add tests

packages/layout/tests/text/fontSubstitution.test.js

@@ -0,0 +1,90 @@
+import { describe, expect, test } from 'vitest';
+import fontSubstitution from '../../src/text/fontSubstitution';
+
+const instance = fontSubstitution();
+
+describe('FontSubstitution', () => {
+  test('should return empty array if no runs passed', () => {
+    const string = instance({ string: '', runs: [] });
+
+    expect(string).toHaveProperty('runs', []);
+    expect(string).toHaveProperty('string', '');
+  });
+
+  test('should merge consecutive runs with same font', () => {
+    const run1 = { start: 0, end: 3, attributes: { font: ['Helvetica'] } };
+    const run2 = { start: 3, end: 5, attributes: { font: ['Helvetica'] } };
+    const string = instance({ string: 'Lorem', runs: [run1, run2] });
+
+    expect(string).toHaveProperty('string', 'Lorem');
+    expect(string.runs).toHaveLength(1);
+    expect(string.runs[0]).toHaveProperty('start', 0);
+    expect(string.runs[0]).toHaveProperty('end', 5);
+    expect(string.runs[0].attributes.font.name).toBe('Helvetica');
+  });
+
+  test('should substitute many runs', () => {
+    const run1 = { start: 0, end: 3, attributes: { font: ['Courier'] } };
+    const run2 = { start: 3, end: 5, attributes: { font: ['Helvetica'] } };
+    const string = instance({ string: 'Lorem', runs: [run1, run2] });
+
+    expect(string).toHaveProperty('string', 'Lorem');
+    expect(string.runs).toHaveLength(2);
+    expect(string.runs[0]).toHaveProperty('start', 0);
+    expect(string.runs[0]).toHaveProperty('end', 3);
+    expect(string.runs[0].attributes.font.name).toBe('Courier');
+    expect(string.runs[1]).toHaveProperty('start', 3);
+    expect(string.runs[1]).toHaveProperty('end', 5);
+    expect(string.runs[1].attributes.font.name).toBe('Helvetica');
+  });
+
+  describe('Fallback Font', () => {
+    const SimplifiedChineseFont = {
+      name: 'SimplifiedChineseFont',
+      hasGlyphForCodePoint: (codePoint) => codePoint === 20320,
+    };
+
+    test('should utilize a fallback font that supports the provided glyph', () => {
+      const run = {
+        start: 0,
+        end: 1,
+        attributes: {
+          font: ['Courier', SimplifiedChineseFont],
+        },
+      };
+
+      const string = instance({ string: '你', runs: [run] });
+
+      expect(string).toHaveProperty('string', '你');
+      expect(string.runs).toHaveLength(1);
+      expect(string.runs[0]).toHaveProperty('start', 0);
+      expect(string.runs[0]).toHaveProperty('end', 1);
+      expect(string.runs[0].attributes.font.name).toBe(
+        SimplifiedChineseFont.name,
+      );
+    });
+
+    test('should split a run when fallback font is used on a portion of the run', () => {
+      const run = {
+        start: 0,
+        end: 2,
+        attributes: {
+          font: ['Courier', SimplifiedChineseFont],
+        },
+      };
+
+      const string = instance({ string: 'A你', runs: [run] });
+
+      expect(string).toHaveProperty('string', 'A你');
+      expect(string.runs).toHaveLength(2);
+      expect(string.runs[0]).toHaveProperty('start', 0);
+      expect(string.runs[0]).toHaveProperty('end', 1);
+      expect(string.runs[0].attributes.font.name).toBe('Courier');
+      expect(string.runs[1]).toHaveProperty('start', 1);
+      expect(string.runs[1]).toHaveProperty('end', 2);
+      expect(string.runs[1].attributes.font.name).toBe(
+        SimplifiedChineseFont.name,
+      );
+    });
+  });
+});