WPF Windows Presentation Foundation A platform for building

WPF, Windows Presentation Foundation A platform for building rich user experiences on Windows An Architect overview By Shahzad sarwar

Presentation Scope • What's covered: Ø XMAL Ø Basic Elements of WPF Ø Architecture Ø Property System / Dependency Property Ø Routed Events Ø Binding System Ø Styling / Templating • What’s Not covered: Ø Controls Library ØGraphics / Multi Media ØDocuments

What is WPF? • Next-generation presentation system for building Windows client applications with visually stunning user experiences. • Resolution-independent • Vector-based rendering engine (advantage of modern graphics hardware) • Coverage: Extensible Application Markup Language (XAML), controls, data binding, layout, 2 -D and 3 -D graphics, animation, styles, templates, documents, media, text, and typography. Types Of Applications: 1. Standalone Applications: Ø Window class to create windows and dialog boxes Ø Accessed from menu bars and tool bars. 2. Browser-Hosted Applications: (XAML browser applications (XBAPs)) Ø Create pages (Page) and page functions (Page. Function(T)) Ø Navigate between using hyperlinks (Hyperlink classes).

Tech Analysis Win. Form s PDF Win. Form s + GDI Windows Media Player Direct 3 D WPF Forms, Controls X X X Complex text X X 2 D Graphics X X 3 D Graphics X X Images Video / Audio Reference: http: //windowsclient. net/wpf/white-papers/when-to-adopt-wpf. aspx

The Application Class Additional application-scoped services, including Ø Creating and managing common application infrastructure. Ø Tracking and interacting with application lifetime. Ø Startup Ø Activated Ø Deactivated Ø Shutdown. Mode (On. Last. Window. Close, On. Main. Window. Close, On. Explicit. Shutdown) Ø Session. Ending (Logging off, Shutting down, Restarting, Hibernating) Ø Exit Ø Ø Ø Retrieving and processing command-line parameters. Example Sharing application-scope properties and resources. Examples in Code Detecting and responding to unhandled exceptions. Example in Code

The Application Class Ø Returning exit codes. Example in Code Ø Managing windows in standalone applications Ø Tracking and managing navigation using System. Windows. Navigation; 1. <Hyperlink Control <Hyperlink Navigate. Uri="Uri. Of. Page. To. Navigate. To. xaml"> Navigate to Another Page </Hyperlink> 2. Via Navigation. Service // Instantiate the page to navigate to Page. With. Non. Default. Constructor page = new Page. With. Non. Default. Constructor("Hello!"); // Navigate to the page, using the Navigation. Service this. Navigation. Service. Navigate(page);

The Application Class 3. Programmatic Navigation with a Pack URI // Create a pack URI Uri uri = new Uri("Another. Page. xaml", Uri. Kind. Relative); // Get the navigation service that was used to // navigate to this page, and navigate to // Another. Page. xaml this. Navigation. Service. Navigate(uri); Ø Configuring the Host Window's Title, Width, and Height Ø Fragment Navigation to a content fragment Page. URI#Element. Name

Navigation Lifetime • Navigating. Occurs when a new navigation is requested. Can be used to cancel the navigation. • Navigation. Progress. Occurs periodically during a download to provide navigation progress information. • Navigated. Occurs when the page has been located and downloaded. • Navigation. Stopped. Occurs when the navigation is stopped (by calling Stop. Loading), or when a new navigation is requested while a current navigation is in progress. • Navigation. Failed. Occurs when an error is raised while navigating to the requested content. • Load. Completed. Occurs when content that was navigated to is loaded and parsed, and has begun rendering. • Fragment. Navigation Occurs when navigation to a content fragment begins, which happens: – Immediately, if the desired fragment is in the current content. – After the source content has been loaded, if the desired fragment is in different content.

