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  • Why doesn't my GameMaker step event work?

    - by exceltior
    So I want to make some kind of floor that which the player when walks in gets his movement reduced but im having thousand of different issues implementing this since it doesnt appear to do anything ... So i have tried different way: 1 - I have tried Step Event which had the following script: if keyboard_check(ord('A')) { player.x = -5; } if keyboard_check(ord('D')) { player.x = -5; } if keyboard_check(ord('W')) { player.x = -5; } if keyboard_check(ord('S')) { player.x = -5; } 2 - I have tried a Collision Event with the same code 3- I have tried a Step event with collision detection on a script None of these options seem to work at all ... Can you help me?

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  • How do engines avoid "Phase Lock" (multiple objects in same location) in a Physics Engine?

    - by C0M37
    Let me explain Phase Lock first: When two objects of non zero mass occupy the same space but have zero energy (no velocity). Do they bump forever with zero velocity resolution vectors or do they just stay locked together until an outside force interacts? In my home brewed engine, I realized that if I loaded a character into a tree and moved them, they would signal a collision and hop back to their original spot. I suppose I could fix this by implementing impulses in the event of a collision instead of just jumping back to the last spot I was in (my implementation kind of sucks). But while I make my engine more robust, I'm just curious on how most other physics engines handle this case. Do objects that start in the same spot with no movement speed just shoot out from each other in a random direction? Or do they sit there until something happens? Which option is generally the best approach?

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  • Making more complicated systems(entity-component-system model question)

    - by winch
    I'm using a model where entities are collections of components and components are just data. All the logic goes into systems which operate on components. Making basic systems(for Rendering and handling collision) was easy. But how do I do more compilcated systems? For example, in a CollisionSystem I can check if entity A collides with entity B. I have this code in CollisionSystem for checking if B damages A: if(collides(a, b)) { HealthComponent* hc = a->get<HealthComponent(); hc.reduceHealth(b->get<DamageComponent>()->getDamage()); But I feel that this code shouldn't belong to Collision system. Where should code like this be and which additional systems should I create to make this code generic?

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  • How to perform efficient 2D picking in HTML5?

    - by jSepia
    I'm currently using an R-Tree for both picking and collision testing. Each entity on screen has a bounding box for collisions and a separate one for picking. Since entities may change position very frequently, both trees must be updated/reordered once per frame. While this is very efficient for collisions, because the tree is used in hundreds of collision queries every frame, I'm finding it too costly for picking, because it only gets queried when the user clicks, thus leading to a lot of wasted tree updates. What would be a more efficient way to implement picking without as much overhead?

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  • How can I get my meshes to work with Bullet Physics?

    - by Molmasepic
    The problem is that I'm trying to use my meshes with Bullet Physics for the collision part of my game. When I attempted doing this method with my GLM(model loading library by nate robins) model, I get a segmentation fault in the debug, so I figured that it doesnt like the coordinate variables of the model. If i use blender to export my model as a collision file, what type of file should I use? I have heard of a .bullet exporter, but i dont know hot to integrate this python script into my Blender 2.5 program.

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  • How to implement the light trails for a tron game?

    - by Link
    Well I was creating a TRON style game, but had an issue with creating the actual light trails for the game. What I'm doing currently is I have an array the same size as my window in pixel size, implemented like this: int* collision[800][600]; Then when the bike goes on a certain pixel, it is marked with a 1 for traveled on. However what is the most efficient way to create a working light trail display? I tried to do something like this: int i, j; for(i=0; i<800; i++) for(j=0; j<600; j++) if(*collision[i][j] == 1) Image::applySurface(i, j, trailSurface, gameScreen); But it isn't working properly? It just fills the whole screen with a sprite instead. Whats a better/faster/working way to do this?

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  • Sprite rotation

    - by Kipras
    I'm using OpenGL and people suggest using glRotate for sprite rotation, but I find that strange. My problem with it is that it rotates the whole matrix, which sort of screws up all my collision detection and so on and so forth. Imagine I had a sprite at position (100, 100) and in position (100, 200) is an obstacle and the sprite's facing it. I rotate the sprite away from the obstacle and when move upwards my y axis, even though the projection shows like it's going away from the obstacle, the sprite will intersect it. So I don't see another way of a rotating a sprite and not screwing up all collision detection other than doing mathematical operations on the image itself. Am I right or am I missing something?

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  • What Java class should I use to represent a Vector?

    - by user8363
    Does Java have a built-in Vector class suitable for handling collision detection / response? It should have methods like subtract(Vector v), normalize(), dotProduct(Vector v), ... It seems logical to use java.awt.Rectangle and java.awt.Polygon to calculate collisions. Would I be right to use these classes for this purpose? I understand collision detection; I'm only wondering what approach to it is idiomatic in Java. I'm new to the language and to application development in general.

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  • Get available screen area in autohotkey

    - by Herms
    I'm trying to write a few simple AutoHotkey scripts for moving windows around, and I'm having trouble getting the correct screen size values. I'm trying to get the size of the usable area on the screen (generally the full screen resolution minus the taskbar, and maybe any other docked windows like the sidebar in Vista). Neither of the methods I've found for getting the screen width seems to work. None of the 3 methods I found to get the screen size are giving me the right values. Here's the test script I'm using (running on XP with the taskbar on the bottom at its default size): #7:: WinMove A,,0,0,A_ScreenWidth,A_ScreenHeight return #8:: ;SM_CXMAXIMIZED and SM_CYMAXIMIZED SysGet, ScreenWidth, 61 SysGet, ScreenHeight, 62 WinMove A,,0,0,ScreenWidth,ScreenHeight return #9:: ;SM_CXFULLSCREEN and SM_CYFULLSCREEN SysGet, ScreenWidth, 16 SysGet, ScreenHeight, 17 WinMove A,,0,0,ScreenWidth,ScreenHeight return #7 causes the window to take up the entire resolution, so it overlaps the taskbar. #8 causes the width to be larger than the resolution (I see the window's right edge show up on my secondary monitor) and the height is slightly too large, so the window partially overlaps the taskbar area. Looks like this is correct except for not taking into account the window decorations at the edges. #9 seems to have the correct width, but the height is too short. It looks like it's subtracting the taskbar's height from the resolution's height, but then subtracting another 30 pixels from it. I could just use what I have in #9 and add 30 to the height I get, but that feels too much like a hack that would break in other configurations. It seems like there has to be a way to get the available screen size properly, but I can't find it in AutoHotkey. For reference, this seems to give me what I need in Java: Toolkit.getDefaultToolkit().getScreenSize();

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  • How big can I make an Android application's canvas in terms of pixels?

