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• Do logged in users need to browse a site over https?

  - by Luke

  I've never thought it was necessary, but a client has requested that all webpages served to logged in users be delivered over HTTPS. Aside from the implementation standpoint, which I don't think I'm going to pursue is there any real reason for this request ? For clarity, the login / logout process, account settings, registration preferences and all user related scripts are served over https. but I can't see the point in my news articles, press releases, events etc... being served in this manner? Am I missing something ?

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• Google I/O 2010 - Exploring the Google PowerMeter API

  Google I/O 2010 - Exploring the Google PowerMeter API Google I/O 2010 - Knowledge is (less) power: Exploring the Google PowerMeter API Google APIs 101 Srikanth Rajagopalan, Rus Heywood In this session we will discuss interesting ways to make users understand and manage their home energy use through Google PowerMeter. The Google PowerMeter API currently available allows devices to integrate with Google PowerMeter. Come learn how you can build with the API and about exciting developments ahead. We will dig into the implementation details for integrations and open up the floor for other ideas that may be relevant. For all I/O 2010 sessions, please go to code.google.com From: GoogleDevelopers Views: 5 0 ratings Time: 58:20 More in Science & Technology

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• Think Global, Act Regional with Identity Globe Trotters

  - by Tanu Sood

  This month we will be introducing a new section on our blog. Titled “Identity Globe Trotters”, this will be a monthly series that would feature a regional topic the last Friday of every month. We would invite guest contributors from different regions to highlight a region-specific business issue, solution, highlight a customer implementation or a regional discussion of interest. If you have an Identity management topic in mind that you’d like featured in this section, do let us know. We look forward to engaging in meaningful discussions with you on global perspectives, regional solutions.

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• Why isn't the source code of programs shown in research papers released?

  - by Antoine

  Is there a reason why the source code of programs shown in research papers are not released ? I understand that research papers are more about the general idea of accomplishing something than implementation details, but I don't get why they don't release the code. For example, in this paper ends with: Results The human line drawing system is implemented through the Qt framework in C++ using OpenGL, and runs on a 2.00 GHz Intel dual core processor workstation without any additional hardware assistance. We can interactively draw lines while the system synthesizes the new path and texture. Do they keep the source code closed intentionally because of a monetization they intend to make with it, or because of copyright ?

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• Trying to detect collision between two polygons using Separating Axis Theorem

  - by Holly

  The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(vertices[0]); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(vertices[i]); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if( other.x <= y || other.y >= x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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• JavaOne 2012 Sunday Strategy Keynote

