Enhance Tooltip Customization with decoration Property for Advanced Styling


Hi! 👋 @imaNNeo

First of all, thank you for this awesome package—it's incredibly useful! 🙌

I noticed that tooltips in fl_chart currently allow customization of colors but lack full support for advanced styling, such as gradients, borders,Shapes and shadows. To enhance this, I have successfully added a decoration property to tooltips, enabling users to fully customize their tooltip backgrounds using ShapeDecoration.

This improvement makes it much easier to create visually appealing tooltips without manually painting decorations. I’ve tested a few, and it works great! 🎉

I’d love to hear your thoughts on whether this could be added to the official package. Let me know if I should raise a PR! 🚀

Thanks again! 😊

Review the tooltip customization area of fl_chart and the proposed ShapeDecoration-based decoration property. Confirm the intended public API and supported styling behavior from the issue description, then verify that the completed change lets users customize tooltip backgrounds without manual painting.

Written by the indexing model from the issue text.