feat: dark mode / color scheme support in Theme config #256
Description
Summary
React Grab's overlay UI (toolbar, element labels, selection box, etc.) is currently hardcoded to a light color scheme (bg-white, text-black, border-#D9D9D9, etc.). This makes it visually jarring when used in apps that run in dark mode.
Proposal
Add a colorScheme option to the Theme interface that supports multiple integration strategies, similar to how libraries like Mantine, Radix, and shadcn/ui handle it:
interface Theme {
// ...existing options
/**
* Controls the color scheme of the React Grab overlay UI.
*
* - 'light' | 'dark': Force a specific scheme
* - 'auto': Follow `prefers-color-scheme` media query
* - 'class': Read from a `.dark` class on <html> or <body> (Tailwind convention)
* - 'attribute': Read from `data-theme` or `data-color-scheme` attribute on <html>
* - (element: HTMLElement) => 'light' | 'dark': Custom resolver for any other setup
*
* @default 'auto'
*/
colorScheme?:
| 'light'
| 'dark'
| 'auto'
| 'class'
| 'attribute'
| ((root: HTMLElement) => 'light' | 'dark');
}Why multiple strategies?
Different ecosystems set dark mode differently:
| Strategy | Used by |
|---|---|
prefers-color-scheme media query |
OS-level / browser default |
.dark class on <html> |
Tailwind CSS, most utility-first setups |
data-mantine-color-scheme attribute |
Mantine |
data-theme / data-color-scheme attribute |
Radix, daisyUI, many component libraries |
| Custom JS toggle | App-specific state (React context, localStorage, etc.) |
A single 'dark' boolean won't cover these. The function escape hatch ((root) => 'light' | 'dark') ensures any setup not covered by the built-in strategies can still integrate.
Minimal CSS impact
Since the overlay already uses Tailwind internally, adding dark variants for the existing utility classes should be straightforward. The shadow DOM host just needs to resolve which scheme is active and apply a dark class (or CSS custom properties) to its internal root.
Alternatives considered
- CSS custom properties only — Exposing
--rg-bg,--rg-text, etc. would work but puts the burden on every consumer to define a full palette. AcolorSchemeoption with sensible dark defaults is more ergonomic. huerotation — The existinghueoption shifts colors but doesn't invert lightness, so it can't achieve a dark theme.
Context
React Grab renders inside a Shadow DOM host with all: initial, so it can't inherit the page's dark mode styles automatically. This makes explicit color scheme support necessary rather than optional.