feat: powerline and block character rendering with visual tests

.gitignore

@@ -6,3 +6,6 @@ dist/
 
 # WASM build output (built locally and in CI)
 ghostty-vt.wasm
+
+# Visual render test failure artifacts
+demo/baselines/*.fail.png

demo/bin/render-test.ts

@@ -0,0 +1,285 @@
+#!/usr/bin/env bun
+/**
+ * Headless visual regression test runner for the renderer.
+ *
+ * Usage:
+ *   bun demo/bin/render-test.ts           # Run tests against baselines
+ *   bun demo/bin/render-test.ts --update  # Update baselines from current renders
+ *
+ * Baselines are stored in demo/baselines/*.png
+ */
+
+import { existsSync, mkdirSync, readFileSync, writeFileSync } from 'fs';
+import { dirname, join } from 'path';
+import { fileURLToPath } from 'url';
+
+// Get script directory
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+const DEMO_DIR = dirname(__dirname);
+const BASELINES_DIR = join(DEMO_DIR, 'baselines');
+const PROJECT_ROOT = dirname(DEMO_DIR);
+
+// Parse args
+const args = process.argv.slice(2);
+const updateMode = args.includes('--update') || args.includes('-u');
+const helpMode = args.includes('--help') || args.includes('-h');
+
+if (helpMode) {
+  console.log(`
+Visual Render Test Runner
+
+Usage:
+  bun demo/bin/render-test.ts [options]
+
+Options:
+  --update, -u    Update baselines from current renders
+  --help, -h      Show this help message
+
+Baselines are stored in demo/baselines/*.png
+`);
+  process.exit(0);
+}
+
+// Ensure baselines directory exists
+if (!existsSync(BASELINES_DIR)) {
+  mkdirSync(BASELINES_DIR, { recursive: true });
+}
+
+interface TestResult {
+  id: string;
+  name: string;
+  status: 'pass' | 'fail' | 'new' | 'error';
+  diffPercent?: number;
+  error?: string;
+}
+
+async function main() {
+  console.log('🧪 Visual Render Test Runner\n');
+
+  // Dynamic import puppeteer (install if needed)
+  let puppeteer: typeof import('puppeteer');
+  try {
+    puppeteer = await import('puppeteer');
+  } catch {
+    console.log('📦 Installing puppeteer...');
+    const proc = Bun.spawn(['bun', 'add', '-d', 'puppeteer'], {
+      cwd: PROJECT_ROOT,
+      stdout: 'inherit',
+      stderr: 'inherit',
+    });
+    await proc.exited;
+    puppeteer = await import('puppeteer');
+  }
+
+  // Start local server
+  console.log('🌐 Starting local server...');
+  const server = Bun.serve({
+    port: 0, // Let OS pick a free port
+    async fetch(req) {
+      const url = new URL(req.url);
+      let filePath = join(PROJECT_ROOT, url.pathname);
+
+      // Default to index.html for directories
+      if (filePath.endsWith('/')) {
+        filePath += 'index.html';
+      }
+
+      try {
+        const file = Bun.file(filePath);
+        if (await file.exists()) {
+          // Set content type based on extension
+          const ext = filePath.split('.').pop() || '';
+          const contentTypes: Record<string, string> = {
+            html: 'text/html',
+            js: 'application/javascript',
+            css: 'text/css',
+            json: 'application/json',
+            wasm: 'application/wasm',
+            png: 'image/png',
+            ttf: 'font/ttf',
+          };
+          return new Response(file, {
+            headers: { 'Content-Type': contentTypes[ext] || 'application/octet-stream' },
+          });
+        }
+      } catch {
+        // Fall through to 404
+      }
+      return new Response('Not found', { status: 404 });
+    },
+  });
+
+  const serverUrl = `http://localhost:${server.port}`;
+  console.log(`   Server running at ${serverUrl}`);
+
+  // Launch browser
+  console.log('🚀 Launching headless browser...');
+  const browser = await puppeteer.default.launch({
+    headless: true,
+    args: ['--no-sandbox', '--disable-setuid-sandbox'],
+  });
+
+  const page = await browser.newPage();
+
+  // Set viewport for consistent rendering
+  await page.setViewport({ width: 1200, height: 800, deviceScaleFactor: 1 });
+
+  try {
+    // Navigate to test page
+    console.log('📄 Loading test page...\n');
+    await page.goto(`${serverUrl}/demo/render-test.html`, {
+      waitUntil: 'networkidle0',
+      timeout: 30000,
+    });
+
+    // Wait for the page's runAllTests() to complete.
+    // render-test.html sets window.__testsComplete = true when done.
+    await page.waitForFunction('window.__testsComplete === true', { timeout: 60000 });
+
+    // Get test cases from the page
+    const testCases = await page.evaluate(() => {
+      // Access the module's test cases through the window exports
+      // We need to extract test info from the DOM since testCases is module-scoped
+      const cards = document.querySelectorAll('.test-case');
+      return Array.from(cards).map((card) => {
+        const id = card.id.replace('test-', '');
