layout: Remove by-ref animation_snapshot() getter

It was used in only one place, and that place was due for an update to use the
cached data.

niri-visual-tests/src/test_window.rs

@@ -255,10 +255,6 @@ impl LayoutElement for TestWindow {
         &EMPTY
     }
 
-    fn animation_snapshot(&self) -> Option<&LayoutElementRenderSnapshot> {
-        None
-    }
-
     fn take_animation_snapshot(&mut self) -> Option<LayoutElementRenderSnapshot> {
         None
     }

src/layout/mod.rs

@@ -270,7 +270,6 @@ pub trait LayoutElement {
     /// Runs periodic clean-up tasks.
     fn refresh(&self);
 
-    fn animation_snapshot(&self) -> Option<&LayoutElementRenderSnapshot>;
     fn take_animation_snapshot(&mut self) -> Option<LayoutElementRenderSnapshot>;
 
     fn set_interactive_resize(&mut self, data: Option<InteractiveResizeData>);

src/layout/scrolling.rs

@@ -4041,15 +4041,13 @@ impl<W: LayoutElement> Column<W> {
             .find(|(_, tile)| tile.window().id() == window)
             .unwrap();
 
-        let height = f64::from(tile.window().size().h);
-        let offset = tile
-            .window()
-            .animation_snapshot()
-            .map_or(0., |from| from.size.h - height);
+        let prev_height = self.data[tile_idx].size.h;
 
         tile.update_window();
         self.data[tile_idx].update(tile);
 
+        let offset = prev_height - self.data[tile_idx].size.h;
+
         let is_tabbed = self.display_mode == ColumnDisplay::Tabbed;
 
         // Move windows below in tandem with resizing.

src/layout/tests.rs

@@ -244,10 +244,6 @@ impl LayoutElement for TestWindow {
         &EMPTY
     }
 
-    fn animation_snapshot(&self) -> Option<&LayoutElementRenderSnapshot> {
-        None
-    }
-
     fn take_animation_snapshot(&mut self) -> Option<LayoutElementRenderSnapshot> {
         None
     }

src/window/mapped.rs

@@ -1174,10 +1174,6 @@ impl LayoutElement for Mapped {
         &self.rules
     }
 
-    fn animation_snapshot(&self) -> Option<&LayoutElementRenderSnapshot> {
-        self.animation_snapshot.as_ref()
-    }
-
     fn take_animation_snapshot(&mut self) -> Option<LayoutElementRenderSnapshot> {
         self.animation_snapshot.take()
     }