Navigation Lifetime

Navigation Lifetime Ø Journal / journal entry(Journal. Entry class) The back stack, the forward stack 1. Declarative mechanisms provided by WPF <Hyperlink Members of the Navigation. Service class. Command="Navigation. Commands. Browse. Back">Back</Hyper link> 2. Programmatic mechanisms provided by WPF Go. Back Go. Forward Can. Go. Back Can. Go. Forward Ø Retaining Content State with Navigation History Ø New Page, so data is destroyed, But there is a mechanism to restore state via Journal like navigation history. Ø Custom implementation is also provided System. Windows. Navigation. Custom. Content. State

Navigation Lifetime Ø Structured Navigation Overview Structured Navigation with Page. Function Other Types of Structured Navigation Ø Navigation. Window Class browser-style navigation into your standalone applications Navigation Hosts Ø Configuring the Application Definition for MSBuild In MSBuild project <Application. Definition Include="App. xaml" /> Getting the Current Application // Get strongly-typed current application App app = (App)App. Current; Ø Two way to Start Window or Page 1. By. Code void App_Startup(object sender, Startup. Event. Args e) { ((Navigation. Window)this. Main. Window). Navigate(new Uri("Home. Page. xaml", Uri. Kind. Relative)); } 2. Startup. Uri="Main. Window. xaml"

WPF Architecture

WPF Architecture Ø More declarative, "property centric" model of programming Ø System. Threading. Dispatcher. Object Ø Support for concurrency and threading. Ø messaging system implemented by the dispatcher. Ø Create a CLR object that has STA behavior. Ø Thread affinity: Ø A component uses the identity of the executing thread to store some type of state. Ø OLE 2. 0, the clipboard, and Internet Explorer all require single thread affinity (STA) execution. Ø The dispatcher: Ø Basic message dispatching system, with multiple prioritized queues Ø Examples of messages include: Ø Raw input notifications (mouse moved) Ø Framework functions (layout) Ø User commands (execute this method).

WPF Architecture Ø System. Windows. Dependency. Object Ø Dependency Properties: To compute the value of a property based on the value of other inputs Ø System properties such as themes and user preference Ø Just-in-time property determination mechanisms such as data binding and animations/storyboards Ø Multiple-use templates such as resources and styles Ø Values known through parent-child relationships with other elements in the element tree Also For: Ø Self-contained validation Ø Default values Ø Callbacks that monitor changes to other properties Ø A system that can coerce property values based on potentially runtime information.

WPF Architecture Ø System. Windows. Media. Visual Ø Building a tree of visual objects Ø Drawing instructions and metadata about how to render those instructions (clipping, transformation, etc. ). Ø Point of connection between these two subsystems, the managed API and the unmanaged milcore.

WPF Architecture Ø Composition: Ø In User 32 and GDI: Ø (Immediate mode clipping system) Ø a clipping bounds outside of which the component isn’t allowed to touch the pixels, and then the component is asked to paint pixels in that box. Ø Good for memory constrained environment. Ø In WPF: Ø Ø Ø "Painter's algorithm" painting model. To render from the back to the front of the display. Each component to paint over the previous component's display. Complex, partially transparent shapes. Better for new type of graphics object.

WPF Architecture Ø System. Windows. UIElement Core subsystems including Layout, Input, and Events. Ø Layout: 1. A fixed set of layout models (HTML supports three models for layout; flow, absolute, and tables) 2. No model for layout (User 32 really only supports absolute positioning) A flexible, extensible layout model, which could be driven by property values rather than imperative logic. Ø A two phase model with Measure and Arrange passes. Ø Measure Phase: To determine how much size it would like to take. Ø A parent element will ask a child to measure several times to determine its optimal position and size. Ø Rule: Size to content. Ø Ø Arrange phase: To allows a parent to position and determine the final size of each child. Input: Ø Ø Ø On a kernel mode device driver. Gets routed to the correct process and thread by involving the Windows kernel and User 32. Routed to WPF raw input message and sent to the dispatcher. Raw input events to be converted to multiple actual events.

