feat(skin): improved responsive design

packages/utils/src/dom/style.ts

@@ -17,23 +17,22 @@ export function resolveCSSLength(el: Element, value: string): number {
 
   const parsed = Number.parseFloat(trimmed);
 
-  if (Number.isNaN(parsed)) return 0;
-  if (/^-?\d*\.?\d+$/.test(trimmed) || trimmed.endsWith('px')) return parsed;
+  if (!Number.isNaN(parsed) && (/^-?\d*\.?\d+$/.test(trimmed) || trimmed.endsWith('px'))) return parsed;
 
   const doc = el.ownerDocument;
   const root = doc?.documentElement;
 
-  if (trimmed.endsWith('rem')) {
+  if (!Number.isNaN(parsed) && trimmed.endsWith('rem')) {
     const rootFontSize = root ? Number.parseFloat(getComputedStyle(root).fontSize) || 16 : 16;
     return parsed * rootFontSize;
   }
 
-  if (trimmed.endsWith('em')) {
+  if (!Number.isNaN(parsed) && trimmed.endsWith('em')) {
     const fontSize = el instanceof HTMLElement ? Number.parseFloat(getComputedStyle(el).fontSize) || 16 : 16;
     return parsed * fontSize;
   }
 
-  if (!doc) return parsed;
+  if (!doc) return Number.isNaN(parsed) ? 0 : parsed;
 
   const measurementEl = doc.createElement('div');
   measurementEl.style.position = 'absolute';
@@ -45,14 +44,27 @@ export function resolveCSSLength(el: Element, value: string): number {
   measurementEl.style.border = '0';
   measurementEl.style.inset = '0';
 
+  const computed = getComputedStyle(el);
+  measurementEl.style.fontSize = computed.fontSize;
+
+  for (let i = 0; i < computed.length; i++) {
+    const name = computed.item(i);
+
+    if (name.startsWith('--')) {
+      measurementEl.style.setProperty(name, computed.getPropertyValue(name));
+    }
+  }
+
   const parent = doc.body ?? doc.documentElement;
 
-  if (!parent) return parsed;
+  if (!parent) return Number.isNaN(parsed) ? 0 : parsed;
 
   parent.appendChild(measurementEl);
 
   const pixels = measurementEl.getBoundingClientRect().width;
   measurementEl.remove();
 
-  return Number.isFinite(pixels) ? pixels : parsed;
+  if (Number.isFinite(pixels)) return pixels;
+
+  return Number.isNaN(parsed) ? 0 : parsed;
 }

packages/utils/src/dom/tests/style.test.ts

@@ -1,8 +1,12 @@
-import { describe, expect, it, vi } from 'vitest';
+import { afterEach, describe, expect, it, vi } from 'vitest';
 
 import { resolveCSSLength } from '../style';
 
 describe('resolveCSSLength', () => {
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
   it('Returns px values directly', () => {
     const el = document.createElement('div');
 
@@ -98,4 +102,75 @@ describe('resolveCSSLength', () => {
 
     createElementSpy.mockRestore();
   });
+
+  it('Falls back to measurement for calc values', () => {
+    const el = document.createElement('div');
+    const createElement = document.createElement.bind(document);
+    const createElementSpy = vi.spyOn(document, 'createElement').mockImplementation((tagName: string) => {
+      const node = createElement(tagName);
+
+      if (tagName === 'div') {
+        vi.spyOn(node, 'getBoundingClientRect').mockImplementation(() => ({
+          x: 0,
+          y: 0,
+          width: node.style.inlineSize.startsWith('calc(') ? 8 : 0,
+          height: 0,
+          top: 0,
+          left: 0,
+          right: 8,
+          bottom: 0,
+          toJSON() {},
+        }));
+      }
+
+      return node;
+    });
+
+    expect(resolveCSSLength(el, 'calc(0.5 * 16px)')).toBe(8);
+
+    createElementSpy.mockRestore();
+  });
+
+  it('Copies custom properties from the source element when measuring', () => {
+    const el = document.createElement('div');
+
+    const createElement = document.createElement.bind(document);
+    const getComputedStyleSpy = vi.spyOn(globalThis, 'getComputedStyle').mockImplementation(
+      () =>
+        ({
+          length: 1,
+          fontSize: '14px',
+          item(index: number) {
+            return index === 0 ? '--size' : '';
+          },
+          getPropertyValue(name: string) {
+            return name === '--size' ? '16px' : '';
+          },
+        }) as CSSStyleDeclaration
+    );
+    const createElementSpy = vi.spyOn(document, 'createElement').mockImplementation((tagName: string) => {
+      const node = createElement(tagName);
+
+      if (tagName === 'div') {
+        vi.spyOn(node, 'getBoundingClientRect').mockImplementation(() => ({
+          x: 0,
+          y: 0,
+          width: node.style.getPropertyValue('--size') === '16px' ? 8 : 0,
+          height: 0,
+          top: 0,
+          left: 0,
+          right: 8,
+          bottom: 0,
+          toJSON() {},
+        }));
+      }
+
+      return node;
+    });
+
+    expect(resolveCSSLength(el, 'calc(0.5 * var(--size))')).toBe(8);
+
+    createElementSpy.mockRestore();
+    getComputedStyleSpy.mockRestore();
+  });
 });