  - by Janice J. Heiss

  At the Sunday Strategy Keynote, held at the Masonic Auditorium, Hasan Rizvi, EVP, Middleware and Java Development, stated that the theme for this year's JavaOne is: “Make the future Java”-- meaning that Java continues in its role as the most popular, complete, productive, secure, and innovative development platform. But it also means, he qualified, the process by which we make the future Java -- an open, transparent, collaborative, and community-driven evolution. "Many of you have bet your businesses and your careers on Java, and we have bet our business on Java," he said.Rizvi detailed the three factors they consider critical to the success of Java--technology innovation, community participation, and Oracle's leadership/stewardship. He offered a scorecard in these three realms over the past year--with OS X and Linux ARM support on Java SE, open sourcing of JavaFX by the end of the year, the release of Java Embedded Suite 7.0 middleware platform, and multiple releases on the Java EE side. The JCP process continues, with new JSR activity, and JUGs show a 25% increase in participation since last year. Oracle, meanwhile, continues its commitment to both technology and community development/outreach--with four regional JavaOne conferences last year in various part of the world, as well as the release of Java Magazine, with over 120,000 current subscribers. Georges Saab, VP Development, Java SE, next reviewed features of Java SE 7--the first major revision to the platform under Oracle's stewardship, which has included near-monthly update releases offering hundreds of fixes, performance enhancements, and new features. Saab indicated that developers, ISVs, and hosting providers have all been rapid adopters of the platform. He also noted that Oracle's entire Fusion middleware stack is supported on SE 7. The supported platforms for SE 7 has also increased--from Windows, Linux, and Solaris, to OS X, Linux ARM, and the emerging ARM micro-server market. "In the last year, we've added as many new platforms for Java, as were added in the previous decade," said Saab.Saab also explored the upcoming JDK 8 release--including Project Lambda, Project Nashorn (a modern implementation of JavaScript running on the JVM), and others. He noted that Nashorn functionality had already been used internally in NetBeans 7.3, and announced that they were planning to contribute the implementation to OpenJDK. Nandini Ramani, VP Development, Java Client, ME and Card, discussed the latest news pertaining to JavaFX 2.0--releases on Windows, OS X, and Linux, release of the FX Scene Builder tool, the JavaFX WebView component in NetBeans 7.3, and an OpenJFX project in OpenJDK. Nandini announced, as of Sunday, the availability for download of JavaFX on Linux ARM (developer preview), as well as Scene Builder on Linux. She noted that for next year's JDK 8 release, JavaFX will offer 3D, as well as third-party component integration. Avinder Brar, Senior Software Engineer, Navis, and Dierk König, Canoo Fellow, next took the stage and demonstrated all that JavaFX offers, with a feature-rich, animation-rich, real-time cargo management application that employs Canoo's just open-sourced Dolphin technology.Saab also explored Java SE 9 and beyond--Jigsaw modularity, Penrose Project for interoperability with OSGi, improved multi-tenancy for Java in the cloud, and Project Sumatra. Phil Rogers, HSA Foundation President and AMD Corporate Fellow, explored heterogeneous computing platforms that combine the CPU and the parallel processor of the GPU into a single piece of silicon and shared memory—a hardware technology driven by such advanced functionalities as HD video, face recognition, and cloud workloads. Project Sumatra is an OpenJDK project targeted at bringing Java to such heterogeneous platforms--with hardware and software experts working together to modify the JVM for these advanced applications and platforms.Ramani next discussed the latest with Java in the embedded space--"the Internet of things" and M2M--declaring this to be "the next IT revolution," with Java as the ideal technology for the ecosystem. Last week, Oracle released Java ME Embedded 3.2 (for micro-contollers and low-power devices), and Java Embedded Suite 7.0 (a middleware stack based on Java SE 7). Axel Hansmann, VP Strategy and Marketing, Cinterion, explored his company's use of Java in M2M, and their new release of EHS5, the world's smallest 3G-capable M2M module, running Java ME Embedded. Hansmaan explained that Java offers them the ability to create a "simple to use, scalable, coherent, end-to-end layer" for such diverse edge devices.Marc Brule, Chief Financial Office, Royal Canadian Mint, also explored the fascinating use-case of JavaCard in his country's MintChip e-cash technology--deployable on smartphones, USB device, computer, tablet, or cloud. In parting, Ramani encouraged developers to download the latest releases of Java Embedded, and try them out.Cameron Purdy, VP, Fusion Middleware Development and Java EE, summarized the latest developments and announcements in the Enterprise space--greater developer productivity in Java EE6 (with more on the way in EE 7), portability between platforms, vendors, and even cloud-to-cloud portability. The earliest version of the Java EE 7 SDK is now available for download--in GlassFish 4--with WebSocket support, better JSON support, and more. The final release is scheduled for April of 2013. Nicole Otto, Senior Director, Consumer Digital Technology, Nike, explored her company's Java technology driven enterprise ecosystem for all things sports, including the NikeFuel accelerometer wrist band. Looking beyond Java EE 7, Purdy mentioned NoSQL database functionality for EE 8, the concurrency utilities (possibly in EE 7), some of the Avatar projects in EE 7, some in EE 8, multi-tenancy for the cloud, supporting SaaS applications, and more.Rizvi ended by introducing Dr. Robert Ballard, oceanographer and National Geographic Explorer in Residence--part of Oracle's philanthropic relationship with the National Geographic Society to fund K-12 education around ocean science and conservation. Ballard is best known for having discovered the wreckage of the Titanic. He offered a fascinating video and overview of the cutting edge technology used in such deep-sea explorations, noting that in his early days, high-bandwidth exploration meant that you’d go down in a submarine and "stick your face up against the window." Now, it's a remotely operated, technology telepresence--"I think of my Hercules vehicle as my equivalent of a Na'vi. When I go beneath the sea, I actually send my spirit." Using high bandwidth satellite links, such amazing explorations can now occur via smartphone, laptop, or whatever platform. Ballard’s team regularly offers live feeds and programming out to schools and the world, spanning 188 countries--with embedding educators as part of the expeditions. It's technology at its finest, inspiring the next-generation of scientists and explorers!