WPF Architecture Ø Routing through the element tree. Ø Events are said to "bubble" if they traverse from a target up the tree to the root. Ø Events are said to "tunnel" if that start at the root and traverse down to a target. Ø In the dispatcher for your application you would call Translate. Accelerator which would sniff the input messages in User 32 and determine if any matched a registered accelerator. Ø Command. Bindings. Ø To define functionality in terms of a command end point – something that implements ICommand. Ø Enable an element to define a mapping between an input gesture (Ctrl+N) and a command (New).

WPF Architecture Ø System. Windows. Framework. Element Ø A set of policies and customizations on the subsystems introduced in lower layers of WPF. Ø A set of new subsystems Ø Policies: Ø Application layout Ø Direct access to animation through the Begin. Storyboard method Ø The data binding subsystem: one or more properties from a given element to be bound to a piece of data Ø Styling Subsystem: Bind a set of properties from a shared definition to one or more instances of an element. Ø System. Windows. Control Ø Templating allows a control to describe it’s rendering in a parameterized, declarative manner. Ø The implementation of a control provides a data model and interaction model Ø This split between the data model (properties), interaction model (commands and events), and display model (templates) enables complete customization of a control’s look and behavior.

WPF property system Ø A set of services that can be used to extend the functionality of a common language runtime (CLR) property. Ø Dependency property: A property that is backed by the WPF property system. Ø What For? Ø 1. A way to compute the value of a property based on the value of other inputs Ø System properties such as themes and user preference Ø Just-in-time property determination mechanisms such as data binding and animations/storyboards Multiple-use templates such as resources and styles Ø Values known through parent-child relationships with other elements in the element tree. Ø 2. To provide self-contained validation, default values, callbacks that monitor changes to other properties Ø 3. A system that can coerce property values based on potentially runtime information. Ø 4. Derived classes can also change some specific characteristics of an existing property by overriding dependency property metadata, rather than overriding the actual implementation of existing properties or creating new properties.

Common Terms Ø Dependency. Property: Extend property functionality by providing a type that backs a property Ø Dependency. Object: The base class that can register and own a dependency property Ø Dependency property identifier: A Dependency. Property instance, which is obtained as a return value when registering a dependency property, and then stored as a member of a class. Ø CLR "wrapper": The actual get and set implementations for the property public static readonly Dependency. Property Is. Spinning. Property = Dependency. Property. Register(. . . ); public bool Is. Spinning { get { return (bool)Get. Value(Is. Spinning. Property); } set { Set. Value(Is. Spinning. Property, value); } }

Setting Property Values Ø 1. XAML attribute <Button Background="Red" Content="Button!"/> Ø 2. Property element syntax. <Button Content="Button!"> <Button. Background> <Image. Brush Image. Source="wavy. jpg"/> </Button. Background> </Button> Ø 3. Setting Properties in Code Button my. Button = new Button(); my. Button. Width = 200. 0;

Routed events Ø A type of event that can invoke handlers on multiple listeners in an element tree, rather than just on the object that raised the event. Ø CLR event that is backed by an instance of the Routed. Event class and is processed by the Windows Presentation Foundation (WPF) event system. Ø Routed events are events who navigate up or down the visual tree acording to their Routing. Strategy. Ø Top-level Scenarios for Routed Events Ø Control composition and encapsulation: Ø Eg: Rich content model. Like an image inside of a Button. Ø Singular handler attachment points: Ø To attach the same handler multiple times to process events that could be raised from multiple elements. Ø Example Code Ø Class handling: Permit a static handler that is defined by the class. Ø (the opportunity to handle an event before any attached instance handlers can. Ø Referencing an event without reflection: Ø Creates a Routed. Event field as an identifier, which provides a robust event identification technique that does not require static or run-time reflection.

