Implementing the UI Automation Scroll Control Pattern
Note
This documentation is intended for .NET Framework developers who want to use the managed UI Automation classes defined in the System.Windows.Automation namespace. For the latest information about UI Automation, see Windows Automation API: UI Automation.
This topic introduces guidelines and conventions for implementing IScrollProvider, including information about events and properties. Links to additional references are listed at the end of the topic.
The ScrollPattern control pattern is used to support a control that acts as a scrollable container for a collection of child objects. The control is not required to use scrollbars to support the scrolling functionality, although it commonly does.
Example of a Scrolling Control that Does Not Use Scrollbars
For examples of controls that implement this control, see Control Pattern Mapping for UI Automation Clients.
Implementation Guidelines and Conventions
When implementing the Scroll control pattern, note the following guidelines and conventions:
The children of this control must implement IScrollItemProvider.
The scrollbars of a container control do not support the ScrollPattern control pattern. They must support the RangeValuePattern control pattern instead.
When scrolling is measured in percentages, all values or amounts related to scroll graduation must be normalized to a range of 0 to 100.
HorizontallyScrollableProperty and VerticallyScrollableProperty are independent of the IsEnabledProperty.
If HorizontallyScrollableProperty =
falsethen HorizontalViewSizeProperty should be set to 100% and HorizontalScrollPercentProperty should be set to NoScroll. Likewise, if VerticallyScrollableProperty =falsethen VerticalViewSizeProperty should be set to 100 percent and VerticalScrollPercentProperty should be set to NoScroll. This allows a UI Automation client to use these property values within the SetScrollPercent method while avoiding a race condition if a direction the client is not interested in scrolling becomes activated.HorizontalScrollPercent is locale-specific. Setting HorizontalScrollPercent = 100.0 must set the scrolling location of the control to the equivalent of its rightmost position for languages such as English that read left to right. Alternately, for languages such as Arabic that read right to left, setting HorizontalScrollPercent = 100.0 must set the scroll location to the leftmost position.
Required Members for IScrollProvider
The following properties and methods are required for implementing IScrollProvider.
| Required member | Member type | Notes |
|---|---|---|
| HorizontalScrollPercent | Property | None |
| VerticalScrollPercent | Property | None |
| HorizontalViewSize | Property | None |
| VerticalViewSize | Property | None |
| HorizontallyScrollable | Property | None |
| VerticallyScrollable | Property | None |
| Scroll | Method | None |
| SetScrollPercent | Method | None |
This control pattern has no associated events.
Exceptions
Providers must throw the following exceptions.
| Exception Type | Condition |
|---|---|
| ArgumentException | Scroll throws this exception if a control supports SmallIncrement values exclusively for horizontal or vertical scrolling, but a LargeIncrement value is passed in. |
| ArgumentException | SetScrollPercent throws this exception when a value that cannot be converted to a double is passed in. |
| ArgumentOutOfRangeException | SetScrollPercent throws this exception when a value greater than 100 or less than 0 is passed in (except -1 which is equivalent to NoScroll). |
| InvalidOperationException | Both Scroll and SetScrollPercent throw this exception when an attempt is made to scroll in an unsupported direction. |