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Thumb Control Type

This topic provides information about Microsoft UI Automation support for the Thumb control type.

Thumb controls provide the functionality that enables a control to be moved (or dragged), such as a scroll bar button, or resized, such as a window resizing widget. Note that a thumb control does not provide drag-and-drop functionality. Thumb controls can receive mouse focus but not keyboard focus. The control developer must implement the control so that it acts appropriately (can be dragged or resized).

The following sections define the required UI Automation tree structure, properties, control patterns, and events for the Thumb control type. The UI Automation requirements apply all thumb controls where the UI framework/platform integrates UI Automation support for control types and control patterns.

This topic contains the following sections.

Typical Tree Structure

The following table depicts a typical control and content view of the UI Automation tree that pertains to thumb controls and describes what can be contained in each view. For more information about the UI Automation tree, see UI Automation Tree Overview.

Control ViewContent View
  • Thumb
(Not applicable)


Thumb controls never appear in the content view because they exist only to be manipulated with a mouse. They are exposed though another control pattern, such as the Scroll control pattern, Transform control pattern, or RangeValue control pattern, being supported on the thumb control's container.

Relevant Properties

The following table lists the UI Automation properties whose value or definition is especially relevant to thumb controls. For more information about UI Automation properties, see Retrieving Properties from UI Automation Elements.

UI Automation PropertyValueNotes
UIA_AutomationIdPropertyIdSee notes.The value of this property must be unique among all peer elements in the raw view of the UI Automation tree.
UIA_BoundingRectanglePropertyIdSee notes.The outermost rectangle that contains the whole control.
UIA_ClickablePointPropertyIdSee notes.A point within the visible client area of the thumb control.
UIA_IsContentElementPropertyIdFALSEThe thumb control is never included in the content view of the UI Automation tree.
UIA_IsControlElementPropertyIdTRUEThe thumb control is always included in the control view of the UI Automation tree.
UIA_IsKeyboardFocusablePropertyIdSee notes.If the control can receive keyboard focus, it must support this property. A thumb control can receive the focus if it is used as a "gripper" object for sizing a window or a pane. A thumb control in a slider or scroll bar should never receive the focus.
UIA_LabeledByPropertyIdNULLThumb controls never have a label.
UIA_LocalizedControlTypePropertyIdSee notes.Localized string corresponding to the Thumb control type. The default value is "thumb" for en-US or English (United States).
UIA_NamePropertyIdNULLBecause the thumb control is not available in the content view of the UI Automation tree, it does not require a name.


Required Control Patterns

The following table lists the UI Automation control patterns required to be supported by thumb controls. For more information on control patterns, see UI Automation Control Patterns Overview.

Control PatternSupportNotes
ITransformProvider RequiredEnables the thumb control to be moved on the screen. Because the thumb control typically cannot be resized or rotated, the Transform control pattern primarily supports the Move function.


Required Events

The following table lists the UI Automation events that thumb controls are required to support. For more information on events, see UI Automation Events Overview.

UI Automation EventNotes
UIA_BoundingRectanglePropertyId property-changed event.
UIA_IsEnabledPropertyId property-changed event.If the control supports the IsEnabled property, it must support this event.
UIA_IsOffscreenPropertyId property-changed event.If the control supports the IsOffscreen property, it must support this event.


Related topics

UI Automation Control Types Overview
UI Automation Overview



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