Support HSL, RGB, and RGBA theme colors (CHARTS-138)

- Updated global-charts-provider to use normalizeColorToHex for all color processing
- Added support for RGB, RGBA, and HSL color formats in theme colors
- Updated normalizeColorToHex to handle rgba() colors (previously rejected)
- Added comprehensive tests for RGB, HSL, and RGBA color support
- Updated existing tests to reflect new color normalization behavior

Fixes: https://linear.app/a8c/issue/CHARTS-138

Author: Copilot

projects/js-packages/charts/changelog/charts-138-support-hsl-rgb-rgba-colors

@@ -0,0 +1,4 @@
+Significance: patch
+Type: changed
+
+Support HSL, RGB, and RGBA theme colors in addition to hex format

projects/js-packages/charts/src/providers/chart-context/global-charts-provider.tsx

@@ -69,25 +69,24 @@ export const GlobalChartsProvider: FC< GlobalChartsProviderProps > = ( { childre
 		if ( Array.isArray( colors ) ) {
 			for ( const color of colors ) {
 				if ( color && typeof color === 'string' ) {
-					let colorValue = color;
-
-					// Handle CSS custom properties - resolve them to actual values
-					// Supports both '--var-name' and 'var(--var-name)' formats
-					// Use wrapper element to resolve scoped CSS variables
-					if ( color.startsWith( '--' ) || color.startsWith( 'var(' ) ) {
-						const resolved = resolveCssVariable( color, wrapperRef.current );
-
-						if ( resolved === null || resolved === '' ) {
-							continue;
-						}
-
-						colorValue = resolved;
+					// Normalize color to hex format, handling CSS variables, RGB, HSL, etc.
+					// This uses normalizeColorToHex which resolves CSS variables and converts
+					// rgb(), rgba(), hsl() formats to hex
+					const normalizedColor = normalizeColorToHex(
+						color,
+						wrapperRef.current,
+						resolveCssVariable
+					);
+
+					// Skip if normalization failed or returned empty string
+					if ( ! normalizedColor ) {
+						continue;
 					}
 
-					// Process hex colors
-					if ( colorValue.startsWith( '#' ) ) {
-						resolvedColors.push( colorValue );
-						const hslColor = d3Hsl( colorValue );
+					// Only process valid hex colors (normalizeColorToHex ensures this)
+					if ( normalizedColor.startsWith( '#' ) ) {
+						resolvedColors.push( normalizedColor );
+						const hslColor = d3Hsl( normalizedColor );
 						// d3Hsl returns NaN values for invalid colors
 						if ( ! isNaN( hslColor.h ) ) {
 							const hslTuple: [ number, number, number ] = [

projects/js-packages/charts/src/providers/chart-context/test/chart-context.test.tsx

@@ -1901,7 +1901,7 @@ describe( 'ChartContext', () => {
 				};
 
 				const cssVarTheme: ChartTheme = {
-					colors: [ '--rgb-color', '#ff0000' ],
+					colors: [ '--rgb-color', '#00ff00' ],
 				} as ChartTheme;
 
 				render(
@@ -1910,14 +1910,135 @@ describe( 'ChartContext', () => {
 					</GlobalChartsProvider>
 				);
 
-				// Non-hex colors are currently skipped, should use second color
+				// RGB colors should now be converted to hex and used
 				const color = contextValue.getElementStyles( {
 					data: undefined,
 					index: 0,
 				} ).color;
 
 				expect( color ).toBe( '#ff0000' );
 			} );
+
+			it( 'handles CSS variables resolving to HSL colors', () => {
+				window.getComputedStyle = jest.fn( () => ( {
+					getPropertyValue: ( prop: string ) => {
+						if ( prop === '--hsl-color' ) {
+							return 'hsl(120, 100%, 50%)'; // HSL format (green)
+						}
+						return '';
+					},
+				} ) ) as unknown as typeof window.getComputedStyle;
+
+				let contextValue: GlobalChartsContextValue;
+
+				const TestComponent = () => {
+					contextValue = useGlobalChartsContext();
+					return <div>Test</div>;
+				};
+
+				const cssVarTheme: ChartTheme = {
+					colors: [ '--hsl-color', '#ff0000' ],
+				} as ChartTheme;
+
+				render(
+					<GlobalChartsProvider theme={ cssVarTheme }>
+						<TestComponent />
+					</GlobalChartsProvider>
+				);
+
+				// HSL colors should be converted to hex and used
+				const color = contextValue.getElementStyles( {
+					data: undefined,
+					index: 0,
+				} ).color;
+
+				expect( color ).toBe( '#00ff00' );
+			} );
+
+			it( 'handles CSS variables resolving to RGBA colors', () => {
+				window.getComputedStyle = jest.fn( () => ( {
+					getPropertyValue: ( prop: string ) => {
+						if ( prop === '--rgba-color' ) {
+							return 'rgba(0, 0, 255, 0.5)'; // RGBA format (blue with transparency)
+						}
+						return '';
+					},
+				} ) ) as unknown as typeof window.getComputedStyle;
+
+				let contextValue: GlobalChartsContextValue;
+
+				const TestComponent = () => {
+					contextValue = useGlobalChartsContext();
+					return <div>Test</div>;
+				};
+
+				const cssVarTheme: ChartTheme = {
+					colors: [ '--rgba-color', '#ff0000' ],
+				} as ChartTheme;
+
+				render(
+					<GlobalChartsProvider theme={ cssVarTheme }>
+						<TestComponent />
+					</GlobalChartsProvider>
+				);
+
+				// RGBA colors should be converted to hex (transparency info is lost)
+				const color = contextValue.getElementStyles( {
+					data: undefined,
+					index: 0,
+				} ).color;
+
+				expect( color ).toBe( '#0000ff' );
+			} );
+
+			it( 'handles mix of RGB, HSL, and hex in theme colors', () => {
+				window.getComputedStyle = jest.fn( () => ( {
+					getPropertyValue: ( prop: string ) => {
+						if ( prop === '--rgb-red' ) {
+							return 'rgb(255, 0, 0)';
+						}
+						if ( prop === '--hsl-green' ) {
+							return 'hsl(120, 100%, 50%)';
+						}
+						return '';
+					},
+				} ) ) as unknown as typeof window.getComputedStyle;
+
+				let contextValue: GlobalChartsContextValue;
+
+				const TestComponent = () => {
+					contextValue = useGlobalChartsContext();
+					return <div>Test</div>;
+				};
+
+				const cssVarTheme: ChartTheme = {
+					colors: [ '--rgb-red', '--hsl-green', '#0000ff' ],
+				} as ChartTheme;
+
+				render(
+					<GlobalChartsProvider theme={ cssVarTheme }>
+						<TestComponent />
+					</GlobalChartsProvider>
+				);
+
+				// All color formats should be properly converted
+				const color1 = contextValue.getElementStyles( {
+					data: undefined,
+					index: 0,
+				} ).color;
+				const color2 = contextValue.getElementStyles( {
+					data: undefined,
+					index: 1,
+				} ).color;
+				const color3 = contextValue.getElementStyles( {
+					data: undefined,
+					index: 2,
+				} ).color;
+
+				expect( color1 ).toBe( '#ff0000' ); // RGB red
+				expect( color2 ).toBe( '#00ff00' ); // HSL green
+				expect( color3 ).toBe( '#0000ff' ); // Hex blue
+			} );
 		} );
 
