feat(editor): Implement pixel-based scrolling for the Editor (#418)

Refactors the Editor's scrolling implementation to be pixel-based instead of line-based. This provides smoother and more granular scrolling, which works more consistently across different input devices (like trackpads).

- The `Action::Scroll` variant now takes `pixels: f32`.
- The `Editor` now processes scroll actions using pixel values directly.
- Examples have been updated to reflect the new scrolling behavior.

examples/editor/src/main.rs

@@ -65,7 +65,6 @@ fn main() {
     let mut mouse_x = 0.0;
     let mut mouse_y = 0.0;
     let mut mouse_left = ElementState::Released;
-    let mut unapplied_scroll_delta = 0.0;
 
     event_loop
         .run(|event, elwt| {
@@ -294,9 +293,9 @@ fn main() {
 
                         // Scroll if cursor is near edge of window while dragging
                         if mouse_y <= 5.0 {
-                            editor.action(Action::Scroll { lines: -1 });
+                            editor.action(Action::Scroll { pixels: -20.0 });
                         } else if mouse_y - 5.0 >= window.inner_size().height as f64 {
-                            editor.action(Action::Scroll { lines: 1 });
+                            editor.action(Action::Scroll { pixels: 20.0 });
                         }
 
                         window.request_redraw();
@@ -323,17 +322,14 @@ fn main() {
                     delta,
                     phase: _,
                 } => {
-                    let line_delta = match delta {
+                    let pixel_delta = match delta {
-                        MouseScrollDelta::LineDelta(_x, y) => y as i32,
+                        MouseScrollDelta::LineDelta(_x, y) => y * 20.0,
-                        MouseScrollDelta::PixelDelta(PhysicalPosition { x: _, y }) => {
+                        MouseScrollDelta::PixelDelta(PhysicalPosition { x: _, y }) => y as f32,
-                            unapplied_scroll_delta += y;
-                            let line_delta = (unapplied_scroll_delta / 20.0).floor();
-                            unapplied_scroll_delta -= line_delta * 20.0;
-                            line_delta as i32
-                        }
                     };
-                    if line_delta != 0 {
+                    if pixel_delta != 0.0 {
-                        editor.action(Action::Scroll { lines: -line_delta });
+                        editor.action(Action::Scroll {
+                            pixels: -pixel_delta,
+                        });
                     }
                     window.request_redraw();
                 }

examples/rich-text/src/main.rs

@@ -186,7 +186,6 @@ fn main() {
     let mut mouse_x = 0.0;
     let mut mouse_y = 0.0;
     let mut mouse_left = ElementState::Released;
-    let mut unapplied_scroll_delta = 0.0;
 
     let bg_color = tiny_skia::Color::from_rgba8(0x34, 0x34, 0x34, 0xFF);
     let font_color = Color::rgb(0xFF, 0xFF, 0xFF);
@@ -340,9 +339,9 @@ fn main() {
 
                         // Scroll if cursor is near edge of window while dragging
                         if mouse_y <= 5.0 {
-                            editor.action(Action::Scroll { lines: -1 });
+                            editor.action(Action::Scroll { pixels: -20.0 });
                         } else if mouse_y - 5.0 >= window.inner_size().height as f64 {
-                            editor.action(Action::Scroll { lines: 1 });
+                            editor.action(Action::Scroll { pixels: 20.0 });
                         }
 
                         window.request_redraw();
@@ -369,17 +368,14 @@ fn main() {
                     delta,
                     phase: _,
                 } => {
-                    let line_delta = match delta {
+                    let pixel_delta = match delta {
-                        MouseScrollDelta::LineDelta(_x, y) => y as i32,
+                        MouseScrollDelta::LineDelta(_x, y) => y * 20.0,
-                        MouseScrollDelta::PixelDelta(PhysicalPosition { x: _, y }) => {
+                        MouseScrollDelta::PixelDelta(PhysicalPosition { x: _, y }) => y as f32,
-                            unapplied_scroll_delta += y;
-                            let line_delta = (unapplied_scroll_delta / 20.0).floor();
-                            unapplied_scroll_delta -= line_delta * 20.0;
-                            line_delta as i32
-                        }
                     };
-                    if line_delta != 0 {
+                    if pixel_delta != 0.0 {
-                        editor.action(Action::Scroll { lines: -line_delta });
+                        editor.action(Action::Scroll {
+                            pixels: -pixel_delta,
+                        });
                     }
                     window.request_redraw();
                 }

src/edit/editor.rs

@@ -858,11 +858,11 @@ impl<'buffer> Edit<'buffer> for Editor<'buffer> {
                     }
                 }
             }
-            Action::Scroll { lines } => {
+            Action::Scroll { pixels } => {
                 self.with_buffer_mut(|buffer| {
                     let mut scroll = buffer.scroll();
                     //TODO: align to layout lines
-                    scroll.vertical += lines as f32 * buffer.metrics().line_height;
+                    scroll.vertical += pixels;
                     buffer.set_scroll(scroll);
                 });
             }

src/edit/mod.rs

@@ -20,7 +20,7 @@ pub use self::vi::*;
 mod vi;
 
 /// An action to perform on an [`Editor`]
-#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub enum Action {
     /// Move the cursor with some motion
     Motion(Motion),
@@ -58,9 +58,9 @@ pub enum Action {
         x: i32,
         y: i32,
     },
-    /// Scroll specified number of lines
+    /// Scroll specified number of pixels
     Scroll {
-        lines: i32,
+        pixels: f32,
     },
 }