Scroll cursor and page together (neovim-like scrolling) (#8015)

* neovim like scroll function

* clear line annotations outside of move_vertically/_visual

* add nvim scroll function to commands

* assign nvim-scroll to C-d and C-u (half page scrolls)

* dont remove backspace and space mapping

* move non-softwrap logic to seperate function, call this in nvim-scroll fn

* Revert "move non-softwrap logic to seperate function, call this in nvim-scroll fn"

This reverts commit e4905729c338a2260e6981f1d8fac022897b4191.

* Revert "clear line annotations outside of move_vertically/_visual"

This reverts commit 1df3fefe55afc840d1ab5094b2116d1127fc363f.

* add TODO for when inline diagnostics gets merged

* move nvim-scroll logic into scroll(), dont respect scrolloff

* run cargo fmt

* run cargo clippy

* update documenation for Ctrl-d and Ctrl-u remap

3 files changed, 67 insertions, 15 deletions

diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index e46109c0..51a1ede9 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -277,6 +277,10 @@ 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",
@@ -1608,7 +1612,7 @@ fn switch_to_lowercase(cx: &mut Context) {
     });
 }
 
-pub fn scroll(cx: &mut Context, offset: usize, direction: Direction) {
+pub fn scroll(cx: &mut Context, offset: usize, direction: Direction, sync_cursor: bool) {
     use Direction::*;
     let config = cx.editor.config();
     let (view, doc) = current!(cx.editor);
@@ -1628,7 +1632,7 @@ pub fn scroll(cx: &mut Context, offset: usize, direction: Direction) {
     let doc_text = doc.text().slice(..);
     let viewport = view.inner_area(doc);
     let text_fmt = doc.text_format(viewport.width, None);
-    let annotations = view.text_annotations(doc, 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,
@@ -1638,6 +1642,30 @@ pub fn scroll(cx: &mut Context, offset: usize, direction: Direction) {
         &annotations,
     );
 
+    if sync_cursor {
+        let movement = match cx.editor.mode {
+            Mode::Select => Movement::Extend,
+            _ => Movement::Move,
+        };
+        // TODO: When inline diagnostics gets merged- 1. move_vertically_visual removes
+        // line annotations/diagnostics so the cursor may jump further than the view.
+        // 2. If the cursor lands on a complete line of virtual text, the cursor will
+        // jump a different distance than the view.
+        let selection = doc.selection(view.id).clone().transform(|range| {
+            move_vertically_visual(
+                doc_text,
+                range,
+                direction,
+                offset.unsigned_abs(),
+                movement,
+                &text_fmt,
+                &mut annotations,
+            )
+        });
+        doc.set_selection(view.id, selection);
+        return;
+    }
+
     let mut head;
     match direction {
         Forward => {
@@ -1688,25 +1716,49 @@ pub fn scroll(cx: &mut Context, offset: usize, direction: Direction) {
 fn page_up(cx: &mut Context) {
     let view = view!(cx.editor);
     let offset = view.inner_height();
-    scroll(cx, offset, Direction::Backward);
+    scroll(cx, offset, Direction::Backward, false);
 }
 
 fn page_down(cx: &mut Context) {
     let view = view!(cx.editor);
     let offset = view.inner_height();
-    scroll(cx, offset, Direction::Forward);
+    scroll(cx, offset, Direction::Forward, false);
 }
 
 fn half_page_up(cx: &mut Context) {
     let view = view!(cx.editor);
     let offset = view.inner_height() / 2;
-    scroll(cx, offset, Direction::Backward);
+    scroll(cx, offset, Direction::Backward, false);
 }
 
 fn half_page_down(cx: &mut Context) {
     let view = view!(cx.editor);
     let offset = view.inner_height() / 2;
-    scroll(cx, offset, Direction::Forward);
+    scroll(cx, offset, Direction::Forward, false);
+}
+
+fn page_cursor_up(cx: &mut Context) {
+    let view = view!(cx.editor);
+    let offset = view.inner_height();
+    scroll(cx, offset, Direction::Backward, true);
+}
+
+fn page_cursor_down(cx: &mut Context) {
+    let view = view!(cx.editor);
+    let offset = view.inner_height();
+    scroll(cx, offset, Direction::Forward, true);
+}
+
+fn page_cursor_half_up(cx: &mut Context) {
+    let view = view!(cx.editor);
+    let offset = view.inner_height() / 2;
+    scroll(cx, offset, Direction::Backward, true);
+}
+
+fn page_cursor_half_down(cx: &mut Context) {
+    let view = view!(cx.editor);
+    let offset = view.inner_height() / 2;
+    scroll(cx, offset, Direction::Forward, true);
 }
 
 #[allow(deprecated)]
@@ -4856,11 +4908,11 @@ fn align_view_middle(cx: &mut Context) {
 }
 
 fn scroll_up(cx: &mut Context) {
-    scroll(cx, cx.count(), Direction::Backward);
+    scroll(cx, cx.count(), Direction::Backward, false);
 }
 
 fn scroll_down(cx: &mut Context) {
-    scroll(cx, cx.count(), Direction::Forward);
+    scroll(cx, cx.count(), Direction::Forward, false);
 }
 
 fn goto_ts_object_impl(cx: &mut Context, object: &'static str, direction: Direction) {
diff --git a/helix-term/src/keymap/default.rs b/helix-term/src/keymap/default.rs
index 763ed4ae..92d6b590 100644
--- a/helix-term/src/keymap/default.rs
+++ b/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,
diff --git a/helix-term/src/ui/editor.rs b/helix-term/src/ui/editor.rs
index bb749d2e..a87e6cbc 100644
--- a/helix-term/src/ui/editor.rs
+++ b/helix-term/src/ui/editor.rs
@@ -1156,7 +1156,7 @@ impl EditorView {
                 }
 
                 let offset = config.scroll_lines.unsigned_abs();
-                commands::scroll(cxt, offset, direction);
+                commands::scroll(cxt, offset, direction, false);
 
                 cxt.editor.tree.focus = current_view;
                 cxt.editor.ensure_cursor_in_view(current_view);