    - by user279112
    I've determined an estimate of the size of my Android emulator's screen in pixels, although I think its resolution can be changed to other numbers. Quite frankly though that doesn't eliminate the general problem of not knowing how many pixels on each axis I have to work with on my Android applications in general. The main problem I'm trying to solve is this: How do I make sure I don't use a faulty resolution on Android applications if I want to keep things' sizes constant (so that if the application screen shrinks, for instances, objects will still show up just as big - there just won't be as many of them being shown) if I wish to do this with a single universal resolution for each program? Failing that, how do I make sure everything's alright if I try to do everything the same way with maybe a few different pre-set resolutions? Mainly it seems like a relevant question that must be answered before I can come across a complete answer for the general problem is how big can I always make my application in pixels, NOT regarding if and when a user resizes the application's screen to something smaller than the maximum size permitted by the phone and its operating system. I really want to try to keep this simple. If I were doing this for a modern desktop, for instance, I know that if I design the application with a 800x600 canvas, the user can still shrink the application to the point they're not doing themselves any favors, but at least I can basically count on it working right and not being too big for the monitor or something. Is there such a magic resolution for Android, assuming that I'm designing for API levels 3+ (Android 1.5+)? Thanks

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  • remove versioning on boost xml serialization

    - by cppanda
    hi, i just can't find a way to remove the version tracking from the boost xmlarchives. example <Settings class_id="0" tracking_level="0" version="1"> <px class_id="1" tracking_level="1" version="0" object_id="_0"> <TestInt>3</TestInt> <Resolution class_id="2" tracking_level="0" version="0"> <x>800</x> <y>600</y> </Resolution> <SomeStuff>0</SomeStuff> </px> </Settings> I want to get ride of the class_id="0" tracking_level="0" version="1" stuff, because for in this case i just don't need it and want a simple clean config like file code void serialize(Archive & ar, const unsigned int version) { ar & make_nvp("TestInt", TestInt); ar & make_nvp("Resolution", resolution); ar & make_nvp("SomeStuff", SomeStuff); } i found boost::serialization::track_never, but nowhere to use it

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  • DirectShow: Video-Preview and Image (with working code)

