From 5a377a21988b7f92d2cf0f49461a6f5168f1d129 Mon Sep 17 00:00:00 2001
From: mithral <mithral@mithral.local>
Date: Fri, 9 Oct 2026 21:43:43 -0400
Subject: [PATCH] PDF reading via pdf.js

- PdfReader renders PDFs to canvas with page navigation and page-number
  progress, reusing the same integer progress model as comics.
- Reader routes by file container, not media kind, so a PDF in a comics
  library and a PDF ebook both open in the PDF reader.
- pdf.js is dynamically imported: the main bundle stays 443 kB and the 474 kB
  pdf chunk plus 1.26 MB worker load only when a PDF is actually opened.
- comics cover extractor now only handles zip archives. A PDF in a comics
  library is a valid item but not a zip, so it returns no cover instead of
  logging an error on every request.
- fixed the page scale to leave slack for the vertical scrollbar, which was
  otherwise forcing a horizontal scrollbar on tall pages.

Verified live: a 3-page PDF renders, navigates, and reports 33% progress.
---
 internal/modules/comics/cover.go        |  10 ++
 web/package.json                        |   3 +-
 web/pnpm-lock.yaml                      | 134 ++++++++++++++++
 web/src/lib/components/PdfReader.svelte | 194 ++++++++++++++++++++++++
 web/src/lib/components/Reader.svelte    |   5 +
 5 files changed, 345 insertions(+), 1 deletion(-)
 create mode 100644 web/src/lib/components/PdfReader.svelte

diff --git a/internal/modules/comics/cover.go b/internal/modules/comics/cover.go
index c37ee41..885c18a 100644
--- a/internal/modules/comics/cover.go
+++ b/internal/modules/comics/cover.go
@@ -18,7 +18,17 @@ func init() {
 
 // ExtractCover writes the first page of the archive into the cache and returns
 // its path. A comic's first page is its cover by convention.
+//
+// Only zip-based archives are handled. A PDF in a comics library is a valid
+// item but not a zip, so it returns no cover rather than logging an error on
+// every request — the grid falls back to a placeholder.
 func ExtractCover(ctx context.Context, db *sql.DB, item media.Item, absPath, cacheDir string) (string, error) {
+	switch strings.ToLower(filepath.Ext(item.Path)) {
+	case ".cbz", ".zip":
+	default:
+		return "", nil
+	}
+
 	pages, err := ListPages(absPath)
 	if err != nil {
 		return "", err
diff --git a/web/package.json b/web/package.json
index e037e7c..e67e4bb 100644
--- a/web/package.json
+++ b/web/package.json
@@ -10,7 +10,8 @@
     "check": "svelte-check --tsconfig ./tsconfig.json"
   },
   "dependencies": {
-    "epubjs": "^0.3.93"
+    "epubjs": "^0.3.93",
+    "pdfjs-dist": "^6.4.299"
   },
   "devDependencies": {
     "@sveltejs/vite-plugin-svelte": "^5.0.3",
diff --git a/web/pnpm-lock.yaml b/web/pnpm-lock.yaml
index fa881d1..4aba9e1 100644
--- a/web/pnpm-lock.yaml
+++ b/web/pnpm-lock.yaml
@@ -11,6 +11,9 @@ importers:
       epubjs:
         specifier: ^0.3.93
         version: 0.3.93
+      pdfjs-dist:
+        specifier: ^6.4.299
+        version: 6.4.299
     devDependencies:
       '@sveltejs/vite-plugin-svelte':
         specifier: ^5.0.3
@@ -202,6 +205,81 @@ packages:
   '@jridgewell/trace-mapping@0.3.31':
     resolution: {integrity: sha512-zzNR+SdQSDJzc8joaeP8QQoCQr8NuYx2dIIytl1QeBEZHJ9uW6hebsrYgbz8hJwUQao3TWCMtmfV8Nu1twOLAw==}
 
