Use new scroll delta field in viewport event for smooth scrolling

src/bridge/events.rs

@@ -230,6 +230,7 @@ pub enum RedrawEvent {
         current_line: f64,
         current_column: f64,
         line_count: Option<f64>,
+        scroll_delta: Option<f64>,
     },
     CommandLineShow {
         content: StyledContent,
@@ -642,20 +643,14 @@ fn parse_win_float_pos(win_float_pos_arguments: Vec<Value>) -> Result<RedrawEven
     let ([grid, _window, anchor, anchor_grid, anchor_row, anchor_column, focusable], [sort_order]) =
         extract_values_with_optional(win_float_pos_arguments)?;
 
-    let sort_order = if let Some(sort_order) = sort_order {
-        Some(parse_u64(sort_order)?)
-    } else {
-        None
-    };
-
     Ok(RedrawEvent::WindowFloatPosition {
         grid: parse_u64(grid)?,
         anchor: parse_window_anchor(anchor)?,
         anchor_grid: parse_u64(anchor_grid)?,
         anchor_row: parse_f64(anchor_row)?,
         anchor_column: parse_f64(anchor_column)?,
         focusable: parse_bool(focusable)?,
-        sort_order,
+        sort_order: sort_order.map(parse_u64).transpose()?,
     })
 }
 
@@ -697,22 +692,17 @@ fn parse_msg_set_pos(msg_set_pos_arguments: Vec<Value>) -> Result<RedrawEvent> {
 fn parse_win_viewport(win_viewport_arguments: Vec<Value>) -> Result<RedrawEvent> {
     let (
         [grid, _window, top_line, bottom_line, current_line, current_column],
-        [line_count, _scroll_delta],
+        [line_count, scroll_delta],
     ) = extract_values_with_optional(win_viewport_arguments)?;
 
-    let line_count = if let Some(line_count) = line_count {
-        Some(parse_f64(line_count)?)
-    } else {
-        None
-    };
-
     Ok(RedrawEvent::WindowViewport {
         grid: parse_u64(grid)?,
         top_line: parse_f64(top_line)?,
         bottom_line: parse_f64(bottom_line)?,
         current_line: parse_f64(current_line)?,
         current_column: parse_f64(current_column)?,
-        line_count,
+        line_count: line_count.map(parse_f64).transpose()?,
+        scroll_delta: scroll_delta.map(parse_f64).transpose()?,
     })
 }
 

src/editor/mod.rs

@@ -214,10 +214,10 @@ impl Editor {
                 }
                 RedrawEvent::WindowViewport {
                     grid,
-                    top_line,
-                    bottom_line,
+                    // Don't send viewport events if they don't have a scroll delta
+                    scroll_delta: Some(scroll_delta),
                     ..
-                } => self.send_updated_viewport(grid, top_line, bottom_line),
+                } => self.send_updated_viewport(grid, scroll_delta),
                 _ => {}
             },
             EditorCommand::RedrawScreen => self.redraw_screen(),
@@ -463,9 +463,9 @@ impl Editor {
         }
     }
 
-    fn send_updated_viewport(&mut self, grid: u64, top_line: f64, bottom_line: f64) {
+    fn send_updated_viewport(&mut self, grid: u64, scroll_delta: f64) {
         if let Some(window) = self.windows.get_mut(&grid) {
-            window.update_viewport(top_line, bottom_line);
+            window.update_viewport(scroll_delta);
         } else {
             trace!("viewport event received before window initialized");
         }

src/editor/window.rs

@@ -324,11 +324,8 @@ impl Window {
         self.send_command(WindowDrawCommand::Close);
     }
 
-    pub fn update_viewport(&self, top_line: f64, bottom_line: f64) {
-        self.send_command(WindowDrawCommand::Viewport {
-            top_line,
-            bottom_line,
-        });
+    pub fn update_viewport(&self, scroll_delta: f64) {
+        self.send_command(WindowDrawCommand::Viewport { scroll_delta });
     }
 }
 

src/renderer/cursor_renderer/mod.rs

@@ -252,7 +252,7 @@ impl CursorRenderer {
         if let Some(window) = windows.get(&self.cursor.parent_window_id) {
             let grid_x = cursor_grid_x as f32 + window.grid_current_position.x;
             let mut grid_y = cursor_grid_y as f32 + window.grid_current_position.y
-                - (window.current_scroll - window.current_surface.top_line as f32);
+                - (window.current_scroll - window.current_surface.vertical_position);
 
