't really seem to apply to applicants that are fresh out of school, nor does it seem to apply to these "legacy" programmers. Here is how I (loosely) define a "legacy" programmer. Spent a significant amount of their career working almost exclusively with Assembly/Machine Languages. Primary accomplishments include work done with TANDEM systems. Has extensive experience with technologies like FoxPro and ColdFusion It's not that we somehow think that what we do is "better" than what they do, on the contrary, we respect these types of applicants and we are scared that we may be missing a good candidate. It is just very difficult to get a good read on someone who is essentially speaking a different language than you. To someone like this, it seems a little strange to ask a question like: What is the difference between an abstract class and an interface? Because, I would think that they would almost never know the answer or even what I'm talking about. However, I don't want to eliminate someone who could be a very good candidate in their own right and could be able to eventually learn the stuff that we do. But, I also don't want to just ask a bunch of behavioral questions, because I want to know about their technical background as well. Am I being too naive? Should "legacy" programmers like this already know about things like TDD, source control strategies, and best practices for object-oriented programming? If not, what questions should we ask to get a good representation about whether or not they are still able to learn them and be able to keep up in our fast-paced environment? EDIT: I'm not concerned with whether or not applicants that meet these criteria are in general capable or incapable, as I have already stated that I believe that they can be 100% capable. I am more interested in figuring out how to evaluate their talents, as I am having a hard time figuring out how to determine if they are an A+ "legacy" programmer or if they are a D- "legacy" programmer. I've worked with both.

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• What source code organization approach helps improve modularity and API/Implementation separation?

  - by Berin Loritsch

  Few languages are as restrictive as Java with file naming standards and project structure. In that language, the file name must match the public class declared in the file, and the file must live in a directory structure matching the class package. I have mixed feelings about that approach. While I never have to guess where a file lives, there's still a lot of empty directories and artificial constraints. There's several languages that define everything about a class in one file, at least by convention. C#, Python (I think), Ruby, Erlang, etc. The commonality in most these languages is that they are object oriented, although that statement can probably be rebuffed (there is one non-OO language in the list already). Finally, there's quite a few languages mostly in the C family that have a separate header and implementation file. For C I think this makes sense, because it is one of the few ways to separate the API interface from implementations. With C it seems that feature is used to promote modularity. Yet, with C++ the way header and implementation files are split seems rather forced. You don't get the same clean API separation that you do with C, and you are forced to include some private details in the header you would rather keep only in the implementation. There's quite a few languages that have a concept that overlaps with interfaces like Java, C#, Go, etc. Some languages use what feels like a hack to provide the same concept like C# using pure virtual abstract classes. Still others don't really have an interface concept and rely on "duck" typing--for example Ruby. Ruby has modules, but those are more along the lines of mixing in behaviors to a class than they are for defining how to interact with a class. In OO terms, interfaces are a powerful way to provide separation between an API client and an API implementation. So to hurry up and ask the question, from a personal experience point of view: Does separation of header and implementation help you write more modular code, or does it get in the way? (it helps to specify the language you are referring to) Does the strict file name to class name scheme of Java help maintainability, or is it unnecessary structure for structure's sake? What would you propose to promote good API/Implementation separation and project maintenance, how would you prefer to do it?

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• How to build a 4x game?

  - by Marco

  I'm trying to study how succefully implement a 4x game. Area of interest: 1) map data: how to store stellars systems (graphs?), how to generate them and so on.. 2) multiplayer: how to organize code in a non graphical server and a client to display it 3) command system: what are patters to catch user and ai decisions and handle them, adding at first "explore" and "colonize" then "combat", "research", "spy" and so on (commands can affect ships, planets, research, etc..) 4) ai system: ai can use commands to expand, upgrade planets and ship I know is a big questions, so help is appreciated :D 1) Map data Best choice is have a graph to model a galaxy. A node is a stellar system and every system have a list of planets. Ship cannot travel outside of predefined paths, like in Ascendancy: http://www.abandonia.com/files/games/221/Ascendancy_2.png Every connection between two stellar systems have a cost, in turns. Generate a galaxy is only a matter of: - dimension: number of stellar systems, - variety: randomize number of planets and types (desertic, earth, etc..), - positions of each stellar system on game space - connections: assure that exist a path between every node, so graph is "connected" (not sure if this a matematically correct term) 2) Multiplayer Game is organized in turns: player 1, player 2, ai1, ai2. Server take care of all data and clients just diplay it and collect data change. Because is a turn game, latency is not a problem :D 3) Command system I would like to design a hierarchy of commands to take care of this aspect: abstract Genericcommand (target) ExploreCommand (Ship) extends genericcommand colonizeCommand (Ship) buildcommand(planet, object) and so on. In my head all this commands are stored in a queue for every planets, ships or reasearch center or spy, and each turn a command is sent to a server to apply command and change data state 4) ai system I don't have any idea about this. Is a big topic and what I want is a simple ai. Something like "expand and fight against everyone". I think about a behaviour tree to control ai moves, so I can develop an ai that try to build ships to expand and then colonize planets, upgrade them throught science and combat enemies. Could be done with a finite state machine too ? any ideas, resources, article are welcome!

