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• What good books are out there on program execution models? [on hold]

  - by murungu

  Can anyone out there name a few books that address the topic of program execution models?? I want a book that can answer questions such as... What is the difference between interpreted and compiled languages and what are the performance consequences at runtime?? What is the difference between lazy evaluation, eager evaluation and short circuit evaluation?? Why would one choose to use one evaluation strategy over another?? How do you simulate lazy evaluation in a language that favours eager evaluation??

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• responsibility for storage

  - by Stefano Borini

  A colleague and I were brainstorming about where to put the responsibility of an object to store itself on the disk in our own file format. There are basically two choices: object.store(file) fileformatWriter.store(object) The first one gives the responsibility of serialization on the disk to the object itself. This is similar to the approach used by python pickle. The second groups the representation responsibility on a file format writer object. The data object is just a plain data container (eventually with additional methods not relevant for storage). We agreed on the second methodology, because it centralizes the writing logic from generic data. We also have cases of objects implementing complex logic that need to store info while the logic is in progress. For these cases, the fileformatwriter object can be passed and used as a delegate, calling storage operations on it. With the first pattern, the complex logic object would instead accept the raw file, and implement the writing logic itself. The first method, however, has the advantage that the object knows how to write and read itself from any file containing it, which may also be convenient. I would like to hear your opinion before starting a rather complex refactoring.

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• CircuitLab Offers Easy Circuit Building on the Web and iPad

  - by Jason Fitzpatrick

  If you like to sketch out your circuit designs rapidly, cleanly, and on the web or your iPad, CircuitLab makes it dead simple. The free tool includes an easy drag-and-drop interface, circuit analysis, easy printing, and more. Watch the video above to see the creators of CircuitLab whipping up a simple circuit to showcase the app, then hit up the link below to try it out. CircuitLab [via Hacked Gadgets] How to Make Your Laptop Choose a Wired Connection Instead of Wireless HTG Explains: What Is Two-Factor Authentication and Should I Be Using It? HTG Explains: What Is Windows RT and What Does It Mean To Me?

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• Why are Javascript for/in loops so verbose?

  - by Matthew Scharley

  I'm trying to understand the reasoning behind why the language designers would make the for (.. in ..) loops so verbose. For example: for (var x in Drupal.settings.module.stuff) { alert("Index: " + x + "\nValue: " + Drupal.settings.module.stuff[x]); } It makes trying to loop over anything semi-complex like the above a real pain as you either have to alias the value locally inside the loop yourself, or deal with long access calls. This is especially painful if you have two to three nested loops. I'm assuming there is a reason why they would do things this way, but I'm struggling with the reasoning.

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• Is event sourcing ready for prime time?

  - by Dakotah North

  Event Sourcing was popularized by LMAX as a means to provide speed, performance scalability, transparent persistence and transparent live mirroring. Before being rebranded as Event Sourcing, this type of architectural pattern was known as System Prevalence but yet I was never familiar with this pattern before the LMAX team went public. Has this pattern proved itself in numerous production systems and therefore even conservative individuals should feel empowered to embrace this pattern or is event sourcing / system prevalence an exotic pattern that is best left for the fearless?

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• DDD and Value Objects. Are mutable Value Objects a good candidate for Non Aggr. Root Entity?

  - by Tony

  Here is a little problem Have an entity, with a value object. Not a problem. I replace a value object for a new one, then nhibernate inserts the new value and orphan the old one, then deletes it. Ok, that's a problem. Insured is my entity in my domain. He has a collection of Addresses (value objects). One of the addresses is the MailingAddress. When we want to update the mailing address, let's say zipcode was wrong, following Mr. Evans doctrine, we must replace the old object for a new one since it's immutable (a value object right?). But we don't want to delete the row thou, because that address's PK is a FK in a MailingHistory table. So, following Mr. Evans doctrine, we are pretty much screwed here. Unless i make my addressses Entities, so i don't have to "replace" it, and simply update its zipcode member, like the old good days. What would you suggest me in this case? The way i see it, ValueObjects are only useful when you want to encapsulate a group of database table's columns (component in nhibernate). Everything that has a persistence id in the database, is better off to make it an Entity (not necessarily an aggregate root) so you can update its members without recreating the whole object graph, specially if that's a deep-nested object. Do you concur? Is it allowed by Mr. Evans to have a mutable value object? Or is a mutable value object a candidate for an Entity? Thanks

