vim: Fix scrolling

After #2641 we noticed that scrolling didn't take a count parameter.

The PageDown/PageUp logic was also broken by an additional -1 (for both
vim mode and not).

crates/vim/src/normal/scroll.rs

@@ -0,0 +1,120 @@
+use std::cmp::Ordering;
+
+use crate::Vim;
+use editor::{display_map::ToDisplayPoint, scroll::scroll_amount::ScrollAmount, Editor};
+use gpui::{actions, AppContext, ViewContext};
+use language::Bias;
+use workspace::Workspace;
+
+actions!(
+    vim,
+    [LineUp, LineDown, ScrollUp, ScrollDown, PageUp, PageDown,]
+);
+
+pub fn init(cx: &mut AppContext) {
+    cx.add_action(|_: &mut Workspace, _: &LineDown, cx| {
+        scroll(cx, |c| ScrollAmount::Line(c.unwrap_or(1.)))
+    });
+    cx.add_action(|_: &mut Workspace, _: &LineUp, cx| {
+        scroll(cx, |c| ScrollAmount::Line(-c.unwrap_or(1.)))
+    });
+    cx.add_action(|_: &mut Workspace, _: &PageDown, cx| {
+        scroll(cx, |c| ScrollAmount::Page(c.unwrap_or(1.)))
+    });
+    cx.add_action(|_: &mut Workspace, _: &PageUp, cx| {
+        scroll(cx, |c| ScrollAmount::Page(-c.unwrap_or(1.)))
+    });
+    cx.add_action(|_: &mut Workspace, _: &ScrollDown, cx| {
+        scroll(cx, |c| {
+            if let Some(c) = c {
+                ScrollAmount::Line(c)
+            } else {
+                ScrollAmount::Page(0.5)
+            }
+        })
+    });
+    cx.add_action(|_: &mut Workspace, _: &ScrollUp, cx| {
+        scroll(cx, |c| {
+            if let Some(c) = c {
+                ScrollAmount::Line(-c)
+            } else {
+                ScrollAmount::Page(-0.5)
+            }
+        })
+    });
+}
+
+fn scroll(cx: &mut ViewContext<Workspace>, by: fn(c: Option<f32>) -> ScrollAmount) {
+    Vim::update(cx, |vim, cx| {
+        let amount = by(vim.pop_number_operator(cx).map(|c| c as f32));
+        vim.update_active_editor(cx, |editor, cx| scroll_editor(editor, &amount, cx));
+    })
+}
+
+fn scroll_editor(editor: &mut Editor, amount: &ScrollAmount, cx: &mut ViewContext<Editor>) {
+    let should_move_cursor = editor.newest_selection_on_screen(cx).is_eq();
+    editor.scroll_screen(amount, cx);
+    if should_move_cursor {
+        let selection_ordering = editor.newest_selection_on_screen(cx);
+        if selection_ordering.is_eq() {
+            return;
+        }
+
+        let visible_rows = if let Some(visible_rows) = editor.visible_line_count() {
+            visible_rows as u32
+        } else {
+            return;
+        };
+
+        let top_anchor = editor.scroll_manager.anchor().anchor;
+
+        editor.change_selections(None, cx, |s| {
+            s.replace_cursors_with(|snapshot| {
+                let mut new_point = top_anchor.to_display_point(&snapshot);
+
+                match selection_ordering {
+                    Ordering::Less => {
+                        new_point = snapshot.clip_point(new_point, Bias::Right);
+                    }
+                    Ordering::Greater => {
+                        *new_point.row_mut() += visible_rows - 1;
+                        new_point = snapshot.clip_point(new_point, Bias::Left);
+                    }
+                    Ordering::Equal => unreachable!(),
+                }
+
+                vec![new_point]
+            })
+        });
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{state::Mode, test::VimTestContext};
+    use gpui::geometry::vector::vec2f;
+    use indoc::indoc;
+
+    #[gpui::test]
+    async fn test_scroll(cx: &mut gpui::TestAppContext) {
+        let mut cx = VimTestContext::new(cx, true).await;
+
+        cx.set_state(indoc! {"ˇa\nb\nc\nd\ne\n"}, Mode::Normal);
+
+        cx.update_editor(|editor, cx| {
+            assert_eq!(editor.snapshot(cx).scroll_position(), vec2f(0., 0.))
+        });
+        cx.simulate_keystrokes(["ctrl-e"]);
+        cx.update_editor(|editor, cx| {
+            assert_eq!(editor.snapshot(cx).scroll_position(), vec2f(0., 1.))
+        });
+        cx.simulate_keystrokes(["2", "ctrl-e"]);
+        cx.update_editor(|editor, cx| {
+            assert_eq!(editor.snapshot(cx).scroll_position(), vec2f(0., 3.))
+        });
+        cx.simulate_keystrokes(["ctrl-y"]);
+        cx.update_editor(|editor, cx| {
+            assert_eq!(editor.snapshot(cx).scroll_position(), vec2f(0., 2.))
+        });
+    }
+}