    - by xsl
    Questions / Issues If someone can recommend me a good free hosting site I can provide the whole project file. As mentioned in the text below the TakePicture() method is not working properly on the HTC HD 2 device. It would be nice if someone could look at the code below and tell me if it is right or wrong what I'm doing. Introduction I recently asked a question about displaying a video preview, taking camera image and rotating a video stream with DirectShow. The tricky thing about the topic is, that it's very hard to find good examples and the documentation and the framework itself is very hard to understand for someone who is new to windows programming and C++ in general. Nevertheless I managed to create a class that implements most of this features and probably works with most mobile devices. Probably because the DirectShow implementation depends a lot on the device itself. I could only test it with the HTC HD and HTC HD2, which are known as quite incompatible. HTC HD Working: Video preview, writing photo to file Not working: Set video resolution (CRASH), set photo resolution (LOW quality) HTC HD 2 Working: Set video resolution, set photo resolution Problematic: Video Preview rotated Not working: Writing photo to file To make it easier for others by providing a working example, I decided to share everything I have got so far below. I removed all of the error handling for the sake of simplicity. As far as documentation goes, I can recommend you to read the MSDN documentation, after that the code below is pretty straight forward. void Camera::Init() { CreateComObjects(); _captureGraphBuilder->SetFiltergraph(_filterGraph); InitializeVideoFilter(); InitializeStillImageFilter(); } Dipslay a video preview (working with any tested handheld): void Camera::DisplayVideoPreview(HWND windowHandle) { IVideoWindow *_vidWin; _filterGraph->QueryInterface(IID_IMediaControl,(void **) &_mediaControl); _filterGraph->QueryInterface(IID_IVideoWindow, (void **) &_vidWin); _videoCaptureFilter->QueryInterface(IID_IAMVideoControl, (void**) &_videoControl); _captureGraphBuilder->RenderStream(&PIN_CATEGORY_PREVIEW, &MEDIATYPE_Video, _videoCaptureFilter, NULL, NULL); CRect rect; long width, height; GetClientRect(windowHandle, &rect); _vidWin->put_Owner((OAHWND)windowHandle); _vidWin->put_WindowStyle(WS_CHILD | WS_CLIPSIBLINGS); _vidWin->get_Width(&width); _vidWin->get_Height(&height); height = rect.Height(); _vidWin->put_Height(height); _vidWin->put_Width(rect.Width()); _vidWin->SetWindowPosition(0,0, rect.Width(), height); _mediaControl->Run(); } HTC HD2: If set SetPhotoResolution() is called FindPin will return E_FAIL. If not, it will create a file full of null bytes. HTC HD: Works void Camera::TakePicture(WCHAR *fileName) { CComPtr<IFileSinkFilter> fileSink; CComPtr<IPin> stillPin; CComPtr<IUnknown> unknownCaptureFilter; CComPtr<IAMVideoControl> videoControl; _imageSinkFilter.QueryInterface(&fileSink); fileSink->SetFileName(fileName, NULL); _videoCaptureFilter.QueryInterface(&unknownCaptureFilter); _captureGraphBuilder->FindPin(unknownCaptureFilter, PINDIR_OUTPUT, &PIN_CATEGORY_STILL, &MEDIATYPE_Video, FALSE, 0, &stillPin); _videoCaptureFilter.QueryInterface(&videoControl); videoControl->SetMode(stillPin, VideoControlFlag_Trigger); } Set resolution: Works great on HTC HD2. HTC HD won't allow SetVideoResolution() and only offers one low resolution photo resolution: void Camera::SetVideoResolution(int width, int height) { SetResolution(true, width, height); } void Camera::SetPhotoResolution(int width, int height) { SetResolution(false, width, height); } void Camera::SetResolution(bool video, int width, int height) { IAMStreamConfig *config; config = NULL; if (video) { _captureGraphBuilder->FindInterface(&PIN_CATEGORY_PREVIEW, &MEDIATYPE_Video, _videoCaptureFilter, IID_IAMStreamConfig, (void**) &config); } else { _captureGraphBuilder->FindInterface(&PIN_CATEGORY_STILL, &MEDIATYPE_Video, _videoCaptureFilter, IID_IAMStreamConfig, (void**) &config); } int resolutions, size; VIDEO_STREAM_CONFIG_CAPS caps; config->GetNumberOfCapabilities(&resolutions, &size); for (int i = 0; i < resolutions; i++) { AM_MEDIA_TYPE *mediaType; if (config->GetStreamCaps(i, &mediaType, reinterpret_cast<BYTE*>(&caps)) == S_OK ) { int maxWidth = caps.MaxOutputSize.cx; int maxHeigth = caps.MaxOutputSize.cy; if(maxWidth == width && maxHeigth == height) { VIDEOINFOHEADER *info = reinterpret_cast<VIDEOINFOHEADER*>(mediaType->pbFormat); info->bmiHeader.biWidth = maxWidth; info->bmiHeader.biHeight = maxHeigth; info->bmiHeader.biSizeImage = DIBSIZE(info->bmiHeader); config->SetFormat(mediaType); DeleteMediaType(mediaType); break; } DeleteMediaType(mediaType); } } } Other methods used to build the filter graph and create the COM objects: void Camera::CreateComObjects() { CoInitialize(NULL); CoCreateInstance(CLSID_CaptureGraphBuilder, NULL, CLSCTX_INPROC_SERVER, IID_ICaptureGraphBuilder2, (void **) &_captureGraphBuilder); CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, IID_IGraphBuilder, (void **) &_filterGraph); CoCreateInstance(CLSID_VideoCapture, NULL, CLSCTX_INPROC, IID_IBaseFilter, (void**) &_videoCaptureFilter); CoCreateInstance(CLSID_IMGSinkFilter, NULL, CLSCTX_INPROC, IID_IBaseFilter, (void**) &_imageSinkFilter); } void Camera::InitializeVideoFilter() { _videoCaptureFilter->QueryInterface(&_propertyBag); wchar_t deviceName[MAX_PATH] = L"\0"; GetDeviceName(deviceName); CComVariant comName = deviceName; CPropertyBag propertyBag; propertyBag.Write(L"VCapName", &comName); _propertyBag->Load(&propertyBag, NULL); _filterGraph->AddFilter(_videoCaptureFilter, L"Video Capture Filter Source"); } void Camera::InitializeStillImageFilter() { _filterGraph->AddFilter(_imageSinkFilter, L"Still image filter"); _captureGraphBuilder->RenderStream(&PIN_CATEGORY_STILL, &MEDIATYPE_Video, _videoCaptureFilter, NULL, _imageSinkFilter); } void Camera::GetDeviceName(WCHAR *deviceName) { HRESULT hr = S_OK; HANDLE handle = NULL; DEVMGR_DEVICE_INFORMATION di; GUID guidCamera = { 0xCB998A05, 0x122C, 0x4166, 0x84, 0x6A, 0x93, 0x3E, 0x4D, 0x7E, 0x3C, 0x86 }; di.dwSize = sizeof(di); handle = FindFirstDevice(DeviceSearchByGuid, &guidCamera, &di); StringCchCopy(deviceName, MAX_PATH, di.szLegacyName); } Full header file: #ifndef __CAMERA_H__ #define __CAMERA_H__ class Camera { public: void Init(); void DisplayVideoPreview(HWND windowHandle); void TakePicture(WCHAR *fileName); void SetVideoResolution(int width, int height); void SetPhotoResolution(int width, int height); private: CComPtr<ICaptureGraphBuilder2> _captureGraphBuilder; CComPtr<IGraphBuilder> _filterGraph; CComPtr<IBaseFilter> _videoCaptureFilter; CComPtr<IPersistPropertyBag> _propertyBag; CComPtr<IMediaControl> _mediaControl; CComPtr<IAMVideoControl> _videoControl; CComPtr<IBaseFilter> _imageSinkFilter; void GetDeviceName(WCHAR *deviceName); void InitializeVideoFilter(); void InitializeStillImageFilter(); void CreateComObjects(); void SetResolution(bool video, int width, int height); }; #endif