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• The First Microsoft Dynamics NAV Builds on TFS 2010 Server

  - by ssmantha

  We are now successfully, able build Dynamics NAV solutions using the TFS Build workflow mechanisms. Lots of test builds were made, the builds can restore the NAV Database and start from a fresh solution, take latest of the NAV objects and then import it to Navision and call the compile method. The workflow is also able to generate FOB files as output which can be directly shipped to the customers. I think this is the First in the world implementation of the TFS build concepts in conjunction with NAV. I think this is a time to change the thinking caps and try to approach ERP development and include the practises of ALM into ERP Product Development.

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• Why should I use List<T> over IEnumerable<T>?

  - by Rowan Freeman

  In my ASP.net MVC4 web application I use IEnumerables, trying to follow the mantra to program to the interface, not the implementation. Return IEnumerable(Of Student) vs Return New List(Of Student) People are telling me to use List and not IEnumerable, because lists force the query to be executed and IEumerable does not. Is this really best practice? Is there any alternative? I feel strange using concrete objects where an interface could be used. Is my strange feeling justified?

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• Would a multitouch capable PC allow me to do Android development simulating the touch UI without an Android device ?

  - by Scott Davies

  Hi, I recently purchased a Samsung Galaxy Tab as a reference implementation (phone and first gen Android tablet), of Android 2.x for app development. I have noticed a slew of Android 3.0 slates being talked about at CES 2011 (Motorola XOOM, etc.). If I had a multitouch PC with the Android SDK/Emulator on it, would this allow me to more closely approximate device simulation by allowing user input via the multitouch screen ? Would it work via touch just like Windows 7 recognizes touch as mouse style input ? Has anyone done this ? Thanks, Scott

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• How to efficiently map tokens to code in a script interpreter?

  - by lithander

  I'm writing an interpreter for a simple scripting language where each line is a complete, executable command. (Like the instructions in assembler) When parsing a line I have to map the requested command to actual code. My current solution looks like this: std::string op, param1, param2; //parse line, identify op, param1, param2 ... //call command specific code if(op == "MOV") ExecuteMov(AsNumber(param1)); else if(op == "ROT") ExecuteRot(AsNumber(param1)); else if(op == "SZE") ExecuteSze(AsNumber(param1)); else if(op == "POS") ExecutePos((AsNumber(param1), AsNumber(param2)); else if(op == "DIR") ExecuteDir((AsNumber(param1), AsNumber(param2)); else if(op == "SET") ExecuteSet(param1, AsNumber(param2)); else if(op == "EVL") ... The more commands are supported the more string comparisions I'll have to do to identify and call the associated method. Can you point me to a more efficient implementation in the described scenario?

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• What threading pratice is good 90% of the time?

  - by acidzombie24

  Since my SO thread was closed i guess i can ask it here. What practice or practices are good 90% of the time when working with threading with multiple cores? Personally all i have done was share immutable classes and pass (copy) data to a queue to the destine thread. Note: This is for research and when i say 90% of the time i dont mean it is allowed to fail 10% of the time (thats ridiculous!) i mean 90% it is a good solution while the other 10% it is not so desirable due to implementation or efficiently reasons (or plainly another technique fits the problem domain a lot better).

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• Who is likely to need the most this high-quality, measurable, reliable approach to software? [closed]

  - by Marek Cruz

  Software engineering is the application of principles of engineering to software. Trouble is, most of those who like to flatter with the title "software engineer" don't do that. They just keep writing code and patching it until it's stable enough to foist off on users. That's not software engineering. Who is likely to need the most the practice of software engineering? (with all the project planning, requirements engineering, software design, implementation based on the design, testing, deployment, awareness of IEEE standards, metrics, security, dependability, usability, etc.)

