Introduce absolute_offset_reversed to scrollable::Viewport

widget/src/scrollable.rs

@@ -554,14 +554,7 @@ pub fn update<Message>(
 
  state.scroll(delta, direction, bounds, content_bounds);
 
- notify_on_scroll(
- state,
- on_scroll,
- bounds,
- content_bounds,
- direction,
- shell,
- );
+ notify_on_scroll(state, on_scroll, bounds, content_bounds, shell);
 
  return event::Status::Captured;
  }
@@ -599,7 +592,6 @@ pub fn update<Message>(
  on_scroll,
  bounds,
  content_bounds,
- direction,
  shell,
  );
  }
@@ -645,7 +637,6 @@ pub fn update<Message>(
  on_scroll,
  bounds,
  content_bounds,
- direction,
  shell,
  );
 
@@ -681,7 +672,6 @@ pub fn update<Message>(
  on_scroll,
  bounds,
  content_bounds,
- direction,
  shell,
  );
  }
@@ -722,7 +712,6 @@ pub fn update<Message>(
  on_scroll,
  bounds,
  content_bounds,
- direction,
  shell,
  );
  }
@@ -758,7 +747,6 @@ pub fn update<Message>(
  on_scroll,
  bounds,
  content_bounds,
- direction,
  shell,
  );
 
@@ -974,7 +962,6 @@ fn notify_on_scroll<Message>(
  on_scroll: &Option<Box<dyn Fn(Viewport) -> Message + '_>>,
  bounds: Rectangle,
  content_bounds: Rectangle,
- direction: Direction,
  shell: &mut Shell<'_, Message>,
 ) {
  if let Some(on_scroll) = on_scroll {
@@ -984,23 +971,11 @@ fn notify_on_scroll<Message>(
  return;
  }
 
- let horizontal_alignment = direction
- .horizontal()
- .map(|p| p.alignment)
- .unwrap_or_default();
-
- let vertical_alignment = direction
- .vertical()
- .map(|p| p.alignment)
- .unwrap_or_default();
-
  let viewport = Viewport {
  offset_x: state.offset_x,
  offset_y: state.offset_y,
  bounds,
  content_bounds,
- vertical_alignment,
- horizontal_alignment,
  };
 
  // Don't publish redundant viewports to shell
@@ -1105,8 +1080,6 @@ pub struct Viewport {
  offset_y: Offset,
  bounds: Rectangle,
  content_bounds: Rectangle,
- vertical_alignment: Alignment,
- horizontal_alignment: Alignment,
 }
 
 impl Viewport {
@@ -1122,6 +1095,20 @@ impl Viewport {
  AbsoluteOffset { x, y }
  }
 
+ /// Returns the [`AbsoluteOffset`] of the current [`Viewport`], but with its
+ /// alignment reversed.
+ ///
+ /// This method can be useful to switch the alignment of a [`Scrollable`]
+ /// while maintaining its scrolling position.
+ pub fn absolute_offset_reversed(&self) -> AbsoluteOffset {
+ let AbsoluteOffset { x, y } = self.absolute_offset();
+
+ AbsoluteOffset {
+ x: (x - self.content_bounds.width - self.bounds.width).max(0.0),
+ y: (y - self.content_bounds.height - self.bounds.height).max(0.0),
+ }
+ }
+
  /// Returns the [`RelativeOffset`] of the current [`Viewport`].
  pub fn relative_offset(&self) -> RelativeOffset {
  let AbsoluteOffset { x, y } = self.absolute_offset();
@@ -1131,36 +1118,6 @@ impl Viewport {
 
  RelativeOffset { x, y }
  }
-
- /// Returns a new [`Viewport`] with the supplied vertical [`Alignment`].
- pub fn with_vertical_alignment(self, alignment: Alignment) -> Self {
- if self.vertical_alignment != alignment {
- let relative = 1.0 - self.relative_offset().y;
-
- Self {
- offset_y: Offset::Relative(relative),
- vertical_alignment: alignment,
- ..self
- }
- } else {
- self
- }
- }
-
- /// Returns a new [`Viewport`] with the supplied horizontal [`Alignment`].
- pub fn with_horizontal_alignment(self, alignment: Alignment) -> Self {
- if self.horizontal_alignment != alignment {
- let relative = 1.0 - self.relative_offset().x;
-
- Self {
- offset_x: Offset::Relative(relative),
- horizontal_alignment: alignment,
- ..self
- }
- } else {
- self
- }
- }
 }
 
 impl State {