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  • New features of C# 4.0

    This article covers New features of C# 4.0. Article has been divided into below sections. Introduction. Dynamic Lookup. Named and Optional Arguments. Features for COM interop. Variance. Relationship with Visual Basic. Resources. Other interested readings… 22 New Features of Visual Studio 2008 for .NET Professionals 50 New Features of SQL Server 2008 IIS 7.0 New features Introduction It is now close to a year since Microsoft Visual C# 3.0 shipped as part of Visual Studio 2008. In the VS Managed Languages team we are hard at work on creating the next version of the language (with the unsurprising working title of C# 4.0), and this document is a first public description of the planned language features as we currently see them. Please be advised that all this is in early stages of production and is subject to change. Part of the reason for sharing our plans in public so early is precisely to get the kind of feedback that will cause us to improve the final product before it rolls out. Simultaneously with the publication of this whitepaper, a first public CTP (community technology preview) of Visual Studio 2010 is going out as a Virtual PC image for everyone to try. Please use it to play and experiment with the features, and let us know of any thoughts you have. We ask for your understanding and patience working with very early bits, where especially new or newly implemented features do not have the quality or stability of a final product. The aim of the CTP is not to give you a productive work environment but to give you the best possible impression of what we are working on for the next release. The CTP contains a number of walkthroughs, some of which highlight the new language features of C# 4.0. Those are excellent for getting a hands-on guided tour through the details of some common scenarios for the features. You may consider this whitepaper a companion document to these walkthroughs, complementing them with a focus on the overall language features and how they work, as opposed to the specifics of the concrete scenarios. C# 4.0 The major theme for C# 4.0 is dynamic programming. Increasingly, objects are “dynamic” in the sense that their structure and behavior is not captured by a static type, or at least not one that the compiler knows about when compiling your program. Some examples include a. objects from dynamic programming languages, such as Python or Ruby b. COM objects accessed through IDispatch c. ordinary .NET types accessed through reflection d. objects with changing structure, such as HTML DOM objects While C# remains a statically typed language, we aim to vastly improve the interaction with such objects. A secondary theme is co-evolution with Visual Basic. Going forward we will aim to maintain the individual character of each language, but at the same time important new features should be introduced in both languages at the same time. They should be differentiated more by style and feel than by feature set. The new features in C# 4.0 fall into four groups: Dynamic lookup Dynamic lookup allows you to write method, operator and indexer calls, property and field accesses, and even object invocations which bypass the C# static type checking and instead gets resolved at runtime. Named and optional parameters Parameters in C# can now be specified as optional by providing a default value for them in a member declaration. When the member is invoked, optional arguments can be omitted. Furthermore, any argument can be passed by parameter name instead of position. COM specific interop features Dynamic lookup as well as named and optional parameters both help making programming against COM less painful than today. On top of that, however, we are adding a number of other small features that further improve the interop experience. Variance It used to be that an IEnumerable<string> wasn’t an IEnumerable<object>. Now it is – C# embraces type safe “co-and contravariance” and common BCL types are updated to take advantage of that. Dynamic Lookup Dynamic lookup allows you a unified approach to invoking things dynamically. With dynamic lookup, when you have an object in your hand you do not need to worry about whether it comes from COM, IronPython, the HTML DOM or reflection; you just apply operations to it and leave it to the runtime to figure out what exactly those operations mean for that particular object. This affords you enormous flexibility, and can greatly simplify your code, but it does come with a significant drawback: Static typing is not maintained for these operations. A dynamic object is assumed at compile time to support any operation, and only at runtime will you get an error if it wasn’t so. Oftentimes this will be no loss, because the object wouldn’t have a static type anyway, in other cases it is a tradeoff between brevity and safety. In order to facilitate this tradeoff, it is a design goal of C# to allow you to opt in or opt out of dynamic behavior on every single call. The dynamic type C# 4.0 introduces a new static type called dynamic. When you have an object of type dynamic you can “do things to it” that are resolved only at runtime: dynamic d = GetDynamicObject(…); d.M(7); The C# compiler allows you to call a method with any name and any arguments on d because it is of type dynamic. At runtime the actual object that d refers to will be examined to determine what it means to “call M with an int” on it. The type dynamic can be thought of as a special version of the type object, which signals that the object can be used dynamically. It is easy to opt in or out of dynamic behavior: any object can be implicitly converted to dynamic, “suspending belief” until runtime. Conversely, there is an “assignment conversion” from dynamic to any other type, which allows implicit conversion in assignment-like constructs: dynamic d = 7; // implicit conversion int i = d; // assignment conversion Dynamic operations Not only method calls, but also field and property accesses, indexer and operator calls and even delegate invocations can be dispatched dynamically: dynamic d = GetDynamicObject(…); d.M(7); // calling methods d.f = d.P; // getting and settings fields and properties d[“one”] = d[“two”]; // getting and setting thorugh indexers int i = d + 3; // calling operators string s = d(5,7); // invoking as a delegate The role of the C# compiler here is simply to package up the necessary information about “what is being done to d”, so that the runtime can pick it up and determine what the exact meaning of it is given an actual object d. Think of it as deferring part of the compiler’s job to runtime. The result of any dynamic operation is itself of type dynamic. Runtime lookup At runtime a dynamic operation is dispatched according to the nature of its target object d: COM objects If d is a COM object, the operation is dispatched dynamically through COM IDispatch. This allows calling to COM types that don’t have a Primary Interop Assembly (PIA), and relying on COM features that don’t have a counterpart in C#, such as indexed properties and default properties. Dynamic objects If d implements the interface IDynamicObject d itself is asked to perform the operation. Thus by implementing IDynamicObject a type can completely redefine the meaning of dynamic operations. This is used intensively by dynamic languages such as IronPython and IronRuby to implement their own dynamic object models. It will also be used by APIs, e.g. by the HTML DOM to allow direct access to the object’s properties using property syntax. Plain objects Otherwise d is a standard .NET object, and the operation will be dispatched using reflection on its type and a C# “runtime binder” which implements C#’s lookup and overload resolution semantics at runtime. This is essentially a part of the C# compiler running as a runtime component to “finish the work” on dynamic operations that was deferred by the static compiler. Example Assume the following code: dynamic d1 = new Foo(); dynamic d2 = new Bar(); string s; d1.M(s, d2, 3, null); Because the receiver of the call to M is dynamic, the C# compiler does not try to resolve the meaning of the call. Instead it stashes away information for the runtime about the call. This information (often referred to as the “payload”) is essentially equivalent to: “Perform an instance method call of M with the following arguments: 1. a string 2. a dynamic 3. a literal int 3 4. a literal object null” At runtime, assume that the actual type Foo of d1 is not a COM type and does not implement IDynamicObject. In this case the C# runtime binder picks up to finish the overload resolution job based on runtime type information, proceeding as follows: 1. Reflection is used to obtain the actual runtime types of the two objects, d1 and d2, that did not have a static type (or rather had the static type dynamic). The result is Foo for d1 and Bar for d2. 