From 7b6658cc427085b85857fbcd7022a9660c53dc81 Mon Sep 17 00:00:00 2001
From: Kyle Isom <kyle@imap.cc>
Date: Wed, 1 Apr 2026 00:26:08 -0700
Subject: [PATCH] Fix preview panel UTF-8 panics and preserve whitespace in
 redactions

Snap byte offsets to character boundaries in the preview layout to
prevent slicing inside multi-byte characters. Preserve all whitespace
(not just newlines) in redacted regions. Force dark theme explicitly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 src/main.rs | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 81c6d56..1b30d5f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -55,6 +55,7 @@ fn configure_fonts(ctx: &egui::Context) {
 }
 
 fn apply_nord_theme(ctx: &egui::Context) {
+    ctx.set_theme(egui::Theme::Dark);
     let mut style = (*ctx.style()).clone();
     let v = &mut style.visuals;
 
@@ -403,8 +404,8 @@ impl eframe::App for RedactorApp {
                             &self_redactions,
                             r.end,
                         );
-                        let os = out_start.min(text.len());
-                        let oe = out_end.min(text.len());
+                        let os = snap_to_char_boundary(text, out_start.min(text.len()));
+                        let oe = snap_to_char_boundary(text, out_end.min(text.len()));
 
                         if pos < os {
                             job.append(&text[pos..os], 0.0, normal.clone());
@@ -437,6 +438,13 @@ impl eframe::App for RedactorApp {
     }
 }
 
+fn snap_to_char_boundary(s: &str, mut i: usize) -> usize {
+    while i > 0 && !s.is_char_boundary(i) {
+        i -= 1;
+    }
+    i
+}
+
 #[allow(unused_assignments)]
 fn byte_to_preview_byte_static(
     source: &str,
@@ -471,7 +479,7 @@ fn byte_to_preview_byte_static(
         }
 
         for ch in source[r_start..r_end].chars() {
-            if ch == '\n' || ch == '\r' {
+            if ch.is_whitespace() {
                 preview_pos += ch.len_utf8();
             } else {
                 preview_pos += '\u{2588}'.len_utf8();