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Perf: cut crosshair/hover hot-path cost (shared UI, both apps) (P2) #1113

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Merged
erikdarlingdata merged 1 commit into from
Jun 11, 2026
+87 −42
Merged

Perf: cut crosshair/hover hot-path cost (shared UI, both apps) (P2) #1113

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46 changes: 30 additions & 16 deletions PerformanceMonitor.Ui/ChartHoverHelper.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ internal sealed class ChartHoverHelper
private readonly TextBlock _text;
private string _unit;
private DateTime _lastUpdate;
private bool _needsReanchor = true;

public ChartHoverHelper(ScottPlot.WPF.WpfPlot chart, string unit)
{
Expand Down Expand Up @@ -79,14 +80,17 @@ public void Dispose()
_barPlots.Clear();
}

private void OnChartVisibilityChanged(object sender, DependencyPropertyChangedEventArgs e) =>
_popup.IsOpen = false;

private void OnChartUnloaded(object sender, RoutedEventArgs e) =>
_popup.IsOpen = false;
private void OnChartVisibilityChanged(object sender, DependencyPropertyChangedEventArgs e) => ForceReanchor();
private void OnChartUnloaded(object sender, RoutedEventArgs e) => ForceReanchor();
private void OnChartLoaded(object sender, RoutedEventArgs e) => ForceReanchor();

private void OnChartLoaded(object sender, RoutedEventArgs e) =>
/* A tab visibility/load transition can wedge the popup open with a stale anchor; flag a
re-anchor so the next mouse move toggles it once instead of toggling on every move. */
private void ForceReanchor()
{
_popup.IsOpen = false;
_needsReanchor = true;
}

public void Clear()
{
Expand Down Expand Up @@ -151,14 +155,17 @@ private void FindNearestBar(ScottPlot.Pixel pixel, ref double bestYDistance,
{
foreach (var (barPlot, label) in _barPlots)
{
/* Bar width in pixels is the same for every bar on a linear axis, so compute it once
per plot (lazily on the first bar) instead of two GetPixel calls per bar. */
double? halfWidthPx = null;
foreach (var bar in barPlot.Bars)
{
halfWidthPx ??= Math.Abs(
_chart.Plot.GetPixel(new ScottPlot.Coordinates(bar.Size / 2, 0)).X
- _chart.Plot.GetPixel(new ScottPlot.Coordinates(0, 0)).X);
var topPixel = _chart.Plot.GetPixel(new ScottPlot.Coordinates(bar.Position, bar.Value));
double halfWidthPx = Math.Abs(
_chart.Plot.GetPixel(new ScottPlot.Coordinates(bar.Position + bar.Size / 2, bar.Value)).X
- topPixel.X);
double dx = Math.Abs(topPixel.X - pixel.X);
if (dx > halfWidthPx + 4) continue;
if (dx > halfWidthPx.Value + 4) continue;
double dy = Math.Abs(topPixel.Y - pixel.Y);
if (dy < bestYDistance)
{
Expand Down Expand Up @@ -229,12 +236,19 @@ pick the series closest in Y (nearest line to cursor). */
_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;
/* Updating the offsets above moves an already-open popup, so only toggle IsOpen
when a re-anchor is actually needed (a tab visibility/load transition wedged it).
Toggling every move tore down and recreated the popup's native window each frame. */
if (_needsReanchor)
{
if (_popup.IsOpen) _popup.IsOpen = false;
_popup.IsOpen = true;
_needsReanchor = false;
}
else if (!_popup.IsOpen)
{
_popup.IsOpen = true;
}
}
else
{
Expand Down
83 changes: 57 additions & 26 deletions PerformanceMonitor.Ui/CorrelatedCrosshairManager.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,8 @@ internal sealed class CorrelatedCrosshairManager : IDisposable
private readonly Popup _tooltip;
private readonly TextBlock _tooltipText;
private DateTime _lastUpdate;
private double _lastPixelX = double.NaN;
private bool _needsReanchor = true;