2. Method lookup and overload resolution is performed on the type Foo with the call M(string,Bar,3,null) using ordinary C# semantics. 3. If the method is found it is invoked; otherwise a runtime exception is thrown. Overload resolution with dynamic arguments Even if the receiver of a method call is of a static type, overload resolution can still happen at runtime. This can happen if one or more of the arguments have the type dynamic: Foo foo = new Foo(); dynamic d = new Bar(); var result = foo.M(d); The C# runtime binder will choose between the statically known overloads of M on Foo, based on the runtime type of d, namely Bar. The result is again of type dynamic. The Dynamic Language Runtime An important component in the underlying implementation of dynamic lookup is the Dynamic Language Runtime (DLR), which is a new API in .NET 4.0. The DLR provides most of the infrastructure behind not only C# dynamic lookup but also the implementation of several dynamic programming languages on .NET, such as IronPython and IronRuby. Through this common infrastructure a high degree of interoperability is ensured, but just as importantly the DLR provides excellent caching mechanisms which serve to greatly enhance the efficiency of runtime dispatch. To the user of dynamic lookup in C#, the DLR is invisible except for the improved efficiency. However, if you want to implement your own dynamically dispatched objects, the IDynamicObject interface allows you to interoperate with the DLR and plug in your own behavior. This is a rather advanced task, which requires you to understand a good deal more about the inner workings of the DLR. For API writers, however, it can definitely be worth the trouble in order to vastly improve the usability of e.g. a library representing an inherently dynamic domain. Open issues There are a few limitations and things that might work differently than you would expect. · The DLR allows objects to be created from objects that represent classes. However, the current implementation of C# doesn’t have syntax to support this. · Dynamic lookup will not be able to find extension methods. Whether extension methods apply or not depends on the static context of the call (i.e. which using clauses occur), and this context information is not currently kept as part of the payload. · Anonymous functions (i.e. lambda expressions) cannot appear as arguments to a dynamic method call. The compiler cannot bind (i.e. “understand”) an anonymous function without knowing what type it is converted to. One consequence of these limitations is that you cannot easily use LINQ queries over dynamic objects: dynamic collection = …; var result = collection.Select(e => e + 5); If the Select method is an extension method, dynamic lookup will not find it. Even if it is an instance method, the above does not compile, because a lambda expression cannot be passed as an argument to a dynamic operation. There are no plans to address these limitations in C# 4.0. Named and Optional Arguments Named and optional parameters are really two distinct features, but are often useful together. Optional parameters allow you to omit arguments to member invocations, whereas named arguments is a way to provide an argument using the name of the corresponding parameter instead of relying on its position in the parameter list. Some APIs, most notably COM interfaces such as the Office automation APIs, are written specifically with named and optional parameters in mind. Up until now it has been very painful to call into these APIs from C#, with sometimes as many as thirty arguments having to be explicitly passed, most of which have reasonable default values and could be omitted. Even in APIs for .NET however you sometimes find yourself compelled to write many overloads of a method with different combinations of parameters, in order to provide maximum usability to the callers. Optional parameters are a useful alternative for these situations. Optional parameters A parameter is declared optional simply by providing a default value for it: public void M(int x, int y = 5, int z = 7); Here y and z are optional parameters and can be omitted in calls: M(1, 2, 3); // ordinary call of M M(1, 2); // omitting z – equivalent to M(1, 2, 7) M(1); // omitting both y and z – equivalent to M(1, 5, 7) Named and optional arguments C# 4.0 does not permit you to omit arguments between commas as in M(1,,3). This could lead to highly unreadable comma-counting code. Instead any argument can be passed by name. Thus if you want to omit only y from a call of M you can write: M(1, z: 3); // passing z by name or M(x: 1, z: 3); // passing both x and z by name or even M(z: 3, x: 1); // reversing the order of arguments All forms are equivalent, except that arguments are always evaluated in the order they appear, so in the last example the 3 is evaluated before the 1. Optional and named arguments can be used not only with methods but also with indexers and constructors. Overload resolution Named and optional arguments affect overload resolution, but the changes are relatively simple: A signature is applicable if all its parameters are either optional or have exactly one corresponding argument (by name or position) in the call which is convertible to the parameter type. Betterness rules on conversions are only applied for arguments that are explicitly given – omitted optional arguments are ignored for betterness purposes. If two signatures are equally good, one that does not omit optional parameters is preferred. M(string s, int i = 1); M(object o); M(int i, string s = “Hello”); M(int i); M(5); Given these overloads, we can see the working of the rules above. M(string,int) is not applicable because 5 doesn’t convert to string. M(int,string) is applicable because its second parameter is optional, and so, obviously are M(object) and M(int). M(int,string) and M(int) are both better than M(object) because the conversion from 5 to int is better than the conversion from 5 to object. Finally M(int) is better than M(int,string) because no optional arguments are omitted. Thus the method that gets called is M(int). Features for COM interop Dynamic lookup as well as named and optional parameters greatly improve the experience of interoperating with COM APIs such as the Office Automation APIs. In order to remove even more of the speed bumps, a couple of small COM-specific features are also added to C# 4.0. Dynamic import Many COM methods accept and return variant types, which are represented in the PIAs as object. In the vast majority of cases, a programmer calling these methods already knows the static type of a returned object from context, but explicitly has to perform a cast on the returned value to make use of that knowledge. These casts are so common that they constitute a major nuisance. In order to facilitate a smoother experience, you can now choose to import these COM APIs in such a way that variants are instead represented using the type dynamic. In other words, from your point of view, COM signatures now have occurrences of dynamic instead of object in them. This means that you can easily access members directly off a returned object, or you can assign it to a strongly typed local variable without having to cast. To illustrate, you can now say excel.Cells[1, 1].Value = "Hello"; instead of ((Excel.Range)excel.Cells[1, 1]).Value2 = "Hello"; and Excel.Range range = excel.Cells[1, 1]; instead of Excel.Range range = (Excel.Range)excel.Cells[1, 