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• Adding complexity to remove duplicate code

  - by Phil

  I have several classes that all inherit from a generic base class. The base class contains a collection of several objects of type T. Each child class needs to be able to calculate interpolated values from the collection of objects, but since the child classes use different types, the calculation varies a tiny bit from class to class. So far I have copy/pasted my code from class to class and made minor modifications to each. But now I am trying to remove the duplicated code and replace it with one generic interpolation method in my base class. However that is proving to be very difficult, and all the solutions I have thought of seem way too complex. I am starting to think the DRY principle does not apply as much in this kind of situation, but that sounds like blasphemy. How much complexity is too much when trying to remove code duplication? EDIT: The best solution I can come up with goes something like this: Base Class: protected T GetInterpolated(int frame) { var index = SortedFrames.BinarySearch(frame); if (index >= 0) return Data[index]; index = ~index; if (index == 0) return Data[index]; if (index >= Data.Count) return Data[Data.Count - 1]; return GetInterpolatedItem(frame, Data[index - 1], Data[index]); } protected abstract T GetInterpolatedItem(int frame, T lower, T upper); Child class A: public IGpsCoordinate GetInterpolatedCoord(int frame) { ReadData(); return GetInterpolated(frame); } protected override IGpsCoordinate GetInterpolatedItem(int frame, IGpsCoordinate lower, IGpsCoordinate upper) { double ratio = GetInterpolationRatio(frame, lower.Frame, upper.Frame); var x = GetInterpolatedValue(lower.X, upper.X, ratio); var y = GetInterpolatedValue(lower.Y, upper.Y, ratio); var z = GetInterpolatedValue(lower.Z, upper.Z, ratio); return new GpsCoordinate(frame, x, y, z); } Child class B: public double GetMph(int frame) { ReadData(); return GetInterpolated(frame).MilesPerHour; } protected override ISpeed GetInterpolatedItem(int frame, ISpeed lower, ISpeed upper) { var ratio = GetInterpolationRatio(frame, lower.Frame, upper.Frame); var mph = GetInterpolatedValue(lower.MilesPerHour, upper.MilesPerHour, ratio); return new Speed(frame, mph); }

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• Diving into Scala with Cay Horstmann

  - by Janice J. Heiss

  A new interview with Java Champion Cay Horstmann, now up on otn/java, titled  "Diving into Scala: A Conversation with Java Champion Cay Horstmann," explores Horstmann's ideas about Scala as reflected in his much lauded new book,  Scala for the Impatient.  None other than Martin Odersky, the inventor of Scala, called it "a joy to read" and the "best introduction to Scala". Odersky was so enthused by the book that he asked Horstmann if the first section could be made available as a free download on the Typesafe Website, something Horstmann graciously assented to. Horstmann acknowledges that some aspects of Scala are very complex, but he encourages developers to simply stay away from those parts of the language. He points to several ways Java developers can benefit from Scala: "For example," he says, " you can write classes with less boilerplate, file and XML handling is more concise, and you can replace tedious loops over collections with more elegant constructs. Typically, programmers at this level report that they write about half the number of lines of code in Scala that they would in Java, and that's nothing to sneeze at. Another entry point can be if you want to use a Scala-based framework such as Akka or Play; you can use these with Java, but the Scala API is more enjoyable. " Horstmann observes that developers can do fine with Scala without grasping the theory behind it. He argues that most of us learn best through examples and not through trying to comprehend abstract theories. He also believes that Scala is the most attractive choice for developers who want to move beyond Java and C++.  When asked about other choices, he comments: "Clojure is pretty nice, but I found its Lisp syntax a bit off-putting, and it seems very focused on software transactional memory, which isn't all that useful to me. And it's not statically typed. I wanted to like Groovy, but it really bothers me that the semantics seems under-defined and in flux. And it's not statically typed. Yes, there is Groovy++, but that's in even sketchier shape. There are a couple of contenders such as Kotlin and Ceylon, but so far they aren't real. So, if you want to do work with a statically typed language on the JVM that exists today, Scala is simply the pragmatic choice. It's a good thing that it's such a nice choice." Learn more about Scala by going to the interview here.

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• Visual WebGui's XAML based programming for web developers

  - by Webgui

  While ASP.NET provides an event base approach it is completely dismissed when working with AJAX and the richness of the server is lost and replaced with JavaScript programming and couple with a very high security risk. Visual WebGui reinstates the power of the server to AJAX development and provides a statefull yet scalable, server centric architecture that provides the benefits and user productivity of AJAX with the security and developer productivity we had before AJAX stormed into our lives. "When I first came up with the concept of Visual WebGui , I was frustrated by the fragile and complex nature of developing web applications. The contrast in productivity between working in a fully OOP compiled environment vs. scripting even today, with JQuery, Dojo and such, is still huge. Even today the greatest sponsor of JavaScript programming, Google, is offering a framework to avoid JavaScript using Java that compiles to JavaScript (GWT). So I decided to find a way to abstract the complexity or rather delegate the complex job to enable developers to concentrate on the “What” instead of the “How” and embraced the Form based approach," said Guy Peled the inventor of Visual WebGui. Although traditional OOP development still rules the enterprise, the differences between web sites and web applications have blurred and so did the differences between classic developers and web developers. As a result, we now see declarative languages in desktop / backend development environments (WPF / WF) and we see OOP, gaining more and more power in web development (ASP.NET MVC / ASP.NET DOM). However, what has not changed is enterprise need for security, development ROI, reach, highly responsive and interactive UIs and scalability. The advantages that declarative languages and 'on demand' compilation provide over classic development are mostly the flexibility and a more readable initialize component it offers which is what Gizmox is aspiring to do by replacing the designer initialize component with XAML code. The code in this new project template will be compiled on demand using the build provider mechanism ASP.NET has. This means that the performance hit is only on the first request and after that the performance is the same as a prebuilt solution. This will allow the flexibility of a dynamically updated sites and the power of fully blown enterprise applications over web. You can also use prebuilt features available in ASP.NET to enjoy both worlds in production. VWG XAML implementation (VWG Sites) will be the first truly compliable XAML implementation as Microsoft implemented Silverlight and WPF as a runtime markup interpretation opposed to the ASP.NET markup implementation which is compiled to CLR code once. We have chosen to implement the VWG Sites parser as a different way to create CLR code that provides greater performance over the reflection alternative. VWG Sites will also be the first server side XAML UI engine which, while giving the power of XAML, it will not require any plug-ins or installations on the client side. Short demo video of VWG Sites markup. There is also a live sample available here.

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• How do we keep dependent data structures up to date?

