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  • What level of detail to use in an interface members descriptions?

    - by famousgarkin
    I am extracting interfaces from some classes in .NET, and I am not completely sure about what level of detail of description to use for some of the interface members (properties, methods). An example: interface ISomeInterface { /// <summary> /// Checks if the object is checked out. /// </summary> /// <returns> /// Returns true if the object is checked out, or if the object locking is not enabled, /// otherwise returns false. /// </returns> bool IsObjectCheckedOut(); } class SomeImplementation : ISomeInterface { public bool IsObjectCheckedOut() { // An implementation of the method that returns true if the object is checked out, // or if the object locking is not enabled } } The part in question is the <returns>...</returns> section of the IsObjectCheckedOut description in the interface. Is it ok to include such a detail about return value in the interface itself, as the code that will work with the interface should know exactly what that method will do? All the current implementations of the method will do just that. But is it ok to limit the possible other/future implementations by description this way? Or should this not be included in the interface description, as there is no way to actually ensure that other/future implementations will do exactly this? Is it better to be as general as possible regarding the interface in such circumstances? I am currently inclined to the latter option.

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  • Questions before I revamp my rendering engine to use shaders (GLSL)

    - by stephelton
    I've written a fairly robust rendering engine using OpenGL ES 1.1 (fixed-function.) I've been looking into revamping the engine to use OpenGL ES 2.0, which necessitates that I use shaders. I've been absorbing information all day long and still have some questions. Firstly, lighting. The fixed-function pipeline is guaranteed to have at least 8 lights available. My current engine finds lights that are "close" to the primitives being drawn and enables them; I don't know how many lights are going to be enabled until I draw a given model. Nothing is dynamically allocated in GLSL, so I have to define in a shader some number of lights to be used, right? So if I want to stick with 8, should I write my general purpose shader to have 8 lights and then use uniforms to tell it how many / which lights to use? Which brings me to another question: should I be concerned with the amount of data I'm allocating in a shader? Recent video cards have hundreds of "stream processors." If I've got a fragment shader being used on some number of fragments in a given triangle, I assume they must each have their own stack to work on. Are read-only variables copied here, or read when needed? My initial goal is to rework my code so that it is virtually identical to the current implementation. What I have in mind is to create my own matrix stack so that I can implement something along the lines of push/popMatrix and apply all my translations, rotations, and scales to this matrix, then provide the matrix to the vertex shader so that it can make very quick vertex translations. Is this approach sound? Edit: My original intention was to ask if there was a tutorial that would explain the bare minimum necessary to jump from fixed-function to using shaders. Thanks!

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  • Please, tell us how you made Agile work for you?

    - by Paul
    I've been seeing many questions related to Agile. There seems to be confusion between the people who are doing Agile successfully, and those of us who don't understand it. So I'm wondering if some of the successful teams would be willing to give the result of us some examples of how you succeeded. Some of the things I know I wonder What steps did you use? (ie. Talk to users, mock up, tests, code, testing, (whatever)) Tools that helped you? Did you generate any artifacts, other than a working implementation? How did you prevent spaghetti architecture / code? How do you pass along to new team members, or is the team stable for the project How did you determine exit criteria, or was it open ended. (Scope of project?) Did you do this as contracting? How did you develop a contract up-front? Did the business do any up front work? Or did they come to the table with "We want to implement a "bleh bleh blah"? What types of tests did you use? Unit, Integration, UAT? Or did the process make some/all of those unnecessary? Bonus: Do you have an situations / links to "How To" Agile articles, books, etc? Wiki, describes what but not how (to the uninitiated) At least to me, not a duplicate

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  • Static DataTable or DataSet in a class - bad idea?

