feat: add packer

app/composables/usePdfExport.ts

@@ -0,0 +1,35 @@
+/**
+ * "Save as PDF" through the browser's print dialog. While printing (also with ⌘ P) the page title is `fileName`, which
+ * browsers name the PDF after, and dark mode is off, so the PDF is dark text on white.
+ */
+export function usePdfExport(fileName: MaybeRefOrGetter<string>, onBeforePrint?: () => void) {
+  // What to restore after printing; null while not printing. Browsers can fire beforeprint twice before afterprint.
+  let screen: { title: string, dark: boolean } | null = null
+
+  function beforePrint() {
+    onBeforePrint?.()
+    if (screen) return
+    screen = { title: document.title, dark: document.documentElement.classList.contains('dark') }
+    document.title = toValue(fileName)
+    document.documentElement.classList.remove('dark')
+  }
+
+  function afterPrint() {
+    if (!screen) return
+    document.title = screen.title
+    if (screen.dark) document.documentElement.classList.add('dark')
+    screen = null
+  }
+
+  onMounted(() => {
+    window.addEventListener('beforeprint', beforePrint)
+    window.addEventListener('afterprint', afterPrint)
+  })
+  onBeforeUnmount(() => {
+    window.removeEventListener('beforeprint', beforePrint)
+    window.removeEventListener('afterprint', afterPrint)
+  })
+
+  // Opens the browser's print dialog, which offers "Save as PDF"
+  return { savePdf: () => window.print() }
+}