I'd like to know whether applications designed for WinRT are run within a Virtual Machine or compiled in bytecode in order to be compiled once and run everywhere as the slogan says.
The slogan isn't that. WinRT apps rely on COM for runtime cross-environment calls and a metadata format (winmd) to describe the types.
A WinRT app can be fully native (as is most/all of the framework and even the XAML engine).
Individual DLLs or the app itself could be written in a .NET language, and it will interop almost seamlessly with the rest of WinRT thanks to the extended interop code added to the CLR. Under the hood, it's mostly COM interop as usual, but with added "projections" of chosen WinRT types. This is what makes a WinRT IVector look like an IList in .NET. They're just automatically wrapped.
The strength of WinRT is the binary method calling abstraction of COM and the metadata system (without which the language "projections" wouldn't exist). But it is definitely native, just like COM is, and you can stay in C++ without revving up the .NET CLR if you like.
I'm new to Chrome Application development and the Native Client/PNaCL pipeline. I'm a bit confused over the process of using existing C code/libraries in a chrome application. The FAQs and NaCL official docs suggest that using existing code is easy, and one of the advantages of developing Chrome applications.
However, there is also mention of nacl-ports, an official list of ported C libraries to be used in Native Client apps.
If I have some random C library I've used, what is the process for actually using it in my Chrome application? This question feels silly, but I'm quite confused over the process. Do I have to recompile the source with a NaCL compiler? Where in the SDK can I find this?
The FAQ also mentions that things like forks, file i/o is not allowed in the library, so I will have to rewrite any code that does these things, is that correct?
Bottomline: I have an existing C library. What is the process for using it correctly, and making calls to it, in a Chrome application?
The short answer is that you'll have to recompile your library with a NaCl C compiler.
You may want to take a look at naclports: this repository contains ports of many common C libraries to Native Client. You can browse the source more easily here.
As for File I/O, we often suggest using the nacl_io library when porting existing code. This provides a POSIX interface (e.g. fopen/fclose/fread, etc.) Many ported libraries require no modifications when using nacl_io.
I am looking for an alternative to swt for building the interface of an Eclipse plugin I want to develop.
Is it possible to build the interface of the plugin with JavaFX or HTML5 instead of swt ?.
I am targeting Eclipse Juno 4.2 or later.
Eclipse 4 defines an application model, i.e. a model of all the parts forming the application UI. The application model is decoupled from its presentation.
This means that different UI toolkits (SWT,XWT,JavaFX,etc.), can be used to implement the model. Theoretically you can build a UI using any presentation technology you want.
That said, Eclipse 4.2 (the IDE) still relies on good ol' SWT for it's UI. Which means, your plug-in will require some additional dependencies to be able to use a different toolkit.
e(fx)clipse (already mentioned by jewelsea), provides the necessary Eclipse tooling to build your plug-in. Among other things it plugs a JavaFX ViewPart plug-in template, which creates an example plug-in and adds the necessary bundle dependencies for you.
Imho, this would be your best bet.
There are lots of things going on, Eclipse versioning can be a bit confusing nowadays (at least for me), you can take a look at E4 but it is not widely used. It has the ability of desining UI with Eclipse RCP/CSS.
An other posibility is XWT. I've seen some business ready application using XWT so it seems to be mature enough. Even WindowBuilder can be used to build UI with XWT. Which is actually declarative UI constructing with XML. If you want to have only the OSGi "goodies" you can take a look at Apache Felix or Eclipse Virgo (Spring-powered). They are application servers based on OSGi so you can build module based enterprise applications.
Last but not least if you are OK with SWT/JFace but want to have web application, take a look at RAP. I have seen a full RCP application converted to RAP running in a regular browser.
I am trying to profile my app to see where I can tweak memory management and speed. I have read into Garbage collection and I am trying to use
GC::Profiler.enable
In my app. However when I call this in Jruby I am getting a
org.jruby.exceptions.RaiseException: (NameError) uninitialized
I know that the garbage collection is done in the JVM on Jruby - so this might be why it is not initialized Which makes sense, what is the alternative to use in Jruby?
That's a MRI specific API - there's not an API equivalent for JRuby probably due the way the JVM works (there are multiple GC strategies with most VMs and there's no consistent API to work with the GC, even a System.gc() call does not necessary trigger garbage-collection immediately).
