Make CursorVFX a trait, tweak cursor trail with cubic easing function

src/renderer/cursor_renderer/animation_utils.rs

@@ -25,6 +25,28 @@ pub fn ease_in_out_quad(t: f32) -> f32 {
     }
 }
 
+#[allow(dead_code)]
+pub fn ease_in_cubic(t: f32) -> f32 {
+    t * t * t
+}
+
+#[allow(dead_code)]
+pub fn ease_out_cubic(t: f32) -> f32 {
+    let n = t - 1.0;
+    n * n * n + 1.0
+}
+
+#[allow(dead_code)]
+pub fn ease_in_out_cubic(t: f32) -> f32 {
+    let n = 2.0 * t;
+    if n < 1.0 {
+        0.5 * n * n * n
+    } else {
+        let n = n - 2.0;
+        0.5 * (n * n * n + 2.0)
+    }
+}
+
 pub fn lerp(start: f32, end: f32, t: f32) -> f32 {
     start + (end - start) * t
 }

src/renderer/cursor_renderer/cursor_vfx.rs

@@ -2,26 +2,29 @@ use skulpin::skia_safe::{BlendMode, Canvas, Color, Paint, Point, Rect};
 
 use crate::editor::{Colors, Cursor};
 
+pub trait CursorVFX {
+    fn update(&mut self, current_cursor_destination: Point, dt: f32) -> bool;
+    fn restart(&mut self, position: Point);
+    fn render(&self, _paint: &mut Paint, canvas: &mut Canvas, cursor: &Cursor, colors: &Colors);
+}
 
-// TODO -- Make this a trait to have several impls
-// TODO -- Rename this impl as SonicBoom
-pub struct CursorVFX {
+pub struct SonicBoom {
     pub t: f32,
     pub center_position: Point,
 }
 
-impl CursorVFX {
-    pub fn update(&mut self, dt: f32) -> bool {
+impl CursorVFX for SonicBoom {
+    fn update(&mut self, _current_cursor_destination: Point, dt: f32) -> bool {
         self.t = (self.t + dt * 5.0).min(1.0); // TODO - speed config
-        return self.t < 1.0
+        return self.t < 1.0;
     }
 
-    pub fn restart(&mut self, position: Point) {
+    fn restart(&mut self, position: Point) {
         self.t = 0.0;
         self.center_position = position;
     }
 
-    pub fn render(&self, _paint: &mut Paint, canvas: &mut Canvas, cursor: &Cursor, colors: &Colors) {
+    fn render(&self, _paint: &mut Paint, canvas: &mut Canvas, cursor: &Cursor, colors: &Colors) {
         if self.t == 1.0 {
             return;
         }
@@ -36,9 +39,13 @@ impl CursorVFX {
         let size = 40.0; // TODO -- Compute from font size
         let radius = self.t * size;
         let hr = radius * 0.5;
-        let rect = Rect::from_xywh(self.center_position.x - hr, self.center_position.y - hr, radius, radius);
+        let rect = Rect::from_xywh(
+            self.center_position.x - hr,
+            self.center_position.y - hr,
+            radius,
+            radius,
+        );
 
         canvas.draw_oval(&rect, &paint);
     }
 }
-

src/renderer/cursor_renderer/mod.rs

@@ -13,7 +13,7 @@ use animation_utils::*;
 mod cursor_vfx;
 
 const BASE_ANIMATION_LENGTH_SECONDS: f32 = 0.06;
-const CURSOR_TRAIL_SIZE: f32 = 0.6;
+const CURSOR_TRAIL_SIZE: f32 = 0.7;
 const COMMAND_LINE_DELAY_FRAMES: u64 = 5;
 const DEFAULT_CELL_PERCENTAGE: f32 = 1.0 / 8.0;
 
@@ -162,7 +162,7 @@ impl Corner {
         let direction_alignment = travel_direction.dot(corner_direction);
 
         self.current_position =
-            ease_point(ease_linear, self.start_position, corner_destination, self.t);
+            ease_point(ease_out_cubic, self.start_position, corner_destination, self.t);
 
         if self.t == 1.0 {
             // We are at destination, move t out of 0-1 range to stop the animation
@@ -182,7 +182,7 @@ pub struct CursorRenderer {
     pub command_line_delay: u64,
     blink_status: BlinkStatus,
     previous_cursor_shape: Option<CursorShape>,
-    cursor_vfx: cursor_vfx::CursorVFX,
+    cursor_vfx: Box<dyn cursor_vfx::CursorVFX>,
 }
 
 impl CursorRenderer {
@@ -193,7 +193,7 @@ impl CursorRenderer {
             command_line_delay: 0,
             blink_status: BlinkStatus::new(),
             previous_cursor_shape: None,
-            cursor_vfx:  cursor_vfx::CursorVFX{t: 0.0, center_position: Point{x:0.0, y:0.0}},
+            cursor_vfx: Box::new(cursor_vfx::SonicBoom{t: 0.0, center_position: Point{x:0.0, y:0.0}}),
         };
         renderer.set_cursor_shape(&CursorShape::Block, DEFAULT_CELL_PERCENTAGE);
         renderer
@@ -293,7 +293,7 @@ impl CursorRenderer {
                 let corner_animating = corner.update(font_dimensions, center_destination, dt);
                 animating |= corner_animating;
             }
-            let vfx_animating = self.cursor_vfx.update(dt);
+            let vfx_animating = self.cursor_vfx.update(center_destination, dt);
             animating |= vfx_animating;
         }