Scroll cursor and page together (neovim-like scrolling)

helix-term/src/commands.rs

@@ -276,6 +276,10 @@ impl MappableCommand {
         page_down, "Move page down",
         half_page_up, "Move half page up",
         half_page_down, "Move half page down",
+        page_cursor_up, "Move page and cursor up",
+        page_cursor_down, "Move page and cursor down",
+        page_cursor_half_up, "Move page and cursor half up",
+        page_cursor_half_down, "Move page and cursor half down",
         select_all, "Select whole document",
         select_regex, "Select all regex matches inside selections",
         split_selection, "Split selections on regex matches",
@@ -1501,6 +1505,57 @@ fn switch_to_lowercase(cx: &mut Context) {
     });
 }
 
+pub fn scroll_page_and_cursor(cx: &mut Context, offset: usize, direction: Direction) {
+    let config = cx.editor.config();
+    let cursor_pos = cx.editor.cursor().0.unwrap();
+    let (view, doc) = current!(cx.editor);
+
+    let height = view.inner_height();
+    let scrolloff = config.scrolloff.min(height.saturating_sub(1) / 2);
+
+    let offset = match direction {
+        Direction::Forward => offset as isize,
+        Direction::Backward => -(offset as isize),
+    };
+
+    let doc_text = doc.text().slice(..);
+    let viewport = view.inner_area(doc);
+    let text_fmt = doc.text_format(viewport.width, None);
+    let mut annotations = view.text_annotations(doc, None);
+
+    (view.offset.anchor, view.offset.vertical_offset) = char_idx_at_visual_offset(
+        doc_text,
+        view.offset.anchor,
+        view.offset.vertical_offset as isize + offset,
+        0,
+        &text_fmt,
+        &annotations,
+    );
+
+    let movement = match cx.editor.mode {
+        Mode::Select => Movement::Extend,
+        _ => Movement::Move,
+    };
+
+    let mut offset = offset.abs() as usize;
+    if cursor_pos.row <= scrolloff {
+        offset += scrolloff - cursor_pos.row + 1;
+    }
+
+    let selection = doc.selection(view.id).clone().transform(|range| {
+            move_vertically_visual(
+                doc_text,
+                range,
+                direction,
+                offset,
+                movement,
+                &text_fmt,
+                &mut annotations,
+            )
+        });
+    doc.set_selection(view.id, selection);
+}
+
 pub fn scroll(cx: &mut Context, offset: usize, direction: Direction) {
     use Direction::*;
     let config = cx.editor.config();
@@ -1602,6 +1657,30 @@ fn half_page_down(cx: &mut Context) {
     scroll(cx, offset, Direction::Forward);
 }
 
+fn page_cursor_up(cx: &mut Context) {
+    let view = view!(cx.editor);
+    let offset = view.inner_height();
+    scroll_page_and_cursor(cx, offset, Direction::Backward);
+}
+
+fn page_cursor_down(cx: &mut Context) {
+    let view = view!(cx.editor);
+    let offset = view.inner_height();
+    scroll_page_and_cursor(cx, offset, Direction::Forward);
+}
+
+fn page_cursor_half_up(cx: &mut Context) {
+    let view = view!(cx.editor);
+    let offset = view.inner_height() / 2;
+    scroll_page_and_cursor(cx, offset, Direction::Backward);
+}
+
+fn page_cursor_half_down(cx: &mut Context) {
+    let view = view!(cx.editor);
+    let offset = view.inner_height() / 2;
+    scroll_page_and_cursor(cx, offset, Direction::Forward);
+}
+
 #[allow(deprecated)]
 // currently uses the deprecated `visual_coords_at_pos`/`pos_at_visual_coords` functions
 // as this function ignores softwrapping (and virtual text) and instead only cares

helix-term/src/keymap/default.rs

@@ -178,8 +178,8 @@ pub fn default() -> HashMap<Mode, KeyTrie> {
         "esc" => normal_mode,
         "C-b" | "pageup" => page_up,
         "C-f" | "pagedown" => page_down,
-        "C-u" => half_page_up,
-        "C-d" => half_page_down,
+        "C-u" => page_cursor_half_up,
+        "C-d" => page_cursor_half_down,
 
         "C-w" => { "Window"
             "C-w" | "w" => rotate_view,
@@ -287,8 +287,8 @@ pub fn default() -> HashMap<Mode, KeyTrie> {
             "j" | "down" => scroll_down,
             "C-b" | "pageup" => page_up,
             "C-f" | "pagedown" => page_down,
-            "C-u" | "backspace" => half_page_up,
-            "C-d" | "space" => half_page_down,
+            "C-u" | "backspace" => page_cursor_half_up,
+            "C-d" | "space" => page_cursor_half_down,
 
             "/" => search,
             "?" => rsearch,
@@ -304,8 +304,8 @@ pub fn default() -> HashMap<Mode, KeyTrie> {
             "j" | "down" => scroll_down,
             "C-b" | "pageup" => page_up,
             "C-f" | "pagedown" => page_down,
-            "C-u" | "backspace" => half_page_up,
-            "C-d" | "space" => half_page_down,
+            "C-u" | "backspace" => page_cursor_half_up,
+            "C-d" | "space" => page_cursor_half_down,
 
             "/" => search,
             "?" => rsearch,