Fix scroll position resetting on resize

In several cases when the terminal was resized the scroll position was
reset back to the top. This was partially by design as a quick fix to
ensure that the top position did not go out of bounds. This change adds
a new function to the scroll position module that will ensure that the
scroll top value stays within the allowed range when the view is
resized.

CHANGELOG.md

@@ -14,6 +14,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 - Change page up and page down to scroll half the height of the view area
 
+### Fixed
+- Scroll position resetting on resize
+
 ## [1.2.1] - 2020-01-26
 
 ### Fixed

src/help/mod.rs

@@ -74,7 +74,12 @@ impl<'h> ProcessModule for Help<'h> {
 				self.scroll_position.page_up(view_height, self.get_help_lines().len());
 			},
 			Input::Resize => {
-				self.scroll_position.reset();
+				self.scroll_position.view_resize(
+					view_height,
+					view_width,
+					self.get_help_lines().len(),
+					self.get_max_help_line_length(),
+				);
 			},
 			_ => {
 				result = result.state(self.return_state.clone());

src/list/mod.rs

@@ -81,6 +81,7 @@ impl<'l> ProcessModule for List<'l> {
 		let (_, view_height) = view.get_view_size();
 		let lines = git_interactive.get_lines();
 		let selected_index = *git_interactive.get_selected_line_index() - 1;
+		// TODO move this to handle_input
 		self.scroll_position
 			.ensure_cursor_visible(selected_index, view_height, lines.len());
 

src/show_commit/mod.rs

@@ -54,9 +54,8 @@ impl ProcessModule for ShowCommit {
 		view: &View,
 	) -> HandleInputResult
 	{
-		let (view_width, view_height) = view.get_view_size();
-
 		let input = input_handler.get_input(InputMode::Default);
+		let (view_width, view_height) = view.get_view_size();
 		let mut result = HandleInputResultBuilder::new(input);
 		match input {
 			Input::MoveCursorLeft => {
@@ -84,8 +83,12 @@ impl ProcessModule for ShowCommit {
 					.page_up(view_height, self.get_commit_stats_length())
 			},
 			Input::Resize => {
-				self.scroll_position
-					.scroll_up(view_height, self.get_commit_stats_length());
+				self.scroll_position.view_resize(
+					view_height,
+					view_width,
+					self.get_commit_stats_length(),
+					self.get_max_line_length(view_height),
+				)
 			},
 			_ => {
 				result = result.state(State::List(false));