Feature: Add StackedPieChart

[jay-k98]

As described in #2003 a "Stacked Pie Chart" was requested. This Pull Request aims to add this feature.

Solution

The Implementation of [StackedPieChart] is very similar to [PieChart]. The biggest difference is drawing a Section with multiple Segments.

The radius of a segment is calculated like this:

SegmentRadius = SectionRadius * SegmentValue / TotalSectionValues

The sweep angles are then calculated like in [PieChart]

Todo's and Improvements

• Add drawing strokes
• Extend the Demo (add icon and more examples)
• Add tests
• Extract duplicate logic from [PieChart] and [StackedPieChart]

[codecov]

Codecov Report

❌ Patch coverage is 0% with 479 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.97%. Comparing base (32e75f5) to head (b88f01f).

Files with missing lines	Patch %	Lines
...t/stacked_pie_chart/stacked_pie_chart_painter.dart	0.00%	262 Missing ⚠️
...hart/stacked_pie_chart/stacked_pie_chart_data.dart	0.00%	111 Missing ⚠️
.../stacked_pie_chart/stacked_pie_chart_renderer.dart	0.00%	74 Missing ⚠️
...src/chart/stacked_pie_chart/stacked_pie_chart.dart	0.00%	20 Missing ⚠️
...rt/stacked_pie_chart/stacked_pie_chart_helper.dart	0.00%	8 Missing ⚠️
lib/src/utils/lerp.dart	0.00%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2004       +/-   ##
===========================================
- Coverage   92.49%   81.97%   -10.53%     
===========================================
  Files          50       55        +5     
  Lines        3731     4210      +479     
===========================================
  Hits         3451     3451               
- Misses        280      759      +479     

Flag	Coverage Δ
flutter	81.97% <0.00%> (-10.53%)	⬇️

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[imaNNeo]

Hi, thanks for your contribution.
I think we can use the current implementation of the PieChart to just add the stacked logic into it.
This way, we reuse a lot of code that we already wrote.

Just like what I did for the stacked bar chart here: #112

Please let me know your thoughts on it.

[jay-k98]

Hi, yeah thank you for responding! I wanted to hear your opinion about that. I'll implement analogous to #112 and add tests :)

[imaNNeo]

I appreciate it!
Thanks in advance.