             // Prevent the cursor from targeting a position outside its current window. Since only
             // the vertical direction is effected by scrolling, we only have to clamp the vertical

src/renderer/rendered_window.rs

@@ -45,8 +45,7 @@ pub enum WindowDrawCommand {
     Hide,
     Close,
     Viewport {
-        top_line: f64,
-        bottom_line: f64,
+        scroll_delta: f64,
     },
 }
 
@@ -100,31 +99,34 @@ fn build_window_surface_with_grid_size(
 
 pub struct LocatedSnapshot {
     image: Image,
-    top_line: u64,
+    vertical_position: f32,
 }
 
 pub struct LocatedSurface {
     surface: Surface,
-    pub top_line: u64,
+    pub vertical_position: f32,
 }
 
 impl LocatedSurface {
     fn new(
         parent_canvas: &mut Canvas,
         grid_renderer: &GridRenderer,
         grid_size: Dimensions,
-        top_line: u64,
+        vertical_position: f32,
     ) -> LocatedSurface {
         let surface = build_window_surface_with_grid_size(parent_canvas, grid_renderer, grid_size);
 
-        LocatedSurface { surface, top_line }
+        LocatedSurface {
+            surface,
+            vertical_position,
+        }
     }
 
     fn snapshot(&mut self) -> LocatedSnapshot {
         let image = self.surface.image_snapshot();
         LocatedSnapshot {
             image,
-            top_line: self.top_line,
+            vertical_position: self.vertical_position,
         }
     }
 }
@@ -168,7 +170,7 @@ impl RenderedWindow {
         grid_size: Dimensions,
         padding: WindowPadding,
     ) -> RenderedWindow {
-        let current_surface = LocatedSurface::new(parent_canvas, grid_renderer, grid_size, 0);
+        let current_surface = LocatedSurface::new(parent_canvas, grid_renderer, grid_size, 0.);
 
         RenderedWindow {
             snapshots: VecDeque::new(),
@@ -306,8 +308,8 @@ impl RenderedWindow {
 
         // Draw scrolling snapshots.
         for snapshot in self.snapshots.iter_mut().rev() {
-            let scroll_offset = (snapshot.top_line * font_height) as f32
-                - (self.current_scroll * font_height as f32);
+            let scroll_offset =
+                (snapshot.vertical_position - self.current_scroll) * font_height as f32;
             let image = &mut snapshot.image;
             root_canvas.draw_image_rect(
                 image,
@@ -318,8 +320,8 @@ impl RenderedWindow {
         }
 
         // Draw current surface.
-        let scroll_offset = (self.current_surface.top_line * font_height) as f32
-            - (self.current_scroll * font_height as f32);
+        let scroll_offset =
+            (self.current_surface.vertical_position - self.current_scroll) * font_height as f32;
         let snapshot = self.current_surface.surface.image_snapshot();
         root_canvas.draw_image_rect(
             snapshot,
@@ -503,20 +505,20 @@ impl RenderedWindow {
                 }
             }
             WindowDrawCommand::Hide => self.hidden = true,
-            WindowDrawCommand::Viewport { top_line, .. } => {
-                if self.current_surface.top_line != top_line as u64 {
+            WindowDrawCommand::Viewport { scroll_delta, .. } => {
+                if scroll_delta.abs() > f64::EPSILON {
                     let new_snapshot = self.current_surface.snapshot();
                     self.snapshots.push_back(new_snapshot);
 
                     if self.snapshots.len() > 5 {
                         self.snapshots.pop_front();
                     }
 
-                    self.current_surface.top_line = top_line as u64;
+                    self.current_surface.vertical_position += scroll_delta as f32;
 
                     // Set new target viewport position and initialize animation timer.
                     self.start_scroll = self.current_scroll;
-                    self.scroll_destination = top_line as f32;
+                    self.scroll_destination = self.current_surface.vertical_position;
                     self.scroll_t = 0.0;
                 }
             }