1]; Compiling without PIAs Primary Interop Assemblies are large .NET assemblies generated from COM interfaces to facilitate strongly typed interoperability. They provide great support at design time, where your experience of the interop is as good as if the types where really defined in .NET. However, at runtime these large assemblies can easily bloat your program, and also cause versioning issues because they are distributed independently of your application. The no-PIA feature allows you to continue to use PIAs at design time without having them around at runtime. Instead, the C# compiler will bake the small part of the PIA that a program actually uses directly into its assembly. At runtime the PIA does not have to be loaded. Omitting ref Because of a different programming model, many COM APIs contain a lot of reference parameters. Contrary to refs in C#, these are typically not meant to mutate a passed-in argument for the subsequent benefit of the caller, but are simply another way of passing value parameters. It therefore seems unreasonable that a C# programmer should have to create temporary variables for all such ref parameters and pass these by reference. Instead, specifically for COM methods, the C# compiler will allow you to pass arguments by value to such a method, and will automatically generate temporary variables to hold the passed-in values, subsequently discarding these when the call returns. In this way the caller sees value semantics, and will not experience any side effects, but the called method still gets a reference. Open issues A few COM interface features still are not surfaced in C#. Most notably these include indexed properties and default properties. As mentioned above these will be respected if you access COM dynamically, but statically typed C# code will still not recognize them. There are currently no plans to address these remaining speed bumps in C# 4.0. Variance An aspect of generics that often comes across as surprising is that the following is illegal: IList<string> strings = new List<string>(); IList<object> objects = strings; The second assignment is disallowed because strings does not have the same element type as objects. There is a perfectly good reason for this. If it were allowed you could write: objects[0] = 5; string s = strings[0]; Allowing an int to be inserted into a list of strings and subsequently extracted as a string. This would be a breach of type safety. However, there are certain interfaces where the above cannot occur, notably where there is no way to insert an object into the collection. Such an interface is IEnumerable<T>. If instead you say: IEnumerable<object> objects = strings; There is no way we can put the wrong kind of thing into strings through objects, because objects doesn’t have a method that takes an element in. Variance is about allowing assignments such as this in cases where it is safe. The result is that a lot of situations that were previously surprising now just work. Covariance In .NET 4.0 the IEnumerable<T> interface will be declared in the following way: public interface IEnumerable<out T> : IEnumerable { IEnumerator<T> GetEnumerator(); } public interface IEnumerator<out T> : IEnumerator { bool MoveNext(); T Current { get; } } The “out” in these declarations signifies that the T can only occur in output position in the interface – the compiler will complain otherwise. In return for this restriction, the interface becomes “covariant” in T, which means that an IEnumerable<A> is considered an IEnumerable<B> if A has a reference conversion to B. As a result, any sequence of strings is also e.g. a sequence of objects. This is useful e.g. in many LINQ methods. Using the declarations above: var result = strings.Union(objects); // succeeds with an IEnumerable<object> This would previously have been disallowed, and you would have had to to some cumbersome wrapping to get the two sequences to have the same element type. Contravariance Type parameters can also have an “in” modifier, restricting them to occur only in input positions. An example is IComparer<T>: public interface IComparer<in T> { public int Compare(T left, T right); } The somewhat baffling result is that an IComparer<object> can in fact be considered an IComparer<string>! It makes sense when you think about it: If a comparer can compare any two objects, it can certainly also compare two strings. This property is referred to as contravariance. A generic type can have both in and out modifiers on its type parameters, as is the case with the Func<…> delegate types: public delegate TResult Func<in TArg, out TResult>(TArg arg); Obviously the argument only ever comes in, and the result only ever comes out. Therefore a Func<object,string> can in fact be used as a Func<string,object>. Limitations Variant type parameters can only be declared on interfaces and delegate types, due to a restriction in the CLR. Variance only applies when there is a reference conversion between the type arguments. For instance, an IEnumerable<int> is not an IEnumerable<object> because the conversion from int to object is a boxing conversion, not a reference conversion. Also please note that the CTP does not contain the new versions of the .NET types mentioned above. In order to experiment with variance you have to declare your own variant interfaces and delegate types. COM Example Here is a larger Office automation example that shows many of the new C# features in action. using System; using System.Diagnostics; using System.Linq; using Excel = Microsoft.Office.Interop.Excel; using Word = Microsoft.Office.Interop.Word; class Program { static void Main(string[] args) { var excel = new Excel.Application(); excel.Visible = true; excel.Workbooks.Add(); // optional arguments omitted excel.Cells[1, 1].Value = "Process Name"; // no casts; Value dynamically excel.Cells[1, 2].Value = "Memory Usage"; // accessed var processes = Process.GetProcesses() .OrderByDescending(p =&gt; p.WorkingSet) .Take(10); int i = 2; foreach (var p in processes) { excel.Cells[i, 1].Value = p.ProcessName; // no casts excel.Cells[i, 2].Value = p.WorkingSet; // no casts i++; } Excel.Range range = excel.Cells[1, 1]; // no casts Excel.Chart chart = excel.ActiveWorkbook.Charts. Add(After: excel.ActiveSheet); // named and optional arguments chart.ChartWizard( Source: range.CurrentRegion, Title: "Memory Usage in " + Environment.MachineName); //named+optional chart.ChartStyle = 45; chart.CopyPicture(Excel.XlPictureAppearance.xlScreen, Excel.XlCopyPictureFormat.xlBitmap, Excel.XlPictureAppearance.xlScreen); var word = new Word.Application(); word.Visible = true; word.Documents.Add(); // optional arguments word.Selection.Paste(); } } The code is much more terse and readable than the C# 3.0 counterpart. Note especially how the Value property is accessed dynamically. This is actually an indexed property, i.e. a property that takes an argument; something which C# does not understand. However the argument is optional. Since the access is dynamic, it goes through the runtime COM binder which knows to substitute the default value and call the indexed property. Thus, dynamic COM allows you to avoid accesses to the puzzling Value2 property of Excel ranges. Relationship with Visual Basic A number of the features introduced to C# 4.0 already exist or will be introduced in some form or other in Visual Basic: · Late binding in VB is similar in many ways to dynamic lookup in C#, and can be expected to make more use of the DLR in the future, leading to further parity with C#. · Named and optional arguments have been part of Visual Basic for a long time, and the C# version of the feature is explicitly engineered with maximal VB interoperability in mind. · NoPIA and variance are both being introduced to VB and C# at the same time. VB in turn is adding a number of features that have hitherto been a mainstay of C#. As a result future versions of C# and VB will have much better feature parity, for the benefit of everyone. Resources All available resources concerning C# 4.0 can be accessed through the C# Dev Center. Specifically, this white paper and other resources can be found at the Code Gallery site. Enjoy! span.fullpost {display:none;}