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• Tyrus 1.1

  - by Pavel Bucek

  It might seem like there is not much time passed since Tyrus 1.0 (Java API for WebSocket reference implementation) release, but the fact is it was frozen several weeks before going public and development in the trunk continued. Tyrus 1.1 brings some new features and improvements: client-side proxy support simple command line client various stability/performance fixes (see below for complete list) Individual blog posts about highlighted features will follow, same as related user guide chapters.. stay tuned! Tyrus 1.1 is already integrated in Glassfish trunk - you can download nightly build or upgrade to newer Tyrus manually (replace all Tyrus jars; I know this is not very user friendly, so I'll try to come up with some better solution or at least simple guide). Complete list of bugfixes/improvements: TYRUS-180 TYRUS-176 TYRUS-192 TYRUS-186 TYRUS-191 TYRUS-187 TYRUS-172 TYRUS-194 TYRUS-179 TYRUS-178 TYRUS-200 TYRUS-177 TYRUS-181 TYRUS-203 TYRUS-205 TYRUS-198 TYRUS-202 TYRUS-188 TYRUS-149 Related links: https://tyrus.java.net https://java.net/jira/browse/TYRUS/

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• Session Report - Java on the Raspberry Pi

  - by Janice J. Heiss

  On mid-day Wednesday, the always colorful Oracle Evangelist Simon Ritter demonstrated Java on the Raspberry Pi at his session, “Do You Like Coffee with Your Dessert?”. The Raspberry Pi consists of a credit card-sized single-board computer developed in the UK with the intention of stimulating the teaching of basic computer science in schools. “I don't think there is a single feature that makes the Raspberry Pi significant,” observed Ritter, “but a combination of things really makes it stand out. First, it's $35 for what is effectively a completely usable computer. You do have to add a power supply, SD card for storage and maybe a screen, keyboard and mouse, but this is still way cheaper than a typical PC. The choice of an ARM (Advanced RISC Machine and Acorn RISC Machine) processor is noteworthy, because it avoids problems like cooling (no heat sink or fan) and can use a USB power brick. When you add in the enormous community support, it offers a great platform for teaching everyone about computing.”Some 200 enthusiastic attendees were present at the session which had the feel of Simon Ritter sharing a fun toy with friends. The main point of the session was to show what Oracle was doing to support Java on the Raspberry Pi in a way that is entertaining and fun. Ritter pointed out that, in addition to being great for teaching, it’s an excellent introduction to the ARM architecture, and runs well with Java and will get better once it has official hard float support. The possibilities are vast.Ritter explained that the Raspberry Pi Project started in 2006 with the goal of devising a computer to inspire children; it drew inspiration from the BBC Micro literacy project of 1981 that produced a series of microcomputers created by the Acorn Computer company. It was officially launched on February 29, 2012, with a first production of 10,000 boards. There were 100,000 pre-orders in one day; currently about 4,000 boards are produced a day. Ritter described the specification as follows:* CPU: ARM 11 core running at 700MHz Broadcom SoC package Can now be overclocked to 1GHz (without breaking the warranty!) * Memory: 256Mb* I/O: HDMI and composite video 2 x USB ports (Model B only) Ethernet (Model B only) Header pins for GPIO, UART, SPI and I2C He took attendees through a brief history of ARM Architecture:* Acorn BBC Micro (6502 based) Not powerful enough for Acorn’s plans for a business computer * Berkeley RISC Project UNIX kernel only used 30% of instruction set of Motorola 68000 More registers, less instructions (Register windows) One chip architecture to come from this was… SPARC * Acorn RISC Machine (ARM) 32-bit data, 26-bit address space, 27 registers First machine was Acorn Archimedes * Spin off from Acorn, Advanced RISC MachinesNext he presented its features:* 32-bit RISC Architecture–  ARM accounts for 75% of embedded 32-bit CPUs today– 6.1 Billion chips sold last year (zero manufactured by ARM)* Abstract architecture and microprocessor core designs– Raspberry Pi is ARM11 using ARMv6 instruction set* Low power consumption– Good for mobile devices– Raspberry Pi can be powered from 700mA 5V only PSU– Raspberry Pi does not require heatsink or fanHe described the current ARM Technology:* ARMv6– ARM 11, ARM Cortex-M* ARMv7– ARM Cortex-A, ARM Cortex-M, ARM Cortex-R* ARMv8 (Announced)– Will support 64-bit data and addressingHe next gave the Java Specifics for ARM: Floating point operations* Despite being an ARMv6 processor it does include an FPU– FPU only became standard as of ARMv7* FPU (Hard Float, or HF) is much faster than a software library* Linux distros and Oracle JVM for ARM assume no HF on ARMv6– Need special build of both– Raspbian distro build now available– Oracle JVM is in the works, release date TBDNot So RISCPerformance Improvements* DSP Enhancements* Jazelle* Thumb / Thumb2 / ThumbEE* Floating Point (VFP)* NEON* Security Enhancements (TrustZone)He spent a few minutes going over the challenges of using Java on the Raspberry Pi and covered:* Sound* Vision * Serial (TTL UART)* USB* GPIOTo implement sound with Java he pointed out:* Sound drivers are now included in new distros* Java Sound API– Remember to add audio to user’s groups– Some bits work, others not so much* Playing (the right format) WAV file works* Using MIDI hangs trying to open a synthesizer* FreeTTS text-to-speech– Should work once sound works properlyHe turned to JavaFX on the Raspberry Pi:* Currently internal builds only– Will be released as technology preview soon* Work involves optimal implementation of Prism graphics engine– X11?* Once the JavaFX implementation is completed there will be little of concern to developers-- It’s just Java (WORA). He explained the basis of the Serial Port:* UART provides TTL level signals (3.3V)* RS-232 uses 12V signals* Use MAX3232 chip to convert* Use this for access to serial consoleHe summarized his key points. The Raspberry Pi is a very cool (and cheap) computer that is great for teaching, a great introduction to ARM that works very well with Java and will work better in the future. The opportunities are limitless. For further info, check out, Raspberry Pi User Guide by Eben Upton and Gareth Halfacree. From there, Ritter tried out several fun demos, some of which worked better than others, but all of which were greeted with considerable enthusiasm and support and good humor (even when he ran into some glitches).  All in all, this was a fun and lively session.