+  '@napi-rs/canvas-android-arm64@1.0.10':
+    resolution: {integrity: sha512-0sDMvme+7fj6bHERUaBs5SvEyWaORc91VUkaB4RrtG7p6dBrBNGy1of8cyEKDxygd1FlHtW+Thunj8lSixzY7A==}
+    engines: {node: '>= 10'}
+    cpu: [arm64]
+    os: [android]
+
+  '@napi-rs/canvas-darwin-arm64@1.0.10':
+    resolution: {integrity: sha512-pdHL1TEfFMrnchRYqmPWXKN7hR4XtOYmzJqnh4XhpfWD4/eeSokOGVzrdFP/iQ3sfr2rf0939gOGq9uCp8BGmg==}
+    engines: {node: '>= 10'}
+    cpu: [arm64]
+    os: [darwin]
+
+  '@napi-rs/canvas-darwin-x64@1.0.10':
+    resolution: {integrity: sha512-iuuk5plGxAcxurxv2ycF2yR20y5zvaBZ4heQdhPpg3EMFD21PhlY1V+YwSRmYRWzbvKL474UYdw3WIg2qfafyw==}
+    engines: {node: '>= 10'}
+    cpu: [x64]
+    os: [darwin]
+
+  '@napi-rs/canvas-linux-arm-gnueabihf@1.0.10':
+    resolution: {integrity: sha512-kH7GFR5Unpm77pKSEsmkqvzeQCRD7/MQ7upmeLLjg4XpQ62dX/R6THFsp6vkF1Pkco2aKUq9KhoLM4W5twdk7g==}
+    engines: {node: '>= 10'}
+    cpu: [arm]
+    os: [linux]
+
+  '@napi-rs/canvas-linux-arm64-gnu@1.0.10':
+    resolution: {integrity: sha512-0/Hj7IwM9pmzdwxiqkp4YLJ8dKqASBrWQ3Y7dWUSU/4dgvCL9O6YNvX7xVUJjonQvdD3IE9ESS/nXa5srQqoVw==}
+    engines: {node: '>= 10'}
+    cpu: [arm64]
+    os: [linux]
+    libc: [glibc]
+
+  '@napi-rs/canvas-linux-arm64-musl@1.0.10':
+    resolution: {integrity: sha512-fmjKM0P2MLF9O6XzCQsRjhB+jlLzaf6tFQU36hMPMsYup+VThYvpjjhqNLOc/Ee3tHUE3r13H2BSJx/yXz4pFA==}
+    engines: {node: '>= 10'}
+    cpu: [arm64]
+    os: [linux]
+    libc: [musl]
+
+  '@napi-rs/canvas-linux-riscv64-gnu@1.0.10':
+    resolution: {integrity: sha512-O/BUrGwrs3pVP9PpD/3++ZiOpjHMJlmiB7aBgswP8rbe4egPfiFkFxmcCczoLvZa72TaQX5lJ8Udedb6rc/Hvg==}
+    engines: {node: '>= 10'}
+    cpu: [riscv64]
+    os: [linux]
+    libc: [glibc]
+
+  '@napi-rs/canvas-linux-x64-gnu@1.0.10':
+    resolution: {integrity: sha512-48HkZPQeAN/R+9NPpY64tceoyCUW5xYYtHKZnC+BG11qiihXJCbH+xfbgGU+OdYp1Q4s84HDl9ILU0KBK6SBOQ==}
+    engines: {node: '>= 10'}
+    cpu: [x64]
+    os: [linux]
+    libc: [glibc]
+
+  '@napi-rs/canvas-linux-x64-musl@1.0.10':
+    resolution: {integrity: sha512-QYHVi7WZ9v+Wm9OQyHLMTnJ8QiBPVX94BgbCHFJC/4bCFMfvX7fRzo4FJPgkRP0ISz3ulYNow/FCbQOPjzhYjg==}
+    engines: {node: '>= 10'}
+    cpu: [x64]
+    os: [linux]
+    libc: [musl]
+
+  '@napi-rs/canvas-win32-arm64-msvc@1.0.10':
+    resolution: {integrity: sha512-bWK+YajM/8sL0mMgLtug2s063FVBPzFV4QAn987CQomMKlmzrBY6Trz43KY+24hq7IOa3qNhUAgP/XMEF50ZEQ==}
+    engines: {node: '>= 10'}
+    cpu: [arm64]
+    os: [win32]
+
+  '@napi-rs/canvas-win32-x64-msvc@1.0.10':
+    resolution: {integrity: sha512-9WtzW85PaIhtB27iXaR/9RrLCqHLbqD3Z8Q+kh17NjFxwQXFXU5vWbYH4vEH+drM307TTyK3hidZgpt09G5T3g==}
+    engines: {node: '>= 10'}
+    cpu: [x64]
+    os: [win32]
+
+  '@napi-rs/canvas@1.0.10':
+    resolution: {integrity: sha512-V+qptzsGnPMFxEbhwc6eDNMe5eDrfiBIp8qGpuRjAVIX4Kn2zxvwQ1Xco6Fwe+3tYIe3iLW8LM9D+SvjyJhqbQ==}
+    engines: {node: '>= 10'}
+
   '@napi-rs/lzma-linux-x64-gnu@1.5.1':
     resolution: {integrity: sha512-oTXEIha4SsuXdTA4Iyskj0kpdx2yVXdhd75c2v3xGrHFfVMsbhTPZU/nMPL4sWKo4pBHm3aucLaqGlF696dTyQ==}
     engines: {node: ^22.20 || ^24.12 || >=25}
@@ -545,6 +623,10 @@ packages:
   path-webpack@0.0.3:
     resolution: {integrity: sha512-AmeDxedoo5svf7aB3FYqSAKqMxys014lVKBzy1o/5vv9CtU7U4wgGWL1dA2o6MOzcD53ScN4Jmiq6VbtLz1vIQ==}
 
