ThemeEditor: add hue sliders

app/soapbox/features/theme-editor/components/palette.tsx

@@ -1,7 +1,9 @@
-import React from 'react';
+import React, { useEffect, useState } from 'react';
 
-import { HStack } from 'soapbox/components/ui';
+import { HStack, Stack, Slider } from 'soapbox/components/ui';
+import { usePrevious } from 'soapbox/hooks';
 import { compareId } from 'soapbox/utils/comparators';
+import { hueShift } from 'soapbox/utils/theme';
 
 import Color from './color';
 
@@ -18,6 +20,9 @@ interface IPalette {
 const Palette: React.FC<IPalette> = ({ palette, onChange }) => {
   const tints = Object.keys(palette).sort(compareId);
 
+  const [hue, setHue] = useState(0);
+  const lastHue = usePrevious(hue);
+
   const handleChange = (tint: string) => {
     return (color: string) => {
       onChange({
@@ -27,12 +32,27 @@ const Palette: React.FC<IPalette> = ({ palette, onChange }) => {
     };
   };
 
+  useEffect(() => {
+    const delta = hue - (lastHue || 0);
+
+    const adjusted = Object.entries(palette).reduce<ColorGroup>((result, [tint, hex]) => {
+      result[tint] = hueShift(hex, delta * 360);
+      return result;
+    }, {});
+
+    onChange(adjusted);
+  }, [hue]);
+
   return (
-    <HStack className='w-full h-8 rounded-md overflow-hidden'>
-      {tints.map(tint => (
-        <Color color={palette[tint]} onChange={handleChange(tint)} />
-      ))}
-    </HStack>
+    <Stack className='w-full'>
+      <HStack className='h-8 rounded-md overflow-hidden'>
+        {tints.map(tint => (
+          <Color color={palette[tint]} onChange={handleChange(tint)} />
+        ))}
+      </HStack>
+
+      <Slider value={hue} onChange={setHue} />
+    </Stack>
   );
 };
 

app/soapbox/utils/theme.ts

@@ -116,3 +116,18 @@ export const colorsToCss = (colors: TailwindColorPalette): string => {
 export const generateThemeCss = (soapboxConfig: SoapboxConfig): string => {
   return colorsToCss(soapboxConfig.colors.toJS() as TailwindColorPalette);
 };
+
+const hexToHsl = (hex: string): Hsl | null => {
+  const rgb = hexToRgb(hex);
+  return rgb ? rgbToHsl(rgb) : null;
+};
+
+export const hueShift = (hex: string, delta: number): string => {
+  const { h, s, l } = hexToHsl(hex)!;
+
+  return hslToHex({
+    h: (h + delta) % 360,
+    s,
+    l,
+  });
+};