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• Component-based design: handling objects interaction

  - by Milo

  I'm not sure how exactly objects do things to other objects in a component based design. Say I have an Obj class. I do: Obj obj; obj.add(new Position()); obj.add(new Physics()); How could I then have another object not only move the ball but have those physics applied. I'm not looking for implementation details but rather abstractly how objects communicate. In an entity based design, you might just have: obj1.emitForceOn(obj2,5.0,0.0,0.0); Any article or explanation to get a better grasp on a component driven design and how to do basic things would be really helpful.

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• Will Unity allow users to change the color/appearance of the top-Panel?

  - by Sam

  I'm very excited by the functional design principles and keyboard shortcuts that are being implemented for Unity. And function of use is more important to me than looks. However, after experiencing the aesthetic beauty of the display of the top panel in gnome-shell, I was wondering if users would be able to alter the color of Unity's top panel? IMHO it does not look as good as the gnome-shell implementation (or mac OS X/iPad). I think if an alternate color/appearance were chosen for the panel, it would make a big difference aesthetically. Is there a way to make it Black like gnome-shell? Or are the color choices limited to theme-designs as pointed out in this answer? For efficiency and clarity, the Panel should be better differentiated from application controls. The panel should be a different color because it has a "constant (always present) state," unlike application controls. For contrast and easy-recognition, I would like to make the Panel black (like gnome-shell) but make the application controls (e.g., those of Firefox) "Inverted"

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• To implement registration page with Vaadin or not?

  - by JVerstry

  This is a tactical implementation question about usage of Vaadin or in some part of my application. Vaadin is a great framework to login users and implement sophisticated web applications with many pages. However, I think it is not very well suited to desgin pages to register new users for my application. Am I right? Am I am wrong? It seems to me that a simple HTML/CSS/Javascript login + email registration + confirmation email with confirmation link cannot be implemented easily with Vaadin. It seems like Vaadin would be overkill. Do you agree? Or am I missing something? I am looking for feedback from experienced Vaadin users.