    - by Superbest
    I have several instances of a class. Each instance stores data in a common database. So, I thought "I'll make the DataTable table field static, that way every instance can just add/modify rows to its own table field, but all the data will actually be in one place!" However, apparently it's a bad idea to do use static fields, especially if it's databases: Don't Use "Static" in C#? Is this a bad idea? Will I run into problems later on if I use it? This is a small project so I can accept no testing as a compromise if that is the only drawback. The benefit of using a static database is that there can be many objects of type MyClass, but only one table they all talk to, so a static field seems to be an implementation of exactly this, while keeping syntax concise. I don't see why I shouldn't use a static field (although I wouldn't really know) but if I had to, the best alternative I can think of is creating one DataTable, and passing a reference to it when creating each instance of MyClass, perhaps as a constructor parameter. But is this really an improvement? It seems less intuitive than a static field.

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  • What technical details should a programmer of a web application consider before making the site public?

    - by Joel Coehoorn
    What things should a programmer implementing the technical details of a web application consider before making the site public? If Jeff Atwood can forget about HttpOnly cookies, sitemaps, and cross-site request forgeries all in the same site, what important thing could I be forgetting as well? I'm thinking about this from a web developer's perspective, such that someone else is creating the actual design and content for the site. So while usability and content may be more important than the platform, you the programmer have little say in that. What you do need to worry about is that your implementation of the platform is stable, performs well, is secure, and meets any other business goals (like not cost too much, take too long to build, and rank as well with Google as the content supports). Think of this from the perspective of a developer who's done some work for intranet-type applications in a fairly trusted environment, and is about to have his first shot and putting out a potentially popular site for the entire big bad world wide web. Also, I'm looking for something more specific than just a vague "web standards" response. I mean, HTML, JavaScript, and CSS over HTTP are pretty much a given, especially when I've already specified that you're a professional web developer. So going beyond that, Which standards? In what circumstances, and why? Provide a link to the standard's specification.

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  • Game Messaging System Design

    - by you786
    I'm making a simple game, and have decided to try to implement a messaging system. The system basically looks like this: Entity generates message - message is posted to global message queue - messageManager notifies every object of the new message through onMessageReceived(Message msg) - if object wants, it acts on the message. The way I'm making message objects is like this: //base message class, never actually instantiated abstract class Message{ Entity sender; } PlayerDiedMessage extends Message{ int livesLeft; } Now my SoundManagerEntity can do something like this in its onMessageReceived() method public void messageReceived(Message msg){ if(msg instanceof PlayerDiedMessage){ PlayerDiedMessage diedMessage = (PlayerDiedMessage) msg; if(diedMessage.livesLeft == 0) playSound(SOUND_DEATH); } } The pros to this approach: Very simple and easy to implement The message can contain as much as information as you want, because you can just create a new Message subclass that has whatever info necessary. The cons: I can't figure out how I can recycle Message objects to a object pool, unless I have a different pool for each subclass of Message. So I have lots and lots of object creation/memory allocation over time. Can't send a message to a specific recipient, but I haven't needed that yet in my game so I don't mind it too much. What am I missing here? There must be a better implementation or some idea that I'm missing.

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  • How to implement behavior in a component-based game architecture?

    - by ghostonline
    I am starting to implement player and enemy AI in a game, but I am confused about how to best implement this in a component-based game architecture. Say I have a following player character that can be stationary, running and swinging a sword. A player can transit to the swing sword state from both the stationary and running state, but then the swing must be completed before the player can resume standing or running around. During the swing, the player cannot walk around. As I see it, I have two implementation approaches: Create a single AI-component containing all player logic (either decoupled from the actual component or embedded as a PlayerAIComponent). I can easily how to enforce the state restrictions without creating coupling between individual components making up the player entity. However, the AI-component cannot be broken up. If I have, for example, an enemy that can only stand and walk around or only walks around and occasionally swing a sword, I have to create new AI-components. Break the behavior up in components, each identifying a specific state. I then get a StandComponent, WalkComponent and SwingComponent. To enforce the transition rules, I have to couple each component. SwingComponent must disable StandComponent and WalkComponent for the duration of the swing. When I have an enemy that only stands around, swinging a sword occasionally, I have to make sure SwingComponent only disables WalkComponent if it is present. Although this allows for better mix-and-matching components, it can lead to a maintainability nightmare as each time a dependency is added, the existing components must be updated to play nicely with the new requirements the dependency places on the character. The ideal situation would be that a designer can build new enemies/players by dragging components into a container, without having to touch a single line of engine or script code. Although I am not sure script coding can be avoided, I want to keep it as simple as possible. Summing it all up: Should I lob all AI logic into one component or break up each logic state into separate components to create entity variants more easily?

