From 9581b801bcf3f165e83dcea46b73dad6cd880a65 Mon Sep 17 00:00:00 2001
From: Erik Darling <2136037+erikdarlingdata@users.noreply.github.com>
Date: Sat, 2 May 2026 10:37:40 -0400
Subject: [PATCH] =?UTF-8?q?Fix=20#916=20(Lite)=20=E2=80=94=20Memory=20tab?=
 =?UTF-8?q?=20tooltip=20stops=20working=20after=20returning=20to=20tab?=
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Mirrors Dashboard fix in 4e58e8a. WPF Popup with PlacementTarget = chart
can wedge when the user navigates away from a TabItem mid-hover: WPF
unloads the parent without firing MouseLeave on the chart, so
_popup.IsOpen stays true with a stale anchor. On return, OnMouseMove
sets IsOpen = true but it is already true — the assignment is a no-op
and the popup never re-anchors or appears.

Lite has the same nested TabControl pattern (parent Memory tab hosting
Memory Overview / Memory Clerks / Memory Grants / Memory Pressure Events
sub-tabs) so the bug surfaces the same way.

- Force _popup.IsOpen = false on chart Loaded / Unloaded / IsVisibleChanged.
- In OnMouseMove, toggle IsOpen off then on so WPF re-evaluates placement
  even when the popup believes it is already open.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 Lite/Helpers/ChartHoverHelper.cs | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/Lite/Helpers/ChartHoverHelper.cs b/Lite/Helpers/ChartHoverHelper.cs
index 28241eb..1e0514d 100644
--- a/Lite/Helpers/ChartHoverHelper.cs
+++ b/Lite/Helpers/ChartHoverHelper.cs
@@ -53,6 +53,16 @@ public ChartHoverHelper(ScottPlot.WPF.WpfPlot chart, string unit)
 
         chart.MouseMove += OnMouseMove;
         chart.MouseLeave += OnMouseLeave;
+
+        /* Tab switching can leave the popup wedged: WPF unloads the parent TabItem
+           without firing MouseLeave, so IsOpen stays true with a stale anchor.
+           When the chart becomes visible again, OnMouseMove sets IsOpen = true
+           but it is already true, so the popup never re-anchors and never shows.
+           Force-close on every visibility/load transition so the next mouse move
+           re-opens cleanly. */
+        chart.IsVisibleChanged += OnChartVisibilityChanged;
+        chart.Unloaded += OnChartUnloaded;
+        chart.Loaded += OnChartLoaded;
     }
 
     public string Unit { get => _unit; set => _unit = value; }
@@ -61,11 +71,23 @@ public void Dispose()
     {
         _chart.MouseMove -= OnMouseMove;
         _chart.MouseLeave -= OnMouseLeave;
+        _chart.IsVisibleChanged -= OnChartVisibilityChanged;
+        _chart.Unloaded -= OnChartUnloaded;
+        _chart.Loaded -= OnChartLoaded;
         _popup.IsOpen = false;
         _scatters.Clear();
         _barPlots.Clear();
     }
 
+    private void OnChartVisibilityChanged(object sender, DependencyPropertyChangedEventArgs e) =>
+        _popup.IsOpen = false;
+
+    private void OnChartUnloaded(object sender, RoutedEventArgs e) =>
+        _popup.IsOpen = false;
+
+    private void OnChartLoaded(object sender, RoutedEventArgs e) =>
+        _popup.IsOpen = false;
+
     public void Clear()
     {
         _scatters.Clear();
@@ -193,6 +215,11 @@ private void OnMouseMove(object sender, MouseEventArgs e)
             _text.Text = $"{bestLabel}\n{valueFormatted} {_unit}\n{time:HH:mm:ss}";
             _popup.HorizontalOffset = pos.X + 15;
             _popup.VerticalOffset = pos.Y + 15;
+            /* Toggle if already open so WPF re-evaluates the placement target.
+               Without this, a popup that was IsOpen = true when its TabItem was
+               unloaded stays "open" with a stale anchor and never appears on
+               return — the assignment below is a no-op. */
+            if (_popup.IsOpen) _popup.IsOpen = false;
             _popup.IsOpen = true;
         }
         else