refactor: make selection_key_y optional

If the UI has no changes to show, then there will be no selected item as well, so we need to be able to represent this case.

src/ui.rs

@@ -611,8 +611,11 @@ impl<'state, 'input> Recorder<'state, 'input> {
  term.clear().map_err(RecordError::RenderFrame)?;
  }
  StateUpdate::EnsureSelectionInViewport => {
- self.scroll_offset_y =
- self.ensure_in_viewport(term_height, &drawn_rects, self.selection_key);
+ if let Some(scroll_offset_y) =
+ self.ensure_in_viewport(term_height, &drawn_rects, self.selection_key)
+ {
+ self.scroll_offset_y = scroll_offset_y;
+ }
  }
  StateUpdate::ScrollTo(scroll_offset_y) => {
  self.scroll_offset_y = scroll_offset_y.clamp(0, {
@@ -1316,12 +1319,20 @@ impl<'state, 'input> Recorder<'state, 'input> {
  None => return SelectionKey::None,
  };
 
- let original_y = self.selection_key_y(drawn_rects, self.selection_key);
+ let original_y = match self.selection_key_y(drawn_rects, self.selection_key) {
+ Some(original_y) => original_y,
+ None => {
+ return SelectionKey::None;
+ }
+ };
  let target_y = original_y.saturating_sub(term_height.unwrap_isize() / 2);
  while index > 0 {
  index -= 1;
- if self.selection_key_y(drawn_rects, keys[index]) <= target_y {
- break;
+ let selection_key_y = self.selection_key_y(drawn_rects, keys[index]);
+ if let Some(selection_key_y) = selection_key_y {
+ if selection_key_y <= target_y {
+ break;
+ }
  }
  }
  keys[index]
@@ -1338,12 +1349,18 @@ impl<'state, 'input> Recorder<'state, 'input> {
  None => return SelectionKey::None,
  };
 
- let original_y = self.selection_key_y(drawn_rects, self.selection_key);
+ let original_y = match self.selection_key_y(drawn_rects, self.selection_key) {
+ Some(original_y) => original_y,
+ None => return SelectionKey::None,
+ };
  let target_y = original_y.saturating_add(term_height.unwrap_isize() / 2);
  while index + 1 < keys.len() {
  index += 1;
- if self.selection_key_y(drawn_rects, keys[index]) >= target_y {
- break;
+ let selection_key_y = self.selection_key_y(drawn_rects, keys[index]);
+ if let Some(selection_key_y) = selection_key_y {
+ if selection_key_y >= target_y {
+ break;
+ }
  }
  }
  keys[index]
@@ -1440,27 +1457,32 @@ impl<'state, 'input> Recorder<'state, 'input> {
  &self,
  drawn_rects: &DrawnRects<ComponentId>,
  selection_key: SelectionKey,
- ) -> isize {
- let rect = self.selection_rect(drawn_rects, selection_key);
- rect.y
+ ) -> Option<isize> {
+ let rect = self.selection_rect(drawn_rects, selection_key)?;
+ Some(rect.y)
  }
 
  fn selection_rect(
  &self,
  drawn_rects: &DrawnRects<ComponentId>,
  selection_key: SelectionKey,
- ) -> Rect {
- let id = ComponentId::SelectableItem(selection_key);
+ ) -> Option<Rect> {
+ let id = match selection_key {
+ SelectionKey::None => return None,
+ SelectionKey::File(_) | SelectionKey::Section(_) | SelectionKey::Line(_) => {
+ ComponentId::SelectableItem(selection_key)
+ }
+ };
  match drawn_rects.get(&id) {
- Some(DrawnRect { rect, timestamp: _ }) => *rect,
+ Some(DrawnRect { rect, timestamp: _ }) => Some(*rect),
  None => {
  if cfg!(debug_assertions) {
  panic!(
  "could not look up drawn rect for component with ID {id:?}; was it drawn?"
  )
  } else {
  warn!(component_id = ?id, "could not look up drawn rect for component; was it drawn?");
- Rect::default()
+ None
  }
  }
  }
@@ -1471,7 +1493,7 @@ impl<'state, 'input> Recorder<'state, 'input> {
  term_height: usize,
  drawn_rects: &DrawnRects<ComponentId>,
  selection_key: SelectionKey,
- ) -> isize {
+ ) -> Option<isize> {
  let menu_bar_height = 1;
  let sticky_file_header_height = match selection_key {
  SelectionKey::None | SelectionKey::File(_) => 0,
@@ -1483,7 +1505,7 @@ impl<'state, 'input> Recorder<'state, 'input> {
  let viewport_height = term_height.unwrap_isize() - top_margin;
  let viewport_bottom_y = viewport_top_y + viewport_height;
 
- let selection_rect = self.selection_rect(drawn_rects, selection_key);
+ let selection_rect = self.selection_rect(drawn_rects, selection_key)?;
  let selection_top_y = selection_rect.y;
  let selection_height = selection_rect.height.unwrap_isize();
  let selection_bottom_y = selection_top_y + selection_height;
@@ -1499,7 +1521,8 @@ impl<'state, 'input> Recorder<'state, 'input> {
  // edge of the component, not the bottom edge. Thus, we should also
  // accept the previous `SelectionKey` and use that when making the
  // decision of where to scroll.
- if viewport_top_y <= selection_top_y && selection_bottom_y < viewport_bottom_y {
+ let result = if viewport_top_y <= selection_top_y && selection_bottom_y < viewport_bottom_y
+ {
  // Component is completely within the viewport, no need to scroll.
  self.scroll_offset_y
  } else if (
@@ -1514,7 +1537,8 @@ impl<'state, 'input> Recorder<'state, 'input> {
  // Component is at least partially below the viewport. Want to satisfy:
  // scroll_offset_y + term_height == rect_bottom_y
  selection_bottom_y - top_margin - viewport_height
- }
+ };
+ Some(result)
  }
 
  fn find_component_at(
@@ -2099,7 +2123,7 @@ struct AppDebugInfo {
  term_height: usize,
  scroll_offset_y: isize,
  selection_key: SelectionKey,
- selection_key_y: isize,
+ selection_key_y: Option<isize>,
  drawn_rects: BTreeMap<ComponentId, DrawnRect>, // sorted for determinism
 }