Allow to scroll diffs horizontally (#1327)

3 files changed, 70 insertions, 24 deletions

diff --git a/src/ui/mod.rs b/src/ui/mod.rs
index eac3e3b6..4b1db6eb 100644
--- a/src/ui/mod.rs
+++ b/src/ui/mod.rs
@@ -6,7 +6,7 @@ pub mod style;
 mod syntax_text;
 
 use filetreelist::MoveSelection;
-pub use scrollbar::draw_scrollbar;
+pub use scrollbar::{draw_scrollbar, Orientation};
 pub use scrolllist::{draw_list, draw_list_block};
 pub use stateful_paragraph::{
 	ParagraphState, ScrollPos, StatefulParagraph,
diff --git a/src/ui/reflow.rs b/src/ui/reflow.rs
index a9937361..81de4b84 100644
--- a/src/ui/reflow.rs
+++ b/src/ui/reflow.rs
@@ -1,6 +1,6 @@
+use crate::string_utils::trim_offset;
 use easy_cast::Cast;
 use tui::text::StyledGrapheme;
-use unicode_segmentation::UnicodeSegmentation;
 use unicode_width::UnicodeWidthStr;
 
 const NBSP: &str = "\u{00a0}";
@@ -233,22 +233,6 @@ impl<'a, 'b> LineComposer<'a> for LineTruncator<'a, 'b> {
 	}
 }
 
-/// This function will return a str slice which start at specified offset.
-/// As src is a unicode str, start offset has to be calculated with each character.
-fn trim_offset(src: &str, mut offset: usize) -> &str {
-	let mut start = 0;
-	for c in UnicodeSegmentation::graphemes(src, true) {
-		let w = c.width();
-		if w <= offset {
-			offset -= w;
-			start += c.len();
-		} else {
-			break;
-		}
-	}
-	&src[start..]
-}
-
 #[cfg(test)]
 mod test {
 	use super::*;
diff --git a/src/ui/scrollbar.rs b/src/ui/scrollbar.rs
index adf4dec1..3a28fe82 100644
--- a/src/ui/scrollbar.rs
+++ b/src/ui/scrollbar.rs
@@ -6,32 +6,40 @@ use tui::{
 	buffer::Buffer,
 	layout::{Margin, Rect},
 	style::Style,
-	symbols::{block::FULL, line::DOUBLE_VERTICAL},
+	symbols::{
+		block::FULL,
+		line::{DOUBLE_HORIZONTAL, DOUBLE_VERTICAL},
+	},
 	widgets::Widget,
 	Frame,
 };
 
+pub enum Orientation {
+	Vertical,
+	Horizontal,
+}
+
 ///
 struct Scrollbar {
 	max: u16,
 	pos: u16,
 	style_bar: Style,
 	style_pos: Style,
+	orientation: Orientation,
 }
 
 impl Scrollbar {
-	fn new(max: usize, pos: usize) -> Self {
+	fn new(max: usize, pos: usize, orientation: Orientation) -> Self {
 		Self {
 			max: u16::try_from(max).unwrap_or_default(),
 			pos: u16::try_from(pos).unwrap_or_default(),
 			style_pos: Style::default(),
 			style_bar: Style::default(),
+			orientation,
 		}
 	}
-}
 
-impl Widget for Scrollbar {
-	fn render(self, area: Rect, buf: &mut Buffer) {
+	fn render_vertical(self, area: Rect, buf: &mut Buffer) {
 		if area.height <= 2 {
 			return;
 		}
@@ -67,6 +75,59 @@ impl Widget for Scrollbar {
 
 		buf.set_string(right, bar_top + pos, FULL, self.style_pos);
 	}
+
+	fn render_horizontal(self, area: Rect, buf: &mut Buffer) {
+		if area.width <= 2 {
+			return;
+		}
+
+		if self.max == 0 {
+			return;
+		}
+
+		let bottom = area.bottom().saturating_sub(1);
+		if bottom <= area.top() {
+			return;
+		};
+
+		let (bar_left, bar_width) = {
+			let scrollbar_area = area.inner(&Margin {
+				horizontal: 1,
+				vertical: 0,
+			});
+
+			(scrollbar_area.left(), scrollbar_area.width)
+		};
+
+		for x in bar_left..(bar_left + bar_width) {
+			buf.set_string(
+				x,
+				bottom,
+				DOUBLE_HORIZONTAL,
+				self.style_bar,
+			);
+		}
+
+		let progress = f32::from(self.pos) / f32::from(self.max);
+		let progress = if progress > 1.0 { 1.0 } else { progress };
+		let pos = f32::from(bar_width) * progress;
+
+		let pos: u16 = pos.cast_nearest();
+		let pos = pos.saturating_sub(1);
+
+		buf.set_string(bar_left + pos, bottom, FULL, self.style_pos);
+	}
+}
+
+impl Widget for Scrollbar {
+	fn render(self, area: Rect, buf: &mut Buffer) {
+		match &self.orientation {
+			Orientation::Vertical => self.render_vertical(area, buf),
+			Orientation::Horizontal => {
+				self.render_horizontal(area, buf);
+			}
+		}
+	}
 }
 
 pub fn draw_scrollbar<B: Backend>(
@@ -75,8 +136,9 @@ pub fn draw_scrollbar<B: Backend>(
 	theme: &SharedTheme,
 	max: usize,
 	pos: usize,
+	orientation: Orientation,
 ) {
-	let mut widget = Scrollbar::new(max, pos);
+	let mut widget = Scrollbar::new(max, pos, orientation);
 	widget.style_pos = theme.scroll_bar_pos();
 	f.render_widget(widget, r);
 }