Only the foreground window can capture mouse input. The lParam parameter of the message specifies a handle to the window that is gaining the mouse capture. When the mouse capture changes, the system sends a WM_CAPTURECHANGED message to the window that is losing the mouse capture. The window receives all mouse messages until the application calls the ReleaseCapture function or specifies another capture window, or until the user clicks a window created by another thread. An application can change this behavior by using the SetCapture function to route mouse messages to a specific window. The system typically posts a mouse message to the window that contains the cursor hot spot when a mouse event occurs. For more information about mouse cursors, see Cursors. You can use the SystemParametersInfo function with the SPI_GETMOUSE or SPI_SETMOUSE flag to retrieve or set mouse speed. The system maintains a variable that controls mouse speed-that is, the distance the cursor moves when the user moves the mouse. The window need not be active or have the keyboard focus to receive a mouse message. ![]() When a mouse event occurs, the window that contains the hot spot typically receives the mouse message resulting from the event. The mouse cursor contains a single-pixel point called the hot spot, a point that the system tracks and recognizes as the position of the cursor. When the user moves the mouse, the system moves a bitmap on the screen called the mouse cursor. This section covers the following topics: The application should provide full keyboard support as well.Īn application receives mouse input in the form of messages that are sent or posted to its windows. A well-written application should include a mouse interface, but it should not depend solely on the mouse for acquiring user input. This particular behavior could also be attached to any existing control that contains an embedded ScrollViewer, such as a GridView, and it would still function correctly.The mouse is an important, but optional, user-input device for applications. This creates a Behaviors collection as an Attached Property on the inner ScrollViewer that contains a BubbleMouseWheelEvents behavior. Add the following line to the namespaces of your XAML. Otherwise, the event is routed as normal.Īttaching the Behavior to an Element in XAMLįirst, the interactivity xml-namespace must be brought in to scope before it can be used in XAML. It then raises a new MouseWheelEvent routed to AssociatedObject. If so, it sets e.Handled to true to prevent the default action of the event. It checks the position to see if it needs to forward the event up the visual tree to any ScrollViewer higher hierarchy. This behavior hooks in to the PreviewMouseWheel event, which gives it a change to intercept the event before the ScrollViewer has a chance to see it. Care should be taken to remove any event handlers, or otherwise clean up objects to avoid memory leaks. A similar method, OnDetached is called when the behavior need to be unhooked from the associated element. This method allows the behavior to hook in to events from the control it is attached to (via AssociatedControl). When the Behavior is instantiated from XAML, the OnAttached method is called. ![]() ![]() Var e2 = new MouseWheelEventArgs(e.MouseDevice, e.Timestamp, e.Delta) Į2.RoutedEvent = UIElement.MouseWheelEvent īehaviors subclass the Behavior base-class, with T being the type of control that it is able to attach to, in this case UIElement. RerouteTo = (UIElement) VisualTreeHelper.GetParent(AssociatedObject) If (ReferenceEquals(scrollViewer, AssociatedObject)) If ((scrollPos = scrollViewer.ScrollableHeight & e.Delta 0)) Var scrollPos = scrollViewer.ContentVerticalOffset Var scrollViewer = AssociatedObject.GetChildOf(includeSelf: true) Private void PreviewMouseWheel(object sender, MouseWheelEventArgs e) public class BubbleMouseWheelEvents : Behavior ![]() Without this behavior, the events will never make it out of the inner ScrollViewer. This behavior will cause mouse wheel events from an inner ScrollViewer to bubble up to the parent ScrollViewer when the inner one is at either its upper or lower limit.
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