+  pdfjs-dist@6.4.299:
+    resolution: {integrity: sha512-AVl138zALtfaAPvADulE0PZThbYzCBS79nL4pOSL/6Sm/4AH5A21BD9VHt97OlCuzJuCpmeZtAtkinisF4Vb1g==}
+    engines: {node: '>=22.13.0 || >=24'}
+
   picocolors@1.1.1:
     resolution: {integrity: sha512-xceH2snhtb5M9liqDsmEw56le376mTZkEX/jEb/RxNFyegNul7eNslCXP9FDj/Lcu0X8KEyMceP2ntpaHrDEVA==}
 
@@ -765,6 +847,54 @@ snapshots:
       '@jridgewell/resolve-uri': 3.1.2
       '@jridgewell/sourcemap-codec': 1.6.0
 
+  '@napi-rs/canvas-android-arm64@1.0.10':
+    optional: true
+
+  '@napi-rs/canvas-darwin-arm64@1.0.10':
+    optional: true
+
+  '@napi-rs/canvas-darwin-x64@1.0.10':
+    optional: true
+
+  '@napi-rs/canvas-linux-arm-gnueabihf@1.0.10':
+    optional: true
+
+  '@napi-rs/canvas-linux-arm64-gnu@1.0.10':
+    optional: true
+
+  '@napi-rs/canvas-linux-arm64-musl@1.0.10':
+    optional: true
+
+  '@napi-rs/canvas-linux-riscv64-gnu@1.0.10':
+    optional: true
+
+  '@napi-rs/canvas-linux-x64-gnu@1.0.10':
+    optional: true
+
+  '@napi-rs/canvas-linux-x64-musl@1.0.10':
+    optional: true
+
+  '@napi-rs/canvas-win32-arm64-msvc@1.0.10':
+    optional: true
+
+  '@napi-rs/canvas-win32-x64-msvc@1.0.10':
+    optional: true
+
+  '@napi-rs/canvas@1.0.10':
+    optionalDependencies:
+      '@napi-rs/canvas-android-arm64': 1.0.10
+      '@napi-rs/canvas-darwin-arm64': 1.0.10
+      '@napi-rs/canvas-darwin-x64': 1.0.10
+      '@napi-rs/canvas-linux-arm-gnueabihf': 1.0.10
+      '@napi-rs/canvas-linux-arm64-gnu': 1.0.10
+      '@napi-rs/canvas-linux-arm64-musl': 1.0.10
+      '@napi-rs/canvas-linux-riscv64-gnu': 1.0.10
+      '@napi-rs/canvas-linux-x64-gnu': 1.0.10
+      '@napi-rs/canvas-linux-x64-musl': 1.0.10
+      '@napi-rs/canvas-win32-arm64-msvc': 1.0.10
+      '@napi-rs/canvas-win32-x64-msvc': 1.0.10
+    optional: true
+
   '@napi-rs/lzma-linux-x64-gnu@1.5.1':
     optional: true
 
