Windows Presentation
Foundation (WPF) and
Dyalog APL
A new era
Dan Baronet and Michael Hughes
Boston 2011
V1.00
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Why WPF?
It is difficult to stay on top of the latest
changes in the GUI world.
Windows Presentation Foundation
(WPF) is a framework (based on .NET)
for describing all kinds of GUI
Easy to use from APL
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WPF is a replacement, not a new wrapper.
DirectX is the technology used underneath
DirectX ±= assembler of graphics
WPF
±= APL
DirectX takes care of all the nitty gritty details
such as drawing.
WPF uses DirectX (and User32 for some
services, eg screen areas)
Does not use GDI/GDI32/GDI+ - essentially
replaces win32
DirectX
• DirectX is more efficient because it
understands higher-level ingredients
such as textures and gradients that can
be rendered directly by the video card.
GDI/GDI+ doesn’t.
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Applications
Controls
Styling
Layout
Data
Content
Action
Presentation Framework
PresentationCore.dll
MilCore.dll
DirectX
Driver
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Goal
The goal of WPF is to offload as much
of the work as possible on the video
card so that complex graphics routines
are render-bound (limited by the GPU)
rather than processor-bound (limited
by your computer’s CPU).
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An ideal choice
• WPF is an ideal choice and it offers the
best prospects for future enhancements
and longevity
• Win32 is a general bucket that includes
any technology that runs on Windows:
DirectX, MFC, WTL, OpenGL, and so
on.
• Resolution Independence
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The Evolution of WPF
Although WPF is a relatively new technology, it already exists in two versions:
• WPF 3.0. The first version of WPF was released with two other
new technologies:
Windows Communication Foundation (WCF) and Windows Workflow
Foundation (WF). Together, these three technologies were called the
.NET Framework 3.0 (even though the core bits of .NET weren’t
changed).
• WPF 3.5. A year later, a new version of WPF was released as part
of the .NET Framework 3.5.
The new features in WPF are mostly minor refinements. Some of these
bug fixes and performance improvements are available to .NET
Framework 3.0 applications through the .NET Framework 3.0 Service
Pack 1.
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Divide and conquer
Separating the design from the code
should be done.
The premise of combining designers and
developers to create a better
experience is not new, but it has also
never been an efficient collaboration.
With the introduction of XAML, walls that
may have existed between designers
and developers are no longer in place.
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XAML
XAML (short for Extensible Application Markup Language, and
pronounced “zammel”) is a markup language used to instantiate .NET
objects
XAML documents define the arrangement of panels, buttons, and
controls that make up the windows in a WPF application
XML-based formats such as XAML are flexible and easily portable to
other tools and platforms. You’re not locked into Visual Studio for ex.
XML was designed to be logical, readable, and straightforward—not
compact
Everything done with XAML can be done entirely in your favorite
.NET language (but note that the reverse is not true).
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XAML: Namespaces
• http://schemas.microsoft.com/winfx/
2006/xaml/presentation maps to the
.NET namespace
System.Windows.Controls
• http://schemas.microsoft.com/winfx/
2006/xaml is the XAML language
namespace, which maps to types in the
System.Windows.Markup namespace
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XAML: Attributes vs Properties
Attribute:
<Button Content=”OK” Background=”White”/>
Property:
<Button>
<Button.Content>OK</Button.Content>
…
<Button.Background>White</Button.Backgr
ound>
</Button>
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No size/pos
Hard-coded sizes are usually not the
ideal approach to creating user
interfaces.
They limit your ability to handle
dynamic content and they make it
more difficult to localize your
application into other languages.
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No fixed coordinates
• Instead, the emphasis is on creating more
flexible layouts that can adapt to changing
content, different languages, and a variety
of window sizes.
• Hard-coded sizes and positions are evil
because they limit your ability to localize
your interface, and they make it much
more difficult to deal with dynamic content.
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Matching arguments with real
values
In order to bridge the gap between string
values and nonstring properties (e.g. a
number) , the XAML parser needs to
perform a conversion.
The conversion is performed by type
converters, a basic piece of .NET
infrastructure that’s existed since .NET
1.0.
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Panels
• Panels are containers
• Panels may contain several elements
• There are many kinds of panels, each
with their own layout logic
• WPF uses Panels extensively
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Panels
• They are parent elements that support
the arrangement of multiple children,
and derive from the abstract
System.Windows.Controls.Panel class.
• All the elements involved in the layout
process (both parents and children)
derive from
System.Windows.UIElement.
