From 13d1ea542e142e130a29266ad1414991e4d2e1e0 Mon Sep 17 00:00:00 2001
From: Blaž Hrastnik
Date: Tue, 29 Sep 2020 01:11:17 +0900
Subject: Clamp character movement to line.

---
 helix-core/src/state.rs | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/helix-core/src/state.rs b/helix-core/src/state.rs
index cac52abc..7cecba29 100644
--- a/helix-core/src/state.rs
+++ b/helix-core/src/state.rs
@@ -147,12 +147,23 @@ impl State {
     ) -> usize {
         let text = &self.doc;
         match (dir, granularity) {
-            // TODO: clamp movement to line, prevent moving onto \n at the end
             (Direction::Backward, Granularity::Character) => {
-                nth_prev_grapheme_boundary(&text.slice(..), pos, count)
+                // Clamp to line
+                let line = text.char_to_line(pos);
+                let start = text.line_to_char(line);
+                std::cmp::max(
+                    nth_prev_grapheme_boundary(&text.slice(..), pos, count),
+                    start,
+                )
             }
             (Direction::Forward, Granularity::Character) => {
-                nth_next_grapheme_boundary(&text.slice(..), pos, count)
+                // Clamp to line
+                let line = text.char_to_line(pos);
+                let start = text.line_to_char(line);
+                let len = text.line(line).len_chars();
+                // convert to 0-indexed, subtract another 1 because len_chars() counts \n
+                let end = start + len.saturating_sub(2);
+                std::cmp::min(nth_next_grapheme_boundary(&text.slice(..), pos, count), end)
             }
             (Direction::Forward, Granularity::Word) => {
                 Self::move_next_word_start(&text.slice(..), pos)
-- 
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