public CorrelatedCrosshairManager()
{
Expand Down Expand Up @@ -89,14 +91,17 @@ public void AddLane(ScottPlot.WPF.WpfPlot chart, string label, string unit)
_lanes.Add(lane);
}

private void OnLaneVisibilityChanged(object sender, DependencyPropertyChangedEventArgs e) =>
_tooltip.IsOpen = false;

private void OnLaneUnloaded(object sender, RoutedEventArgs e) =>
_tooltip.IsOpen = false;
private void OnLaneVisibilityChanged(object sender, DependencyPropertyChangedEventArgs e) => ForceReanchor();
private void OnLaneUnloaded(object sender, RoutedEventArgs e) => ForceReanchor();
private void OnLaneLoaded(object sender, RoutedEventArgs e) => ForceReanchor();

private void OnLaneLoaded(object sender, RoutedEventArgs e) =>
/* A tab visibility/load transition can leave the popup wedged open with a stale anchor; flag a
re-anchor so the next mouse move toggles it once, instead of toggling on every move. */
private void ForceReanchor()
{
_tooltip.IsOpen = false;
_needsReanchor = true;
}

/// <summary>
/// Sets the expected baseline range for a lane (upper/lower bounds).
Expand Down Expand Up @@ -233,10 +238,15 @@ private void OnMouseMove(LaneInfo sourceLane, MouseEventArgs e)
if (sourceLane.VLine == null) return;

var now = DateTime.UtcNow;
if ((now - _lastUpdate).TotalMilliseconds < 16) return;
_lastUpdate = now;
if ((now - _lastUpdate).TotalMilliseconds < 33) return;

var pos = e.GetPosition(sourceLane.Chart);
/* The crosshair only tracks X; skip when the cursor hasn't moved a full pixel
horizontally so a near-still mouse doesn't re-render every lane ~30x/sec. */
if (!double.IsNaN(_lastPixelX) && Math.Abs(pos.X - _lastPixelX) < 1.0) return;
_lastUpdate = now;
_lastPixelX = pos.X;

var dpi = VisualTreeHelper.GetDpi(sourceLane.Chart);
var pixel = new ScottPlot.Pixel(
(float)(pos.X * dpi.DpiScaleX),
Expand All @@ -258,11 +268,10 @@ crosshair update rather than crashing to the dispatcher handler. */
if (_comparisonLabel != null)
_tooltipText.Inlines.Add(new Run($" (dashed = {_comparisonLabel})") { Foreground = DimBrush });

var defaultBrush = new SolidColorBrush(Color.FromRgb(0xE0, 0xE0, 0xE0));

foreach (var lane in _lanes)
{
if (lane.VLine == null) continue;
if (!lane.Chart.IsVisible) continue;

lane.VLine.IsVisible = true;
lane.VLine.X = xValue;
Expand All @@ -277,15 +286,15 @@ crosshair update rather than crashing to the dispatcher handler. */
var indicator = GetBaselineIndicator(lane, value.Value);