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• Solid principles vs YAGNI

  - by KeesDijk

  When do the SOLID principles become YAGNI? As programmers we make trade-offs all the time, between complexity, maintainability, time to build and so forth. Amongst others, two of the smartest guidelines for making choices are in my mind the SOLID principles and YAGNI. If you don't need it; don't build it, and keep it clean. Now for example, when I watch the dimecast series on SOLID, I see it starts out as a fairly simple program, and ends up as a pretty complex one (end yes complexity is also in the eye of the beholder), but it still makes me wonder: when do SOLID principles turn into something you don't need? All solid principles are ways of working that enable use to make changes at a later stage. But what if the problem to solve is a pretty simple one and it's a throwaway application, then what? Or are the SOLID principles something that always apply? As asked in the comments: Solid Principles YAGNI

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• How to "translate" interdependent object states in code?

  - by Earl Grey

  I have the following problem. My UI interace contains several buttons, labels, and other visual information. I am able to describe every possible workflow scenario that should be be allowed on that UI. That means I can describe it like this - when button A is pressed, the following should follow - In the case of that A button, there are three independent factors that influence the possible result when pushing the A button. The state of the session (blank, single, multi, multi special), the actual work that is being done by the system at the moment of pressing the A button (nothing was happening, work was being done, work was paused) and a separate UI element that has two states (on , off)..This gives me a 3 dimensional cube with 24 possible outcomes. I could write code for this using if cycles, switch cycles etc....but the problem is, I have another 7 buttons on that ui, I can enter this UI from different states..some buttons change the state, some change parameters... To sum up, the combinations are mindbogling and I am not able come up with a methodology that scales and is systematically reliable. I am able to describe EVERY workflow with words, I am sure my description is complete and without logical errors. But I am not able to translate that into code. I was trying to draw flowcharts but it soon became visually too complicated due to too many if "emafors". Can you advice how to proceeed?

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• Algorithm for dynamically calculating a level based on experience points?

  - by George

  One of the struggles I've always had in game development is deciding how to implement experience points attributed to gaining a level. There doesn't seem to be a pattern to gaining a level in many of the games I've played, so I assume they have a static dictionary table which contains experience points vs. the level. e.g. Experience Level 0 1 100 2 175 3 280 4 800 5 ...There isn't a rhyme or reason why 280 points is equal to level 4, it just is. I'm not sure how those levels are decided, but it certainly wouldn't be dynamic. I've also thought about the possibility of exponential levels, as not to have to keep a separate lookup table, e.g. Experience Level 0 1 100 2 200 3 400 4 800 5 1600 6 3200 7 6400 8 ...but that seems like it would grow out of control rather quickly, as towards the upper levels, the enemies in the game would have to provide a whopping amount of experience to level -- and that would be to difficult to control. Leveling would become an impossible task. Does anyone have any pointers, or methods they use to decide how to level a character based on experience? I want to be fair in leveling and I want to stay ahead of the players as not to worry about constantly adding new experience/level lookups.

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• Terrain sqaure loading

  - by AndroidXTr3meN

  Games like Skyrim, Morrowind, and more are using quads or sqaure to divide the terrain if im correct. The player is always at #5 1 | 2 | 3 4 | 5 | 6 7 | 8 | 9 So whenever you cross the border you unload and load the new "areas" But if the user goes just over the edge and then the second after goes back previous area a lot of uneccessary loading and unloading is done. Is there a general approach to this becuase I dont think games like skyrim have this issue? Cheers!