But there's a standart monitoring API (called MX) available for Java applications and since your JRuby app is a Java app you can use those, of course you might need to understand some of the internals e.g. how your ruby classes are seen by the JVM, but it ain't that hard.
Try starting here: http://www.engineyard.com/blog/2010/monitoring-the-jvm-heap-with-jruby/
Here's a summary of Java tools available you can use with JRuby as well: http://blog.headius.com/2010/07/browsing-memory-jruby-way.html
Don't forget to check the wiki as well, e.g. there's a page on profiling object allocations:
https://github.com/jruby/jruby/wiki/Profiling-Object-Allocations
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I need some resources that talk about how to design your software to be extensible, i.e. so that other people can write add-ons/plug-ins that adds functionality to it.
What do you recommend? Any books out there that discuss the subject?
I would prefer something that's short and to the point; a bit of theory and a bunch of concrete examples.
I'm not targeting a specific language, I want to be able to understand the core idea so that I can implement it in any language.
And for the same reason, I prefer not to do it using a framework that someone else built (unless the framework is not very high-level, i.e. doesn't hide too much), at the moment I only want to educate myself on the subject and experiment with various ways to implement it. Plus, a framework usually assumes user's knowledge about the subject.
UPDATE
I'm not asking about OOP or allowing my classes to be inherited. I'm talking about designing an application that will be deployed on a system, such that it can be extended by third-party add-ons AFTER its been deployed.
For example, Notepad++ has a plug-in architecture where you can place a .dll file in the plugins folder, and it adds functionality to the application that wasn't there, such as color-picking, or snippet insertion, or many other things (a wide range of functionality).
IF we're talking .NET, try Scripting .NET applications with VBScript over on CodeProject. Lots of concrete examples there.
Below are sites implementing various application extension techniques
ClearScript - Makes V8, VBScript and JScript available to .NET apps
CS-Script - The C# Script Engine
Plugin Architecture using C#
Opinio plugin architecture
Notes on the Eclipse Plug-in Architecture
Plug-in Architecture Framework for Beginners
Gecko plugin architecture
Fungimol plugin architecture
OSGI is a good practical example of a technical framework allowing to do what you are after.
The theory is here.
The (free!) book is there.
Extensibility and the ability to write plugin must deal with service lifecycle
adding / removing service/plugin on the spot
managing dependencies between services
managing states of services (declared, installed, started, stopped,...)
What is OSGI for ?
One of the main functions of a module is as a unit of deployment… something that we can either build or download and install to extend the functionality of our application.
You will find a good introduction here, on the central notion of service (which is related to your question, and which explain some problems around services, key component for extensibility).
Extract:
Why are services then so important if so many applications can be built without them? Well, services are the best known way to decouple software components from each other.
One of the most important aspects of services is that they significantly minimize class loading problems because they work with instances of objects, not with class names. Instances that are created by the provider, not the consumer. The reduction of the complexity is quite surprising
Not only do services minimize configuration, they also significantly reduce the number of shared packages.
Implement SOLID principles in your application.
1. Single responsibility principle: A class should have only a single responsibility (i.e. only one potential change in the software's specification should be able to affect the specification of the class
2.Open/closed principle: Software entities … should be open for extension, but closed for modification
3. Liskov substitution principle: Objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program
4. Interface segregation principle: Many client-specific interfaces are better than one general-purpose interface
5. Dependency inversion principle: One should Depend upon Abstractions. Do not depend upon concretions
Stackoverflow questions:
Example of Single Responsibility Principle
Is the Open/Closed Principle a good idea?
What is the Liskov Substitution Principle?
Interface Segregation Principle- Program to an interface
What is the Dependency Inversion Principle and why is it important?
You try to reach two competing goals:
The components of your software must expose a lot of themselves, so they can be reused
The components of your software must expose very little of themselves, so they can be reused
Explanation: To encourage code reuse, you should be able to extend existing classes and call their methods. This isn't possible when the methods are declared "private" and the classes are "final" (and can't be extended). So to meet this goal, everything should be public and accessible. No private data or methods.
When you release the second version of your software, you will find that many of the ideas of version 1 were plain wrong. You need to change many interfaces or your code, method names, delete methods, break the API. If you do this, many people will turn away. So in order to be able to evolve your software, the components must not expose anything that is not absolutely necessary - at the cost of code reuse.