  - by Geo

  Suppose you have a parse tree, an abstract syntax tree, and a control flow graph, each one logically derived from the one before. In principle it is easy to construct each graph given the parse tree, but how can we manage the complexity of updating the graphs when the parse tree is modified? We know exactly how the tree has been modified, but how can the change be propagated to the other trees in a way that doesn't become difficult to manage? Naturally the dependent graph can be updated by simply reconstructing it from scratch every time the first graph changes, but then there would be no way of knowing the details of the changes in the dependent graph. I currently have four ways to attempt to solve this problem, but each one has difficulties. Nodes of the dependent tree each observe the relevant nodes of the original tree, updating themselves and the observer lists of original tree nodes as necessary. The conceptual complexity of this can become daunting. Each node of the original tree has a list of the dependent tree nodes that specifically depend upon it, and when the node changes it sets a flag on the dependent nodes to mark them as dirty, including the parents of the dependent nodes all the way down to the root. After each change we run an algorithm that is much like the algorithm for constructing the dependent graph from scratch, but it skips over any clean node and reconstructs each dirty node, keeping track of whether the reconstructed node is actually different from the dirty node. This can also get tricky. We can represent the logical connection between the original graph and the dependent graph as a data structure, like a list of constraints, perhaps designed using a declarative language. When the original graph changes we need only scan the list to discover which constraints are violated and how the dependent tree needs to change to correct the violation, all encoded as data. We can reconstruct the dependent graph from scratch as though there were no existing dependent graph, and then compare the existing graph and the new graph to discover how it has changed. I'm sure this is the easiest way because I know there are algorithms available for detecting differences, but they are all quite computationally expensive and in principle it seems unnecessary so I'm deliberately avoiding this option. What is the right way to deal with these sorts of problems? Surely there must be a design pattern that makes this whole thing almost easy. It would be nice to have a good solution for every problem of this general description. Does this class of problem have a name?

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• how to update child records when updating the Master table using Linq [closed]

  - by user20358

  I currently use a general repositry class that can update only a single table like so public abstract class MyRepository<T> : IRepository<T> where T : class { protected IObjectSet<T> _objectSet; protected ObjectContext _context; public MyRepository(ObjectContext Context) { _objectSet = Context.CreateObjectSet<T>(); _context = Context; } public IQueryable<T> GetAll() { return _objectSet.AsQueryable(); } public IQueryable<T> Find(Expression<Func<T, bool>> filter) { return _objectSet.Where(filter); } public void Add(T entity) { _objectSet.AddObject(entity); _context.ObjectStateManager.ChangeObjectState(entity, System.Data.EntityState.Added); _context.SaveChanges(); } public void Update(T entity) { _context.ObjectStateManager.ChangeObjectState(entity, System.Data.EntityState.Modified); _context.SaveChanges(); } public void Delete(T entity) { _objectSet.Attach(entity); _context.ObjectStateManager.ChangeObjectState(entity, System.Data.EntityState.Deleted); _objectSet.DeleteObject(entity); _context.SaveChanges(); } } For every table class generated by my EDMX designer I create another class like this public class CustomerRepo : MyRepository<Customer> { public CustomerRepo (ObjectContext context) : base(context) { } } for any updates that I need to make to a particular table I do this: Customer CustomerObj = new Customer(); CustomerObj.Prop1 = ... CustomerObj.Prop2 = ... CustomerObj.Prop3 = ... CustomerRepo.Update(CustomerObj); This works perfectly well when I am updating just to the specific table called Customer. Now if I need to also update each row of another table which is a child of Customer called Orders what changes do I need to make to the class MyRepository. Orders table will have multiple records for a Customer record and multiple fields too, say for example Field1, Field2, Field3. So my questions are: 1.) If I only need to update Field1 of the Orders table for some rows based on a condition and Field2 for some other rows based on a different condition then what changes I need to do? 2.) If there is no such condition and all child rows need to be updated with the same value for all rows then what changes do I need to do? Thanks for taking the time. Look forward to your inputs...

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• How can I solve the same problems a CB-architecture is trying to solve without using hacks? [on hold]

  - by Jefffrey

  A component based system's goal is to solve the problems that derives from inheritance: for example the fact that some parts of the code (that are called components) are reused by very different classes that, hypothetically, would lie in a very different branch of the inheritance tree. That's a very nice concept, but I've found out that CBS is often hard to accomplish without using ugly hacks. Implementations of this system are often far from clean. But I don't want to discuss this any further. My question is: how can I solve the same problems a CBS try to solve with a very clean interface? (possibly with examples, there are a lot of abstract talks about the "perfect" design already). Here's an example I was going for before realizing I was just reinventing inheritance again: class Human { public: Position position; Movement movement; Sprite sprite; // other human specific components }; class Zombie { Position position; Movement movement; Sprite sprite; // other zombie specific components }; After writing that I realized I needed an interface, otherwise I would have needed N containers for N different types of objects (or to use boost::variant to gather them all together). So I've thought of polymorphism (move what systems do in a CBS design into class specific functions): class Entity { public: virtual void on_event(Event) {} // not pure virtual on purpose virtual void on_update(World) {} virtual void on_draw(Window) {} }; class Human { private: Position position; Movement movement; Sprite sprite; public: virtual void on_event(Event) { ... } virtual void on_update(World) { ... } virtual void on_draw(Window) { ... } }; class Zombie { private: Position position; Movement movement; Sprite sprite; public: virtual void on_event(Event) { ... } virtual void on_update(World) { ... } virtual void on_draw(Window) { ... } }; Which was nice, except for the fact that now the outside world would not even be able to know where a Human is positioned (it does not have access to its position member). That would be useful to track the player position for collision detection or if on_update the Zombie would want to track down its nearest human to move towards him. So I added const Position& get_position() const; to both the Zombie and Human classes. And then I realized that both functionality were shared, so it should have gone to the common base class: Entity. Do you notice anything? Yes, with that methodology I would have a god Entity class full of common functionality (which is the thing I was trying to avoid in the first place).