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• Simplifying C++11 optimal parameter passing when a copy is needed

  - by Mr.C64

  It seems to me that in C++11 lots of attention was made to simplify returning values from functions and methods, i.e.: with move semantics it's possible to simply return heavy-to-copy but cheap-to-move values (while in C++98/03 the general guideline was to use output parameters via non-const references or pointers), e.g.: // C++11 style vector<string> MakeAVeryBigStringList(); // C++98/03 style void MakeAVeryBigStringList(vector<string>& result); On the other side, it seems to me that more work should be done on input parameter passing, in particular when a copy of an input parameter is needed, e.g. in constructors and setters. My understanding is that the best technique in this case is to use templates and std::forward<>, e.g. (following the pattern of this answer on C++11 optimal parameter passing): class Person { std::string m_name; public: template <class T, class = typename std::enable_if < std::is_constructible<std::string, T>::value >::type> explicit Person(T&& name) : m_name(std::forward<T>(name)) { } ... }; A similar code could be written for setters. Frankly, this code seems boilerplate and complex, and doesn't scale up well when there are more parameters (e.g. if a surname attribute is added to the above class). Would it be possible to add a new feature to C++11 to simplify code like this (just like lambdas simplify C++98/03 code with functors in several cases)? I was thinking of a syntax with some special character, like @ (since introducing a &&& in addition to && would be too much typing :) e.g.: class Person { std::string m_name; public: /* Simplified syntax to produce boilerplate code like this: template <class T, class = typename std::enable_if < std::is_constructible<std::string, T>::value >::type> */ explicit Person(std::string@ name) : m_name(name) // implicit std::forward as well { } ... }; This would be very convenient also for more complex cases involving more parameters, e.g. Person(std::string@ name, std::string@ surname) : m_name(name), m_surname(surname) { } Would it be possible to add a simplified convenient syntax like this in C++? What would be the downsides of such a syntax?

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• What's the best Wireframing tool?

  - by Strae

  I'm looking for something similar to iPlotz or Mockup. I've found the Pencil Project, but it requires xulrunner-1.9 (which seems to be incompatible with xulrunner-1.9.2) in order to run as a standalone application. It can be used as a firefox plugin... but it is a bit slower. The error on my desktop (Ubuntu 10.04) is: Could not find compatible GRE between version 1.9.1 and 1.9.2.* Does anyone know other software? Edit: Open-source software is preferred, and it doesn't matter whether or not it's free.

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• Why do Windows Forms / Swing frameworks favour inheritance instead of Composition?

  - by devoured elysium

  Today a professor of mine commented that he found it odd that while SWT's philosophy is one of making your own controls by composition, Swing seems to favour inheritance. I have almost no contact with both frameworks, but from what I remember in C#'s Windows Forms one usually extends controls, just like Swing. Being that generally people tend to prefer composition over inheritance, why didn't Swing/Windows Forms folks favour composition instead of inheritance?

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• Help with this optimization

  - by Milo

  Here is what I do: I have bitmaps which I draw into another bitmap. The coordinates are from the center of the bitmap, thus on a 256 by 256 bitmap, an object at 0.0,0.0 would be drawn at 128,128 on the bitmap. I also found the furthest extent and made the bitmap size 2 times the extent. So if the furthest extent is 200,200 pixels, then the bitmap's size is 400,400. Unfortunately this is a bit inefficient. If a bitmap needs to be drawn at 500,500 and the other one at 300,300, then the target bitmap only needs to be 200,200 in size. I cannot seem to find a correct way to draw in the components correctly with a reduced size. I figure out the target bitmap size like this: float AvatarComposite::getFloatWidth(float& remainder) const { float widest = 0.0f; float widestNeg = 0.0f; for(size_t i = 0; i < m_components.size(); ++i) { if(m_components[i].getSprite() == NULL) { continue; } float w = m_components[i].getX() + ( ((m_components[i].getSprite()->getWidth() / 2.0f) * m_components[i].getScale()) / getWidthToFloat()); float wn = m_components[i].getX() - ( ((m_components[i].getSprite()->getWidth() / 2.0f) * m_components[i].getScale()) / getWidthToFloat()); if(w > widest) { widest = w; } if(wn > widest) { widest = wn; } if(w < widestNeg) { widestNeg = w; } if(wn < widestNeg) { widestNeg = wn; } } remainder = (2 * widest) - (widest - widestNeg); return widest - widestNeg; } And here is how I position and draw the bitmaps: int dw = m_components[i].getSprite()->getWidth() * m_components[i].getScale(); int dh = m_components[i].getSprite()->getHeight() * m_components[i].getScale(); int cx = (getWidth() + (m_remainderX * getWidthToFloat())) / 2; int cy = (getHeight() + (m_remainderY * getHeightToFloat())) / 2; cx -= m_remainderX * getWidthToFloat(); cy -= m_remainderY * getHeightToFloat(); int dx = cx + (m_components[i].getX() * getWidthToFloat()) - (dw / 2); int dy = cy + (m_components[i].getY() * getHeightToFloat()) - (dh / 2); g->drawScaledSprite(m_components[i].getSprite(),0.0f,0.0f, m_components[i].getSprite()->getWidth(),m_components[i].getSprite()->getHeight(),dx,dy, dw,dh,0); I basically store the difference between the original 2 * longest extent bitmap and the new optimized one, then I translate by that much which I would think would cause me to draw correctly but then some of the components look cut off. Any insight would help. Thanks

