| -api-id | -api-type |
|---|---|
M:Windows.UI.Xaml.Media.VisualTreeHelper.FindElementsInHostCoordinates(Windows.Foundation.Point,Windows.UI.Xaml.UIElement,System.Boolean) |
winrt method |
Retrieves a set of objects that are located within a specified x-y coordinate point of an app UI. The set of objects represents the components of a visual tree that share that point.
The point to use as the determination point. This point is using the coordinate space of the app window, not of any specific element (and not of subtree if specified).
An object to search for. If the subtree object exists in the overall set of elements that exist at the specified intersectingPoint coordinates, then the return value contains only the subtree object and any objects that have a higher z-order than subtree, listed by inverse of z-order. If the subtree object doesn't exist at intersectingPoint coordinates, the return value will be empty.
true to include all elements that intersect, including those elements considered to be invisible to hit testing. false to find only visible, hit-testable elements. The default is false.
An enumerable set of UIElement objects that are determined to be located in the visual tree composition at the specified point, listed by inverse of z-order.
An element is considered hit-testable if it both occupies space in the layout and "produces ink". For elements that have a Brush, any non-null Brush is considered something that produces ink, even if the Brush doesn't produce visible pixels. For example, a SolidColorBrush with its color set to Transparent still produces ink. Only a null brush does not produce ink. The Opacity property is not considered. The element still produces ink even if it's Opacity is 0.
When the includeAllElements parameter is set to true, elements that don't produce ink are considered for hit-testing. In this case, as long as the element meets the spatial requirements (the point intersects the element bounds), then it and its ancestors are included in the results.
Note
Some special elements, like SwapChainPanel and MediaElement, don’t have a brush but can still produce ink.
Given this XAML UI:
<Canvas Name="canvas">
<Rectangle Name="outermost" Fill="Red" Width="200" Height="200"/>
<Rectangle Canvas.Left="40" Canvas.Top="40" Name="hidden" Fill="Green" Width="120" Height="120"/>
<Rectangle Canvas.Left="40" Canvas.Top="40" Name="shown" Fill="Orange" Width="120" Height="120"/>
<Rectangle Canvas.Left="80" Canvas.Top="80" Name="center" Fill="Yellow" Width="40" Height="40"/>
<Rectangle Canvas.Left="190" Canvas.Top="190" Name="bottomright" Fill="Pink" Width="10" Height="10"/>
</Canvas>Here are some example usages and results from FindElementsInHostCoordinates, using different subtree values:
private void Test(object sender, RoutedEventArgs e)
{
IEnumerable<UIElement> hits;
hits = VisualTreeHelper.FindElementsInHostCoordinates(
new Point(100,100), canvas, true);
foreach (UIElement element in hits)
{
//run logic here, such as log the results
}
// results in the following set of elements, listed by Name:
// center - the element that is topmost in z-order at 100,100
// shown - also renders at 100,100 but is underneath 'center'
// hidden - is entirely underneath 'shown',
// and lower in z-order because 'hidden' declared before 'shown' in XAML
// outermost - draws under all the above at 100,100
// canvas - the 'subtree' value, so that's the last element reported
hits = VisualTreeHelper.FindElementsInHostCoordinates(
new Point(100, 100), center, true);
foreach (UIElement element in hits) {
//run logic here, such as log the results
}
// results in 'center', because it is 'subtree' and also topmost
hits = VisualTreeHelper.FindElementsInHostCoordinates(
new Point(100, 100), bottomright, true);
// results in an empty set, 'bottomright' doesn't render at 100,100
}Point, FindElementsInHostCoordinates(Point, UIElement), FindElementsInHostCoordinates(Rect, UIElement), FindElementsInHostCoordinates(Rect, UIElement, Boolean), Mouse interactions