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• Particle System in XNA - cannot draw particle

  - by Dave Voyles

  I'm trying to implement a simple particle system in my XNA project. I'm going by RB Whitaker's tutorial, and it seems simple enough. I'm trying to draw particles within my menu screen. Below I've included the code which I think is applicable. I'm coming up with one error in my build, and it is stating that I need to create a new instance of the EmitterLocation from the particleEngine. When I hover over particleEngine.EmitterLocation = new Vector2(Mouse.GetState().X, Mouse.GetState().Y); it states that particleEngine is returning a null value. What could be causing this? /// <summary> /// Base class for screens that contain a menu of options. The user can /// move up and down to select an entry, or cancel to back out of the screen. /// </summary> abstract class MenuScreen : GameScreen ParticleEngine particleEngine; public void LoadContent(ContentManager content) { if (content == null) { content = new ContentManager(ScreenManager.Game.Services, "Content"); } base.LoadContent(); List<Texture2D> textures = new List<Texture2D>(); textures.Add(content.Load<Texture2D>(@"gfx/circle")); textures.Add(content.Load<Texture2D>(@"gfx/star")); textures.Add(content.Load<Texture2D>(@"gfx/diamond")); particleEngine = new ParticleEngine(textures, new Vector2(400, 240)); } public override void Update(GameTime gameTime, bool otherScreenHasFocus, bool coveredByOtherScreen) { base.Update(gameTime, otherScreenHasFocus, coveredByOtherScreen); // Update each nested MenuEntry object. for (int i = 0; i < menuEntries.Count; i++) { bool isSelected = IsActive && (i == selectedEntry); menuEntries[i].Update(this, isSelected, gameTime); } particleEngine.EmitterLocation = new Vector2(Mouse.GetState().X, Mouse.GetState().Y); particleEngine.Update(); } public override void Draw(GameTime gameTime) { // make sure our entries are in the right place before we draw them UpdateMenuEntryLocations(); GraphicsDevice graphics = ScreenManager.GraphicsDevice; SpriteBatch spriteBatch = ScreenManager.SpriteBatch; SpriteFont font = ScreenManager.Font; spriteBatch.Begin(); // Draw stuff logic spriteBatch.End(); particleEngine.Draw(spriteBatch); }

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• Managing accounts on a private website for a real-life community

  - by Smudge

  Hey Pro Webmasters, I'm looking at setting-up a walled-in website for a real-life community of people, and I was wondering if anyone has any experience with managing member accounts for this kind of thing. Some conditions that must be met: This community has a set list of real-life members, each of whom would be eligible for one account on the website. We don't expect or require that they all sign-up. It is purely opt-in, but we anticipate that many of them would be interested in the services we are setting up. Some of the community members emails are known, but some of them have fallen off the grid over the years, so ideally there would be a way for them to get back in touch with us through the public-facing side of the site. (And we'd want to manually verify the identity of anyone who does so). Their names are known, and for similar projects in the past we have assigned usernames derived from their real-life names. This time, however, we are open to other approaches, such as letting them specify their own username or getting rid of usernames entirely. The specific web technology we will use (e.g. Drupal, Joomla, etc) is not really our concern right now -- I am more interested in how this can be approached in the abstract. Our database already includes the full member roster, so we can email many of them generated links to a page where they can create an account. (And internally we can require that these accounts be paired with a known member). Should we have them specify their own usernames, or are we fine letting them use their registered email address to log-in? Are there any paradigms for walled-in community portals that help address security issues if, for example, one of their email accounts is compromised? We don't anticipate attempted break-ins being much of a threat, because nothing about this community is high-profile, but we do want to address security concerns. In addition, we want to make the sign-up process as painless for the members as possible, especially given the fact that we can't just make sign-ups open to anyone. I'm interested to hear your thoughts and suggestions! Thanks!

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• Dadaism and Agility

  - by alexhildyard

  We all have our little bugbears, and something that has given me particular pause over the years is the place of Agility in the software development life cycle. While I have seen it used successfully on both small and Enterprise-level projects, I have also seen many instances in which long-standing technical debt has also originated under its watch. Ironically the problem in such cases seems to me not that the practitioners in question have failed to follow due process (Test, Develop, Refactor -- a common "what" of Agile), but basically that they have missed the point (the "why" of Agile). It's probably a sign of my age that I'm much more interested in the "why" than the "what", since I feel that the latter falls out naturally from the former, but that this is not a reciprocal relationship.Consider Dadaism, precursor to the Surrealist movement in the early part of the twentieth century. Anyone could stand up and proclaim he or she was Dada; anyone could write cut-ups, or pull words out a hat, or produce gibberish on duelling typewriters under the inspiration of Dada. And all that took place at such performances was a manifestation of Dada, and all the artefacts that resulted were also Dada. Hence one commentator's engimatic observation that 'when one speaks of Dada, then one speaks of Dada. But when one does not speak of Dada, one still speaks of Dada.'What is Dada? Literally, Dada is what you say it is. But that's also missing the point. Dada is about erecting a framework within which utterances like this are valid; Dada is about preparing a stage for itself. Dadaism exemplifies the purity of a process-driven ideology -- in fact an ideology that is almost pure process, with nothing extraneous in the way of formal method, and while perhaps Agile delivery should not embrace the liberties of Dadaism too literally, some of the similarities nevertheless are salutary.Agile -- like Dada -- is an attitude; it is about *being* agile; it is not really about doing a specific set of things that are somehow *part* of being Agile. It is an abstract base rather than an implementation, a characteristic rather than a factor. It is the pragmatic response to the need for change in the face of partial information, ephemeral requirements and a healthy dose of systematic uncertainty. In practice this will usually mean repeatedly making the smallest useful changes to a system, recognising that systems evolve, and that all change carries risk. It will usually mean that instead of investing effort in future-proofing a system against a known technology roadmap, one instead invests one's energies in the daily repetition and incremental development of processes best designed to accommodate change quickly. But though it may mean these things in practice, it isn't actually *about* either of these things; it's about the mindset, the attitude that conceives of such responses as sensible solutions given the larger and ultimately unclassifiable thing that constitutes the development lifecycle of a specific project.

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• How to refactor my design, if it seems to require multiple inheritance?