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• Synchronizing local and remote cache in distributed caching

  - by ltfishie

  With a distributed cache, a subset of the cache is kept locally while the rest is held remotely. In a get operation, if the entry is not available locally, the remote cache will be used and and the entry is added to local cache. In a put operation, both the local cache and remote cache are updated. Other nodes in the cluster also need to be notified to invalidate their local cache as well. What's a simplest way to achieve this if you implemented it yourself, assuming that nodes are not aware of each other. Edit My current implementation goes like this: Each cache entry contains a time stamp. Put operation will update local cache and remote cache Get operation will try local cache then remote cache A background thread on each node will check remote cache periodically for each entry in local cache. If the timestamp on remote is newer overwrite the local. If entry is not found in remote, delete it from local.

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• Splitting Graph into distinct polygons in O(E) complexity

  - by Arthur Wulf White

  If you have seen my last question: trapped inside a Graph : Find paths along edges that do not cross any edges How do you split an entire graph into distinct shapes 'trapped' inside the graph(like the ones described in my last question) with good complexity? What I am doing now is iterating over all edges and then starting to traverse while always taking the rightmost turn. This does split the graph into distinct shapes. Then I eliminate all the excess shapes (that are repeats of previous shapes) and return the result. The complexity of this algorithm is O(E^2). I am wondering if I could do it in O(E) by removing edges I already traversed previously. My current implementation of that returns unexpected results.

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• Best resources to learn Game Development from a Java background?

  - by Julio

  I'm an enterprise Java programmer, however something I've been interested in and what got me into the whole programming thing was the idea of being able to create a game. Just wondering if anybody could offer any advice, or book recommendations. The side I am most interested in is game engine design and implementation. People may say "ahh but plenty exist why write your own" - its purely for learning purposes, seeing how things work and so on. So far I've taken a look at LWJGL, but achieved nothing too serious. Thanks.

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• Error in my Separating Axis Theorem collision code

  - by Holly

  The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; int x; int y; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } public void update(int xPos, int yPos){ x = xPos; y = yPos; } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(new Vect(vertices[0].x+x, vertices[0].y+y)); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(new Vect(vertices[i].x+x, vertices[i].y+y)); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if(y > other.x && other.y > x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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• Recording Available: March 2010 Quarterly Customer Update Webcast

  - by michelle.huff

  Missed the last Quarterly Customer Update Webcast? We discussed several product updates on the March quarterly customer Webcast, including the first phase of the Oracle Content Management 11g release. Some of the highlights include Information Rights Management (IRM) 11g and Imaging and Process Management (I/PM) 11g Overviews. Additionally, we covered I/PM 11g new features, implementation and migration topics that existing customers would like to know. You can find quick links to all the resources I mentioned on the call, as well as links to the presentation and recording details in My Oracle Support from the March 2010 Webcast Resource Links page on OTN.

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• Smooth vector based jump

  - by Esa

  I started working on Wolfire's mathematics tutorials. I got the jumping working well using a step by step system, where you press a button and the cube moves to the next point on the jumping curve. Then I tried making the jumping happen during a set time period e.g the jump starts and lands within 1.5 seconds. I tried the same system I used for the step by step implementation, but it happens instantly. After some googling I found that Time.deltatime should be used, but I could not figure how. Below is my current jumping code, which makes the jump happen instantly. while (transform.position.y > 0) { modifiedJumperVelocity -= jumperDrag; transform.position += new Vector3(modifiedJumperVelocity.x, modifiedJumperVelocity.y, 0); } Where modifiedJumperVelocity is starting vector minus the jumper drag. JumperDrag is the value that is substracted from the modifiedJumperVelocity during each step of the jump. Below is an image of the jumping curve:

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• How can I selectively update XNA GameComponents?