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  • Ubuntu 10.04 external monitor problem

    - by Ricky
    I've just installed the 10.04 release on my laptop. I've also installed the nvidia propietary driver as suggested by the system. I've some problem using an external monitor, i'm not able to set the correct resolution using the nvidia-setting utiloty. It doesn't recognize the right resolution of my external monitor. Any advice please? :) I'm a newbie.

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  • Linux LiveCD (or LiveUSB) with custom xorg.conf

    - by Jakub Narebski
    Is there some Live Linux distribution (on CD, DVD or USB), which allow one to use specific xorg.conf file, i.e. specific X11 configuration? The problem I am trying to solve is to find Linux Live distribution for web browsing which would work well with NEC LCD 22WV monitor. It is supposedly DDCCCI capable, but X.Org X Window System autoconfiguration fails to detect proper modeline, and uses fallback 800x600 screen resolution, instead of preferred screen resolution of 1680x1050.

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  • Low framerate on background apps

    - by user1698923
    My problem is that when a game is running in the foreground, in Full Screen mode, any applications on my second monitor (such as youtube videos, videos, not app specific) drop their frame-rate to about 2-3 FPS. It seems like some sort of power management option that I can't track down. As far as I can tell, it's not due to the GPU not being able to keep up. For instance, my PC can play League of Legends at about 280FPS when the framerate is uncapped. If i cap it at 60FPS using the in-game option, it has no affect on the performance of the background app. Summary Operating System Windows 8 Pro 64-bit CPU Intel Core i7 3820 @ 3.60GHz 42 °C Sandy Bridge-E 32nm Technology RAM 12.0GB Triple-Channel DDR3 @ 533MHz (7-7-7-20) Motherboard Gigabyte Technology Co., Ltd. X79-UD3 (SOCKET 0) 37 °C Graphics DELL U2713HM (2560x1440@59Hz) DELL U2713HM (2560x1440@59Hz) 1280MB NVIDIA GeForce GTX 570 (Gigabyte) 58 °C Hard Drives 212GB Volume0 (RAID) 1863GB Western Digital WDC WD20EARS-00MVWB0 (SATA) 36 °C 1863GB Western Digital WDC WD20EARS-00MVWB0 (SATA) 34 °C Optical Drives No optical disk drives detected Audio ASUS Xonar Essence STX Audio Device Operating System Windows 8 Pro 64-bit Computer type: Desktop Graphics Monitor 1 Name DELL U2713HM on NVIDIA GeForce GTX 570 Current Resolution 2560x1440 pixels Work Resolution 2560x1400 pixels State Enabled, Output devices support Multiple displays Extended, Secondary, Enabled Monitor Width 2560 Monitor Height 1440 Monitor BPP 32 bits per pixel Monitor Frequency 59 Hz Device \\.\DISPLAY4\Monitor0 Monitor 2 Name DELL U2713HM on NVIDIA GeForce GTX 570 Current Resolution 2560x1440 pixels Work Resolution 2560x1400 pixels State Enabled, Output devices support Multiple displays Extended, Primary, Enabled Monitor Width 2560 Monitor Height 1440 Monitor BPP 32 bits per pixel Monitor Frequency 59 Hz Device \\.\DISPLAY5\Monitor0 NVIDIA GeForce GTX 570 Manufacturer NVIDIA Model GeForce GTX 570 GPU GF110 Device ID 10DE-1086 Revision A2 Subvendor Gigabyte (1458) Series GeForce GTX 500 Current Performance Level Level 3 Current GPU Clock 845 MHz Current Memory Clock 1900 MHz Current Shader Clock 1690 MHz Voltage 0.988 V Technology 40 nm Die Size 520 mm² Release Date Dec 07, 2010 DirectX Support 11.0 OpenGL Support 5.0 Bus Interface PCI Express x16 Temperature 57 °C Driver version 9.18.13.2018 BIOS Version 70.10.55.00.01 ROPs 40 Shaders 512 unified Memory Type GDDR5 Memory 1280 MB Bus Width 64x5 (320 bit) Filtering Modes 16x Anisotropic Noise Level Moderate Max Power Draw 219 Watts Count of performance levels : 3 Level 1 - "Default" GPU Clock 50 MHz Memory Clock 135 MHz Shader Clock 101 MHz Level 2 - "2D Desktop" GPU Clock 405 MHz Memory Clock 324 MHz Shader Clock 810 MHz Level 3 - "3D Applications" GPU Clock 845 MHz Memory Clock 1900 MHz Shader Clock 1690 MHz Things I've tried: 1) Updating the graphics driver 2) Setting windows power mode to High Performance 3) Reset Nvidia Global Performance settings to default

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  • Cant access a remote server due mistake by setting firewall rule

    - by LMIT
    I need help due a my silly mistake! So for long time i have a dedicate server hosted by register.it Usually i access remotly to this server (Windows 2008 server) by Terminal Server. Today i wanted to block one site that continually send request to my server. So i was adding a new rule in the firewall (the native firewall on windows 2008 server), as i did many time, but this time, probably i was sleeping with my brain i add a general rules that stop everything! So i cant access to the server anymore, as no any users can browse the sites, nothing is working because this rule block everything. I know that is a silly mistake, no need to tell me :) so please what i can do ? The only 1 thing that my provider let me is reboot the server by his control panel, but this not help me in any way because the firewall block me again. i have administrator username and password, so what i really can do ? there are some trick some tecnique, some expert guru that can help me in this very bad situation ? UPDATE i follow the Tony suggest and i did a NMAP to check if some ports are open but look like all closed: NMAP RESULT Starting Nmap 6.00 ( http://nmap.org ) at 2012-05-29 22:32 W. Europe Daylight Time NSE: Loaded 93 scripts for scanning. NSE: Script Pre-scanning. Initiating Parallel DNS resolution of 1 host. at 22:32 Completed Parallel DNS resolution of 1 host. at 22:33, 13.00s elapsed Initiating SYN Stealth Scan at 22:33 Scanning xxx.xxx.xxx.xxx [1000 ports] SYN Stealth Scan Timing: About 29.00% done; ETC: 22:34 (0:01:16 remaining) SYN Stealth Scan Timing: About 58.00% done; ETC: 22:34 (0:00:44 remaining) Completed SYN Stealth Scan at 22:34, 104.39s elapsed (1000 total ports) Initiating Service scan at 22:34 Initiating OS detection (try #1) against xxx.xxx.xxx.xxx Retrying OS detection (try #2) against xxx.xxx.xxx.xxx Initiating Traceroute at 22:34 Completed Traceroute at 22:35, 6.27s elapsed Initiating Parallel DNS resolution of 11 hosts. at 22:35 Completed Parallel DNS resolution of 11 hosts. at 22:35, 13.00s elapsed NSE: Script scanning xxx.xxx.xxx.xxx. Initiating NSE at 22:35 Completed NSE at 22:35, 0.00s elapsed Nmap scan report for xxx.xxx.xxx.xxx Host is up. All 1000 scanned ports on xxx.xxx.xxx.xxx are filtered Too many fingerprints match this host to give specific OS details TRACEROUTE (using proto 1/icmp) HOP RTT ADDRESS 1 ... ... ... 13 ... 30 NSE: Script Post-scanning. Read data files from: D:\Program Files\Nmap OS and Service detection performed. Please report any incorrect results at http://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 145.08 seconds Raw packets sent: 2116 (96.576KB) | Rcvd: 61 (4.082KB) Question: The provider locally can access by username and password ?

