Before theme extensions, properly styling custom widgets was not so easy. Oftentimes, developers bundle their cosmetic details with the component. In cases where the developer has to implement two different theme modes, things could get a bit tricky.

Theme extensions are a way to extend the flutter theming system used by the default widgets of the SDK to custom components and widgets. This ensures that components can look up a particular style meant for them, keeping your styling code out of your raw widgets.