From 2fb09abbf8c3704220ced9e6e3e1c2402c696bb2 Mon Sep 17 00:00:00 2001
From: Ronald Tse <ronald.tse@ribose.com>
Date: Mon, 3 Aug 2026 21:33:01 +0800
Subject: [PATCH] feat: use pdfrb 0.19.0 canvas.text_lines in TextFrameRenderer

TextFrameRenderer batches all broken lines into a single
canvas.text_lines call instead of N separate canvas.text calls.
Reduces PDF content-stream size and improves rendering performance.

TODO 65 documents remaining pdfrb 0.19.0 integration gaps:
- glyph_width returns 0 for TTF (pdfrb bug)
- FontResolver can't find .ttc files
---
 TODO.pdf/65-pdfrb-019-integration.md          | 29 +++++++++++++++++++
 .../render/renderers/text_frame_renderer.rb   | 14 ++++++---
 2 files changed, 39 insertions(+), 4 deletions(-)
 create mode 100644 TODO.pdf/65-pdfrb-019-integration.md

diff --git a/TODO.pdf/65-pdfrb-019-integration.md b/TODO.pdf/65-pdfrb-019-integration.md
new file mode 100644
index 0000000..77ce661
--- /dev/null
+++ b/TODO.pdf/65-pdfrb-019-integration.md
@@ -0,0 +1,29 @@
+# TODO PDF 65: pdfrb 0.19.0 feature integration
+
+## Status: PARTIALLY DONE
+
+## What was implemented
+
+1. **Canvas#text_lines**: TextFrameRenderer uses `canvas.text_lines`
+   instead of N separate `canvas.text` calls per line. Single batch
+   call for all lines within a run.
+
+## What remains (pdfrb bugs)
+
+2. **glyph_width for TTF**: pdfrb 0.19.0 has `Fonts#glyph_width` but
+   returns 0 for TrueType fonts (bug: "undefined method glyph_id_for
+   for String"). Standard 14 Type1 fonts work correctly. Cannot
+   replace FontMetrics/Fontisan until this is fixed.
+
+3. **Pdfrb::FontResolver**: Returns nil for common fonts (Helvetica.ttc
+   on macOS). Cannot replace Fontisan-based resolver yet.
+
+4. **Font subsetting**: `Fonts#add` accepts `**opts` but `subset: true`
+   behavior unverified. Standard 14 fonts don't need FontFile embedding.
+
+## Acceptance criteria
+
+- [x] TextFrameRenderer uses canvas.text_lines
+- [ ] FontMetrics replaced with pdfrb glyph_width (blocked by TTF bug)
+- [ ] FontResolver replaced with Pdfrb::FontResolver (blocked by .ttc)
+- [ ] Font subsetting verified
diff --git a/lib/idml/render/renderers/text_frame_renderer.rb b/lib/idml/render/renderers/text_frame_renderer.rb
index 6e15b9b..696b04d 100644
--- a/lib/idml/render/renderers/text_frame_renderer.rb
+++ b/lib/idml/render/renderers/text_frame_renderer.rb
@@ -95,15 +95,21 @@ def self.render_run_lines(canvas, run, context, box, font, baseline_y)
             glyphs: glyphs, frame_width: box[:width],
           )
 
+          line_texts = []
           lines.each do |line|
             break if baseline_y < box[:y]
 
-            line_text = line.glyphs.map { |g| [g.codepoint].pack("U") }.join
-            canvas.text(line_text, at: [box[:x], baseline_y],
-                                   font: context.font_ps_name,
-                                   size: size)
+            line_texts << line.glyphs.map { |g| [g.codepoint].pack("U") }.join
             baseline_y -= size * LEADING_FACTOR
           end
+
+          if line_texts.any?
+            canvas.text_lines(line_texts,
+                              font: context.font_ps_name,
+                              size: size,
+                              at: [box[:x], box[:y] + box[:height] - size],
+                              leading: size * LEADING_FACTOR)
+          end
           baseline_y
         end
         private_class_method :render_run_lines