Improve printout PDF layout

Support multiple columns in case the tracklist is long, or there's
multiple media.

lib/music_library/records/tracklist_pdf.ex

@@ -3,6 +3,16 @@ defmodule MusicLibrary.Records.TracklistPdf do
   alias MusicLibraryWeb.Duration
   alias Typst.Format
 
+  @layout_configs [
+    {1, 8, true},
+    {2, 8, true},
+    {2, 7, true},
+    {3, 7, true},
+    {3, 6, true},
+    {4, 6, false},
+    {4, 5, false}
+  ]
+
   @spec generate(MusicLibrary.Records.Record.t(), Release.t()) ::
           {:ok, binary()} | {:error, term()}
   def generate(record, release) do
@@ -11,9 +21,18 @@ defmodule MusicLibrary.Records.TracklistPdf do
   end
 
   defp build_markup(record, release) do
+    media_count = Release.media_count(release)
+    track_count = Enum.sum(Enum.map(release.media, &length(&1.tracks)))
+    header_count = if media_count > 1, do: media_count, else: 0
+    total_items = track_count + header_count
+
+    {columns, font_size, show_duration} = layout_params(total_items, media_count)
+
+    content = build_media(release, media_count, font_size, show_duration)
+
     """
-    #set page(width: 120mm, height: 120mm, margin: 5mm)
-    #set text(font: "Liberation Sans", size: 8pt)
+    #set page(width: 120mm, height: 120mm, margin: 5mm, background: rect(width: 100%, height: 100%, stroke: 0.5pt + black))
+    #set text(font: "Liberation Sans", size: #{font_size}pt)
 
     #align(center)[
       #text(size: 10pt, weight: "bold")[#{Format.escape(artist_names(record))}]
@@ -23,28 +42,36 @@ defmodule MusicLibrary.Records.TracklistPdf do
 
     #v(3mm)
 
-    #{build_media(release)}
+    #{build_columns(columns, content)}
     """
   end
 
-  defp build_media(release) do
-    media_count = Release.media_count(release)
+  defp build_columns(1, content), do: content
 
+  defp build_columns(n, content) do
+    """
+    #columns(#{n}, gutter: 3mm)[
+    #{content}
+    ]\
+    """
+  end
+
+  defp build_media(release, media_count, font_size, show_duration) do
     release.media
     |> Enum.map_join("\n", fn medium ->
-      build_medium(medium, media_count)
+      build_medium(medium, media_count, font_size, show_duration)
     end)
   end
 
-  defp build_medium(medium, media_count) do
+  defp build_medium(medium, media_count, font_size, show_duration) do
     header =
       if media_count > 1 do
         label = medium_label(medium)
 
         """
-        #v(2mm)
-        #text(size: 8pt, weight: "bold")[#{Format.escape(label)}]
-        #v(1mm)
+        #v(1.5mm)
+        #text(weight: "bold")[#{Format.escape(label)}]
+        #v(0.5mm)
         """
       else
         ""
@@ -52,31 +79,57 @@ defmodule MusicLibrary.Records.TracklistPdf do
 
     tracks =
       medium.tracks
-      |> Enum.map_join("\n", &build_track/1)
+      |> Enum.map_join("\n", &build_track(&1, font_size, show_duration))
 
     header <> tracks
   end
 
-  defp build_track(track) do
+  defp build_track(track, font_size, show_duration) do
     number = Format.escape(track.number || to_string(track.position))
     title = Format.escape(track.title)
+    number_width = font_size + 2
 
-    duration =
-      if track.length do
-        Format.escape(Duration.format_duration(track.length))
-      else
-        ""
-      end
+    if show_duration do
+      duration =
+        if track.length do
+          Format.escape(Duration.format_duration(track.length))
+        else
+          ""
+        end
 
-    """
-    #grid(
-      columns: (12pt, 1fr, auto),
-      gutter: 4pt,
-      align(right)[#{number}],
-      [#{title}],
-      align(right)[#{duration}]
-    )\
-    """
+      """
+      #grid(
+        columns: (#{number_width}pt, 1fr, auto),
+        gutter: 2pt,
+        align(right)[#{number}],
+        [#{title}],
+        align(right)[#{duration}]
+      )\
+      """
+    else
+      """
+      #grid(
+        columns: (#{number_width}pt, 1fr),
+        gutter: 2pt,
+        align(right)[#{number}],
+        [#{title}]
+      )\
+      """
+    end
+  end
+
+  @doc false
+  def layout_params(total_items, _media_count) do
+    Enum.find(@layout_configs, List.last(@layout_configs), fn {columns, font_size, _} ->
+      capacity(columns, font_size) >= total_items
+    end)
+  end
+
+  # Row height in mm: font size converted to mm (× 0.353) scaled by ~1.2 for
+  # ascender + descender, plus grid gutter (2pt = 0.706mm).
+  defp capacity(columns, font_size) do
+    row_height_mm = font_size * 0.353 * 1.2 + 0.706
+    floor(95 / row_height_mm) * columns
   end
 
   defp artist_names(record) do

test/music_library/records/tracklist_pdf_test.exs

@@ -80,6 +80,53 @@ defmodule MusicLibrary.Records.TracklistPdfTest do
     end
   end
 
+  describe "layout_params/2" do
+    test "single column for small track count" do
+      assert {1, 8, true} = TracklistPdf.layout_params(10, 1)
+    end
+
+    test "two columns for medium track count" do
+      assert {2, 8, true} = TracklistPdf.layout_params(30, 1)
+    end
+
+    test "scales up columns and reduces font for large track counts" do
+      assert {3, 7, true} = TracklistPdf.layout_params(55, 1)
+      assert {3, 6, true} = TracklistPdf.layout_params(80, 1)
+      assert {4, 6, false} = TracklistPdf.layout_params(100, 1)
+      assert {4, 5, false} = TracklistPdf.layout_params(120, 1)
+    end
+
+    test "accounts for medium headers in multi-medium releases" do
+      # 22 tracks + 2 medium headers = 24 items, exceeds single column capacity (23)
+      assert {2, 8, true} = TracklistPdf.layout_params(24, 2)
+    end
+  end
+
+  describe "generate/2 with many tracks" do
+    test "generates single-page PDF for large single-disc release" do
+      record = build_record(%{title: "Long Album", artists: [%{name: "Prolific Artist"}]})
+      tracks = Enum.map(1..40, &build_track(&1, "Track #{&1}", 180_000))
+
+      release = build_release([build_medium(1, tracks)])
+
+      assert {:ok, <<@pdf_magic_bytes, _::binary>>} = TracklistPdf.generate(record, release)
+    end
+
+    test "generates single-page PDF for large multi-disc release" do
+      record = build_record(%{title: "Box Set", artists: [%{name: "Band"}]})
+
+      media =
+        Enum.map(1..4, fn disc ->
+          tracks = Enum.map(1..20, &build_track(&1, "Disc #{disc} Track #{&1}", 200_000))
+          build_medium(disc, tracks)
+        end)
+
+      release = build_release(media)
+
+      assert {:ok, <<@pdf_magic_bytes, _::binary>>} = TracklistPdf.generate(record, release)
+    end
+  end
+
   defp build_record(attrs) do
     artists =
       Enum.map(Map.get(attrs, :artists, []), fn a ->