+        const name = card.querySelector('h3')?.textContent || id;
+        return { id, name };
+      });
+    });
+
+    if (testCases.length === 0) {
+      throw new Error('No test cases found. Make sure the page loaded correctly.');
+    }
+
+    console.log(`Found ${testCases.length} tests\n`);
+
+    // Run tests and collect results
+    const results: TestResult[] = [];
+    let passed = 0;
+    let failed = 0;
+    let newTests = 0;
+
+    for (const test of testCases) {
+      const baselinePath = join(BASELINES_DIR, `${test.id}.png`);
+      const hasBaseline = existsSync(baselinePath);
+
+      // Get the canvas data URL from the page
+      const canvasDataUrl = await page.evaluate((testId: string) => {
+        const canvas = document.getElementById(`canvas-${testId}`) as HTMLCanvasElement;
+        return canvas?.toDataURL('image/png') || null;
+      }, test.id);
+
+      if (!canvasDataUrl) {
+        results.push({ id: test.id, name: test.name, status: 'error', error: 'Canvas not found' });
+        console.log(`  ❌ ${test.name}: Canvas not found`);
+        failed++;
+        continue;
+      }
+
+      // Convert data URL to buffer
+      const base64Data = canvasDataUrl.replace(/^data:image\/png;base64,/, '');
+      const currentBuffer = Buffer.from(base64Data, 'base64');
+
+      if (updateMode) {
+        // Update mode: save current as baseline
+        writeFileSync(baselinePath, currentBuffer);
+        console.log(`  📸 ${test.name}: Baseline ${hasBaseline ? 'updated' : 'created'}`);
+        results.push({ id: test.id, name: test.name, status: 'new' });
+        newTests++;
+      } else if (!hasBaseline) {
+        // No baseline exists
+        console.log(`  🆕 ${test.name}: No baseline (run with --update to create)`);
+        results.push({ id: test.id, name: test.name, status: 'new' });
+        newTests++;
+      } else {
+        // Compare with baseline
+        const baselineBuffer = readFileSync(baselinePath);
+
+        // Simple byte comparison first
+        if (currentBuffer.equals(baselineBuffer)) {
+          console.log(`  ✅ ${test.name}: Pass (identical)`);
+          results.push({ id: test.id, name: test.name, status: 'pass', diffPercent: 0 });
+          passed++;
+        } else {
+          // Buffers differ - calculate difference percentage
+          const diffPercent = calculateDiffPercent(currentBuffer, baselineBuffer);
+
+          if (diffPercent <= 0.1) {
+            // Within threshold
+            console.log(`  ✅ ${test.name}: Pass (${diffPercent.toFixed(3)}% diff)`);
+            results.push({ id: test.id, name: test.name, status: 'pass', diffPercent });
+            passed++;
+          } else {
+            console.log(`  ❌ ${test.name}: Fail (${diffPercent.toFixed(3)}% diff)`);
+            results.push({ id: test.id, name: test.name, status: 'fail', diffPercent });
+            failed++;
+
+            // Save the current render for debugging
+            const failPath = join(BASELINES_DIR, `${test.id}.fail.png`);
+            writeFileSync(failPath, currentBuffer);
+          }
+        }
+      }
+    }
+
+    // Summary
+    console.log('\n' + '─'.repeat(50));
+    console.log(`\n📊 Results: ${passed} passed, ${failed} failed, ${newTests} new\n`);
+
+    if (updateMode) {
+      console.log(`✨ Baselines ${newTests > 0 ? 'updated' : 'unchanged'} in demo/baselines/\n`);
+    }
+
+    // Exit with appropriate code
+    await browser.close();
+    server.stop();
+
+    if (failed > 0) {
+      process.exit(1);
+    } else if (newTests > 0 && !updateMode) {
+      console.log('⚠️  New tests detected. Run with --update to create baselines.\n');
+      process.exit(1);
+    }
+  } catch (error) {
+    console.error('Error:', error);
+    await browser.close();
+    server.stop();
+    process.exit(1);
+  }
+}
+
+/**
+ * Calculate approximate difference percentage between two PNG buffers.
+ * This is a simple comparison - for production you might want pixelmatch.
+ */
+function calculateDiffPercent(buf1: Buffer, buf2: Buffer): number {
+  // Simple approach: compare decoded pixel data
+  // For a more accurate comparison, use a library like pixelmatch
+
+  // Quick heuristic based on buffer size difference and content
+  const sizeDiff = Math.abs(buf1.length - buf2.length);
+  const maxSize = Math.max(buf1.length, buf2.length);
+
+  if (sizeDiff > 0) {
+    // Different sizes means different images
+    return (sizeDiff / maxSize) * 100;
+  }
+
+  // Compare bytes
+  let diffBytes = 0;
+  const minLen = Math.min(buf1.length, buf2.length);
+  for (let i = 0; i < minLen; i++) {
+    if (buf1[i] !== buf2[i]) {
+      diffBytes++;
+    }
+  }
+
+  return (diffBytes / maxSize) * 100;
+}
+
+main().catch((e) => {
+  console.error(e);
+  process.exit(1);
+});