New option to update bar label position

[richardfogaca]

Contribution Summary

This contribution adds a new label positioning feature to bar charts in Apache Superset, allowing users to customize where data labels appear on their bar charts. The implementation provides five position options: Inside, Top, Bottom, Left, and Right, with special styling for "Inside" position to ensure readability.

How It Works

The implementation consists of three main components:

1. Control Panel Addition: A new control section was added to the bar chart configuration panel that allows users to select the label position from a dropdown menu.

2. Transform Props Integration: The transformProps function was updated to handle the new labelPosition property, with a default value of "inside" for bar charts when no position is specified.

3. Label Position Utility: A new utility function updateLabelPosition was created to handle the positioning logic:

   • It maps through the series data
   • For bar charts with "inside" position, it applies special styling (white color, bold font, no text border) to ensure readability
   • For all other positions, it applies the selected position while preserving existing label properties

The changes maintain backward compatibility by:

• Defaulting to "inside" position for bar charts when no position is specified
• Preserving existing label properties when applying new positions
• Using the existing translation system for UI text

Screenshots

Fork with working prototype

The implementation is available in this fork

Why This Matters

1. Enhanced Data Visualization: Users can now choose the most appropriate label position for their data, improving readability and visual appeal.
2. Better User Experience: The "inside" position with special styling ensures labels remain readable even on dark-colored bars.
3. Flexibility: Multiple position options allow users to adapt the visualization to different data densities and chart sizes.
4. Consistency: The implementation follows Superset's existing patterns for chart customization and control panel organization.

This improvement makes bar charts more versatile and user-friendly while maintaining the high standards of Apache Superset's visualization capabilities.

[rusackas]

This is great! I'd just also support "outside" (supported by ECharts) as that also would put the number below bars that are negative in value. (see #20517)

[richardfogaca]

That makes sense @rusackas , I'll work on a PR with your suggestions, thanks!