Fix Git diff rendering

src/app/view/git.rs

@@ -1,5 +1,6 @@
 use super::*;
 use crate::app::git::{GitChangeKind, GitDiffLine, GitDiffLineKind, GitDiffMode, GitDiffRow};
+use crate::app::{git_diff_new_scroll_id, git_diff_old_scroll_id};
 use iced::widget::column;
 
 impl App {
@@ -259,13 +260,7 @@ impl App {
         } else {
             split_diff(diff.split_rows())
         };
-        let diff_scroll = scrollable(content)
-            .direction(scrollable::Direction::Both {
-                vertical: scrollable::Scrollbar::new(),
-                horizontal: scrollable::Scrollbar::new(),
-            })
-            .height(Length::Fill)
-            .width(Length::Fill);
+        let diff_scroll = scrollable(content).height(Length::Fill).width(Length::Fill);
         let dialog = container(
             column![
                 row![
@@ -342,17 +337,59 @@ fn unified_diff(lines: &[GitDiffLine]) -> Element<'_, Message> {
 }
 
 fn split_diff(rows: Vec<GitDiffRow>) -> Element<'static, Message> {
-    let mut content = column![].spacing(0).width(Length::Fill);
+    let width = split_diff_width(&rows);
+    let old = scrollable(split_diff_half(&rows, true, width))
+        .id(git_diff_old_scroll_id())
+        .direction(scrollable::Direction::Horizontal(
+            scrollable::Scrollbar::new(),
+        ))
+        .on_scroll(Message::GitDiffScrolled)
+        .width(Length::Fill);
+    let new = scrollable(split_diff_half(&rows, false, width))
+        .id(git_diff_new_scroll_id())
+        .direction(scrollable::Direction::Horizontal(
+            scrollable::Scrollbar::new(),
+        ))
+        .on_scroll(Message::GitDiffScrolled)
+        .width(Length::Fill);
+    row![old, rule::vertical(1), new].into()
+}
+
+fn split_diff_width(rows: &[GitDiffRow]) -> f32 {
+    rows.iter()
+        .flat_map(|row| match row {
+            GitDiffRow::Header(line) => [Some(line), None],
+            GitDiffRow::Pair { old, new } => [old.as_ref(), new.as_ref()],
+        })
+        .flatten()
+        .map(|line| {
+            line.text
+                .chars()
+                .map(|character| if character == '\t' { 4 } else { 1 })
+                .sum::<usize>()
+        })
+        .max()
+        .unwrap_or_default() as f32
+        * 8.0
+        + 66.0
+}
+
+fn split_diff_half(rows: &[GitDiffRow], old: bool, width: f32) -> Element<'static, Message> {
+    let mut content = column![].spacing(0).width(width);
     for row in rows {
         content = content.push(match row {
-            GitDiffRow::Header(line) => diff_line(&line, false),
-            GitDiffRow::Pair { old, new } => row![
-                diff_half(old.as_ref(), true),
-                rule::vertical(1),
-                diff_half(new.as_ref(), false),
-            ]
-            .height(24)
-            .into(),
+            GitDiffRow::Header(line) => diff_line(line, old),
+            GitDiffRow::Pair {
+                old: old_line,
+                new: new_line,
+            } => diff_half(
+                if old {
+                    old_line.as_ref()
+                } else {
+                    new_line.as_ref()
+                },
+                old,
+            ),
         });
     }
     content.into()
@@ -427,3 +464,28 @@ fn staged_color() -> Color {
 fn modal_backdrop_style(_: &Theme) -> container::Style {
     container::Style::default().background(Color::from_rgba8(0, 0, 0, 0.72))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn split_diff_width_covers_the_longest_side_and_tabs() {
+        let rows = [GitDiffRow::Pair {
+            old: Some(GitDiffLine {
+                kind: GitDiffLineKind::Deletion,
+                old_number: Some(1),
+                new_number: None,
+                text: "short".into(),
+            }),
+            new: Some(GitDiffLine {
+                kind: GitDiffLineKind::Addition,
+                old_number: None,
+                new_number: Some(1),
+                text: "\tlong".into(),
+            }),
+        }];
+
+        assert_eq!(split_diff_width(&rows), 130.0);
+    }
+}