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  • With the outcome of the Oracle vs Google trial, does that mean Mono is now safe from Microsoft [closed]

    - by Evan Plaice
    According to the an article on ArsTechnica the judge of the case ruled that APIs are not patent-able. He referred to the structure of modules/methods/classes/functions as being like libraries/books/chapters. To patent an API would be putting a patent on thought itself. It's the internal implementations that really matter. With that in mind, Mono (C# clone for Linux/Mac) has always been viewed tentatively because, even though C# and the CLI are ECMA standards, Microsoft holds a patent on the technology. Microsoft holds a covenant not to sue open source developers based on their patents but has maintained the ability to pull the plug on the Mono development team if they felt the project was a threat. With the recent ruling, is Mono finally out of the woods. A firm precedent has been established that patents can't be applied to APIs. From what I understand, none of the Mono implementation is copied verbatim, only the API structure and functionality. It's a topic I have been personally interested in for years now as I have spent a lot of time developing cross-platform C# libraries in MonoDevelop. I acknowledge that this is a controversial topic, if you have opinions that's what commenting is for. Try to keep the answers factual and based on established sources.

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  • Does LINQ require significantly more processing cycles and memory than lower-level data iteration techniques?

    - by Matthew Patrick Cashatt
    Background I am recently in the process of enduring grueling tech interviews for positions that use the .NET stack, some of which include silly questions like this one, and some questions that are more valid. I recently came across an issue that may be valid but I want to check with the community here to be sure. When asked by an interviewer how I would count the frequency of words in a text document and rank the results, I answered that I would Use a stream object put the text file in memory as a string. Split the string into an array on spaces while ignoring punctuation. Use LINQ against the array to .GroupBy() and .Count(), then OrderBy() said count. I got this answer wrong for two reasons: Streaming an entire text file into memory could be disasterous. What if it was an entire encyclopedia? Instead I should stream one block at a time and begin building a hash table. LINQ is too expensive and requires too many processing cycles. I should have built a hash table instead and, for each iteration, only added a word to the hash table if it didn't otherwise exist and then increment it's count. The first reason seems, well, reasonable. But the second gives me more pause. I thought that one of the selling points of LINQ is that it simply abstracts away lower-level operations like hash tables but that, under the veil, it is still the same implementation. Question Aside from a few additional processing cycles to call any abstracted methods, does LINQ require significantly more processing cycles to accomplish a given data iteration task than a lower-level task (such as building a hash table) would?

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  • The Power of Specialization – google ads for SOA & BPM Specialized Partners

    - by JuergenKress
    For SOA & BPM specialized partner we offer free google advertisement to promote your Oracle SOA & BPM service offerings on your website or your SOA & BPM events. We will host the complete campaign management. To create your google campaign please send us below: Your campaign text: 3 lines of text each 35 letters (NOT more letters!) Your campaign link: direct link to the website you want to promote Ideas for the website which we will promote with the google ads: Your Oracle SOA Service offerings with concrete offering e.g. SOA Discovery Workshop Oracle SOA Specialized Logo Your Oracle SOA References Your SOA Implementation consultant with pictures Your SOA sales contact persons Example of an SOA Specialization text ad: Oracle SOA Specialized plan to become more agile? eProseed the Oracle SOA Experts An interview with Griffiths Waite's Business Development Director highlighting the benefits of the Oracle Specialization Programme. SOA & BPM Partner Community For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit  www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Technorati Tags: Specializaion,Benefits Specialization,marketing,SOA Community,Oracle SOA,Oracle BPM,Community,OPN,Jürgen Kress

