From 8a0e6a7d6f4636447f3245af509082f4e851a1e5 Mon Sep 17 00:00:00 2001
From: Abimael Martell <abimex@gmail.com>
Date: Mon, 16 Feb 2026 18:56:24 -0800
Subject: [PATCH] fix(extractor): Fix TJ space detection for Type3 fonts with
 non-standard scale

Type3 fonts with FontMatrix [1,0,0,-1,0,0] (units_scale=1.0) had
broken word spacing: intra-word kerns of -4000 exceeded the clamped
threshold of 200, producing "Op en-Domain", "comp etition", etc.

Two fixes:
- Compute space_width fallback after units_scale is known; for
  non-standard scales, estimate from average glyph width (~45%)
  instead of the hardcoded 250 (calibrated for 1/1000-unit fonts)
- Remove upper clamp on space threshold (200 was too low for fonts
  where TJ values naturally range into thousands)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 src/extractor.rs | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/src/extractor.rs b/src/extractor.rs
index 76e0392..647c857 100644
--- a/src/extractor.rs
+++ b/src/extractor.rs
@@ -154,11 +154,6 @@ fn parse_simple_font_widths(
         widths.insert(code, w);
     }
 
-    // If space width wasn't found in the table, use a reasonable default
-    if space_width == 0 {
-        space_width = 250;
-    }
-
     // Determine units_scale: for Type3 fonts, use FontMatrix[0]; for others, use 1/1000
     let units_scale = if let Ok(fm) = font_dict.get(b"FontMatrix") {
         if let Some(arr) = resolve_array(doc, fm) {
@@ -178,6 +173,20 @@ fn parse_simple_font_widths(
         0.001 // Standard 1000-unit system
     };
 
+    // If space width wasn't found in the table, estimate from font metrics.
+    // The default of 250 is calibrated for standard 1000-unit fonts (units_scale=0.001).
+    // For Type3 fonts with different coordinate systems, use average glyph width instead.
+    if space_width == 0 {
+        if !widths.is_empty() && (units_scale - 0.001).abs() > 0.0005 {
+            // Non-standard scale: estimate space as ~45% of average glyph width
+            let sum: u32 = widths.values().map(|&w| w as u32).sum();
+            let avg = sum as f32 / widths.len() as f32;
+            space_width = (avg * 0.45).max(1.0) as u16;
+        } else {
+            space_width = 250;
+        }
+    }
+
     Some(FontWidthInfo {
         widths,
         default_width: 0,
@@ -1190,7 +1199,7 @@ fn extract_page_text_items(
                         let space_threshold = if let Some(font_info) = font_info {
                             let space_em = font_info.space_width as f32 * font_info.units_scale;
                             let threshold = space_em * 1000.0 * 0.4;
-                            threshold.clamp(80.0, 200.0)
+                            threshold.max(80.0)
                         } else {
                             120.0
                         };
@@ -1654,7 +1663,7 @@ fn extract_form_xobject_text(
                         let space_threshold = if let Some(fi) = font_info {
                             let space_em = fi.space_width as f32 * fi.units_scale;
                             let threshold = space_em * 1000.0 * 0.4;
-                            threshold.clamp(80.0, 200.0)
+                            threshold.max(80.0)
                         } else {
                             120.0
                         };