(Updated) Apply motion API refinements (#6078)

* _apply_motion generalization where possible

API encourages users to not forget setting `editor.last_motion` when
applying a motion. But also not setting `last_motion` without applying a
motion first.

* (rename) will_find_char -> find_char

method name makes it sound like it would be returning a boolean.

* use _apply_motion in find_char

Feature that falls out from this is that repetitions of t,T,f,F are
saved with the context extention/move and count. (Not defaulting to extend
by 1 count).

* Finalize apply_motion API

last_motion is now a private field and can only be set by calling
Editor.apply_motion(). Removing need (and possibility) of writing:

`motion(editor); editor.last_motion = motion`

Now it's just: `editor.apply_motion(motion)`

* editor.last_message: rm Box wrap around Arc

* Use pre-existing `Direction` rather than custom `SearchDirection`.

* `LastMotion` type alias for `Option<Arc<dyn Fn(&mut Editor)>>`

* Take motion rather than cloning it.

Co-authored-by: Michael Davis <mcarsondavis@gmail.com>

* last_motion as Option<Motion>.

* Use `Box` over `Arc` for `last_motion`.

---------

Co-authored-by: Michael Davis <mcarsondavis@gmail.com>

2 files changed, 45 insertions, 53 deletions

diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index 10b336ce..b90f418a 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -34,7 +34,7 @@ use helix_core::{
 use helix_view::{
     clipboard::ClipboardType,
     document::{FormatterError, Mode, SCRATCH_BUFFER_NAME},
-    editor::{Action, CompleteAction, Motion},
+    editor::{Action, CompleteAction},
     info::Info,
     input::KeyEvent,
     keyboard::KeyCode,
@@ -1099,8 +1099,7 @@ where
             .transform(|range| move_fn(text, range, count, behavior));
         doc.set_selection(view.id, selection);
     };
-    motion(cx.editor);
-    cx.editor.last_motion = Some(Motion(Box::new(motion)));
+    cx.editor.apply_motion(motion)
 }
 
 fn goto_prev_paragraph(cx: &mut Context) {
@@ -1240,10 +1239,7 @@ fn extend_next_long_word_end(cx: &mut Context) {
     extend_word_impl(cx, movement::move_next_long_word_end)
 }
 
-fn will_find_char<F>(cx: &mut Context, search_fn: F, inclusive: bool, extend: bool)
-where
-    F: Fn(RopeSlice, char, usize, usize, bool) -> Option<usize> + 'static,
-{
+fn find_char(cx: &mut Context, direction: Direction, inclusive: bool, extend: bool) {
     // TODO: count is reset to 1 before next key so we move it into the closure here.
     // Would be nice to carry over.
     let count = cx.count();
@@ -1275,11 +1271,18 @@ where
             } => ch,
             _ => return,
         };
+        let motion = move |editor: &mut Editor| {
+            match direction {
+                Direction::Forward => {
+                    find_char_impl(editor, &find_next_char_impl, inclusive, extend, ch, count)
+                }
+                Direction::Backward => {
+                    find_char_impl(editor, &find_prev_char_impl, inclusive, extend, ch, count)
+                }
+            };
+        };
 
-        find_char_impl(cx.editor, &search_fn, inclusive, extend, ch, count);
-        cx.editor.last_motion = Some(Motion(Box::new(move |editor: &mut Editor| {
-            find_char_impl(editor, &search_fn, inclusive, extend, ch, 1);
-        })));
+        cx.editor.apply_motion(motion);
     })
 }
 
@@ -1358,46 +1361,39 @@ fn find_prev_char_impl(
 }
 
 fn find_till_char(cx: &mut Context) {
-    will_find_char(cx, find_next_char_impl, false, false)
+    find_char(cx, Direction::Forward, false, false);
 }
 
 fn find_next_char(cx: &mut Context) {
-    will_find_char(cx, find_next_char_impl, true, false)
+    find_char(cx, Direction::Forward, true, false)
 }
 
 fn extend_till_char(cx: &mut Context) {
-    will_find_char(cx, find_next_char_impl, false, true)
+    find_char(cx, Direction::Forward, false, true)
 }
 
 fn extend_next_char(cx: &mut Context) {
-    will_find_char(cx, find_next_char_impl, true, true)
+    find_char(cx, Direction::Forward, true, true)
 }
 
 fn till_prev_char(cx: &mut Context) {
-    will_find_char(cx, find_prev_char_impl, false, false)
+    find_char(cx, Direction::Backward, false, false)
 }
 
 fn find_prev_char(cx: &mut Context) {
-    will_find_char(cx, find_prev_char_impl, true, false)
+    find_char(cx, Direction::Backward, true, false)
 }
 
 fn extend_till_prev_char(cx: &mut Context) {
-    will_find_char(cx, find_prev_char_impl, false, true)
+    find_char(cx, Direction::Backward, false, true)
 }
 
