Microsoft Silverlight, versions 3 and greater
Silverlight managed programming model and Silverlight XAML
This technique relates to:
See User Agents Supported for general information on user agent support.
Not all assistive technologies choose to read or present information from the UI Automation tree for Silverlight in cases where the corresponding UI object is not focusable in the tab sequence. This technique provides the support for introducing the information into the UI Automation tree for that element, but cannot guarantee that a given assistive technology provides the user with access to the element information from that UIA tree.
The HelpText property is readable in the UIA framework
by any client that programs against the basic UIA property model, and
that property is forwarded/bridged to MSAA through the get_accHelp method.
However, as of 13 January 2011, no known assistive technology provides
users with a technique or interface option that accesses the HelpText / get_accHelp information.
The objective of this technique is to provide a long text alternative
that serves the same purpose and presents the same information as the
original non-text content when a short text alternative is not sufficient,
and to show the practice of storing that information in a dedicated
property of the Silverlight-supported UI Automation support system.
The technique can also be used on text controls (such as TextBox),
for cases where the control text itself does not provide enough context
to suggest an appropriate user action.
The relevant UI Automation property is named HelpText,
to connote its possible usage to provide imperative instructions for
interactive elements. However, the same property can instead be used
for long text alternatives for nontext objects. The Silverlight API AutomationProperties.HelpText directly
sets HelpText 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.
AutomationProperties.HelpText can be set in code,
but is most typically set as an attribute in XAML that defines a Silverlight
UI.
The same information as is present in AutomationProperties.HelpText could
also be useful to sighted users. In this case, the same text could
be displayed in a Silverlight ToolTip control.
The reason that application authors should use both AutomationProperties.HelpText AND Tooltip in
conjunction is because the Tooltip information is
not introduced into the runtime accessibility framework information
set. This is because a tooltip is transient and not conventionally
focusable. In Silverlight programming, a useful technique for sharing
the same resource is to combine the Silverlight data binding feature
with the .NET Framework embedded resource feature. For more information
on combining Silverlight data binding and resources for common string
sources, see How
to Make XAML Content Localizable.
To introduce the necessary information to Silverlight XAML for an
application UI definition, specify the AutomationProperties.HelpText attribute
on the Image element. The value provided for the attribute
is a meaningful long text alternative for the image content. The value
of AutomationProperties.HelpText should augment rather
than duplicate AutomationProperties.Name, which is
also typically specified to provide accessibility support for an image.
<Image
Height="400" Width="600"
Source="/office.png"
AutomationProperties.Name="Diagram of standard office layout"
AutomationProperties.HelpText=”The standard office layout
includes one corner desk unit in the corner farthest from the
door, and one file cabinet against the same wall as the door.”/>
This example provides instructions for two form fields by using both Tooltip and AutomationProperties.HelpText.
The strings used for these purposes are shared to both methodologies
by defining the strings as resources and binding to them. In this example,
the form submission does not perform client-side validation (although
server-side validation following a data round trip might still exist).
The following is the XAML UI:
<UserControl xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk"
x:Class="HelpTextAndToolTip.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
>
<Grid x:Name="LayoutRoot" Background="White" Margin="10">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="200"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<TextBlock Text="Form With Tooltips" FontSize="16" FontWeight="Bold"
Grid.Column="1" HorizontalAlignment="Center" />
<sdk:Label x:Name="NameLabel" Target="{Binding ElementName=NameTextBox}"
Grid.Row="2" Margin="3"/>
<TextBox x:Name="NameTextBox"
AutomationProperties.Name="{Binding Content, ElementName=NameLabel}"
Text="{Binding Name, Mode=TwoWay, UpdateSourceTrigger=Explicit}"
Grid.Column="1" Grid.Row="2" Margin="3"
AutomationProperties.HelpText="{Binding
NameTextBoxToolTipString,Source={StaticResource TooltipStrings}}">
<ToolTipService.ToolTip>
<ToolTip Content="{Binding NameTextBoxToolTipString,Source={StaticResource TooltipStrings}}" />
</ToolTipService.ToolTip>
</TextBox>
<sdk:Label x:Name="AgeLabel" Target="{Binding ElementName=AgeTextBox}"
Grid.Row="3" Margin="3" HorizontalAlignment="Right"/>
<TextBox x:Name="AgeTextBox"
AutomationProperties.Name="{Binding Content, ElementName=AgeLabel}"
Text="{Binding Age, Mode=TwoWay, UpdateSourceTrigger=Explicit}"
Grid.Column="1" Grid.Row="3" Margin="3"
AutomationProperties.HelpText="{Binding AgeTextBoxToolTipString,Source={StaticResource TooltipStrings}}">
<ToolTipService.ToolTip>
<ToolTip Content="{Binding AgeTextBoxToolTipString,Source={StaticResource TooltipStrings}}" />
</ToolTipService.ToolTip>
</TextBox>
<Button x:Name="SubmitButton" Content="Submit" Click="SubmitButton_Click"
Grid.Column="1" Grid.Row="4" Width="50" Margin="3" />
</Grid>
</UserControl>
The following is the resource definition in app.xaml:
<ResourceDictionary>
<resources:Resource1 x:Key="TooltipStrings"/>
</ResourceDictionary>
The generated resource code that defines the "Resource1" class is not shown here because it is mostly infrastructure that is produced by a generation task in Visual Studio. For more information about embedded resources in Silverlight, see Resources Overview on MSDN. The resources here contain just two strings, each of which would typically be defined in a Visual Studio .resx file. Resources in a .resx file can be localized or changed separately from code by the appropriate localization toolsets for Microsoft localization/development.
NameTextBoxToolTipString: Must be 10 characters or less. Required.
AgeTextBoxToolTipString Must be a value between 0 and 120. Required.
These examples are shown in operation in the working example of Automation Properties Help Text and working example of HelpText and ToolTip.
Resources are for information purposes only, no endorsement implied.
Using a browser that supports Silverlight, open an HTML page that references a Silverlight application through an object tag. To see UI Automation, use Microsoft Windows as platform.
Use a verification tool that is capable of showing the full automation tree, and an object’s long text alternative as part of the tree. (For example, use UIAVerify or Silverlight Spy; see Resources links.)
Focus an element that is known to have a long text alternative.
Check that the AutomationProperties.HelpText as applied to
individual UI elements appears as the HelpText or acc_Help value
in the automation tree.
#3 is true.
If this is a sufficient technique for a success criterion, failing this test procedure does not necessarily mean that the success criterion has not been satisfied in some other way, only that this technique has not been successfully implemented and can not be used to claim conformance.
Techniques are informative—that means they are not required. The basis for determining conformance to WCAG 2.0 is the success criteria from the WCAG 2.0 standard—not the techniques. For important information about techniques, please see the Understanding Techniques for WCAG Success Criteria section of Understanding WCAG 2.0.