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  • 3D physics engine for accurate collision handling on desktop/laptop computers (non-console)

    - by Georges Oates Larsen
    What are your suggestions for a physics engine that satisfies the following criteria? Capable of calculating collisions between multiple concave mesh-based colliders Handles many collisions going on at once (for instance one mesh being wedged between two others, which themselves may be wedged between two meshes) Does not allow for collider passthrough, even at high speeds. For instance, if I am applying force to a programmatically hinged object that makes it spin, I do not want it to pass through another rigidbody that it collides with while spinning. I have this problem using PhysX As implied before, reacts well to hinged objects, preferably has its own implementation of a hinge, but I am willing to program my own. The important part is that it has some sort of interface that guarantees accurate collision tracking even when dealing with these things Platform independent -- runs on mac as well as PC, also not tied down to specific graphics cards I think that's the best way to explain what I am looking for. Basically, I need SUPER reliable collisions. Something that can't be accomplished with a simple ray casting approach that sends a ray from the last position of the object to the current position (as this object may be potentially large and colliding with small objects via rotation) Bonus points for also including an OPEN SOURCE engine.

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  • Challenge Ends on Friday!

    - by Yolande Poirier
    This is your last chance to win a JavaOne trip. Submit a project video and code for the IoT Developer Challenge by this Friday, May 30.  12 JavaOne trips will be awarded to 3 professional teams and one student team. Members of two student teams will win laptops and certification training vouchers. Ask your last minute questions on the coaching form or the Challenge forum. They will be answered promptly. Your project video should explain how your project works. Any common video format such as mp4, avi, mov is fine. Your project must use Java Embedded - whether it is Java SE Embedded or ME Embedded - with the hardware of your choice, including any devices, boards and IoT technology. The project will be judged based on the project implementation, innovation and business usefulness. More details on the IoT Developer Challenge website  Just for fun! Here is a video of Vinicius Senger giving a tour of his home lab, and showing his boards and gadgets. &lt;span id=&quot;XinhaEditingPostion&quot;&gt;&lt;/span&gt;

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  • OpenGL doesn't draw (3.3+) [on hold]

    - by Dhiego Magalhães
    Brief: I've been following this tutorial about OpenGL for 2 days, and I still can't have a triangle drawn, so I'm asking for help here. The tutorial is turned to OpenGL version 3.3 programing, using vertex arrays, buffers, etc. The libraries are: GLFW3 and GLEW, and I setted them by myself. The screen keeps black all the time. Full code: link here (It's just like a Hello World opengl program) Further Details: I get no errors at all. I downloaded a software to test my video card, and it supports OpenGL 4.1+ Standard OpenGL code for drawing (from earlier version) such as this one works normally. I'm using Microsoft Visual Studio 10.0 I presume all the OpenGL implementation was dune right: I added Additional Dependences to the linker as glew32.lib, opengl32.lib, glfw3.lib. The glew.dll was placed at SysWOW64 - because I'm running window 64bits, and glew is 32. Notes: I've been working hard to find out what this is, but I can't find. I would appreciate if anyone could test this code for me, so I can know if I implemented something wrong, and that its not my code.

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  • What is the best way to exploit multicores when making multithread games?