@@ -1049,6 +1179,10 @@ snapshots:
 
   path-webpack@0.0.3: {}
 
+  pdfjs-dist@6.4.299:
+    optionalDependencies:
+      '@napi-rs/canvas': 1.0.10
+
   picocolors@1.1.1: {}
 
   picomatch@4.0.7: {}
diff --git a/web/src/lib/components/PdfReader.svelte b/web/src/lib/components/PdfReader.svelte
new file mode 100644
index 0000000..b0939cc
--- /dev/null
+++ b/web/src/lib/components/PdfReader.svelte
@@ -0,0 +1,194 @@
+<script lang="ts">
+  import workerUrl from 'pdfjs-dist/build/pdf.worker.min.mjs?url'
+  import { onMount, onDestroy } from 'svelte'
+  import { api, ApiError } from '../api'
+
+  let { itemId }: { itemId: number } = $props()
+
+  let canvasEl = $state<HTMLCanvasElement>()
+  let doc: any = null
+  let numPages = $state(0)
+  let current = $state(1)
+  let loading = $state(true)
+  let rendering = $state(false)
+  let error = $state<string | null>(null)
+  let pageInput = $state('1')
+  let saveTimer: number | undefined
+
+  onMount(async () => {
+    try {
+      const prog = await api.progress(itemId)
+
+      // pdf.js is ~1 MB and most people never open a PDF. Load it on demand so
+      // it lands in its own chunk instead of the main bundle.
+      const pdfjs: any = await import('pdfjs-dist')
+      pdfjs.GlobalWorkerOptions.workerSrc = workerUrl
+
+      doc = await pdfjs.getDocument({
+        url: api.fileUrl(itemId),
+        withCredentials: true,
+      }).promise
+      numPages = doc.numPages
+
+      // Progress is stored as a page number, same as comics.
+      if (prog.progress && prog.progress.position > 0 && prog.progress.position <= numPages) {
+        current = prog.progress.position
+      }
+      pageInput = String(current)
+      await render()
+      window.addEventListener('keydown', onKey)
+      window.addEventListener('resize', onResize)
+    } catch (err) {
+      error = err instanceof ApiError ? err.message : 'could not open this document'
+    } finally {
+      loading = false
+    }
+  })
+
+  onDestroy(() => {
+    window.removeEventListener('keydown', onKey)
+    window.removeEventListener('resize', onResize)
+    if (saveTimer) clearTimeout(saveTimer)
+    flush()
+    void doc?.destroy?.()
+  })
+
+  async function render() {
+    if (!doc || !canvasEl) return
+    rendering = true
+    try {
+      const page = await doc.getPage(current)
+      const container = canvasEl.parentElement
+      const base = page.getViewport({ scale: 1 })
+      // Leave slack for the vertical scrollbar that appears on tall pages;
+      // measuring clientWidth before it exists makes the page too wide and
+      // triggers a horizontal scrollbar in turn.
+      const available = container ? container.clientWidth - 28 : base.width
+      const scale = Math.max(available / base.width, 0.1)
+      const viewport = page.getViewport({ scale })
+
+      const dpr = window.devicePixelRatio || 1
+      canvasEl.width = Math.floor(viewport.width * dpr)
+      canvasEl.height = Math.floor(viewport.height * dpr)
+      canvasEl.style.width = `${Math.floor(viewport.width)}px`
+      canvasEl.style.height = `${Math.floor(viewport.height)}px`
+
+      const ctx = canvasEl.getContext('2d')
+      if (!ctx) return
+      await page.render({
+        canvasContext: ctx,
+        viewport,
+        transform: dpr !== 1 ? [dpr, 0, 0, dpr, 0, 0] : undefined,
+      }).promise
+    } finally {
+      rendering = false
+    }
+  }
+
+  let resizeTimer: number | undefined
+  function onResize() {
+    if (resizeTimer) clearTimeout(resizeTimer)
+    resizeTimer = window.setTimeout(() => void render(), 200)
+  }
+
+  function goTo(n: number) {
+    const next = Math.min(Math.max(n, 1), numPages)
+    if (next === current) return
+    current = next
+    pageInput = String(next)