Example: I wanted to observe the position of the cursor (caret) in an SWT StyledText. The caret is not meant to be extended. If you do it, you'll find that the code contains checks like "is this class in the package org.eclipse.swt" and a lot of methods are private and final and whatnot. I had to copy about 28 classes out of SWT into my project just to implement this feature because everything is locked down.
SWT is a nice framework to use and hell to extend.
Of course there is the famous Open Closed Principle - http://en.wikipedia.org/wiki/Open/closed_principle
Well it depends on the language.
In C/C++ I'm pretty sure there is a loadlibrary function that allows you to open a library at runtime and invoke it's exported functions. This is typically how it's done in C/C++.
In .NET, there is Reflection, which is offers similar (but more broad) to loadlibrary. There is also entire libraries built on Reflection like Managed Extension Framework, or Mono.Addins that does most of the heavy lifting for you already.
In Java, there is also Reflection. And there is the JPF (Java Plugin Framework) which is used in stuff like Eclipse IIRC.
Depending on what language you use I could recommend some tutorial/books. I hope this was helpful.
Plugin architecture is becoming very popular for its extensibility and thus flexibility.
For c++, Apache httpd server is actually plugin based, but a concept of module is used instead. Most of apache features are implemented as modules, like cache, rewrite, load balancing, and even threading model. It is a very modular software I ever saw.
And for java, Eclipse is definitely plugin based. The core of Eclipse is an OSGI module system which manage bundles, another concept for plugin. Bundle can provide extension points on which we can build modules with less efforts. The most intricate thing in OSGI is its dynamic characteristic, which means bundles can be installed or uninstalled at runtime. No stop-the-world syndrome any more!
Since I dont have enough rep points to leave a comment, I am posting this as an answer. SharpDevelop is an IDE for developing applications in C#/VB.NET/Boo. It has a pretty impressive architecture that allows itself to be extended in a number of ways - right from new menu items to development support for whole new languages.
It uses a bit of XML configuration to act as a glue layer between a core of the IDE and the plugin implementation. It handles locating, loading and versioning of plugins out of the box. Deploying new plugins is matter of simply copying in the new xml configuration file and the required assemblies (DLLs) and restarting the application. You can read more on this in the book "Dissecting a csharp application" by the original author(s) - Christian Holm, Mike Krüger, Bernhard Spuida of the application from here. The book doesnt seem to be available on that site, but i found a copy that might still be around here
Also found a related question here
Checkout "CAB" - Microsoft's Composition Application Building blocks Framework. I think they've got a "web version" of that too...
I have just started to develop a smart client application. These are two options I am considering.
Using Microsoft's System.AddIn namespace. Looks very promising, however it may be a little complex for our end solution.
Or the Smart Client - Composite UI Application Block from Microsoft
Recently, i have looked at taking components both the Composite UI Application Block and the System.AddIn namespace to build my own. Since source code is available for the CAB it is easy to extend. I think our end solution will be a light weight version of the CAB, definatly using the Unity Application Block
If you work with .Net, our research yielded two approaches: scripting and composition.
Scripting
You extend the functionality of what your classes can do by orchestrating them using scripts. That means exposing what is compiled in your favorite .Net language in a dynamic language.
Some options we found worth exploring:
IronPython
IronRuby
JavaScript: Jint, Jurassic and JavaScript .Net are good starting points.
Script.Net -> this one was the first one to call our attention.
Composition
If you start a project with .Net 4 or above, you must take a good look at the Managed Extensibility Framework (MEF). It allows you to extend the functionality of your apps in a plugin way.
The Managed Extensibility Framework (MEF) is a composition layer for
.NET that improves the flexibility, maintainability and testability of
large applications. MEF can be used for third-party plugin
extensibility, or it can bring the benefits of a loosely-coupled
plugin-like architecture to regular applications.
Managed Add-in Framework is also a good read.
MSDN: http://msdn.microsoft.com/en-us/library/dd460648.aspx
Codeplex: http://mef.codeplex.com/
Rather than re-inventing the wheel, use the frameworks in hand. Eclipse and Netbeans both support plugin based extensions. You have to work in Java though.