| -api-id | -api-type |
|---|---|
M:Windows.UI.Xaml.Media.VisualTreeHelper.FindElementsInHostCoordinates(Windows.Foundation.Rect,Windows.UI.Xaml.UIElement,System.Boolean) |
winrt method |
Retrieves a set of objects that are located within a specified Rect frame of an app UI. The set of objects represents the components of a visual tree that share a rectangular area, and might include elements that overdraw.
The Rect to use as the determination area. This frame 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 within the specified intersectingRect, then the return value contains only the subtree object and elements that are drawing on top of its space. If the subtree object doesn't exist within the intersectingRect frame, 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 in the specified Rect frame.
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 rect 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 Rect(75,75,50,50), 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 last declared XAML element is first returned, if within the area
// shown - renders, underneath 'center' in part of the area but visible on the edges
// hidden - entirely under 'shown', not visible but part of the area, an overdraw
// outermost - draws under all the above
// canvas - the 'subtree' value, and the last element reported
hits = VisualTreeHelper.FindElementsInHostCoordinates(
new Rect(75,75,50,50), center, true);
foreach (UIElement element in hits) {
//run logic here, such as log the results
}
// results in only 'center', because it was 'subtree' and it's also topmost
hits = VisualTreeHelper.FindElementsInHostCoordinates(
new Rect(75,75,50,50), bottomright, true);
// results in an empty set, 'bottomright' isn't in the specified rect
}FindElementsInHostCoordinates(Point, UIElement), FindElementsInHostCoordinates(Rect, UIElement), FindElementsInHostCoordinates(Point, UIElement, Boolean), Mouse interactions