Null value support for Chart for Xamarin Forms, so that if there is a null value, a line chart should appear "disconnected" at the point where the nulls are. Available in the R3 2018 SP release.
Currently the only way to apply different colors to the bars is through the ChartPalette. Provide an option to set the color according to the bound data item.
The VisibleRange property can hold the actual visible minimum and maximum of the axis while the chart is being zoomed and panned.
If series' ItemsSource is a collection of objects implementing INotifyPropertyChanged, the chart should be automatically updated when an item is updated.
When the chart has a lot of data, you may not necessarily want to show it all when the chart initially appears, but you may want to show the chart in a semi-zoomed state. Therefore, there should be properties which govern the ranges by which the chart should appear zoomed initially. So, the end-user should be able to zoom in/out starting from this state and then return to the same state if necessary (avoiding getting the whole data if he zooms out too much).
When you have a Chart with PieSeries and enable the SelectionBehavior - selecting a specific value makes it split from the pie chart and stand out. We should consider exposing another state, where the integrity of the pie chart is not broken and the selected items are just highlighted or probably have a bold border, etc.