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  • How to backup or export PowerStrip display profiles?

    - by Sk8erPeter
    I would like to save two of my saved PowerStrip display profiles. Earlier I set 720x540 resolution and some other settings (frequency, etc.) to another display device usually used in extended mode, which is now NOT connected: But when I go to "Advanced timing options", I see some different settings. I thought I could copy settings with the copy icon , but this way I would copy the wrong ones, not the predefined ones (with the 720x540 resolution): What is the best method to "export" these settings before formatting the hard drive?

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  • Flickering issue in external monitor when used with Acer Aspire One D260 netbook (Intel GMA 3150)

    - by seyenne
    I recently purchased a Acer netbook, Aspire One D260. It runs flawlessly. Yesterday I bought a Samsung 23" TFT with a native resolution of 1920x1080. According to the information found in the internet and my local computer dealer, the Intel chipset can handle the native resolution of the monitor. However, this is only partly the case. I use the VGA cable to connect, the monitor instantly switches to the native resolution and now the problem: Occasionally, especially the first 2 hours after booting up, I have a flickering all over the screen, sometimes the entire screen is shaking and spinning around like crazy. I figured out that lowering the resolution avoids the flicker but this helps only for some time. I can rule out that it's the monitor's problem since I found no issues with another notebook. Right now, I have no problems with the netbook, for about 30 minutes I didn't experience any issues... But I don't know for how long, it occurs without warning :-) I'm worried that if I would bring the netbook back to the dealer and explain my problem, after testing it on an external screen in the local shop, everything works just fine... And I won't get helped with the problem because I can't prove it. (I'm currently in Thailand and over here, customer service is nothing like back home in Germany) What can I do? Is this a driver related issue? (I installed the latest GPU driver) Is it because of the VGA cable? (But why does it work sometimes without any problems and with no issues on the other notebook) I monitored the GPU/CPU temperature, nothing changes really over time.. Can it simply be a faulty GPU and is a replacement justifiable? I'm really stressed now because for the time I'm writing, the flickering didn't occur... but for sure, soon or later it will happen again.. I forgot to mention, the problem also happens if the netbook runs on battery, unplugged. So the only hardware that is plugged is the TFT screen. ...........and here it comes again, flickering has just begun. NEED HELP! Thank you all for reading through this and giving any suggestions if possible. Cheers

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  • Matching monitors

    - by JC
    Does anyone know a good matching monitor setup for multiple displays? Looking for 1920 x 1200 with IPS panel as the main screen and some 1600 x 1200 monitor for the side but no single manufacturer seems to make monitors that match like this. Do you all just deal with the resolution and size differences in multi setups or has anyone found decent IPS panel setups that match (size / vertical resolution)? Three 1920x1200 seems like overkill, that's why I was looking for 4:3 monitors for the sides.

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  • text size on 15.6" and 17.3" laptop screens

    - by Joshi
    I'm I correct in assuming that the size of text etc will be the same on: 17.3" screen with native resolution of 1600x900 15.6" screen with native resolution of 1366x768 The DPI for screen 1 is 106; for screen 2 it's 100 which is near enough the same. So the only real difference is that I could get more text (of the same size) on each line and more lines on the 17.3" screen???? Have I understood this correctly?

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  • Routing and arp

    - by adolgarev
    If I have >ip ro 192.168.14.0/24 dev eth0 another host can obtain my mac address. But if I flush routing info: >ip ro flush table main arp resolution doesn't work. Broadcast packets "Who has 192.168.14.149" reach eth0 but OS (Linux) doesn't respond despite eth0 has address 192.168.14.149. What connection exists between routing and arp resolution?

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  • Force gdm login screen to the primary monitor

    - by JIa3ep
    I have two monitors attached to my video card. Primary monitor has a resolution equal to 1280x1024 and second has 1920x1200. My gdm login screen always appears on the second monitor even if it is switched off. My question is how to force gdm to show login screen always on primary monitor with resolution 1280x1024? I use Ubuntu 10.04.

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  • Can Linux play HDMI 1.4a 3D stereoscopic content?

    - by SofaKng
    I'm aware that there are no Bluray players for Linux but I'm wondering if it's possible to play Full 3D HD (1080p, Side-By-Side) MKV files (or Bluray BDMV folders, etc). Full 3D HD files are actually two 1080p frames "side-by-side" so the effective resolution is 3840x1200. In order to play these properly the software needs to switch to TV into 3D mode (or however HDMI 1.4a works). I don't think simply playing the 3840x1200 resolution file will work so are there any options out there?

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  • Is integrated graphics card Radeon HD 4200 capable to handle full HD?

    - by develroot
    I enjoy my integrated graphics card Radeon HD 4200 at resolution of 1280x1024 pixels on a 19" inches LG Flatron (5:4 aspect ratio) (playing FIFA 10 at max resolution, max quality). But recently i decided to upgrade my monitor and to get an 24" inches BENQ, 1920x1080, fullHD. Would I experience any problems with that graphics card on a such a big monitor? Usually I don't play games, just movies/music/and of programming, but it would be nice to be able to play some Counter Strike without artifacts.

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