    - by Keeper
    Many people suggest to write a program, and then start optimizing it. But I think that when it's coming to multithreading with multicore, a little think ahead is required. I've read about using threads, and experienced it myself during some courses at the university (still a student). The big question is simple, but a bit abstract: What thread related steps in game design do I need to take, before implementation? Now trying to be more specific. Let's say, as an example, that I'm making a small board game (like Monopoly) that I want to be multithreaded. My goal Is that this multithreaded game will exploit the best of the multicore system, lets say 4-6 cores (like in i7 processors). My answer to this question at the moment is, one thread for each of these four basic components: GUI User Input / Output AI (computer rival) Other game related calculations (like shortest path from A to B, or level up status change) I'm not an expert (yet!), and I'm sure there are better answers out there. Any suggestion, answer, different approach will be helpful. Some thoughts: Maybe splitting the main database is a good way.. (or total disaster.. )

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  • How to choose a server side language / framework

    - by pllee
    I am trying to come up with a list / ranking system on determining which server language to choose for a particular website. Assume that familiarity with a certain language is not important and the implementation can be done in any language. Here are some things that might be important but I am not sure how to rank them : Maintainability. Libraries. For example, Memcached and NoSql support right out the box would be really nice addition to a particular framework. 3rd party SDK's. For example, if I need Paypal on my site they openly provide SDK's for all senarios in Java, PHP and .Net. If I choose Django I would have to rely on 3rd party libraries that are don't support everything and are not officially maintained. Would that be dealbreaker for Django? Performance This one is tricky to put on a generic list because it can be a deal breaker but for many websites performance will not be an issue that the language/framework is responsible for. Cost (hosting, open source). edit - Any reason for the votes to close? I didn't see any duplicates mentioned and the question should not drum up a flame war.

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  • best way to send messages to all subscribers with multiple subscriptions and multiple providers

    - by coding_idiot
    I'm writing an application in which - Many users can subsribe to posts made by another users. So for a single publisher there can be many subscribers. When a message is posted by an user X, all users who have subscribed to messages of User X will be sent an email. How to achieve this ? I'm thinking of using publish-subscribe pattern. And then I came through JMS. Which is the best JMS implementation to use according to your experience ? Or else what else solution do you propose to the given problem ? Shall I go for a straight-forward solution ?: User x posts a message, I find all users (from database) who subscribe to user x and then for every user, I call the sendEmail() method. [EDIT] My intention here is not to send-emails. I'm really sorry if it wasn't clear. I also have to send kind of system-notifications apart from Email to all subscribers. Right now, I've implemented the email-sending as a threadPool

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  • Assuming "clean code/architecture" is there a difference in "effort" between PHP or Java/J2EE web application development?

    - by PhD
    A client asked us to estimate effort when selecting PHP as the implementation language for his next web-based application. We spent about a week exploring PHP, prototyping, testing etc., We are quite new to this language - may have hacked around it in the past but, let's go with PHP-noobs but application development experts (for the lack of a better, less flattering word :) It seems, that if we write, clean maintainable code, follow separation of concerns, enterprise architecture patters (DAOs etc.) the 'effort' in creating an object-oriented PHP based web-application seems to be the same for a Java based one. Here's our equation for estimating the effort (development/delivery time): ConstructionEffort = f(analysis, design, coding, testing, review, deployment) We were specifically comparing effort estimates in creating an enterprise application with the following: PHP + CakePHP/CodeIgniter (should we have considered others?) Java + Spring + Restlet It's an end-to-end application: Client: Javascript/jQuery + HTML/CSS Middle tier/Business Logic - (Still evaluating PHP/Java) Database: MySQL The effort estimates of the 1st and 3rd tier are constant and relatively independent of the middle tier's technology. At a high level with an initial breakdown into user stories of the requested features as well as a high-level SWAG on the sheer number of classes/SLOC that would be required for PHP doesn't seem to differ by much from what is required of the same in Java. Is this correct? We are basing our initial estimates on the initial prototyping/coding we've done with PHP - we are currently disregarding fluency with the language as a factor, since that'll be an initial hurdle and not a long term impediment IMHO (we also have sufficient time to become quite fluent with PHP). I'm interested in knowing the programmers' perspective with respect to effort when creating similar applications with either of the languages to justify choosing one over the other. Are we missing something here? It seems we are going against popular belief of PHP being quicker to market (or we being very fluent with Java have our vision clouded). It doesn't seem to have any coding/programming effort saving from what we/ve played around with.

