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BurningLightsjsuarezruizPureWeen
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Android pan fixes (#21547)
### Description of Change Fixes jankiness with using a PanGestureRecognizer to translate a control. <!-- Enter description of the fix in this section --> ### Issues Fixed Fixes #20772 <!-- Are you targeting main? All PRs should target the main branch unless otherwise noted. --> --------- Co-authored-by: Javier Suárez <javiersuarezruiz@hotmail.com> Co-authored-by: Shane Neuville <shneuvil@microsoft.com>
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‎src/Controls/src/Core/Platform/Android/InnerGestureListener.cs‎

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@@ -235,8 +235,8 @@ protected override void Dispose(bool disposing)
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void SetStartingPosition(MotionEvent e1)
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{
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_lastX = e1.GetX();
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_lastY = e1.GetY();
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_lastX = e1.RawX;
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_lastY = e1.RawY;
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}
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bool StartScrolling(MotionEvent e2)
@@ -249,8 +249,8 @@ bool StartScrolling(MotionEvent e2)
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_isScrolling = true;
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float totalX = e2.GetX() - _lastX;
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float totalY = e2.GetY() - _lastY;
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float totalX = e2.RawX - _lastX;
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float totalY = e2.RawY - _lastY;
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return _scrollDelegate(totalX, totalY, e2.PointerCount) || _swipeDelegate(totalX, totalY);
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}

‎src/Controls/src/Core/Platform/GestureManager/GesturePlatformManager.Android.cs‎

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@@ -282,7 +282,7 @@ void OnPlatformViewTouched(object? sender, AView.TouchEventArgs e)
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}
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if (e.Event != null)
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OnTouchEvent(e.Event);
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e.Handled = OnTouchEvent(e.Event);
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}
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void SetupElement(VisualElement? oldElement, VisualElement? newElement)

‎src/Controls/tests/TestCases.HostApp/Issues/Issue20772.cs‎

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using Microsoft.Maui;
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using Microsoft.Maui.Controls;
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using Microsoft.Maui.Graphics;
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using Microsoft.Maui.Layouts;
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namespace Maui.Controls.Sample.Issues
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{
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[Issue(IssueTracker.Github, 20772, "Flickering occurs while updating the width of ContentView through PanGestureRecognizer", PlatformAffected.Android)]
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public partial class Issue20772 : ContentPage
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{
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public Issue20772()
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{
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Content = new CustomView20772();
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}
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}
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public abstract class ControlLayout20772 : Layout
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{
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internal abstract Size LayoutArrangeChildren(Rect bounds);
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internal abstract Size LayoutMeasure(double widthConstraint, double heightConstraint);
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}
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internal class ControlLayoutManager20772 : LayoutManager
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{
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ControlLayout20772 layout;
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internal ControlLayoutManager20772(ControlLayout20772 layout) : base(layout)
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{
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this.layout = layout;
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}
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public override Size ArrangeChildren(Rect bounds) => this.layout.LayoutArrangeChildren(bounds);
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public override Size Measure(double widthConstraint, double heightConstraint) => this.layout.LayoutMeasure(widthConstraint, heightConstraint);
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}
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public class CustomView20772 : ControlLayout20772
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{
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CustomChild20772 _customChild;
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CustomContent20772 _customContent;
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Label _statusLabel;
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public CustomView20772()
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{
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_customChild = new CustomChild20772();
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_customContent = new CustomContent20772();
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_statusLabel = new Label
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{
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AutomationId = "StatusLabel",
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Text = "Waiting for pan gesture...",
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HeightRequest = 50
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};
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// Give status label access to CustomChild for width tracking
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_customContent.ChildView = _customChild;
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_customContent.StatusLabel = _statusLabel;
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this.Children.Add(_customChild);
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this.Children.Add(_customContent);
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this.Children.Add(_statusLabel);
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}
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protected override ILayoutManager CreateLayoutManager()
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{
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return new ControlLayoutManager20772(this);
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}
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internal override Size LayoutArrangeChildren(Rect bounds)
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{
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(_customChild as IView).Arrange(new Rect(0, 0, _customChild.WidthRequest, _customChild.HeightRequest));
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(_customContent as IView).Arrange(new Rect(_customChild.WidthRequest, 0, _customContent.WidthRequest, _customContent.HeightRequest));
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(_statusLabel as IView).Arrange(new Rect(0, 120, bounds.Width, 50));
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return bounds.Size;
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}
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internal override Size LayoutMeasure(double widthConstraint, double heightConstraint)
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{
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(_customChild as IView).Measure(_customChild.WidthRequest, _customChild.HeightRequest);
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(_customContent as IView).Measure(_customContent.WidthRequest, _customContent.HeightRequest);
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(_statusLabel as IView).Measure(widthConstraint, 50);
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return new Size(widthConstraint, heightConstraint);
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}
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}
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public class CustomChild20772 : ContentView
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{
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Label _label;
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public CustomChild20772()
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{
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AutomationId = "CustomChild";
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BackgroundColor = Colors.Pink;
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HeightRequest = 100;
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WidthRequest = 180;
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_label = new Label() { Text = "Custom Child", HeightRequest = 100, WidthRequest = 180 };
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Content = _label;
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}
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}
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public class CustomContent20772 : ContentView
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{
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Label _label;
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double _startingChildWidth;
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double _totalPanDistance;
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#nullable enable
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public Label? StatusLabel { get; set; }
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public ContentView? ChildView { get; set; }
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#nullable restore
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public CustomContent20772()
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{
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AutomationId = "CustomContent";
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BackgroundColor = Colors.Yellow;
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HeightRequest = 100;
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WidthRequest = 180;
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_label = new Label() { Text = "Drag here", HeightRequest = 100, WidthRequest = 180 };
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Content = _label;
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PanGestureRecognizer gestureRecognizer = new PanGestureRecognizer();
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gestureRecognizer.PanUpdated += OnGestureRecognizerPanUpdated;
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GestureRecognizers.Add(gestureRecognizer);
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}
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void OnGestureRecognizerPanUpdated(object sender, PanUpdatedEventArgs e)
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{
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switch (e.StatusType)
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{
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case GestureStatus.Started:
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_startingChildWidth = ChildView?.WidthRequest ?? 180;
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_totalPanDistance = 0;
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break;
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case GestureStatus.Running:
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_totalPanDistance = e.TotalX;
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OnResizing(e);
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break;
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case GestureStatus.Completed:
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case GestureStatus.Canceled:
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// Check if final width matches expected width based on pan distance
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// With the bug: width changes erratically because coordinates jump
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// With fix: width change = pan distance (approximately)
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if (StatusLabel is not null && ChildView is not null)
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{
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var actualWidthChange = ChildView.WidthRequest - _startingChildWidth;
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var expectedWidthChange = _totalPanDistance;
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var difference = Math.Abs(actualWidthChange - expectedWidthChange);
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// Allow some tolerance for timing/rounding
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// With the bug, the difference would be huge due to coordinate jumps
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StatusLabel.Text = $"WidthChange:{actualWidthChange:F0},Expected:{expectedWidthChange:F0}";
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}
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break;
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}
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}
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void OnResizing(PanUpdatedEventArgs e)
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{
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// The key issue: when we update WidthRequest, the view moves
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// With relative coordinates (bug): next TotalX is wrong because view position changed
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// With raw coordinates (fix): TotalX stays consistent
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if (ChildView is not null)
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{
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// Set width directly based on starting width + total pan distance
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// This is the expected behavior with raw coordinates
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ChildView.WidthRequest = _startingChildWidth + e.TotalX;
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ChildView.InvalidateMeasure();
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}
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}
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}
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}

