Add configurable horizontal diff paging

KEY_CONFIG.md

@@ -19,6 +19,14 @@ Create a `key_bindings.ron` file like this:
 )
 ```
 
+Horizontal diff paging defaults to `Ctrl+Left` and `Ctrl+Right`. Override
+`page_left` and `page_right` to use different bindings:
+```
+(
+    page_left: Some(( code: Left, modifiers: "ALT")),
+    page_right: Some(( code: Right, modifiers: "ALT")),
+)
+
 The config file format based on the [Ron file format](https://github.com/ron-rs/ron).
 The location of the file depends on your OS:
 * `$HOME/.config/gitui/key_bindings.ron` (mac)

src/components/diff.rs

@@ -750,8 +750,8 @@ impl Component for DiffComponent {
 		_force_all: bool,
 	) -> CommandBlocking {
 		out.push(CommandInfo::new(
-			strings::commands::scroll(&self.key_config),
-			self.can_scroll(),
+			strings::commands::diff_scroll(&self.key_config),
+			self.can_scroll() || self.max_scroll_right() > 0,
 			self.focused(),
 		));
 		out.push(CommandInfo::new(
@@ -861,6 +861,22 @@ impl Component for DiffComponent {
 				{
 					self.move_selection(ScrollType::PageDown);
 					Ok(EventState::Consumed)
+				} else if key_match(
+					e,
+					self.key_config.keys.page_right,
+				) {
+					self.horizontal_scroll.move_page(
+						HorizontalScrollType::Right,
+						self.current_size.get().0.into(),
+					);
+					Ok(EventState::Consumed)
+				} else if key_match(e, self.key_config.keys.page_left)
+				{
+					self.horizontal_scroll.move_page(
+						HorizontalScrollType::Left,
+						self.current_size.get().0.into(),
+					);
+					Ok(EventState::Consumed)
 				} else if key_match(
 					e,
 					self.key_config.keys.move_right,

src/components/utils/scroll_horizontal.rs

@@ -49,6 +49,34 @@ impl HorizontalScroll {
 		true
 	}
 
+	pub fn move_page(
+		&self,
+		move_type: HorizontalScrollType,
+		page_width: usize,
+	) -> bool {
+		let old = self.right.get();
+		let max = self.max_right.get();
+		let page_width = page_width.saturating_sub(1).max(1);
+
+		let new_scroll_right = match move_type {
+			HorizontalScrollType::Left => {
+				old.saturating_sub(page_width)
+			}
+			HorizontalScrollType::Right => {
+				old.saturating_add(page_width)
+			}
+		};
+
+		let new_scroll_right = new_scroll_right.clamp(0, max);
+
+		if new_scroll_right == old {
+			return false;
+		}
+
+		self.right.set(new_scroll_right);
+
+		true
+	}
 	pub fn update(
 		&self,
 		selection: usize,
@@ -130,4 +158,15 @@ mod tests {
 	fn test_scroll_zero_width() {
 		assert_eq!(calc_scroll_right(4, 0, 4, 3), 0);
 	}
+
+	#[test]
+	fn test_scroll_page_left_right() {
+		let scroll = HorizontalScroll::new();
+		scroll.update_no_selection(100, 20);
+
+		assert!(scroll.move_page(HorizontalScrollType::Right, 20));
+		assert_eq!(scroll.get_right(), 19);
+		assert!(scroll.move_page(HorizontalScrollType::Left, 20));
+		assert_eq!(scroll.get_right(), 0);
+	}
 }

src/keys/key_list.rs

@@ -64,6 +64,8 @@ pub struct KeysList {
 	pub popup_down: GituiKeyEvent,
 	pub page_down: GituiKeyEvent,
 	pub page_up: GituiKeyEvent,
+	pub page_left: GituiKeyEvent,
+	pub page_right: GituiKeyEvent,
 	pub shift_up: GituiKeyEvent,
 	pub shift_down: GituiKeyEvent,
 	pub enter: GituiKeyEvent,
@@ -162,6 +164,8 @@ impl Default for KeysList {
 			popup_down: GituiKeyEvent::new(KeyCode::Down,  KeyModifiers::empty()),
 			page_down: GituiKeyEvent::new(KeyCode::PageDown,  KeyModifiers::empty()),
 			page_up: GituiKeyEvent::new(KeyCode::PageUp,  KeyModifiers::empty()),
+			page_left: GituiKeyEvent::new(KeyCode::Left, KeyModifiers::CONTROL),
+			page_right: GituiKeyEvent::new(KeyCode::Right, KeyModifiers::CONTROL),
 			shift_up: GituiKeyEvent::new(KeyCode::Up,  KeyModifiers::SHIFT),
 			shift_down: GituiKeyEvent::new(KeyCode::Down,  KeyModifiers::SHIFT),
 			enter: GituiKeyEvent::new(KeyCode::Enter,  KeyModifiers::empty()),

src/strings.rs

@@ -649,6 +649,21 @@ pub mod commands {
 			CMD_GROUP_GENERAL,
 		)
 	}
+	pub fn diff_scroll(key_config: &SharedKeyConfig) -> CommandText {
+		CommandText::new(
+			format!(
+				"Scroll [{}{}{}{}{}{}]",
+				key_config.get_hint(key_config.keys.move_up),
+				key_config.get_hint(key_config.keys.move_down),
+				key_config.get_hint(key_config.keys.page_up),
+				key_config.get_hint(key_config.keys.page_down),
+				key_config.get_hint(key_config.keys.page_left),
+				key_config.get_hint(key_config.keys.page_right)
+			),
+			"scroll vertically or horizontally in diff",
+			CMD_GROUP_DIFF,
+		)
+	}
 	pub fn commit_list_mark(
 		key_config: &SharedKeyConfig,
 		marked: bool,