  - by Omega

  Recently I made a question about Java classes implementing methods from two sources (kinda like multiple inheritance). However, it was pointed out that this sort of need may be a sign of a design flaw. Hence, it is probably better to address my current design rather than trying to simulate multiple inheritance. Before tackling the actual problem, some background info about a particular mechanic in this framework: It is a simple game development framework. Several components allocate some memory (like pixel data), and it is necessary to get rid of it as soon as you don't need it. Sprites are an example of this. Anyway, I decided to implement something ala Manual-Reference-Counting from Objective-C. Certain classes, like Sprites, contain an internal counter, which is increased when you call retain(), and decreased on release(). Thus the Resource abstract class was created. Any subclass of this will obtain the retain() and release() implementations for free. When its count hits 0 (nobody is using this class), it will call the destroy() method. The subclass needs only to implement destroy(). This is because I don't want to rely on the Garbage Collector to get rid of unused pixel data. Game objects are all subclasses of the Node class - which is the main construction block, as it provides info such as position, size, rotation, etc. See, two classes are used often in my game. Sprites and Labels. Ah... but wait. Sprites contain pixel data, remember? And as such, they need to extend Resource. But this, of course, can't be done. Sprites ARE nodes, hence they must subclass Node. But heck, they are resources too. Why not making Resource an interface? Because I'd have to re-implement retain() and release(). I am avoiding this in virtue of not writing the same code over and over (remember that there are multiple classes that need this memory-management system). Why not composition? Because I'd still have to implement methods in Sprite (and similar classes) that essentially call the methods of Resource. I'd still be writing the same code over and over! What is your advice in this situation, then?

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• Any ideas on reducing lag in terrain generation?

  - by l5p4ngl312

  Ok so here's the deal. I've written an isometric engine that generates terrain based on camera values using 2D perlin noise. I planned on doing 3D but first I need to work out the lag issues I'm having. I will try to explain how I am doing this so that maybe someone can spot where I am going wrong. I know it should not be this laggy. There is the abstract class Block which right now just contains render(). BlockGrass, etc. extend this class and each has code in the render function to create a textured quad at the given position. Then there is the class Chunk which has the function Generate() and setBlocksInArea(). Generate uses 2D perlin noise to make a height map and stores the heights in a 2D array. It stores the positions of each block it generates in blockarray[x][y][z]. The chunks are 8x8x128. In the main game class there is a 3D array called blocksInArea. The blocks in this array are what gets rendered. When a chunk generates, it adds its blocks to this array at the correct index. It is like this so chunks can be saved to the hard drive (even though they aren't yet) but there can still be optimization with the rendering that you wouldn't have if you rendered each chunk separately. Here's where the laggy part comes in: When the camera moves to a new chunk, a row of chunks generates on the end of the axis that the camera moved on. But it still has to move the other chunks up/down in the blocksInArea (render) array. It does this by calculating the new position in the array and doing the Chunk.setBlocksInArea(): for(int x = 0; x < 8; x++){ for(int y = 0; y < 8; y++){ nx = x+(coordX - camCoordX)*8 ny = y+(coordY - camCoordY)*8 for(int z = 0; z < height[x][y]; z++){ blockarray[x][y][z] = Game.blocksInArea[nx][ny][z]; } } } My reasoning was that this would be much faster than doing the perlin noise all over again, but there are still little spikes of lag when you move in between chunks. Edit: Would it be possible to create a 3 dimensional array list so that shifting of chunks within the array would not be neccessary?

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• How to keep a data structure synchronized over a network?

  - by David Gouveia

  Context In the game I'm working on (a sort of a point and click graphic adventure), pretty much everything that happens in the game world is controlled by an action manager that is structured a bit like: So for instance if the result of examining an object should make the character say hello, walk a bit and then sit down, I simply spawn the following code: var actionGroup = actionManager.CreateGroup(); actionGroup.Add(new TalkAction("Guybrush", "Hello there!"); actionGroup.Add(new WalkAction("Guybrush", new Vector2(300, 300)); actionGroup.Add(new SetAnimationAction("Guybrush", "Sit")); This creates a new action group (an entire line in the image above) and adds it to the manager. All of the groups are executed in parallel, but actions within each group are chained together so that the second one only starts after the first one finishes. When the last action in a group finishes, the group is destroyed. Problem Now I need to replicate this information across a network, so that in a multiplayer session, all players see the same thing. Serializing the individual actions is not the problem. But I'm an absolute beginner when it comes to networking and I have a few questions. I think for the sake of simplicity in this discussion we can abstract the action manager component to being simply: var actionManager = new List<List<string>>(); How should I proceed to keep the contents of the above data structure syncronized between all players? Besides the core question, I'm also having a few other concerns related to it (i.e. all possible implications of the same problem above): If I use a server/client architecture (with one of the players acting as both a server and a client), and one of the clients has spawned a group of actions, should he add them directly to the manager, or only send a request to the server, which in turn will order every client to add that group? What about packet losses and the like? The game is deterministic, but I'm thinking that any discrepancy in the sequence of actions executed in a client could lead to inconsistent states of the world. How do I safeguard against that sort of problem? What if I add too many actions at once, won't that cause problems for the connection? Any way to alleviate that?