+    void render()
+    scheduleSave()
+  }
+
+  function onKey(event: KeyboardEvent) {
+    if (event.key === 'ArrowRight') goTo(current + 1)
+    if (event.key === 'ArrowLeft') goTo(current - 1)
+    if (event.key === 'Home') goTo(1)
+    if (event.key === 'End') goTo(numPages)
+  }
+
+  function scheduleSave() {
+    if (saveTimer) clearTimeout(saveTimer)
+    saveTimer = window.setTimeout(flush, 900)
+  }
+
+  function flush() {
+    if (numPages === 0) return
+    void api.putProgress(itemId, { position: current, percent: current / numPages }).catch(() => {})
+  }
+
+  function submitJump(event: SubmitEvent) {
+    event.preventDefault()
+    const n = parseInt(pageInput, 10)
+    if (!Number.isNaN(n)) goTo(n)
+  }
+</script>
+
+{#if error}
+  <div class="alert">{error}</div>
+{:else}
+  <div class="stage">
+    <canvas bind:this={canvasEl}></canvas>
+    {#if loading || rendering}
+      <div class="overlay"><div class="spinner"></div></div>
+    {/if}
+  </div>
+
+  <footer class="bar">
+    <button class="btn btn-ghost" onclick={() => goTo(current - 1)} disabled={current <= 1}>←</button>
+    <form class="jump" onsubmit={submitJump}>
+      <input class="input page-input" bind:value={pageInput} aria-label="Page number" disabled={loading} />
+      <span class="muted mono">/ {numPages || '–'}</span>
+    </form>
+    <span class="pct mono">{numPages ? Math.round((current / numPages) * 100) : 0}%</span>
+    <button class="btn btn-ghost" onclick={() => goTo(current + 1)} disabled={current >= numPages}>→</button>
+  </footer>
+{/if}
+
+<style>
+  .stage {
+    position: relative;
+    height: calc(100vh - 60px - 96px);
+    border: 1px solid var(--border);
+    border-radius: var(--radius-lg);
+    background: #17171b;
+    overflow: auto;
+    display: grid;
+    place-items: start center;
+    padding: var(--space-4) 0;
+  }
+  canvas {
+    display: block;
+    background: #fff;
+    box-shadow: var(--shadow-cover);
+    border-radius: 2px;
+  }
+  .overlay {
+    position: absolute;
+    inset: 0;
+    display: grid;
+    place-items: center;
+    background: color-mix(in srgb, var(--bg) 60%, transparent);
+  }
+  .bar {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    gap: var(--space-3);
+    height: 56px;
+  }
+  .jump {
+    display: flex;
+    align-items: center;
+    gap: var(--space-2);
+  }
+  .page-input {
+    width: 64px;
+    text-align: center;
+  }
+  .pct {
+    color: var(--faint);
+    min-width: 40px;
+    text-align: right;
+  }
+</style>
diff --git a/web/src/lib/components/Reader.svelte b/web/src/lib/components/Reader.svelte
index 5f03626..a9b5f3c 100644
--- a/web/src/lib/components/Reader.svelte
+++ b/web/src/lib/components/Reader.svelte
@@ -5,6 +5,7 @@
   import ComicReader from './ComicReader.svelte'
   import AudiobookPlayer from './AudiobookPlayer.svelte'
   import PhotoViewer from './PhotoViewer.svelte'
+  import PdfReader from './PdfReader.svelte'
 
   let { itemId }: { itemId: number } = $props()
 
@@ -14,6 +15,7 @@
   let error = $state<string | null>(null)
   let loading = $state(true)
   let percent = $state(0)
+  let fileContainer = $state('')
 
   let book: any = null
   let rendition: any = null
@@ -23,6 +25,7 @@
     try {
       const detail = await api.item(itemId)
       item = detail.item
+      fileContainer = detail.files?.[0]?.container ?? ''
       if (item.kind !== 'ebooks') return
 
       meta = (await api.ebook(itemId)).metadata
@@ -92,6 +95,8 @@
 
 {#if error}
   <div class="alert">{error}</div>
+{:else if item && fileContainer === 'pdf'}
+  <PdfReader {itemId} />
 {:else if item && item.kind === 'comics'}
   <ComicReader {itemId} />
 {:else if item && (item.kind === 'audiobooks' || item.kind === 'music')}