gen-screenshot: fix screenshot width

gen-screenshot.ts

@@ -14,25 +14,28 @@ const slugify = (str: string) =>
     .replace(/[^a-z0-9.]+/g, "-")
     .replace(/(^-|-$)/g, "");
 
-if (Deno.args.length !== 2) {
-  console.error("usage: generate-screenshot.ts name css-file");
-  Deno.exit(1);
-}
-
-const screenshotFile = `${slugify(Deno.args[0])}.png`;
-const cssFile = Deno.args[1];
-
 const saveScreenshot = async (src: string, dest: string) => {
-  const browser = await puppeteer.launch();
+  // For whatever reason, I get screenshots 16 pixels wider than the requested
+  // viewport size.
+  const browser = await puppeteer.launch({
+    defaultViewport: { width: 1024 - 16, height: 1024, deviceScaleFactor: 1 }
+  });
   const page = await browser.newPage();
 
-  await page.setViewport({ width: 1024, height: 1024, deviceScaleFactor: 1 });
   await page.goto(src);
   await page.screenshot({ fullPage: true, path: dest });
 
   await browser.close();
 };
 
+if (Deno.args.length !== 2) {
+  console.error("usage: generate-screenshot.ts name css-file");
+  Deno.exit(1);
+}
+
+const screenshotFile = `${slugify(Deno.args[0])}.png`;
+const cssFile = Deno.args[1];
+
 try {
   const htmlTemplate = await Deno.readTextFile(templateFile);
   const css = await Deno.readTextFile(cssFile);