Support moving arrow relative to window, similar to H/M/L vim motions

yazi-widgets/src/scrollable.rs

@@ -8,7 +8,11 @@ pub trait Scrollable {
 	fn offset_mut(&mut self) -> &mut usize;
 
 	fn scroll(&mut self, step: impl Into<Step>) -> bool {
-		let new = step.into().add(*self.cursor_mut(), self.total(), self.limit());
+		let step = step.into();
+		let new = step
+			.window_position(*self.offset_mut(), self.total(), self.limit(), self.scrolloff())
+			.unwrap_or_else(|| step.add(*self.cursor_mut(), self.total(), self.limit()));
+
 		if new > *self.cursor_mut() { self.next(new) } else { self.prev(new) }
 	}
 

yazi-widgets/src/step.rs

@@ -10,6 +10,7 @@ pub enum Step {
 	Next,
 	Offset(isize),
 	Percent(i8),
+	PercentWindow(i8),
 }
 
 impl Default for Step {
@@ -29,6 +30,7 @@ impl FromStr for Step {
 			"bot" => Self::Bot,
 			"prev" => Self::Prev,
 			"next" => Self::Next,
+			s if s.ends_with("%-window") => Self::PercentWindow(s[..s.len() - 8].parse()?),
 			s if s.ends_with('%') => Self::Percent(s[..s.len() - 1].parse()?),
 			s => Self::Offset(s.parse()?),
 		})
@@ -76,6 +78,31 @@ impl<'de> Deserialize<'de> for Step {
 }
 
 impl Step {
+	pub fn window_position(
+		self,
+		offset: usize,
+		len: usize,
+		limit: usize,
+		scrolloff: usize,
+	) -> Option<usize> {
+		let Self::PercentWindow(n) = self else { return None };
+
+		let window_len = len.saturating_sub(offset).min(limit);
+		if window_len == 0 {
+			return Some(0);
+		}
+
+		let scrolloff = scrolloff.min(window_len.saturating_sub(1) / 2);
+
+		// Clamp relative position in window to not reach into any scrolloff region.
+		// Still allow reaching the real list start and end if already visible.
+		let pos = Self::percent_pos(offset, window_len, n);
+		let min = if offset == 0 { 0 } else { offset + scrolloff };
+		let max = offset + window_len - 1 - if offset + window_len >= len { 0 } else { scrolloff };
+
+		Some(pos.clamp(min, max))
+	}
+
 	pub fn add(self, pos: usize, len: usize, limit: usize) -> usize {
 		if len == 0 {
 			return 0;
@@ -84,6 +111,9 @@ impl Step {
 		let off = match self {
 			Self::Top => return 0,
 			Self::Bot => return len - 1,
+			Self::PercentWindow(n) => {
+				return Self::percent_pos(0, if limit == 0 { len } else { len.min(limit) }, n);
+			}
 			Self::Prev => -1,
 			Self::Next => 1,
 			Self::Offset(n) => n,
@@ -100,4 +130,14 @@ impl Step {
 		}
 		.min(len - 1)
 	}
+
+	fn percent_pos(offset: usize, len: usize, n: i8) -> usize {
+		if len == 0 {
+			return 0;
+		}
+
+		let span = len.saturating_sub(1);
+		let pos = offset.saturating_add_signed(n as isize * span as isize / 100);
+		pos.clamp(offset, offset + span)
+	}
 }