Mouse Input and the WPF - Mouse Input

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Mouse input is directed to whichever element is directly under the mouse cursor. All user interface elements derive from the UIElement base class, which defines a number of mouse input events. These are listed in Table 4-1.

Table 4-1. Mouse input events

Event	Routing	Meaning
GotMouseCapture	Bubble	Element captured the mouse.
LostMouseCapture	Bubble	Element lost mouse capture.
MouseEnter	Direct	Mouse pointer moved into element.
MouseLeave	Direct	Mouse pointer moved out of element.
PreviewMouseLeftButtonDown, MouseLeftButtonDown	Tunnel, Bubble	Left mouse button pressed while pointer inside element.
PreviewMouseLeftButtonUp, MouseLeftButtonUp	Tunnel, Bubble	Left mouse button released while pointer inside element.
PreviewMouseRightButtonDown, MouseRightButtonDown	Tunnel, Bubble	Right mouse button pressed while pointer inside element.
PreviewMouseRightButtonUp, MouseRightButtonUp	Tunnel, Bubble	Right mouse button released while pointer inside element.
PreviewMouseDown, MouseDown	Tunnel, Bubble	Mouse button pressed while pointer inside element (raised for any mouse button).
PreviewMouseUp, MouseUp	Tunnel, Bubble	Mouse button released while pointer inside element (raised for any mouse button).
PreviewMouseMove, MouseMove	Tunnel, Bubble	Mouse pointer moved while pointer inside element.
PreviewMouseWheel, MouseWheel	Tunnel, Bubble	Mouse wheel moved while pointer inside element.
QueryCursor	Bubble	Mouse cursor shape to be determined while pointer inside element.

In addition to the mouse-related events,UIElementalso defines a pair of properties that indicate whether the mouse pointer is currently over the element:IsMouseOverandIsMouseDirectlyOver. The distinction between these two properties is that the former will be true if the cursor is over the element in question or over any of its child elements, but the latter will be true only if the cursor is over the element in question but not one of its children.

Note that the basic set of mouse events shown in Table 4-1 does not include a Clickevent. This is because clicks are a higher-level concept than basic mouse input—a button can be “clicked” with the mouse, the stylus, the keyboard, or through the Windows accessibility API. Moreover, clicking doesn’t necessarily correspond directly to a single mouse event—usually, the user has to press and release the mouse button while the mouse is over the control to register as a click. Accordingly, these higher-level events are provided by more specialized element types. TheControl class adds aPreviewMouseDoubleClickandMouseDoubleClick event pair. Likewise,ButtonBase—the base class ofButton,CheckBox, andRadioButton—goes on to add aClick event.

Next: Mouse Input and Hit Testing >>
 

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