Starting Windows Presentation Foundation(Basics)

Starting with WPF Layouts here, we will move on to cover entire WPF in the next coming articles.Here i am posting basic WPF information and details of WPF Layouts.

WINDOWS PRESENTATION FOUNDATION (WPF) represents a major step forward in user interface technology. This chapter will lay out some of the basic principles of WPF and walk through a quick overview of the entire platform. You can think of this chapter as a preview of the rest of the book.
A primary goal of WPF is to preserve as much developer knowledge as possible. Even though WPF is a new presentation system completely different from Windows Forms, we can write the equivalent program in WPF with very similar code1 (changes are in boldface):
/* sample code */
using System.Windows;using System;
class Program {[STAThread]static void Main()
{Window f = new Window();f.Title = "Hello World";new Application().Run(f);}}
In both cases the call to Run on the Application object is the replacement for the message loop, and the standard CLR (Common Language Runtime) type system is used for defining instances and types. Windows Forms is really a managed layer on top of User32, and it is therefore limited to only the fundamental features that User32 provides.
User32 is a great 2D widget platform. It is based on an on-demand, clipbased painting system; that is, when a widget needs to be displayed, the system calls back to the user code (on demand) to paint within a bounding box that it protects (with clipping). The great thing about clip-based painting systems is that they’re fast; no memory is wasted on buffering the content of a widget, nor are any cycles wasted on painting anything but the widget that has been changed.
The downsides of on-demand, clip-based painting systems relate mainly to responsiveness and composition. In the first case, because the system has to call back to user code to paint anything, often one component may prevent other components from painting. This problem is evident in Windows when an application hangs and goes white, or stops painting correctly. In the second case, it is extremely difficult to have a single pixel affected by two components, yet that capability is desirable in many scenarios—forexample, partial opacity, anti-aliasing, and shadows.
WPF is based on a retained-mode composition system. For each component a list of drawing instructions is maintained, allowing for the system to automatically render the contents of any widget without interacting with user code. In addition, the system is implemented with a painter’s algorithm, which ensures that overlapping widgets are painted from back to front, allowing them to paint on top of each other. This model lets the system manage the graphics resource, in much the same way that the CLR manages memory, to achieve some great effects. The system can perform high-speed animations, send drawing instructions to another machine, or even project the display onto 3D surfaces—all without the widget being aware of the complexity. In WPF’s composition engine, all controls are contained, grouped, and composited. A button in WPF is actually made up of several smaller controls. This move to embrace composition, coupled with a vector-based approach, enables any level of containment.In addition to addressing the limitations of User32 and GDI32, one of WPF’s goals was to bring many of the best features from the Web programming model to Windows developers.
HTML, a.k.a. the Web
One of the biggest assets of Web development is a simple entry to creating content. The most basic HTML “program” is really nothing more than a few HTML tags in a text file:
--

Welcome to my document!
--

In fact, all of the tags can be omitted, and we can simply create a file with the text “Welcome to my document!”, name it .html, and view it in a browser This amazingly low barrier to entry has made developers out of millions of people who never thought they could program anything. In WPF we can accomplish the same thing using a new markup format called XAML (Extensible Application Markup Language), pronounced “zammel.” Because XAML is a dialect of XML, it requires a slightly stricter syntax. Probably the most obvious requirement is that the xmlns directive must be used to associate the namespace with each tag:
In WPF we can accomplish the same thing using a new markup format called XAML (Extensible Application Markup Language), pronounced “zammel.” Because XAML is a dialect of XML, it requires a slightly stricter syntax. Probably the most obvious requirement is that the xmlns directive must be used to associate the namespace with each tag: