Applicability
- Microsoft Silverlight, versions 3 and greater
- Silverlight managed programming model and Silverlight XAML
Microsoft has stopped updating and distributing Silverlight, and authors are encouraged to use HTML for accessible web content.
This technique relates to:
- Success Criterion 1.1.1: Non-text Content (Sufficient)
- Success Criterion 2.4.4: Link Purpose (In Context) (Sufficient as a way to meet G91: Providing link text that describes the purpose of a link)
- Success Criterion 2.4.9: Link Purpose (Link Only) (Sufficient as a way to meet an unwritten technique)
- Success Criterion 4.1.2: Name, Role, Value (Sufficient as a way to meet G10: Creating components using a technology that supports the accessibility notification of changes)
Description
The objective of this technique is to use the Silverlight AutomationProperties.Name property
to provide a short text alternative for controls that do not otherwise
contain text. The text is intended to provide human-readable identifiers
and short-descriptions or user instructions for accessibility frameworks,
which can then be reported to assistive technologies.
"Control" in this technique refers to any element that is
based on the Silverlight Control class, and is keyboard-focusable
either by user action or calling focus to the control programmatically.
The non-text control in question might be something like a button that
communicates information using only an icon or image. For example,
a triangle image rotated 90 degrees clockwise is commonly used in many
user interfaces to indicate a "Play" button control. This "Play" icon
mimics interface metaphors from many non-software consumer products,
and is often presented in a user interface without any nearby visible
text information that explains the purpose of the control. Another
example is a "thumbnail" metaphor where a small image serves
as a control that can be activated, and where the action results in
the display of a larger version of the same image, or enters an editing
mode that loads the same image.
For cases of controls such as buttons that invoke actions, the text alternative also identifies link purpose.
In Silverlight, a text-only identifier for any control can be set
specifically as AutomationProperties.Name on the parent
control. Silverlight control compositing techniques enable either per-control
images that are specified by the application author, or a general-purpose
image/icon for a control that is part of the control's template and
displays that way by default. The Silverlight API AutomationProperties.Name directly
sets Name in the UI Automation tree. The properties
in the UI Automation tree are reported to assistive technologies, when
the assistive technology implements behavior that acts as a UI Automation
client (or as an MSAA client, which relies on the UIA-MSAA bridge).
Examples
Example 1: Applying a text alternative for an icon Button with XAML
Application authors can specify the AutomationProperties.Name attribute
on the Button element, and leave accessibility information
for the composited Image content unspecified. It is
the button and its action that is relevant to users, not the non-interactive
Image component.
The value provided for AutomationProperties.Name is
a meaningful text alternative for the action conveyed by the button's
icon/image, but where the functionality is conceptually embodied in
the button and not its images or other constituent parts in compositing
or visual design.
<Button Height="20" Width="50" AutomationProperties.Name="Pause Media"> <Image Height="12" Width="12" Source="/icon_pause.png"/> </Button>
This example is shown in operation in the working example of Button Text Alternative.
Resources
Resources are for information purposes only, no endorsement implied.
Tests
Accessibility framework view
Procedure
- Using a browser that supports Silverlight, open an HTML page that references a Silverlight application through an object tag.
- Use a verification tool that is capable of showing the full accessibility framework tree, and an object’s "Name" text alternative as part of the tree. Verify that all interactive elements such as buttons without visible text provide a human-readable text identifier "Name" in the automation tree.
Expected Results
#2 is true.
Screen Reader
Procedure
- Using a browser that supports Silverlight, open an HTML page that references a Silverlight application through an object tag.
- Engage the screen reader. Press TAB to traverse the tab sequence
inside the Silverlight content area to focus to a composite control
that has no visible text, but has an
AutomationProperties.Nameapplied. - Check that the "Name" as applied to the control instance, along with the class name of the named control, is read by the screen reader.
Expected Results
#3 is true.