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• Ubuntu Software Centre Issue (unity 11.10) after broken sun-java6-jre package installation

  - by Stephen Myall

  I have been installing software packages from USC and I am getting the following error message. Worked fine one minute then the message below. Tried to search but couldn't find a solution Previously I was installing the sun-java6-jre package in terminal and had an connection outage and it didnt complete. I attempted an apt-get -f install with no success. i dont know what to try next. I'm relatively new to Linux. The answer provided with a similar question on this site didnt resolve the issue for meClick on this link An unhandlable error occured There seems to be a programming error in aptdaemon, the software that allows you to install/remove software and to perform other package management related tasks. Details File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 1092, in _simulate_helper return depends, self._cache.required_download, \ File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 235, in required_download pm.get_archives(fetcher, self._list, self._records) SystemError: E:I wasn't able to locate a file for the sun-java6-jre package. This might mean you need to manually fix this package. Terminal Output Link http://dl.dropbox.com/u/48466855/Terminal%20output.odt

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• Exclusive use of a Jini server during long-running call

  - by Matthew Flint

  I'm trying to use Jini, in a "Masters/Workers" arrangement, but the Worker jobs may be long running. In addition, each worker needs to have exclusive access to a singleton resource on that machine. As it stands, if a Worker receives another request while a previous request is running, then the new request is accepted and executed in a second thread. Are there any best-practices to ensure that a Worker accepts no further jobs until the current job is complete? Things I've considered: synchronize the job on the server, with a lock on the singleton resource. This would work, but is far from ideal. A call from a Master would block until the current Worker thread completes, even if other Workers become free in the meantime unregister the Worker from the registry while the job is running, then re-register when it completes. Might work OK, but something doesn't smell right with this idea... Of course, I'm quite happy to be told that there are more appropriate technologies than Jini... but I wouldn't want anything too heavyweight, like rolling out EJB containers all over the place.

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• Creating user UI using Flixel

  - by Jamie Read

  I am new to game development but familiar with programming languages. I have started using Flixel and have a working Breakout game with score and lives. What I am trying to do is add a Start Screen before actually loading the game. I have a create function that adds all the game elements to the stage: override public function create():void // all game elements { How can I add this pre-load Start Screen? I'm not sure if I have to add in the code to this create function or somewhere else and what code to actually add. Eventually I would also like to add saving, loading, options and upgrades too. So any advice with that would be great. Here is my main game.as: package { import org.flixel.*; public class Game extends FlxGame { private const resolution:FlxPoint = new FlxPoint(640, 480); private const zoom:uint = 2; private const fps:uint = 60; public function Game() { super(resolution.x / zoom, resolution.y / zoom, PlayState, zoom); FlxG.flashFramerate = fps; } } } Thanks.

