Add label colors to legend entries

[pmairoldi]

Adds a color setting to legend entries to customize labels. Addresses the feedback in #2640.

[codecov-io]

Codecov Report

Merging #3558 into 4.0.0 will increase coverage by 0.59%.
The diff coverage is 40.67%.

@@            Coverage Diff             @@
##            4.0.0    #3558      +/-   ##
==========================================
+ Coverage   29.98%   30.58%   +0.59%     
==========================================
  Files         116      116              
  Lines       13197    13478     +281     
==========================================
+ Hits         3957     4122     +165     
- Misses       9240     9356     +116

Impacted Files	Coverage Δ
Source/Charts/Components/LegendEntry.swift	50% <ø> (-30%)	⬇️
Source/Charts/Renderers/LegendRenderer.swift	54.33% <40.67%> (+0.45%)	⬆️
.../Charts/Renderers/HorizontalBarChartRenderer.swift	0% <0%> (ø)	⬆️
Source/Charts/Renderers/BubbleChartRenderer.swift	0% <0%> (ø)	⬆️
...ce/Charts/Renderers/CandleStickChartRenderer.swift	0% <0%> (ø)	⬆️
Source/Charts/Renderers/ScatterChartRenderer.swift	0% <0%> (ø)	⬆️
Source/Charts/Renderers/RadarChartRenderer.swift	0% <0%> (ø)	⬆️
Source/Charts/Renderers/LineChartRenderer.swift	57.25% <0%> (+1.01%)	⬆️
Source/Charts/Renderers/BarChartRenderer.swift	54.61% <0%> (+1.19%)	⬆️
...Charts/Data/Implementations/ChartBaseDataSet.swift	16.55% <0%> (+2.68%)	⬆️
... and 2 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 73183d5...7690b2e. Read the comment docs.

[liuxuan30]

is it possible to use default value? seeing labelColor: nil repeat

[pmairoldi]

We could but the rest of that function doesn’t. Seems weird to have a default at the start of the function. That’s my preference though

[pmairoldi]

We could but the rest of that function doesn’t. Seems weird to have a default at the start of the function. That’s my preference though

[liuxuan30]

ok. if @jjatie has no question or no response for a while, we could merge then.

[pmairoldi]

Cool. Trying to finish up 4.0

[jjatie]

I think the issue is that we are putting too many things in the initializer. It's already pretty big and if we add more functionality and expose through the initializer, it will only get bigger. The only thing we need to create a valid LegendEntry is the label, everything else is optional. The label should be a constant and the rest of the properties remain vars. i.e.

@objc(ChartLegendEntry)
open class LegendEntry: NSObject
{
    public override init()
    {
        super.init()
    }
    
    /// - parameter label:                  The legend entry text.
    ///                                     A `nil` label will start a group.
    @objc public init(label: String?)
    {
        self.label = label
    }
    
    /// The legend entry text.
    /// A `nil` label will start a group.
    @objc open let label: String?
    
    /// The color for drawing the label
    open var labelColor: NSUIColor?
        
    /// The form to draw for this entry.
    ///
    /// `None` will avoid drawing a form, and any related space.
    /// `Empty` will avoid drawing a form, but keep its space.
    /// `Default` will use the Legend's default.
    @objc open var form: Legend.Form = .default
    
    /// Form size will be considered except for when .None is used
    ///
    /// Set as NaN to use the legend's default
    @objc open var formSize: CGFloat = CGFloat.nan
    
    /// Line width used for shapes that consist of lines.
    ///
    /// Set to NaN to use the legend's default.
    @objc open var formLineWidth: CGFloat = CGFloat.nan
    
    /// Line dash configuration for shapes that consist of lines.
    ///
    /// This is how much (in pixels) into the dash pattern are we starting from.
    ///
    /// Set to NaN to use the legend's default.
    @objc open var formLineDashPhase: CGFloat = 0.0
    
    /// Line dash configuration for shapes that consist of lines.
    ///
    /// This is the actual dash pattern.
    /// I.e. [2, 3] will paint [--   --   ]
    /// [1, 3, 4, 2] will paint [-   ----  -   ----  ]
    ///
    /// Set to nil to use the legend's default.
    @objc open var formLineDashLengths: [CGFloat]?
    
    /// The color for drawing the form
    @objc open var formColor: NSUIColor?
}

[jjatie]

It might even make sense to only allow the entry group to be created through the empty initializer, i.e.:

@objc(ChartLegendEntry)
open class LegendEntry: NSObject
{    
    /// A label to start a group.
    public override init()
    {
        super.init()
    }
    
    /// - parameter label: The legend entry text.
    @objc public init(label: String)
    {
        self.label = label
    }
    
    // ...
}

[pmairoldi]

Don’t know if the empty initializer is useful but I agree with your points. I’ll change some stuff

[pmairoldi]

@jjatie I have addressed your comments

[jjatie]

Wow, that got rid of more than I was expecting. I'm still not sure how I feel about leaving the label as a var(instead of a let).

[pmairoldi]

I was thinking the same thing but with all the variables. I’d rather they all be immutable.

[pmairoldi]

We can go through the whole API in maybe v5 to address having too many mutable variables