Shared backDrawRodData between multiple rods

[ospaarmann]

First of all: Thanks for the great library.

I try to implement a graph where I have two rods for each day and a shared backgorund. This seems to not be possible. Maybe I'm missing something. If not: That is in my opinion a very common design and would be a great addition to the library.

This is how it should look like:

This is what I managed to do:

The code that does not achieve it... If I add backDrawRodData to both rods, I just get two distinct backgrounds.

  List<BarChartGroupData> _barGroupsData(
      List<double> firstScoresByWeekday, List<double> secondScoresByWeekday) {
    return List.generate(7, (index) {
      final double firstScore = firstScoresByWeekday[index];
      final double secondScore = secondScoresByWeekday[index];

      return BarChartGroupData(
        x: index,
        barRods: [
          BarChartRodData(
            toY: firstScore * 10, 
            color: AppColors.blue900,
            width: 12, 
            borderRadius: const BorderRadius.all(Radius.circular(20)),
            backDrawRodData: BackgroundBarChartRodData(
              show: true,
              toY: 10,
              color: AppColors.blue100,
            ),
          ),
          BarChartRodData(
              toY:
                  secondScore * 10, 
              color:
                  AppColors.blue300, 
              width: 12, 
              borderRadius: const BorderRadius.all(Radius.circular(20)),
              backDrawRodData: BackgroundBarChartRodData(
                show: true,
                toY: 10,
                color: AppColors.blue100,
              )),
        ],
        // Optional: Add some space between the rods
        barsSpace: 0,
      );
    });
  }

[ospaarmann]

To add to this: If it was possible to set the background on BarChartGroupData, that would fix the issue. If this is something people want I would offer to raise a PR.

[imaNNeo]

Yes exactly, we can add a property in the BarChartGroupData that accepts a background. But I'm not sure what type can we use, maybe a BoxDecoration and paint it like this:

https://github.com/flutter/flutter/blob/14f9b568fc57c14d67b5b40bd48b7e6cb780319c/packages/flutter/lib/src/rendering/proxy_box.dart#L2313-L2321

[imaNNeo]

But you definitely can work on it.