Refactor editor scrolling and implement scroll commands from vim mode

crates/editor/src/scroll.rs

@@ -0,0 +1,339 @@
+pub mod actions;
+pub mod autoscroll;
+pub mod scroll_amount;
+
+use std::{
+    cmp::Ordering,
+    time::{Duration, Instant},
+};
+
+use gpui::{
+    geometry::vector::{vec2f, Vector2F},
+    Axis, MutableAppContext, Task, ViewContext,
+};
+use language::Bias;
+
+use crate::{
+    display_map::{DisplaySnapshot, ToDisplayPoint},
+    hover_popover::hide_hover,
+    Anchor, DisplayPoint, Editor, EditorMode, Event, MultiBufferSnapshot, ToPoint,
+};
+
+use self::{
+    autoscroll::{Autoscroll, AutoscrollStrategy},
+    scroll_amount::ScrollAmount,
+};
+
+pub const SCROLL_EVENT_SEPARATION: Duration = Duration::from_millis(28);
+const SCROLLBAR_SHOW_INTERVAL: Duration = Duration::from_secs(1);
+
+#[derive(Default)]
+pub struct ScrollbarAutoHide(pub bool);
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct ScrollAnchor {
+    pub offset: Vector2F,
+    pub top_anchor: Anchor,
+}
+
+impl ScrollAnchor {
+    fn new() -> Self {
+        Self {
+            offset: Vector2F::zero(),
+            top_anchor: Anchor::min(),
+        }
+    }
+
+    pub fn scroll_position(&self, snapshot: &DisplaySnapshot) -> Vector2F {
+        let mut scroll_position = self.offset;
+        if self.top_anchor != Anchor::min() {
+            let scroll_top = self.top_anchor.to_display_point(snapshot).row() as f32;
+            scroll_position.set_y(scroll_top + scroll_position.y());
+        } else {
+            scroll_position.set_y(0.);
+        }
+        scroll_position
+    }
+
+    pub fn top_row(&self, buffer: &MultiBufferSnapshot) -> u32 {
+        self.top_anchor.to_point(buffer).row
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct OngoingScroll {
+    last_event: Instant,
+    axis: Option<Axis>,
+}
+
+impl OngoingScroll {
+    fn new() -> Self {
+        Self {
+            last_event: Instant::now() - SCROLL_EVENT_SEPARATION,
+            axis: None,
+        }
+    }
+
+    pub fn filter(&self, delta: &mut Vector2F) -> Option<Axis> {
+        const UNLOCK_PERCENT: f32 = 1.9;
+        const UNLOCK_LOWER_BOUND: f32 = 6.;
+        let mut axis = self.axis;
+
+        let x = delta.x().abs();
+        let y = delta.y().abs();
+        let duration = Instant::now().duration_since(self.last_event);
+        if duration > SCROLL_EVENT_SEPARATION {
+            //New ongoing scroll will start, determine axis
+            axis = if x <= y {
+                Some(Axis::Vertical)
+            } else {
+                Some(Axis::Horizontal)
+            };
+        } else if x.max(y) >= UNLOCK_LOWER_BOUND {
+            //Check if the current ongoing will need to unlock
+            match axis {
+                Some(Axis::Vertical) => {
+                    if x > y && x >= y * UNLOCK_PERCENT {
+                        axis = None;
+                    }
+                }
+
+                Some(Axis::Horizontal) => {
+                    if y > x && y >= x * UNLOCK_PERCENT {
+                        axis = None;
+                    }
+                }
+
+                None => {}
+            }
+        }
+
+        match axis {
+            Some(Axis::Vertical) => *delta = vec2f(0., delta.y()),
+            Some(Axis::Horizontal) => *delta = vec2f(delta.x(), 0.),
+            None => {}
+        }
+
+        axis
+    }
+}
+
+pub struct ScrollManager {
+    vertical_scroll_margin: f32,
+    anchor: ScrollAnchor,
+    ongoing: OngoingScroll,
+    autoscroll_request: Option<(Autoscroll, bool)>,
+    last_autoscroll: Option<(Vector2F, f32, f32, AutoscrollStrategy)>,
+    show_scrollbars: bool,
+    hide_scrollbar_task: Option<Task<()>>,
+    visible_line_count: Option<f32>,
+}
+
+impl ScrollManager {
+    pub fn new() -> Self {
+        ScrollManager {
+            vertical_scroll_margin: 3.0,
+            anchor: ScrollAnchor::new(),
+            ongoing: OngoingScroll::new(),
+            autoscroll_request: None,
+            show_scrollbars: true,
+            hide_scrollbar_task: None,
+            last_autoscroll: None,
+            visible_line_count: None,
+        }
+    }
+
+    pub fn clone_state(&mut self, other: &Self) {
+        self.anchor = other.anchor;
+        self.ongoing = other.ongoing;
+    }
+
+    pub fn anchor(&self) -> ScrollAnchor {
+        self.anchor
+    }
+
+    pub fn ongoing_scroll(&self) -> OngoingScroll {
+        self.ongoing
+    }
+
+    pub fn update_ongoing_scroll(&mut self, axis: Option<Axis>) {
+        self.ongoing.last_event = Instant::now();
+        self.ongoing.axis = axis;
+    }
+
+    pub fn scroll_position(&self, snapshot: &DisplaySnapshot) -> Vector2F {
+        self.anchor.scroll_position(snapshot)
+    }
+
+    fn set_scroll_position(
+        &mut self,
+        scroll_position: Vector2F,
+        map: &DisplaySnapshot,
+        local: bool,
+        cx: &mut ViewContext<Editor>,
+    ) {
+        let new_anchor = if scroll_position.y() <= 0. {
+            ScrollAnchor {
+                top_anchor: Anchor::min(),
+                offset: scroll_position.max(vec2f(0., 0.)),
+            }
+        } else {
+            let scroll_top_buffer_offset =