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• The Internet Key Wave MW833UP is not recognized in Ubuntu

  - by gio900

  I can't use my Onda MW833UP... :( Any advice? Here is something that someone else may understand: ~$: lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 11.10 Release: 11.10 Codename: oneiric ~$: lsusb Bus 001 Device 005: ID 1ee8:0012 ~$: dmesg [ 22.709475] cdc_acm 1-1:1.0: ttyACM0: USB ACM device [ 22.714856] usbcore: registered new interface driver cdc_acm [ 22.714866] cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters [ 23.520490] ieee80211 phy0: wl_ops_bss_info_changed: arp filtering: enabled true, count 1 (implement) [ 24.244530] usbcore: registered new interface driver usbserial [ 24.244575] USB Serial support registered for generic [ 24.244673] usbcore: registered new interface driver usbserial_generic [ 24.244681] usbserial: USB Serial Driver core [ 24.265879] USB Serial support registered for GSM modem (1-port) [ 24.285680] usbcore: registered new interface driver option [ 24.285691] option: v0.7.2:USB Driver for GSM modems [ 24.425878] EXT4-fs (sda9): re-mounted. Opts: errors=remount-ro,commit=600 [ 24.736540] EXT4-fs (sda8): re-mounted. Opts: commit=600 [ 35.705796] Easy slow down manager: checking for SABI support. [ 35.706002] Easy slow down manager: SABI is supported (f5189) [ 36.060099] usbcore: deregistering interface driver uvcvideo [ 139.508061] CE: hpet increased min_delta_ns to 20113 nsec [ 6798.378917] usb 1-1: USB disconnect, device number 5 [ 6809.108232] usb 1-1: new high speed USB device number 6 using ehci_hcd [ 6809.242692] scsi5 : usb-storage 1-1:1.0 [ 6810.241257] scsi 5:0:0:0: CD-ROM Onda Datacard CD-ROM 0001 PQ: 0 ANSI: 0 [ 6810.241841] scsi 5:0:0:1: Direct-Access Onda Storage 0001 PQ: 0 ANSI: 0 [ 6810.271410] sr0: scsi3-mmc drive: 0x/0x caddy [ 6810.272099] sr 5:0:0:0: Attached scsi CD-ROM sr0 [ 6810.272852] sr 5:0:0:0: Attached scsi generic sg1 type 5 [ 6810.279954] sd 5:0:0:1: [sdb] Attached SCSI removable disk [ 6810.281210] sd 5:0:0:1: Attached scsi generic sg2 type 0 [ 6810.380591] sr0: CDROM (ioctl) error, command: Xpwrite, Read disk info 51 00 00 00 00 00 00 00 02 00 [ 6810.380617] sr: Sense Key : Hardware Error [current] [ 6810.380625] sr: Add. Sense: No additional sense information [ 6810.613937] sr0: CDROM (ioctl) error, command: Xpwrite, Read disk info 51 00 00 00 00 00 00 00 02 00 [ 6810.613972] sr: Sense Key : Hardware Error [current] [ 6810.613984] sr: Add. Sense: No additional sense information [ 6810.673716] usb 1-1: USB disconnect, device number 6 [ 6815.572142] usb 1-1: new high speed USB device number 7 using ehci_hcd [ 6815.706828] cdc_acm 1-1:1.0: ttyACM0: USB ACM device The last 3 lines are where I inserted the Internet key, then reconnected it. usb-device T: Bus=01 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 7 Spd=480 MxCh= 0 D: Ver= 2.00 Cls=ef(misc ) Sub=02 Prot=01 MxPS=64 #Cfgs= 1 P: Vendor=1ee8 ProdID=0012 Rev=00.01 S: Manufacturer=Onda S: Product=MW833UP S: SerialNumber=9230B35D870F9CB7AE684EACC5C12BE5EC33B26E C: #Ifs= 2 Cfg#= 1 Atr=a0 MxPwr=500mA I: If#= 0 Alt= 0 #EPs= 1 Cls=02(commc) Sub=02 Prot=01 Driver=cdc_acm I: If#= 1 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=cdc_acm Then there is /dev/ttyACM0. When the key is connected to the USB port, everything that will meant...

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• Managing accounts on a private website for a real-life community

  - by Smudge

  I'm looking at setting-up a walled-in website for a real-life community of people, and I was wondering if anyone has any experience with managing member accounts for this kind of thing. Some conditions that must be met: This community has a set list of real-life members, each of whom would be eligible for one account on the website. We don't expect or require that they all sign-up. It is purely opt-in, but we anticipate that many of them would be interested in the services we are setting up. Some of the community members emails are known, but some of them have fallen off the grid over the years, so ideally there would be a way for them to get back in touch with us through the public-facing side of the site. (And we'd want to manually verify the identity of anyone who does so). Their names are known, and for similar projects in the past we have assigned usernames derived from their real-life names. This time, however, we are open to other approaches, such as letting them specify their own username or getting rid of usernames entirely. The specific web technology we will use (e.g. Drupal, Joomla, etc) is not really our concern right now -- I am more interested in how this can be approached in the abstract. Our database already includes the full member roster, so we can email many of them generated links to a page where they can create an account. (And internally we can require that these accounts be paired with a known member). Should we have them specify their own usernames, or are we fine letting them use their registered email address to log-in? Are there any paradigms for walled-in community portals that help address security issues if, for example, one of their email accounts is compromised? We don't anticipate attempted break-ins being much of a threat, because nothing about this community is high-profile, but we do want to address security concerns. In addition, we want to make the sign-up process as painless for the members as possible, especially given the fact that we can't just make sign-ups open to anyone. I'm interested to hear your thoughts and suggestions! Thanks!

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• Feedback from SQLBits 8

  - by Peter Larsson

  This years SQLBits occurred in Brighton. Although I didn’t have the opportunity to attend the full conference, I did a presentation at Saturday. Getting to Brighton was easy. Drove to Copenhagen airport at 0415, flew 0605 and arrived at Gatwick 0735. Then I took the direct train to Brighton and showed up at 0830, just one hour before presenting. This was the easy part. Getting home was much worse. Presentation ended at 1030 and I had to rush to the train station to get back to London, change to tube for Heathrow. Made it at the gate just 15 seconds before closing. That included a half mile run in the airport… Anyway, yesterday I got the feedback for my presentation. It does look good, especially since English is not my first language. This is the first graph Seems to be just halfway between conference average and best session. I can live with that. Second graph shows more detail about attendees voting. It also look acceptable. A wider spread for the 9’s, but it is an inevitable effect from how attendees percept the session. I did get a lot of 8’s and the lower grades in an descending order. The two people voting 4 and 5 didn’t say why they voted this so I don’t know how to remedy this. Third graph is about each category of votes.   Again, I find this acceptable. The Session abstract and Speaker’s knowledge seems to follow attendees expectations compared to conference average. I seem to have met the attendees expectations (and some more) for the other four categories, also compared to conference average. Since this did encourage me, I believe I will present some more at future meetings. I do have a new presentation about something all developers are doing every day but they may not know it. I will also cover this new topic in the next Deep Dives II book. Stay tuned! //Peter