  - by Bill

  I have a small 2D game I'm working on in XNA. So far, I have a player-controlled ship that operates on vector thrust and is terribly fun to spin around in circles. I've implemented this as a DrawableGameComponent and registered it with the game using game.Components.Add(this) in the Ship object constructor. How can I implement features like pausing and a menu system with my current implementation? Is it possible to set certain GameComponents to not update? Is this something for which I should even be using a DrawableGameComponent? If not, what are more appropriate uses for this?

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• MVVM - how to make creating viewmodels at runtime less painfull

  - by Mr Happy

  I apologize for the long question, it reads a bit as a rant, but I promise it's not! I've summarized my question(s) below In the MVC world, things are straightforward. The Model has state, the View shows the Model, and the Controller does stuff to/with the Model (basically), a controller has no state. To do stuff the Controller has some dependencies on web services, repository, the lot. When you instantiate a controller you care about supplying those dependencies, nothing else. When you execute an action (method on Controller), you use those dependencies to retrieve or update the Model or calling some other domain service. If there's any context, say like some user wants to see the details of a particular item, you pass the Id of that item as parameter to the Action. Nowhere in the Controller is there any reference to any state. So far so good. Enter MVVM. I love WPF, I love data binding. I love frameworks that make data binding to ViewModels even easier (using Caliburn Micro a.t.m.). I feel things are less straightforward in this world though. Let's do the exercise again: the Model has state, the View shows the ViewModel, and the ViewModel does stuff to/with the Model (basically), a ViewModel does have state! (to clarify; maybe it delegates all the properties to one or more Models, but that means it must have a reference to the model one way or another, which is state in itself) To do stuff the ViewModel has some dependencies on web services, repository, the lot. When you instantiate a ViewModel you care about supplying those dependencies, but also the state. And this, ladies and gentlemen, annoys me to no end. Whenever you need to instantiate a ProductDetailsViewModel from the ProductSearchViewModel (from which you called the ProductSearchWebService which in turn returned IEnumerable<ProductDTO>, everybody still with me?), you can do one of these things: call new ProductDetailsViewModel(productDTO, _shoppingCartWebService /* dependcy */);, this is bad, imagine 3 more dependencies, this means the ProductSearchViewModel needs to take on those dependencies as well. Also changing the constructor is painfull. call _myInjectedProductDetailsViewModelFactory.Create().Initialize(productDTO);, the factory is just a Func, they are easily generated by most IoC frameworks. I think this is bad because Init methods are a leaky abstraction. You also can't use the readonly keyword for fields that are set in the Init method. I'm sure there are a few more reasons. call _myInjectedProductDetailsViewModelAbstractFactory.Create(productDTO); So... this is the pattern (abstract factory) that is usually recommended for this type of problem. I though it was genious since it satisfies my craving for static typing, until I actually started using it. The amount of boilerplate code is I think too much (you know, apart from the ridiculous variable names I get use). For each ViewModel that needs runtime parameters you'll get two extra files (factory interface and implementation), and you need to type the non-runtime dependencies like 4 extra times. And each time the dependencies change, you get to change it in the factory as well. It feels like I don't even use an DI container anymore. (I think Castle Windsor has some kind of solution for this [with it's own drawbacks, correct me if I'm wrong]). do something with anonymous types or dictionary. I like my static typing. So, yeah. Mixing state and behavior in this way creates a problem which don't exist at all in MVC. And I feel like there currently isn't a really adequate solution for this problem. Now I'd like to observe some things: People actually use MVVM. So they either don't care about all of the above, or they have some brilliant other solution. I haven't found an indepth example of MVVM with WPF. For example, the NDDD-sample project immensely helped me understand some DDD concepts. I'd really like it if someone could point me in the direction of something similar for MVVM/WPF. Maybe I'm doing MVVM all wrong and I should turn my design upside down. Maybe I shouldn't have this problem at all. Well I know other people have asked the same question so I think I'm not the only one. To summarize Am I correct to conclude that having the ViewModel being an integration point for both state and behavior is the reason for some difficulties with the MVVM pattern as a whole? Is using the abstract factory pattern the only/best way to instantiate a ViewModel in a statically typed way? Is there something like an in depth reference implementation available? Is having a lot of ViewModels with both state/behavior a design smell?

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