From 1182ce69ec1cbdcbf5d6d3f0c8b0eb70918a4baf Mon Sep 17 00:00:00 2001
From: Xerxes-2 <dspxue@gmail.com>
Date: Sun, 30 Jun 2024 20:04:59 +1000
Subject: [PATCH] fix: support cjk

---
 yazi-core/src/input/commands/move_.rs |  5 +++--
 yazi-core/src/input/snap.rs           | 21 +++++++++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/yazi-core/src/input/commands/move_.rs b/yazi-core/src/input/commands/move_.rs
index 3973779a..b050455d 100644
--- a/yazi-core/src/input/commands/move_.rs
+++ b/yazi-core/src/input/commands/move_.rs
@@ -39,8 +39,9 @@ impl Input {
 		));
 
 		let (limit, snap) = (self.limit(), self.snap_mut());
-		let offset =
-			snap.cursor.saturating_sub(limit / 2).min(snap.len().saturating_sub(limit.saturating_sub(1)));
+		let offset = InputSnap::find_window_backward(&snap.value, snap.cursor, limit / 2)
+			.start
+			.min(InputSnap::find_window_backward(&snap.value, snap.value.chars().count(), limit).start);
 		if snap.offset != offset {
 			snap.offset = offset;
 		} else if snap.value.is_empty() {
diff --git a/yazi-core/src/input/snap.rs b/yazi-core/src/input/snap.rs
index e6f98232..d23cf3cd 100644
--- a/yazi-core/src/input/snap.rs
+++ b/yazi-core/src/input/snap.rs
@@ -87,4 +87,25 @@ impl InputSnap {
 		}
 		*v.first().unwrap()..v.last().unwrap() + 1
 	}
+
+	#[inline]
+	pub(super) fn find_window_backward(s: &str, offset: usize, limit: usize) -> Range<usize> {
+		let mut width = 0;
+		let len = s.chars().count();
+		let v: Vec<_> = s
+			.chars()
+			.rev()
+			.enumerate()
+			.skip(len.saturating_sub(offset + 1))
+			.map_while(|(i, c)| {
+				width += c.width().unwrap_or(0);
+				if width < limit { Some(len.saturating_sub(i + 1)) } else { None }
+			})
+			.collect();
+
+		if v.is_empty() {
+			return 0..0;
+		}
+		*v.last().unwrap()..v.first().unwrap() + 1
+	}
 }