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  • BPI On Demand achieves both Oracle Fusion CRM Cloud Service 2013 Specialisation and Reseller status!

    - by Richard Lefebvre
    Oracle is delighted to share with you that BPI OnDemand has achieved the Oracle Fusion CRM Cloud Service 2013 Specialization and is the EMEA first ever Oracle Sales Cloud reseller ! One of Oracle's most active CRM SaaS partners across EMEA, BPI OnDemand operates out of the UK with subsidiaries in Spain and South Africa that will also benefit locally from the specialization and reseller status. Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} BPI OnDemand distinguishes itself from other Oracle Sales Cloud integrators with 2 unique implementation options: 1) Rapid Advantage Fixed Scope for as low as £20,000 or their famous 2) Zero upfront cost Fully Managed Cloud CRM Service which has no equivalent in Europe. BPI OnDemand has already 2 Oracle Sales Cloud live customers and is engaging in many other opportunities including large corporate accounts. Meet BPI OnDemand here or on LinkedIn or on Twitter

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  • Endeca Information Discovery 3-Day Hands-on Training Boot-Camp

    - by Mike.Hallett(at)Oracle-BI&EPM
    For Oracle Partners, on October 15-17, 2012 in Paris, France: Register here. The Oracle Endeca Information Discovery (OEID) Boot-Camp is designed to give partners an understanding of OEID’s features, and how it complements the existing Oracle Business Intelligence suite. Participants will learn how to develop & implement solutions using a Data Discovery method.  Training is in English. What will be covered? The Oracle Endeca Information Discovery (OEID) Boot Camp is a three-day class with a combination of lecture and hands-on exercises, tailored to make participants aware of the Oracle Endeca Information Discovery platform, and to gain valuable skills for the implementation of projects.   Prerequisites You must bring a laptop with you for the Hands-on labs: Attendees should have experience and familiarity with the basic concepts of business intelligence and be OPN Partners with Gold or above membership.  This training is free to OPN Partners. Click here for more information. Where and When ? Monday, October 15th until Wednesday, October 17th included  9:00 - 18:00 Oracle France 15, boulevard Charles de Gaulle 92715 Colombes: Access Venue Map Register here  : NOTE there is a Limited number of seats, you will get confirmation within 2 weeks.

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  • Moving away from PHP and running towards server-side JavaScript [on hold]

    - by Sosukodo
    I've decided to start moving away from PHP and server-side JavaScript looks like an attractive replacement. However, I'm having a hard time wrapping my head around how others are using Node.js for web applications. I'm currently using Lighttpd with FastCGI PHP. The one thing I like about PHP is that I can "inline" my scripts in the document like so: <?php echo 'Hello, World!'; ?> My question is: Is there any server-side JavaScript solution that I can use in this manor? For instance, I'd love to be able to do this: <?js print('Hello, World!'); ?> Is there such a thing? I'm not looking for opinions about "which is better". I just want to know what's out there and I'll explore each of them on my own. The important thing is that I'd like to use it like I demonstrated above. Links to the software along with implementation examples will be considered above other answers.

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  • What's so great about Clojure?

    - by marco-fiset
    I've been taking a look at Clojure lately and I stumbled upon this post on Stackoverflow that indicates some projects following best practices, and overall good Clojure code. I wanted to get my head around the language after reading some basic tutorials so I took a look at some "real-world" projects. After looking at ClojureScript and Compojure (two the the aforementioned "good" projects), I just feel like Clojure is a joke. I don't understand why someone would pick Clojure over say, Ruby or Python, two languages that I love and have such a clean syntax and are very easy to pick up whereas Clojure uses so much parenthesis and symbols everywhere that it ruins the readability for me. I think that Ruby and Python are beautiful, readable and elegant. They are easy to read even for someone who does not know the language inside out. However, Clojure is opaque to me and I feel like I must know every tiny detail about the language implementation in order to be able to understand any code. So please, enlighten me! What is so good about Clojure? What is the absolute minimum that I should know about the language in order to appreciate it?