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• RTS Game Style Application [closed]

  - by Daniel Wynand van Wyk

  My question may seem somewhat odd, but I hope that my specifications will clarify EXACTLY what it is that I am after. I need some help choosing the right tooling for a particular endeavour. My background is in desktop application development and large back-end systems. I have worked primarily on the Microsoft stack using C# and the .Net framework. My goal is to develop a 2D, RTS style, interactive office simulation. The simulation will model various office spaces, office equipment, employees and their interactions with one another. The idea is to abstract the concept of an office completely. Under the hood the application will do many things that are nothing like a game. This includes P2P networking, VPN tunnelling, streaming video, instant messaging, document collaboration, remote screen sharing, file-sharing, virus scanning, VOIP, document scanning, faxing, emailing, distributed computing, content management and much more! A somewhat similar thing has been attempted by IBM, where they created a virtual office in second life. If their attempt was a game, the game-play would be notably horrible, to say the least! The users/players will drive and control my application through the various objects modelled in the simulation. A single application capable of performing all of these various tasks would be a nightmare to navigate for even the most expert user. Using the concept of a game, I can easily separate functionality by assigning them to objects that relate 1-1 with their real world counter-parts. This can greatly simplify computing for novice users, with many added benefits in terms of visibility, transparency of process and centralized configuration. My hope is to make complex computing tasks accessible to all kinds of users and to greatly reduce the cognitive load associated with using the many different utilities and applications inside office settings. The complexity is therefore limited to the complexity of the space in which you find yourself. I want the application to target as many platforms as possible and run on computers that have no accelerated graphics capabilities. The simulation won't contain any of the fancy eye-candy you find in modern games, to the contrary, my "game" will purposefully be clean and simple. The closest thing I could imagine would be an old game like "Theme Hospital" or the first instalment of "The Sims". All the content will be pre-created and not user-generated like Second Life. New functionality will be added via a plugin system. Given my background and nature of my "game", I would like to spend most of my time writing code that does not have to do with the simulated office, as the "game" is really just a glorified application menu. I have done much reading about existing engines, frameworks and tools. I need the help of an experienced game developer who has tried and tested various products over the years who can guide me in the right direction given my very particular needs. I would appreciate any help I can get!

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• SQL Saturday 194 - Exeter

  - by Dave Ballantyne

  Many kudos goes to Jonathan and Annette Allen and the others on the team for confirming SQL Saturday 194 in Exeter on the 8th and 9th of March.  The event home page is here http://www.sqlsaturday.com/194/eventhome.aspx and I delighted that myself and Dave Morrison will be presenting a full day pre-con on the 8th on favourite subjects “TSQL and Internals”. Here is the full abstract : TSQL and internals - When faced with performance issues there are many lines of attack. Tuning the engine itself can get you so far, however for maximum effect you need to understand how the engine and how it translates SQL statements into performable actions. This is not a simple task, it is a massive task to deal with a multi-table join and the number of permutations can be immense. To back up this knowledge, we can create better performing TSQL and understand the impact that is has upon the engine and recognize the pitfalls and gotcha’s that exist in SQLServer. Ultimately, there is no ‘best way’ to perform a single task only many variations of ‘it depends’ , but now we can pick the most appropriate option for the required dataload. Over the years, there have been many myths and misconceptions have grown around the product, some have basis in older versions and some are just wrong. Continuing to build on the knowledge given so far these issue will be explored and broken down and proved or disproved. Finally we will look to the future and explore SQL Server 2012 and the new functionality that that brings and some of the common uses that we will be able to address. After completion of this days pre-con, attendees will have a more complete knowledge of execution plans, and how they relate to the physical and logical actions that SQLServer will be executing on their behalf. The attendees will also have a more rounded and fuller knowledge of TSQL and the implications of incorrectly defining a query. Dave is a fountain of knowledge on execution plans and optimizer internals and ,though i may flatter myself, I’m no shrinking violet when it comes to TSQL and such matters.  I hope that if you cant join us, then there are other pre-cons available from other experts in their fields that may ‘float you boat’ too.  The pre-con page is http://sqlsouthwest.co.uk/SQLSaturday_precon.htm Also, excitingly, this pre-con day is sponsored by Fusion-IO which is a great boon for the day. If you want a more of this then i am offering a 2 day TSQL course starting on the 19th of March. More details on this are available here

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• Identifying which pattern fits better.

  - by Daniel Grillo

  I'm developing a software to program a device. I have some commands like Reset, Read_Version, Read_memory, Write_memory, Erase_memory. Reset and Read_Version are fixed. They don't need parameters. Read_memory and Erase_memory need the same parameters that are Length and Address. Write_memory needs Lenght, Address and Data. For each command, I have the same steps in sequence, that are something like this sendCommand, waitForResponse, treatResponse. I'm having difficulty to identify which pattern should I use. Factory, Template Method, Strategy or other pattern. Edit I'll try to explain better taking in count the given comments and answers. I've already done this software and now I'm trying to refactoring it. I'm trying to use patterns, even if it is not necessary because I'm taking advantage of this little software to learn about some patterns. Despite I think that one (or more) pattern fits here and it could improve my code. When I want to read version of the software of my device, I don't have to assembly the command with parameters. It is fixed. So I have to send it. After wait for response. If there is a response, treat (or parse) it and returns. To read a portion of the memory (maximum of 256 bytes), I have to assembly the command using the parameters Len and Address. So I have to send it. After wait for response. If there is a response, treat (or parse) it and returns. To write a portion in the memory (maximum of 256 bytes), I have to assembly the command using the parameters Len, Address and Data. So I have to send it. After wait for response. If there is a response, treat (or parse) it and returns. I think that I could use Template Method because I have almost the same algorithm for all. But the problem is some commands are fixes, others have 2 or 3 parameters. I think that parameters should be passed on the constructor of the class. But each class will have a constructor overriding the abstract class constructor. Is this a problem for the template method? Should I use other pattern?

