Add shadow for Pie Chart

[samir7osny]

This adds the drop shadow to the Pie Chart with some cool customizations

1. You can add simply a drop shadow like this (check the pie chart sample 4 here)

2. Also you can simulate the third dimension like this (check the pie chart sample 5 here)

solves #1482

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 9.25926% with 49 lines in your changes missing coverage. Please review.

Please upload report for BASE (main@0ae88cf). Learn more about missing BASE report.

Files	Patch %	Lines
lib/src/chart/pie_chart/pie_chart_painter.dart	9.25%	49 Missing :warning:

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1497   +/-   ##
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  Coverage        ?   85.34%           
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  Files           ?       45           
  Lines           ?     3078           
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  Hits            ?     2627           
  Misses          ?      451           
  Partials        ?        0           

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[imaNNeo]

It seems there is an issue, it freezes the app (tested on iPhone and macOS)

[samir7osny]

It seems there is an issue, it freezes the app (tested on iPhone and macOS)

Can you test again? I changed the number of layers to be drawn, it should fix this issue.

[3DExtended]

Tested on iPhone 15 Pro and simulator on MacBook Pro (2023). Seems to work now!

[imaNNeo]

Okay, I found the freeze issue, if you change the offset to Offset(0, 0), it freezes the app process (it seems a low-level exception happens)

[imaNNeo]

Please update the pie_chart.md and base_chart.md docs. Also please write some unit-tests. Read more about the contributing guideline here

[imaNNeo]

Also, please use different style/color/value for the new charts. You just copy-pasted the sample1 and they look exactly the same except the shadow. It doesn't feel good to see some duplicate charts. You can combine the sample 4 and 5 together and add some options to change the shadow style (it helps users/developers to understand how it works). For example you can add a slider to allow user/developer to increase the shadow layers, offset, ... Or when you hover/touch it, instead of adding stroke radius, you can increase/decrease the shadow.