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StackPanel
• StackPanel Places elements in a
horizontal or vertical stack. This
layout container is typically used for
small sections of a larger, more
complex window.
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DockPanel
Aligns elements against an entire edge of
the container.
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WrapPanel
• Places elements in a series of wrapped
lines. In horizontal orientation, the
WrapPanel lays items out in a row from
left to right and then onto subsequent
lines. In vertical orientation, the
WrapPanel lays out items in a top-tobottom column and then uses additional
columns to fit the remaining items
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Grid
• Arranges elements in rows and
columns according to an invisible
table.
• This is one of the most flexible and
commonly used layout containers
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UniformGrid
• Places elements in an invisible table but
forces all cells to have the same size.
• This layout container is used
infrequently.
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Canvas
• Allows elements to be positioned
absolutely using fixed coordinates.
• This layout container is the most similar
to traditional Windows Forms, but it
doesn’t provide anchoring or docking
features. As a result, it’s an unsuitable
choice for a resizable window unless
you’re willing to do a fair bit of work.
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Other features
• There are many features not found in
[]WC objects
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Routed Events
• It allows an event to originate in one
element but be raised by another one.
• For example, event routing allows a
click that begins in a toolbar button to
rise up to the toolbar and then to the
containing window before it’s handled
by your code.
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Routed Events
Routed events actually come in the following three flavors:
•
•
•
Direct events are like ordinary .NET events. They originate in one
element and don’t pass to any other. For example, MouseEnter (which
fires when the mouse pointer moves over an element) is a direct event.
Bubbling events are events that travel up the containment hierarchy.
For example, MouseDown is a bubbling event. It’s raised first by the
element that is clicked. Next, it’s raised by that element’s parent, and
then by that element’s parent, and so on, until WPF reaches the top of
the element tree.
Tunneling events are events that travel down the containment
hierarchy. They give you the chance to preview (and possibly stop) an
event before it reaches the appropriate control. For example,
PreviewKeyDown allows you to intercept a key press, first at the window
level, and then in increasingly more specific containers until you reach
the element
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Dependency Properties
• Change notification
• Property value inheritance
• Support for multiple providers
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Styles?
•
•
•
•
•
•
•
•
•
•
•
•
<Button MinWidth=”75” Margin=”10”>
<Button.Style>
<Style TargetType=”{x:Type Button}”>
<Style.Triggers>
<Trigger Property=”IsMouseOver” Value=”True”>
<Setter Property=”Foreground” Value=”Blue”/>
</Trigger>
</Style.Triggers>
</Style>
</Button.Style>
OK
</Button>
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Data Binding
• Data binding is about tying together arbitrary .NET
objects. The classic scenario is providing a visual
representation (for example, in a ListBox or ListView) of
items in an XML file, database, or an in-memory
collection.
• For example, instead of iterating through a data source
and manually adding a ListBoxItem to a ListBox for each
one, it would be nice to just say, “Hey, ListBox! Get your
items from over here. And keep them up to date, please.
Oh yeah, and format them to look like this.” Data binding
enables this and much more.
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Data Binding
• XmlDataProvider could be considered a
“killer app” for data binding, as it makes
retrieving, parsing, navigating, and
displaying remote XML data incredibly
easy.
• The ability to get asynchronous behavior
on any Binding or data provider simply by
setting a Boolean property also makes
data binding a compelling alternative to
performing such work manually.
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Triggers
• Property triggers—Invoked when the
value of a dependency property
changes
• Data triggers—Invoked when the value
of a plain .NET property changes
• Event triggers—Invoked when a routed
event is raised
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Expressing More Complex
Logic with Triggers
• Multiple triggers can be applied to the
same element (to get a logical OR).
• Multiple properties can be evaluated for
the same trigger (to get a logical AND).
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Easy Graphics
• The ability to create and use vector-based
2D graphics is not unique to WPF; even
GDI enabled the drawing of paths and
shapes.
• The main difference with drawing in WPF
versus GDI or any previous Window
technology is that WPF is a completely
retained-mode graphics system rather
than an immediate-mode graphics system.
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SilverLight
SilverLight is a slightly cut-down version
of WPF, which can run in most popular
browsers & includes a small .NET
Framework.
Applications built on SilverLight (like
”APL#”) can run in the browser
”without installation” on the client
(Windows only) computer
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3 examples
• A windows application
• A web app
• A Silverlight app
+ how to store XAML in e.g. SVN and use
it other dev interfaces.
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