How Routed Events Are Implemented Ø // Register the routed event public static readonly Routed. Event Selected. Event = Event. Manager. Register. Routed. Event( "Selected", Routing. Strategy. Bubble, typeof(Routed. Event. Handler), typeof(My. Custom. Control)); Ø //. NET wrapper public event Routed. Event. Handler Selected{ add { Add. Handler(Selected. Event, value); } remove { Remove. Handler(Selected. Event, value); }} Ø // Raise the routed event "selected“ Raise. Event(new Routed. Event. Args(My. Custom. Control. Selected. Event));

Routing Strategies: Ø Bubbling: Ø Event handlers on the event source are invoked. Ø Then routes to successive parent elements until reaching the element tree root. Ø To report input or state changes from distinct controls or other UI elements. Ø Direct: Ø Only the source element itself is given the opportunity to invoke handlers in response. Ø Analogous to the "routing" that Windows Forms uses for events. Ø unlike a standard CLR event, direct routed events support class handling. Ø Tunneling: Ø Event handlers at the element tree root are invoked. Ø Then The routed event then travels a route through successive child elements along the route, towards the node element that is the routed event source. Ø Compositing for a control, such that events from composite parts can be deliberately suppressed or replaced by events that are specific to the complete control. Ø Input events provided in WPF often come implemented as a tunneling/bubbling pair. Ø Tunneling events are also sometimes referred to as Preview events, because of a naming convention that is used for the pairs.

Resource Static. Resource: Ø A simple way to reuse commonly defined objects and values. Ø Provides a value for a XAML property by substituting the value of an already defined resource. Static resource lookup behavior Ø For the requested key within the resource dictionary defined by the element that sets the property. Ø Traverses the logical tree upward, to the parent element and its resource dictionary. Ø Application resources When: Ø No intention of changing the value of the resource after it is referenced the first time. Ø Not reevaluated based on runtime behaviors such as reloading a page. So some performance benefit. Ø For Value of property that is not on a Dependency. Object or a Freezable. Ø Compiled into a DLL, and packaged as part of the application or shared between applications Ø Creating a theme for a custom control, and are defining resources that are used within themes.

Dynamic. Resource Ø Provides a value for a XAML property by deferring that value to be a run-time reference to a resource. When: Ø The value of the resource depends on conditions that are not known until runtime. Ø Like System. Colors, System. Fonts, or System. Parameters Ø Creating or referencing theme styles for a custom control. Ø To adjust the contents of a Resource. Dictionary during an application lifetime. Ø A forward reference may be required Ø The resource might not be used immediately when the page loads. Ø (Static resource references always load from XAML when the page loads; however, Ø a dynamic resource reference does not load until it is actually used. ) Ø Applying resources to elements that might be reparented in the logical tree during application lifetime.

Dynamic resource Ø Dynamic resource lookup behavior Ø Within the resource dictionary defined by the element that sets the property. Ø If the element defines a Style property, the Resources dictionary within the Style is checked. Ø If the element defines a Template property, the Resources dictionary within the Framework. Template is checked. Ø Traverses the logical tree upward, to the parent element and its resource dictionary. Ø Application resources Ø Theme resource dictionary Ø System resources Ø Merged Resource Dictionary Ø A way to define the resources portion of a WPF application outside of the compiled XAML application. Ø (Resources can then be shared across applications)

Data Binding Overview Ø The process that establishes a connection between the application UI and business logic. Ø Elements can be bound to data from a variety of data sources in the form of common language runtime (CLR) objects and XML. Ø Features: Ø Content. Controls such as Button and Items. Controls such as List. Box and List. View have built-in functionality to enable flexible styling of single data items or collections of data items. Ø Sort, filter, and group views can be generated on top of the data. Ø Basic Data Binding Concepts

Data Binding Overview Ø Direction of the Data Flow Ø What Triggers Source Updates

References: Ø Ø Ø Ø http: //msdn. microsoft. com http: //windowsclient. net http: //www. wpftutorial. net http: //joshsmithonwpf. wordpress. com http: //idealprogrammer. com http: //www. msdev. com http: //www. wpfdev. com http: //WPFpedia. com

A soft copy will be available at: http: //softarchitect. wordpress. com For Future discussion, join http: //tech. groups. yahoo. com/group/Soft. Architect/

If you want to master a technology, start teaching it to others.