feat: allow titles to overlay on chart area

[alettsy]

Hello! 👋

First of all, thank you for an awesome chart package 😊

This contribution is to resolve #1946.

What I did

I added an optional Boolean property for the AxisTitles class to allow each side title to be overlayed on the chart area if the user so desires.

For example, in Line Chart Sample 9, I added the property to the left titles and now it is placed on the chart area.

You can see the example use here:

With the result:

[Copilot]

Pull Request Overview

This PR adds the ability to overlay axis titles on the chart area instead of positioning them outside the chart boundaries. This addresses issue #1946 by introducing an optional overlayOnChart boolean property to the AxisTitles class.

• Added overlayOnChart property to AxisTitles class with default value of false
• Modified padding calculation logic to exclude reserved space when titles are overlayed
• Added test coverage for the new overlay functionality

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
lib/src/chart/base/axis_chart/axis_chart_data.dart	Added overlayOnChart boolean property to AxisTitles class
lib/src/extensions/fl_titles_data_extension.dart	Updated padding calculation to consider overlay flag
test/chart/base/axis_chart/side_titles/side_titles_test.dart	Added test for overlay functionality

[imaNNeo]

Sorry, I just decided to test the copilot review feature in your branch for the first time. But I liked the result actually xD

I also like the feature you added. I think it is needed by some users. And there might be a similar issue.
So I have a suggestion to have extra customizability (as it is one of our core values)
Can you add a concept like Alignment here? For example, it can be a value between -1 and 1
If it is -1, it is fully outside the chart (default)
If it is 1, it is fully inside the chart
If it is 0, it is exactly on the borderline of the chart (half outside, half inside)

So this way, people have a high level of customization. For example, someone can pass 0.75 to have it mostly inside the chart (but 25% of it is outside)

[alettsy]

Haha no problem! It looks like it did a good job code reviewing my pull requests.

I will take a look at adding this tomorrow 😊

[alettsy]

Hi 👋

I have added changes to make the positions of the side titles changeable via the property sideTitleAlignment which accepts an enum:

SideTitleAlignment.inside   // for displaying inside the chart bounds
SideTitleAlignment.border   // for displaying on the borderline 
SideTitleAlignment.outside  // default, displays outside the chart

I am still looking at a different way to do that unit test 😊

[alettsy]

I have pushed a test that finds the left side title labelled L-0 in order to check the positioning is correct.

Please let me know if there are any issues 😊

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.47%. Comparing base (9e51b11) to head (199e4a4).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1959      +/-   ##
==========================================
+ Coverage   92.44%   92.47%   +0.02%     
==========================================
  Files          50       50              
  Lines        3681     3693      +12     
==========================================
+ Hits         3403     3415      +12     
  Misses        278      278              

Flag	Coverage Δ
flutter	92.47% <100.00%> (+0.02%)	⬆️

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[imaNNeo]

Please also add the property to the base_chart.md file (our documentation)
You also need to do a rebase to get rid of the validation errors, I think.

After doing that, it looks good to get merged into the main!
Thanks for contributing.

[alettsy]

Hi, @imaNNeo 👋 I have updated the code with your requested changes and rebased for the main branch.

Please let me know if there are any other issues 😊

[imaNNeo]

Thanks for your valuable contribution!