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• How To Scale Canvas In Android

  - by Daniel Braithwaite

  I am writing a android game using Canvas as the way to draw everything, the problem is that when i run it on different android phones the canvas dosn't change size i tried using canvas.scale() but that didn't make a i difference. The code i use for drawing is ... public void draw( Canvas c, int score ) { Obstical2[] obstmp = Queue.toArray(this.o); Coin[] cointmp = QueueC.toArray(this.c); for( int i = 0; i < obstmp.length; i++ ) { obstmp[i].draw(c); } for( int i = 0; i < cointmp.length; i++ ) { cointmp[i].draw(c); } c.drawText(String.format("%d", score ), 20, 50, textPaint); if( isWon && isStarted ) c.drawText("YOU WON", 20, 400, resPaint); else if( isLost && isStarted ) c.drawText("YOU LOST", 20, 400, resPaint); } The function above calls the draw functions for the entity's on the screen, theses function are as follows Draw Function For Obstical : public void draw( Canvas c ) { Log.i("D", "COIN"); coin.draw(c); } Draw Function For Coin : public void draw( Canvas c ) { obstical.draw(c); } How could i make the canvas re-size to it would look the same on any screen ? Cheers Daniel

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• Making a Background Scrolling in Stacking Game

  - by David Dimalanta

  Hmmm...Is it a good idea to use a LibGDX parallax background for making a stacking game (i.e. PAPA STACKer Lite)? For example, I'm starting to use the blocks to drag-n-drop it. Next, when the next piece reaches the top of the screen, it automatically scrolls to the next one where the available space left. Aside from that, is it also involved with the camera code (Orthographic Camera) that the screen size appeared like 720x1280 but actually it's 1440x2560 for example? And another thing, does the background scrolling have the option to scroll from start to finish and infinite?

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• [News] Excursion dans le monde Java d'un (bon) d?veloppeur .NET

  Ayende, l'architecte principal de l'outil NHibernate a d?cid? il y a quelques temps de se former ? JEE pour parfaire ses connaissances. Dans ce billet, qui date de quelques jours, mais qui n'a pas ?t? ?norm?ment relay?, il d?crit son exp?rience. Le constat est assez cinglant et forc?ment emprunt d'une certaine partialit?, mais toujours tr?s int?ressant ? lire : (...) "All in all, I find myself unimpressed by the amount of work that was shuffled to the tools, it doesn?t seem right. And it seems like a justification of a bad practice. When I consider my own design principles (Zero Friction!) in light of this, I am much happier that I am mainly working in the .NET world. But I think that having this understanding is going to be very helpful moving forward"

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• Box2D how to implement a camera?

  - by Romeo

  By now i have this Camera class. package GameObjects; import main.Main; import org.jbox2d.common.Vec2; public class Camera { public int x; public int y; public int sx; public int sy; public static final float PIXEL_TO_METER = 50f; private float yFlip = -1.0f; public Camera() { x = 0; y = 0; sx = x + Main.APPWIDTH; sy = y + Main.APPHEIGHT; } public Camera(int x, int y) { this.x = x; this.y = y; sx = x + Main.APPWIDTH; sy = y + Main.APPHEIGHT; } public void update() { sx = x + Main.APPWIDTH; sy = y + Main.APPHEIGHT; } public void moveCam(int mx, int my) { if(mx >= 0 && mx <= 80) { this.x -= 2; } else if(mx <= Main.APPWIDTH && mx >= Main.APPWIDTH - 80) { this.x += 2; } if(my >= 0 && my <= 80) { this.y += 2; } else if(my <= Main.APPHEIGHT && my >= Main.APPHEIGHT - 80) { this.y -= 2; } this.update(); } public float meterToPixel(float meter) { return meter * PIXEL_TO_METER; } public float pixelToMeter(float pixel) { return pixel / PIXEL_TO_METER; } public Vec2 screenToWorld(Vec2 screenV) { return new Vec2(screenV.x + this.x, yFlip * screenV.y + this.y); } public Vec2 worldToScreen(Vec2 worldV) { return new Vec2(worldV.x - this.x, yFlip * worldV.y - this.y); } } I need to know how to modify the screenToWorld and worldToScreen functions to include the PIXEL_TO_METER scaling.

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• Why maven so slow compared to automake?