 		describe( 'Error Handling', () => {
@@ -2052,7 +2173,7 @@ describe( 'ChartContext', () => {
 				} ).color;
 
 				expect( color1 ).toBe( '#ff0000' );
-				expect( color2 ).toBe( '#bad' ); // Invalid color is still in palette
+				expect( color2 ).toBe( '#bbaadd' ); // #bad is expanded to #bbaadd by normalizeColorToHex
 				expect( color3 ).toBe( '#0000ff' );
 			} );
 		} );

projects/js-packages/charts/src/utils/color-utils.ts

@@ -91,14 +91,17 @@ export const parseHslString = ( hslString: string ): [ number, number, number ]
 
 /**
  * Parse an RGB string like 'rgb(255, 0, 0)' into a hex color.
+ * Note: This function specifically handles rgb() format only, not rgba().
+ * For general color normalization including rgba(), use normalizeColorToHex() instead.
  *
- * @param rgbString - RGB color string
+ * @param rgbString - RGB color string (not RGBA)
  * @return hex color string or null if invalid
  */
 export const parseRgbString = ( rgbString: string ): string | null => {
 	const lower = rgbString.toLowerCase().trim();
 
 	// Check prefix - only handle rgb(), not rgba()
+	// This is intentional - use normalizeColorToHex for rgba() support
 	if ( ! lower.startsWith( 'rgb(' ) || lower.startsWith( 'rgba(' ) ) {
 		return null;
 	}
@@ -160,12 +163,12 @@ export const normalizeColorToHex = (
 		return color;
 	}
 
-	// Handle HSL and RGB strings using d3-color
-	if ( trimmed.startsWith( 'hsl(' ) || trimmed.startsWith( 'rgb(' ) ) {
-		// Reject rgba() - we only handle rgb()
-		if ( trimmed.startsWith( 'rgba(' ) ) {
-			return color;
-		}
+	// Handle HSL, RGB, and RGBA strings using d3-color
+	if (
+		trimmed.startsWith( 'hsl(' ) ||
+		trimmed.startsWith( 'rgb(' ) ||
+		trimmed.startsWith( 'rgba(' )
+	) {
 		const parsed = d3Color( trimmed );
 		if ( parsed ) {
 			return parsed.formatHex();

projects/js-packages/charts/src/utils/test/color-utils.test.ts

@@ -494,6 +494,22 @@ describe( 'normalizeColorToHex', () => {
 		} );
 	} );
 
+	describe( 'RGBA strings', () => {
+		it( 'converts rgba(255, 0, 0, 1) to #ff0000', () => {
+			expect( normalizeColorToHex( 'rgba(255, 0, 0, 1)' ) ).toBe( '#ff0000' );
+		} );
+
+		it( 'converts rgba(0, 0, 255, 0.5) to #0000ff', () => {
+			// Alpha channel is lost in hex conversion
+			expect( normalizeColorToHex( 'rgba(0, 0, 255, 0.5)' ) ).toBe( '#0000ff' );
+		} );
+
+		it( 'converts rgba(128, 128, 128, 0) to #000000', () => {
+			// d3-color converts fully transparent colors (alpha=0) to black
+			expect( normalizeColorToHex( 'rgba(128, 128, 128, 0)' ) ).toBe( '#000000' );
+		} );
+	} );
+
 	describe( 'CSS variables', () => {
 		it( 'returns original if no resolveCss function provided', () => {
 			expect( normalizeColorToHex( '--my-color' ) ).toBe( '--my-color' );