Refactor editor scrolling and implement scroll commands from vim mode

crates/editor/src/scroll/autoscroll.rs

@@ -0,0 +1,246 @@
+use std::cmp;
+
+use gpui::{text_layout, ViewContext};
+use language::Point;
+
+use crate::{display_map::ToDisplayPoint, Editor, EditorMode};
+
+#[derive(PartialEq, Eq)]
+pub enum Autoscroll {
+    Next,
+    Strategy(AutoscrollStrategy),
+}
+
+impl Autoscroll {
+    pub fn fit() -> Self {
+        Self::Strategy(AutoscrollStrategy::Fit)
+    }
+
+    pub fn newest() -> Self {
+        Self::Strategy(AutoscrollStrategy::Newest)
+    }
+
+    pub fn center() -> Self {
+        Self::Strategy(AutoscrollStrategy::Center)
+    }
+}
+
+#[derive(PartialEq, Eq, Default)]
+pub enum AutoscrollStrategy {
+    Fit,
+    Newest,
+    #[default]
+    Center,
+    Top,
+    Bottom,
+}
+
+impl AutoscrollStrategy {
+    fn next(&self) -> Self {
+        match self {
+            AutoscrollStrategy::Center => AutoscrollStrategy::Top,
+            AutoscrollStrategy::Top => AutoscrollStrategy::Bottom,
+            _ => AutoscrollStrategy::Center,
+        }
+    }
+}
+
+impl Editor {
+    pub fn autoscroll_vertically(
+        &mut self,
+        viewport_height: f32,
+        line_height: f32,
+        cx: &mut ViewContext<Editor>,
+    ) -> bool {
+        let visible_lines = viewport_height / line_height;
+        let display_map = self.display_map.update(cx, |map, cx| map.snapshot(cx));
+        let mut scroll_position = self.scroll_manager.scroll_position(&display_map);
+        let max_scroll_top = if matches!(self.mode, EditorMode::AutoHeight { .. }) {
+            (display_map.max_point().row() as f32 - visible_lines + 1.).max(0.)
+        } else {
+            display_map.max_point().row() as f32
+        };
+        if scroll_position.y() > max_scroll_top {
+            scroll_position.set_y(max_scroll_top);
+            self.set_scroll_position(scroll_position, cx);
+        }
+
+        let (autoscroll, local) =
+            if let Some(autoscroll) = self.scroll_manager.autoscroll_request.take() {
+                autoscroll
+            } else {
+                return false;
+            };
+
+        let first_cursor_top;
+        let last_cursor_bottom;
+        if let Some(highlighted_rows) = &self.highlighted_rows {
+            first_cursor_top = highlighted_rows.start as f32;
+            last_cursor_bottom = first_cursor_top + 1.;
+        } else if autoscroll == Autoscroll::newest() {
+            let newest_selection = self.selections.newest::<Point>(cx);
+            first_cursor_top = newest_selection.head().to_display_point(&display_map).row() as f32;
+            last_cursor_bottom = first_cursor_top + 1.;
+        } else {
+            let selections = self.selections.all::<Point>(cx);
+            first_cursor_top = selections
+                .first()
+                .unwrap()
+                .head()
+                .to_display_point(&display_map)
+                .row() as f32;
+            last_cursor_bottom = selections
+                .last()
+                .unwrap()
+                .head()
+                .to_display_point(&display_map)
+                .row() as f32
+                + 1.0;
+        }
+
+        let margin = if matches!(self.mode, EditorMode::AutoHeight { .. }) {
+            0.
