Questions

This was actually converted to a support ticket, but for the benefit of the community, here is the answer:

We were able to reproduce this in a simple unit test:

   [Test]
    public void WhenSelect_SetStroke_Deselect_ShouldKeepColor()
    {
        var flrs = new FastLineRenderableSeries() {Stroke = Colors.Red};
        flrs.SelectedSeriesStyle = new Style(typeof(FastLineRenderableSeries)) { Setters = { new Setter() { Property = FastLineRenderableSeries.StrokeProperty, Value = Colors.Green}}};

        Assert.That(flrs.Stroke, Is.EqualTo(Colors.Red));

        // Apply SelectedSeriesStyle
        flrs.IsSelected = true;
        Assert.That(flrs.Stroke, Is.EqualTo(Colors.Green));

        // Deselect, should revert 
        flrs.IsSelected = false;
        Assert.That(flrs.Stroke, Is.EqualTo(Colors.Red));

        // Select, apply again
        flrs.IsSelected = true;
        Assert.That(flrs.Stroke, Is.EqualTo(Colors.Green));
        // Change color
        flrs.Stroke = Colors.Purple;
        flrs.IsSelected = false;
        Assert.That(flrs.Stroke, Is.EqualTo(Colors.Purple));
    }

Now with discussion with the team, we don’t think this is a bug, but a side effect of how we implement selection. When the series is selected the SelectedSeriesStyle is applied. When you deselect, the old style is applied.

To workaround, you can do this:

• Handle RenderableSeries.SelectionChanged

• On Deselection, apply your chosen color

   [Test]
  public void WhenSelect_SetStroke_Deselect_ShouldKeepColor()
  {
      var flrs = new FastLineRenderableSeries() {Stroke = Colors.Red};
      flrs.SelectedSeriesStyle = new Style(typeof(FastLineRenderableSeries)) { Setters = { new Setter() { Property = FastLineRenderableSeries.StrokeProperty, Value = Colors.Green}}};
      Color? selectedColor = null;
      flrs.SelectionChanged += (s, e) =>
      {
          if (selectedColor != null && flrs.IsSelected == false)
          {
              flrs.Stroke = selectedColor.Value;
              selectedColor = null;
          }
      };
  
      // Select
      flrs.IsSelected = true;
      Assert.That(flrs.Stroke, Is.EqualTo(Colors.Green));
      // Change color
      selectedColor = Colors.Purple;            
      // Deselect 
      flrs.IsSelected = false;
      // Check
      Assert.That(flrs.Stroke, Is.EqualTo(Colors.Purple)); // Passes
  }
  

This code works as expected.

Best regards
Andrew