+                DisplayPoint::new(scroll_position.y() as u32, 0).to_offset(&map, Bias::Right);
+            let top_anchor = map
+                .buffer_snapshot
+                .anchor_at(scroll_top_buffer_offset, Bias::Right);
+
+            ScrollAnchor {
+                top_anchor,
+                offset: vec2f(
+                    scroll_position.x(),
+                    scroll_position.y() - top_anchor.to_display_point(&map).row() as f32,
+                ),
+            }
+        };
+
+        self.set_anchor(new_anchor, local, cx);
+    }
+
+    fn set_anchor(&mut self, anchor: ScrollAnchor, local: bool, cx: &mut ViewContext<Editor>) {
+        self.anchor = anchor;
+        cx.emit(Event::ScrollPositionChanged { local });
+        self.show_scrollbar(cx);
+        self.autoscroll_request.take();
+        cx.notify();
+    }
+
+    pub fn show_scrollbar(&mut self, cx: &mut ViewContext<Editor>) {
+        if !self.show_scrollbars {
+            self.show_scrollbars = true;
+            cx.notify();
+        }
+
+        if cx.default_global::<ScrollbarAutoHide>().0 {
+            self.hide_scrollbar_task = Some(cx.spawn_weak(|editor, mut cx| async move {
+                cx.background().timer(SCROLLBAR_SHOW_INTERVAL).await;
+                if let Some(editor) = editor.upgrade(&cx) {
+                    editor.update(&mut cx, |editor, cx| {
+                        editor.scroll_manager.show_scrollbars = false;
+                        cx.notify();
+                    });
+                }
+            }));
+        } else {
+            self.hide_scrollbar_task = None;
+        }
+    }
+
+    pub fn scrollbars_visible(&self) -> bool {
+        self.show_scrollbars
+    }
+
+    pub fn has_autoscroll_request(&self) -> bool {
+        self.autoscroll_request.is_some()
+    }
+
+    pub fn clamp_scroll_left(&mut self, max: f32) -> bool {
+        if max < self.anchor.offset.x() {
+            self.anchor.offset.set_x(max);
+            true
+        } else {
+            false
+        }
+    }
+}
+
+impl Editor {
+    pub fn vertical_scroll_margin(&mut self) -> usize {
+        self.scroll_manager.vertical_scroll_margin as usize
+    }
+
+    pub fn set_vertical_scroll_margin(&mut self, margin_rows: usize, cx: &mut ViewContext<Self>) {
+        self.scroll_manager.vertical_scroll_margin = margin_rows as f32;
+        cx.notify();
+    }
+
+    pub fn visible_line_count(&self) -> Option<f32> {
+        self.scroll_manager.visible_line_count
+    }
+
+    pub(crate) fn set_visible_line_count(&mut self, lines: f32) {
+        self.scroll_manager.visible_line_count = Some(lines)
+    }
+
+    pub fn set_scroll_position(&mut self, scroll_position: Vector2F, cx: &mut ViewContext<Self>) {
+        self.set_scroll_position_internal(scroll_position, true, cx);
+    }
+
+    pub(crate) fn set_scroll_position_internal(
+        &mut self,
+        scroll_position: Vector2F,
+        local: bool,
+        cx: &mut ViewContext<Self>,
+    ) {
+        let map = self.display_map.update(cx, |map, cx| map.snapshot(cx));
+
+        hide_hover(self, cx);
+        self.scroll_manager
+            .set_scroll_position(scroll_position, &map, local, cx);
+    }
+
+    pub fn scroll_position(&self, cx: &mut ViewContext<Self>) -> Vector2F {
+        let display_map = self.display_map.update(cx, |map, cx| map.snapshot(cx));
+        self.scroll_manager.anchor.scroll_position(&display_map)
+    }
+
+    pub fn set_scroll_anchor(&mut self, scroll_anchor: ScrollAnchor, cx: &mut ViewContext<Self>) {
+        hide_hover(self, cx);
+        self.scroll_manager.set_anchor(scroll_anchor, true, cx);
+    }
+
+    pub fn scroll_screen(&mut self, amount: &ScrollAmount, cx: &mut ViewContext<Self>) {
+        if matches!(self.mode, EditorMode::SingleLine) {
+            cx.propagate_action();
+            return;
+        }
+
+        if self.take_rename(true, cx).is_some() {
+            return;
+        }
+
+        if amount.move_context_menu_selection(self, cx) {
+            return;
+        }
+
+        let cur_position = self.scroll_position(cx);
+        let new_pos = cur_position + vec2f(0., amount.lines(self) - 1.);
+        self.set_scroll_position(new_pos, cx);
+    }
+
+    /// Returns an ordering. The newest selection is:
+    ///     Ordering::Equal => on screen
+    ///     Ordering::Less => above the screen
+    ///     Ordering::Greater => below the screen
+    pub fn newest_selection_on_screen(&self, cx: &mut MutableAppContext) -> Ordering {
+        let snapshot = self.display_map.update(cx, |map, cx| map.snapshot(cx));
+        let newest_head = self
+            .selections
+            .newest_anchor()
+            .head()
+            .to_display_point(&snapshot);
+        let screen_top = self
+            .scroll_manager
+            .anchor
+            .top_anchor
+            .to_display_point(&snapshot);
+
+        if screen_top > newest_head {
+            return Ordering::Less;
+        }
+
+        if let Some(visible_lines) = self.visible_line_count() {
+            if newest_head.row() < screen_top.row() + visible_lines as u32 {
+                return Ordering::Equal;
+            }
+        }
+
+        Ordering::Greater
+    }
+}