  - by ???'Lenik

  I have a Maven project consists of around 100 modules. I have reason to decompose the project to so many modules, and I don't think I should merge them in order to speed up the build process. I have read a lot of projects by other people, e.g., the Maven project itself, and Apache Archiva, and Hudson project, they all consists of a lot of modules, nearly 100 maybe, more or less. The problem is, to build them all need so much time, 3 hours for the first time build (this is acceptable because a lot of artifacts to download), and 15 minutes for the second build (this is not acceptable). For automake, things are similarly, the first time you need to configure the project, to prepare the magical config.h file, it's far more complex then what maven does. But it's still fast, maybe 10 seconds on my Debian box. After then, make install requires maybe 10 minutes for the first time build. However, when everything get prepared, the .o object files are generated, they don't have to be rebuild at all for the second time build. (In Maven, everything rebuild at everytime.) I'm very wondering, how guys working for Maven projects can bare this long time for each build, I'm just can't sit down calmly during each time Maven build, it took too long time, really.

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• Will a polled event system cause lag for a server?

  - by Milo

  I'm using a library called ENet. It is a reliable UDP library. The way it works is a polled event system like this: ENetEvent event; /* Wait up to 1000 milliseconds for an event. */ while (enet_host_service (client, & event, 1000) > 0) { switch (event.type) { case ENET_EVENT_TYPE_CONNECT: printf ("A new client connected from %x:%u.\n", event.peer -> address.host, event.peer -> address.port); /* Store any relevant client information here. */ event.peer -> data = "Client information"; break; case ENET_EVENT_TYPE_RECEIVE: printf ("A packet of length %u containing %s was received from %s on channel %u.\n", event.packet -> dataLength, event.packet -> data, event.peer -> data, event.channelID); /* Clean up the packet now that we're done using it. */ enet_packet_destroy (event.packet); break; case ENET_EVENT_TYPE_DISCONNECT: printf ("%s disconected.\n", event.peer -> data); /* Reset the peer's client information. */ event.peer -> data = NULL; } } It waits up to 1000 milliseconds for an event. If I'm hosting say 75 event driven card games and a lobby on the same thread as this code, will it cause any problems. If my understanding is correct, the process will simply sleep until there is an event, when there is one, it will process the event then come back here where potentially 5 or so events have queued up since so enet_host_services would return right away and not cause lag. I have been advised not to use multiple threads, will that be alright like this? Thanks

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• Draw Rectangle To All Dimensions of Image

  - by opiop65

  I have some rudimentary collision code: public class Collision { static boolean isColliding = false; static Rectangle player; static Rectangle female; public static void collision(){ Rectangle player = Game.Playerbounds(); Rectangle female = Game.Femalebounds(); if(player.intersects(female)){ isColliding = true; }else{ isColliding = false; } } } And this is the rectangle code: public static Rectangle Playerbounds() { return(new Rectangle(posX, posY, 25, 25)); } public static Rectangle Femalebounds() { return(new Rectangle(femaleX, femaleY, 25, 25)); } My InputHandling class: public static void movePlayer(GameContainer gc, int delta){ Input input = gc.getInput(); if(input.isKeyDown(input.KEY_W)){ Game.posY -= walkSpeed * delta; walkUp = true; if(Collision.isColliding == true){ Game.posY += walkSpeed * delta; } } if(input.isKeyDown(input.KEY_S)){ Game.posY += walkSpeed * delta; walkDown = true; if(Collision.isColliding == true){ Game.posY -= walkSpeed * delta; } } if(input.isKeyDown(input.KEY_D)){ Game.posX += walkSpeed * delta; walkRight = true; if(Collision.isColliding == true){ Game.posX -= walkSpeed * delta; } } if(input.isKeyDown(input.KEY_A)){ Game.posX -= walkSpeed * delta; walkLeft = true; if(Collision.isColliding == true){ Game.posX += walkSpeed * delta; } } } The code works partially. Only the right and top side of the images collide. How do I correct the rectangle so it will draw on all sides? Thanks for any suggestions!

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• Stop map from scrolling but let player still move?

  - by ChocoMan

  I have a basic method of scrolling around on a map (moving the map instead of the player), but at when the player gets to a certain proximity to the edge, how do you stop the map from scrolling, but still allow the player to move around until it is away from that proximity? I'm not looking for any code. Just a suggestion so that I can implement it myself. I can see it visually (creating 4 boxed intersecting boundaries for the player to enter), but not sure how to come about stopping and resuming the scrolling of the map.

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