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  • How do I drag my widgets without dragging other widgets?

    - by Cypher
    I have a bunch of drag-able widgets on screen. When I am dragging one of the widgets around, if I drag the mouse over another widget, that widget then gets "snagged" and is also dragged around. While this is kind of a neat thing and I can think of a few game ideas based on that alone, that was not intended. :-P Background Info I have a Widget class that is the basis for my user interface controls. It has a bunch of properties that define it's size, position, image information, etc. It also defines some events, OnMouseOver, OnMouseOut, OnMouseClick, etc. All of the event handler functions are virtual, so that child objects can override them and make use of their implementation without duplicating code. Widgets are not aware of each other. They cannot tell each other, "Hey, I'm dragging so bugger off!" Source Code Here's where the widget gets updated (every frame): public virtual void Update( MouseComponent mouse, KeyboardComponent keyboard ) { // update position if the widget is being dragged if ( this.IsDragging ) { this.Left -= (int)( mouse.LastPosition.X - mouse.Position.X ); this.Top -= (int)( mouse.LastPosition.Y - mouse.Position.Y ); } ... // define and throw other events if ( !this.WasMouseOver && this.IsMouseOver && mouse.IsButtonDown( MouseButton.Left ) ) { this.IsMouseDown = true; this.MouseDown( mouse, new EventArgs() ); } ... // define and throw other events } And here's the OnMouseDown event where the IsDraggable property gets set: public virtual void OnMouseDown( object sender, EventArgs args ) { if ( this.IsDraggable ) { this.IsDragging = true; } } Problem Looking at the source code, it's obvious why this is happening. The OnMouseDown event gets fired whenever the mouse is hovered over the Widget and when the left mouse button is "down" (but not necessarily in that order!). That means that even if I hold the mouse down somewhere else on screen, and simply move it over anything that IsDraggable, it will "hook" onto the mouse and go for a ride. So, now that it's obvious that I'm Doing It Wrong™, how do I do this correctly?

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  • WCF REST Error Handler

    - by Elton Stoneman
    I’ve put up on GitHub a sample WCF error handler for REST services, which returns proper HTTP status codes in response to service errors.   The code is very simple – a ServiceBehavior implementation which can be specified in config to tag the RestErrorHandler to a service. Any uncaught exceptions will be routed to the error handler, which sets the HTTP status code and description in the response, based on the type of exception.   The sample defines a ClientException which can be thrown in code to indicate a problem with the client’s request, and the response will be a status 400 with a friendly error message:       throw new ClientException("Invalid userId. Must be provided as a positive integer");   - responds:   Request URL http://localhost/Sixeyed.WcfRestErrorHandler.Sample/ErrorProneService.svc/lastLogin?userId=xyz   Error Status Code: 400, Description: Invalid userId. Must be provided as a positive integer   Any other uncaught exceptions are hidden from the client. The full details are logged with a GUID to identify the error, and the response to the client is a status 500 with a generic message giving them the GUID to follow up on:       var iUserId = 0;     var dbz = 1 / iUserId;   - logs the divide-by-zero error and responds:   Request URL http://localhost/Sixeyed.WcfRestErrorHandler.Sample/ErrorProneService.svc/dbz     Error Status Code: 500, Description: Something has gone wrong. Please contact our support team with helpdesk ID: C9C5A968-4AEA-48C7-B90A-DEC986F80DA5   The sample demonstrates two techniques for building the response. For client exceptions, a friendly HTML response is sent in the body as well as the status code and description. Personally I prefer not to do that – it doesn’t make sense to get a 400 error and find text/html when you’re expecting application/json, but it’s easy to do if that’s the functionality you want. The other option is to send an empty response, which the sample does with server exceptions.   The obvious extension is to have multiple exceptions representing all the status codes you want to provide, then your code is as simple as throwing the relevant exception – UnauthorizedException, ForbiddenExeption, NotImplementedException etc – anywhere in the stack, and it will be handled nicely.