+        } else {
+            ((visible_lines - (last_cursor_bottom - first_cursor_top)) / 2.0).floor()
+        };
+        if margin < 0.0 {
+            return false;
+        }
+
+        let strategy = match autoscroll {
+            Autoscroll::Strategy(strategy) => strategy,
+            Autoscroll::Next => {
+                let last_autoscroll = &self.scroll_manager.last_autoscroll;
+                if let Some(last_autoscroll) = last_autoscroll {
+                    if self.scroll_manager.anchor.offset == last_autoscroll.0
+                        && first_cursor_top == last_autoscroll.1
+                        && last_cursor_bottom == last_autoscroll.2
+                    {
+                        last_autoscroll.3.next()
+                    } else {
+                        AutoscrollStrategy::default()
+                    }
+                } else {
+                    AutoscrollStrategy::default()
+                }
+            }
+        };
+
+        match strategy {
+            AutoscrollStrategy::Fit | AutoscrollStrategy::Newest => {
+                let margin = margin.min(self.scroll_manager.vertical_scroll_margin);
+                let target_top = (first_cursor_top - margin).max(0.0);
+                let target_bottom = last_cursor_bottom + margin;
+                let start_row = scroll_position.y();
+                let end_row = start_row + visible_lines;
+
+                if target_top < start_row {
+                    scroll_position.set_y(target_top);
+                    self.set_scroll_position_internal(scroll_position, local, cx);
+                } else if target_bottom >= end_row {
+                    scroll_position.set_y(target_bottom - visible_lines);
+                    self.set_scroll_position_internal(scroll_position, local, cx);
+                }
+            }
+            AutoscrollStrategy::Center => {
+                scroll_position.set_y((first_cursor_top - margin).max(0.0));
+                self.set_scroll_position_internal(scroll_position, local, cx);
+            }
+            AutoscrollStrategy::Top => {
+                scroll_position.set_y((first_cursor_top).max(0.0));
+                self.set_scroll_position_internal(scroll_position, local, cx);
+            }
+            AutoscrollStrategy::Bottom => {
+                scroll_position.set_y((last_cursor_bottom - visible_lines).max(0.0));
+                self.set_scroll_position_internal(scroll_position, local, cx);
+            }
+        }
+
+        self.scroll_manager.last_autoscroll = Some((
+            self.scroll_manager.anchor.offset,
+            first_cursor_top,
+            last_cursor_bottom,
+            strategy,
+        ));
+
+        true
+    }
+
+    pub fn autoscroll_horizontally(
+        &mut self,
+        start_row: u32,
+        viewport_width: f32,
+        scroll_width: f32,
+        max_glyph_width: f32,
+        layouts: &[text_layout::Line],
+        cx: &mut ViewContext<Self>,
+    ) -> bool {
+        let display_map = self.display_map.update(cx, |map, cx| map.snapshot(cx));
+        let selections = self.selections.all::<Point>(cx);
+
+        let mut target_left;
+        let mut target_right;
+
+        if self.highlighted_rows.is_some() {
+            target_left = 0.0_f32;
+            target_right = 0.0_f32;
+        } else {
+            target_left = std::f32::INFINITY;
+            target_right = 0.0_f32;
+            for selection in selections {
+                let head = selection.head().to_display_point(&display_map);
+                if head.row() >= start_row && head.row() < start_row + layouts.len() as u32 {
+                    let start_column = head.column().saturating_sub(3);
+                    let end_column = cmp::min(display_map.line_len(head.row()), head.column() + 3);
+                    target_left = target_left.min(
+                        layouts[(head.row() - start_row) as usize]
+                            .x_for_index(start_column as usize),
+                    );
+                    target_right = target_right.max(
+                        layouts[(head.row() - start_row) as usize].x_for_index(end_column as usize)
+                            + max_glyph_width,
+                    );
+                }
+            }
+        }
+
+        target_right = target_right.min(scroll_width);
+
+        if target_right - target_left > viewport_width {
+            return false;
+        }
+
+        let scroll_left = self.scroll_manager.anchor.offset.x() * max_glyph_width;
+        let scroll_right = scroll_left + viewport_width;
+
+        if target_left < scroll_left {
+            self.scroll_manager
+                .anchor
+                .offset
+                .set_x(target_left / max_glyph_width);
+            true
+        } else if target_right > scroll_right {
+            self.scroll_manager
+                .anchor
+                .offset
+                .set_x((target_right - viewport_width) / max_glyph_width);
+            true
+        } else {
+            false
+        }
+    }
+
+    pub fn request_autoscroll(&mut self, autoscroll: Autoscroll, cx: &mut ViewContext<Self>) {
+        self.scroll_manager.autoscroll_request = Some((autoscroll, true));
+        cx.notify();
+    }
+
+    pub(crate) fn request_autoscroll_remotely(
+        &mut self,
+        autoscroll: Autoscroll,
+        cx: &mut ViewContext<Self>,
+    ) {
+        self.scroll_manager.autoscroll_request = Some((autoscroll, false));
+        cx.notify();
+    }
+}