‎src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue20772.cs‎

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using NUnit.Framework;
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using UITest.Appium;
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using UITest.Core;
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namespace Microsoft.Maui.TestCases.Tests.Issues
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{
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public class Issue20772 : _IssuesUITest
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{
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public Issue20772(TestDevice device) : base(device) { }
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public override string Issue => "Flickering occurs while updating the width of ContentView through PanGestureRecognizer";
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[Test]
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[Category(UITestCategories.Gestures)]
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public void PanGestureDoesNotFlickerWhenResizingView()
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{
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// Wait for the page to load
18+
App.WaitForElement("CustomContent");
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// Get initial width of the child element
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var childBefore = App.WaitForElement("CustomChild").GetRect();
22+
var initialWidth = childBefore.Width;
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// Get the element to pan on
25+
var element = App.WaitForElement("CustomContent").GetRect();
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var startX = element.X + (element.Width / 2);
27+
var startY = element.Y + (element.Height / 2);
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// Perform a pan gesture that drags to the right by 100 pixels
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// This will trigger the view resize during the pan
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var dragDistance = 100;
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App.DragCoordinates(startX, startY, startX + dragDistance, startY);
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// Wait for the status label to update with the result
35+
App.WaitForElement("StatusLabel");
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// Get final width of the child element
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var childAfter = App.WaitForElement("CustomChild").GetRect();
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var finalWidth = childAfter.Width;
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var actualWidthChange = finalWidth - initialWidth;
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// The test passes if the width change approximately matches the drag distance
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// With the bug (before fix): coordinates jump around, width change is erratic
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// With the fix: width change should be close to drag distance (within tolerance)
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// We allow 30 pixel tolerance for timing variations
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Assert.That(actualWidthChange, Is.EqualTo(dragDistance).Within(30),
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$"Width change ({actualWidthChange}) should approximately match drag distance ({dragDistance}). " +
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$"Initial: {initialWidth}, Final: {finalWidth}");
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}
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}
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}

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