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  • Dealing with Fine-Grained Cache Entries in Coherence

    - by jpurdy
    On occasion we have seen significant memory overhead when using very small cache entries. Consider the case where there is a small key (say a synthetic key stored in a long) and a small value (perhaps a number or short string). With most backing maps, each cache entry will require an instance of Map.Entry, and in the case of a LocalCache backing map (used for expiry and eviction), there is additional metadata stored (such as last access time). Given the size of this data (usually a few dozen bytes) and the granularity of Java memory allocation (often a minimum of 32 bytes per object, depending on the specific JVM implementation), it is easily possible to end up with the case where the cache entry appears to be a couple dozen bytes but ends up occupying several hundred bytes of actual heap, resulting in anywhere from a 5x to 10x increase in stated memory requirements. In most cases, this increase applies to only a few small NamedCaches, and is inconsequential -- but in some cases it might apply to one or more very large NamedCaches, in which case it may dominate memory sizing calculations. Ultimately, the requirement is to avoid the per-entry overhead, which can be done either at the application level by grouping multiple logical entries into single cache entries, or at the backing map level, again by combining multiple entries into a smaller number of larger heap objects. At the application level, it may be possible to combine objects based on parent-child or sibling relationships (basically the same requirements that would apply to using partition affinity). If there is no natural relationship, it may still be possible to combine objects, effectively using a Coherence NamedCache as a "map of maps". This forces the application to first find a collection of objects (by performing a partial hash) and then to look within that collection for the desired object. This is most naturally implemented as a collection of entry processors to avoid pulling unnecessary data back to the client (and also to encapsulate that logic within a service layer). At the backing map level, the NIO storage option keeps keys on heap, and so has limited benefit for this situation. The Elastic Data features of Coherence naturally combine entries into larger heap objects, with the caveat that only data -- and not indexes -- can be stored in Elastic Data.

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  • TXPAUSE : polite waiting for hardware transactional memory

    - by Dave
    Classic locks are an appropriate tool to prevent potentially conflicting operations A and B, invoked by different threads, from running at the same time. In a sense the locks cause either A to run before B or vice-versa. Similarly, we can replace the locks with hardware transactional memory, or use transactional lock elision to leverage potential disjoint access parallelism between A and B. But often we want A to wait until B has run. In a Pthreads environment we'd usually use locks in conjunction with condition variables to implement our "wait until" constraint. MONITOR-MWAIT is another way to wait for a memory location to change, but it only allows us to track one cache line and it's only available on x86. There's no similar "wait until" construct for hardware transactions. At the instruction-set level a simple way to express "wait until" in transactions would be to add a new TXPAUSE instruction that could be used within an active hardware transaction. TXPAUSE would politely stall the invoking thread, possibly surrendering or yielding compute resources, while at the same time continuing to track the transaction's address-set. Once a transaction has executed TXPAUSE it can only abort. Ideally that'd happen when some other thread modifies a variable that's in the transaction's read-set or write-set. And since we're aborting all writes would be discarded. In a sense this gives us multi-location MWAIT but with much more flexibility. We could also augment the TXPAUSE with a cycle-count bound to cap the time spent stalled. I should note that we can already enter a tight spin loop in a transaction to wait for updates to address-set to cause an abort. Assuming that the implementation monitors the address-set via cache-coherence probes, by waiting in this fashion we actually communicate via the probes, and not via memory values. That is the updating thread signals the waiter via probes instead of by traditional memory values. But TXPAUSE gives us a polite way to spin.

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