// Tooltip: value + arrow + "30d avg" context
_tooltipText.Inlines.Add(new Run($"\n{lane.Label}: {value.Value:N1} {lane.Unit}") { Foreground = defaultBrush });
_tooltipText.Inlines.Add(new Run($"\n{lane.Label}: {value.Value:N1} {lane.Unit}") { Foreground = DefaultBrush });
if (indicator != null)
{
_tooltipText.Inlines.Add(new Run($" {indicator.Value.Symbol}") { Foreground = indicator.Value.Brush });
}
}
else
{
_tooltipText.Inlines.Add(new Run($"\n{lane.Label}: —") { Foreground = defaultBrush });
_tooltipText.Inlines.Add(new Run($"\n{lane.Label}: —") { Foreground = DefaultBrush });
}
}
else if (lane.Series.Count > 1)
Expand All @@ -296,31 +305,38 @@ crosshair update rather than crashing to the dispatcher handler. */
string unit = series.Unit ?? lane.Unit;
if (value.HasValue)
{
_tooltipText.Inlines.Add(new Run($"\n{series.Name}: {value.Value:N0} {unit}") { Foreground = defaultBrush });
_tooltipText.Inlines.Add(new Run($"\n{series.Name}: {value.Value:N0} {unit}") { Foreground = DefaultBrush });
var indicator = GetBaselineIndicator(lane, value.Value);
if (indicator != null)
_tooltipText.Inlines.Add(new Run($" {indicator.Value.Symbol}") { Foreground = indicator.Value.Brush });
}
else
_tooltipText.Inlines.Add(new Run($"\n{series.Name}: —") { Foreground = defaultBrush });
_tooltipText.Inlines.Add(new Run($"\n{series.Name}: —") { Foreground = DefaultBrush });
}
}
else
{
_tooltipText.Inlines.Add(new Run($"\n{lane.Label}: —") { Foreground = defaultBrush });
_tooltipText.Inlines.Add(new Run($"\n{lane.Label}: —") { Foreground = DefaultBrush });
}

lane.Chart.Refresh();
}
_tooltip.PlacementTarget = sourceLane.Chart;
_tooltip.HorizontalOffset = pos.X + 15;
_tooltip.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 (_tooltip.IsOpen) _tooltip.IsOpen = false;
_tooltip.IsOpen = true;
/* Updating the offsets above moves an already-open popup, so only toggle IsOpen when a
re-anchor is actually needed (a tab visibility/load transition wedged it with a stale
anchor). Toggling every move tore down and recreated the popup's native window each frame. */
if (_needsReanchor)
{
if (_tooltip.IsOpen) _tooltip.IsOpen = false;
_tooltip.IsOpen = true;
_needsReanchor = false;
}
else if (!_tooltip.IsOpen)
{
_tooltip.IsOpen = true;
}
}

private static double? FindNearestValue(DataSeries series, double targetX)
Expand Down Expand Up @@ -358,9 +374,19 @@ unloaded stays "open" with a stale anchor and never appears on
return val;
}

private static readonly SolidColorBrush RedBrush = new(Color.FromRgb(0xFF, 0x52, 0x52));
private static readonly SolidColorBrush GreenBrush = new(Color.FromRgb(0x69, 0xF0, 0x69));
private static readonly SolidColorBrush DimBrush = new(Color.FromRgb(0x90, 0x96, 0xA0));
private static readonly SolidColorBrush RedBrush = Frozen(0xFF, 0x52, 0x52);
private static readonly SolidColorBrush GreenBrush = Frozen(0x69, 0xF0, 0x69);
private static readonly SolidColorBrush DimBrush = Frozen(0x90, 0x96, 0xA0);
/* Reused on every mouse-move; cached + frozen so each move doesn't allocate a brush and they
carry no dispatcher-affinity / change-notification overhead. */
private static readonly SolidColorBrush DefaultBrush = Frozen(0xE0, 0xE0, 0xE0);

private static SolidColorBrush Frozen(byte r, byte g, byte b)
{
var brush = new SolidColorBrush(Color.FromRgb(r, g, b));
brush.Freeze();
return brush;
}

private record struct BaselineIndicator(string Symbol, SolidColorBrush Brush);

Expand Down Expand Up @@ -393,11 +419,16 @@ private record struct BaselineIndicator(string Symbol, SolidColorBrush Brush);
private void OnMouseLeave()
{
_tooltip.IsOpen = false;
_lastPixelX = double.NaN;
foreach (var lane in _lanes)
{
if (lane.VLine != null)
/* Only refresh lanes whose VLine was actually showing — crossing the stacked lanes
fires MouseLeave per boundary, so refreshing already-hidden lanes is wasted work. */
if (lane.VLine != null && lane.VLine.IsVisible)
{
lane.VLine.IsVisible = false;
lane.Chart.Refresh();
lane.Chart.Refresh();
}
}
}

Expand Down
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