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• Defining a service layer: the text-based adventure

  - by Stacy Vicknair

  Applications these days have more options than ever for a user interface, and it’s only going to grow. A successful product might require native applications for mobile devices, a regular web implementation, or even a gaming console. These systems often will be centralized and data driven. The solution is one that’s fairly solitary, a service layer! Simply put, take what’s shared and put it behind a physical or abstract layer that defines the boundary between the specific user interface and the shared content.   I know, I know, none of this is complicated. But some times it can be difficult to discern what belongs on which side of the line. For instance, say we’re creating a service that will provide content for both an ASP.NET MVC application and a WP7 application. Although the content served to each application is the same, there are different paradigms and patterns for displaying that data in the different environments. In ASP.NET MVC, you may create a model specific to a page that combines necessary information. In the WP7 application you might require different sets of data that you will connect via MVVM with the view. The general rule of thumb is that any shared content, business rules, or data should exist separately. Any element that is specific to the current UI implementation should be included in a separate library or with the UI implementation itself. The WP7 application doesn’t need my MVC specific model classes. My MVC application doesn’t require those INotifyPropertyChanged viewmodels that the WP7 application depends on. In both cases, there should be additional processing done above the service layer to massage the data to the application’s specific needs.   Service-ocalypse: the text based adventure What helps me the most about deciding whether or not something belongs coupled to the UI implementation or in the shared implementation is thinking of the simplest implementation you could have: a console application. You might have played a game like Peasant’s Quest: The console app is the text based adventure game version of your application. If you’re service was consumed in its simplest form, you would simply have a console based API for it that issues requests. Maybe those requests aren’t SWIM TO BOAT, but they might be CREATE USER JOHN. If I issue a request, I expect that request to be issued to the service. If the service has any exceptions or issues with my input, that business logic should be encapsulated in that service, not implemented in the UI. The service layer should be your functional application in its entirety, and anything above that layer should only assist with the display of that information.

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• How can I cleanly and elegantly handle data and dependancies between classes

  - by Neophyte

  I'm working on 2d topdown game in SFML 2, and need to find an elegant way in which everything will work and fit together. Allow me to explain. I have a number of classes that inherit from an abstract base that provides a draw method and an update method to all the classes. In the game loop, I call update and then draw on each class, I imagine this is a pretty common approach. I have classes for tiles, collisions, the player and a resource manager that contains all the tiles/images/textures. Due to the way input works in SFML I decided to have each class handle input (if required) in its update call. Up until now I have been passing in dependencies as needed, for example, in the player class when a movement key is pressed, I call a method on the collision class to check if the position the player wants to move to will be a collision, and only move the player if there is no collision. This works fine for the most part, but I believe it can be done better, I'm just not sure how. I now have more complex things I need to implement, eg: a player is able to walk up to an object on the ground, press a key to pick it up/loot it and it will then show up in inventory. This means that a few things need to happen: Check if the player is in range of a lootable item on keypress, else do not proceed. Find the item. Update the sprite texture on the item from its default texture to a "looted" texture. Update the collision for the item: it might have changed shape or been removed completely. Inventory needs to be updated with the added item. How do I make everything communicate? With my current system I will end up with my classes going out of scope, and method calls to each other all over the place. I could tie up all the classes in one big manager and give each one a reference to the parent manager class, but this seems only slightly better. Any help/advice would be greatly appreciated! If anything is unclear, I'm happy to expand on things.

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• StringBuffer behavior in LWJGL

  - by Michael Oberlin

  Okay, I've been programming in Java for about ten years, but am entirely new to LWJGL. I have a specific problem whilst attempting to create a text console. I have built a class meant to abstract input polling to it, which (in theory) captures key presses from the Keyboard object and appends them to a StringBuilder/StringBuffer, then retrieves the completed string after receiving the ENTER key. The problem is, after I trigger the String return (currently with ESCAPE), and attempt to print it to System.out, I consistently get a blank line. I can get an appropriate string length, and I can even sample a single character out of it and get complete accuracy, but it never prints the actual string. I could swear that LWJGL slipped some kind of thread-safety trick in while I wasn't looking. Here's my code: static volatile StringBuffer command = new StringBuffer(); @Override public void chain(InputPoller poller) { this.chain = poller; } @Override public synchronized void poll() { //basic testing for modifier keys, to be used later on boolean shift = false, alt = false, control = false, superkey = false; if(Keyboard.isKeyDown(Keyboard.KEY_LSHIFT) || Keyboard.isKeyDown(Keyboard.KEY_RSHIFT)) shift = true; if(Keyboard.isKeyDown(Keyboard.KEY_LMENU) || Keyboard.isKeyDown(Keyboard.KEY_RMENU)) alt = true; if(Keyboard.isKeyDown(Keyboard.KEY_LCONTROL) || Keyboard.isKeyDown(Keyboard.KEY_RCONTROL)) control = true; if(Keyboard.isKeyDown(Keyboard.KEY_LMETA) || Keyboard.isKeyDown(Keyboard.KEY_RMETA)) superkey = true; while(Keyboard.next()) if(Keyboard.getEventKeyState()) { command.append(Keyboard.getEventCharacter()); } if (Framework.isConsoleEnabled() && Keyboard.isKeyDown(Keyboard.KEY_ESCAPE)) { System.out.println("Escape down"); System.out.println(command.length() + " characters polled"); //works System.out.println(command.toString().length()); //works System.out.println(command.toString().charAt(4)); //works System.out.println(command.toString().toCharArray()); //blank line! System.out.println(command.toString()); //blank line! Framework.disableConsole(); } //TODO: Add command construction and console management after that } } Maybe the answer's obvious and I'm just feeling tired, but I need to walk away from this for a while. If anyone sees the issue, please let me know. This machine is running the latest release of Java 7 on Ubuntu 12.04, Mate desktop environment. Many thanks.

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