 fn extend_prev_char(cx: &mut Context) {
-    will_find_char(cx, find_prev_char_impl, true, true)
+    find_char(cx, Direction::Backward, true, true)
 }
 
 fn repeat_last_motion(cx: &mut Context) {
-    let count = cx.count();
-    let last_motion = cx.editor.last_motion.take();
-    if let Some(m) = &last_motion {
-        for _ in 0..count {
-            m.run(cx.editor);
-        }
-        cx.editor.last_motion = last_motion;
-    }
+    cx.editor.repeat_last_motion(cx.count())
 }
 
 fn replace(cx: &mut Context) {
@@ -3248,8 +3244,7 @@ fn goto_next_change_impl(cx: &mut Context, direction: Direction) {
 
         doc.set_selection(view.id, selection)
     };
-    motion(cx.editor);
-    cx.editor.last_motion = Some(Motion(Box::new(motion)));
+    cx.editor.apply_motion(motion);
 }
 
 /// Returns the [Range] for a [Hunk] in the given text.
@@ -4584,8 +4579,7 @@ fn expand_selection(cx: &mut Context) {
             }
         }
     };
-    motion(cx.editor);
-    cx.editor.last_motion = Some(Motion(Box::new(motion)));
+    cx.editor.apply_motion(motion);
 }
 
 fn shrink_selection(cx: &mut Context) {
@@ -4609,8 +4603,7 @@ fn shrink_selection(cx: &mut Context) {
             doc.set_selection(view.id, selection);
         }
     };
-    motion(cx.editor);
-    cx.editor.last_motion = Some(Motion(Box::new(motion)));
+    cx.editor.apply_motion(motion);
 }
 
 fn select_sibling_impl<F>(cx: &mut Context, sibling_fn: &'static F)
@@ -4628,8 +4621,7 @@ where
             doc.set_selection(view.id, selection);
         }
     };
-    motion(cx.editor);
-    cx.editor.last_motion = Some(Motion(Box::new(motion)));
+    cx.editor.apply_motion(motion);
 }
 
 fn select_next_sibling(cx: &mut Context) {
@@ -4912,8 +4904,7 @@ fn goto_ts_object_impl(cx: &mut Context, object: &'static str, direction: Direct
             editor.set_status("Syntax-tree is not available in current buffer");
         }
     };
-    motion(cx.editor);
-    cx.editor.last_motion = Some(Motion(Box::new(motion)));
+    cx.editor.apply_motion(motion);
 }
 
 fn goto_next_function(cx: &mut Context) {
@@ -5034,8 +5025,7 @@ fn select_textobject(cx: &mut Context, objtype: textobject::TextObject) {
                 });
                 doc.set_selection(view.id, selection);
             };
-            textobject(cx.editor);
-            cx.editor.last_motion = Some(Motion(Box::new(textobject)));
+            cx.editor.apply_motion(textobject);
         }
     });
 
diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
index 630ea5cf..affe87dd 100644
--- a/helix-view/src/editor.rs
+++ b/helix-view/src/editor.rs
@@ -834,18 +834,6 @@ impl Default for SearchConfig {
     }
 }
 
-pub struct Motion(pub Box<dyn Fn(&mut Editor)>);
-impl Motion {
-    pub fn run(&self, e: &mut Editor) {
-        (self.0)(e)
-    }
-}
-impl std::fmt::Debug for Motion {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        f.write_str("motion")
-    }
-}
-
 #[derive(Debug, Clone, Default)]
 pub struct Breakpoint {
     pub id: Option<usize>,
@@ -910,8 +898,7 @@ pub struct Editor {
     pub auto_pairs: Option<AutoPairs>,
 
     pub idle_timer: Pin<Box<Sleep>>,
-    pub last_motion: Option<Motion>,
-
+    last_motion: Option<Motion>,
     pub last_completion: Option<CompleteAction>,
 
     pub exit_code: i32,
@@ -945,6 +932,8 @@ pub struct Editor {
     pub completion_request_handle: Option<oneshot::Sender<()>>,
 }
 
+pub type Motion = Box<dyn Fn(&mut Editor)>;
+
 pub type RedrawHandle = (Arc<Notify>, Arc<RwLock<()>>);
 
 #[derive(Debug)]
@@ -1051,6 +1040,19 @@ impl Editor {
         }
     }
 
+    pub fn apply_motion<F: Fn(&mut Self) + 'static>(&mut self, motion: F) {
+        motion(self);
+        self.last_motion = Some(Box::new(motion));
+    }
+
+    pub fn repeat_last_motion(&mut self, count: usize) {
+        if let Some(motion) = self.last_motion.take() {
+            for _ in 0..count {
+                motion(self);
+            }
+            self.last_motion = Some(motion);
+        }
+    }
     /// Current editing mode for the [`Editor`].
     pub fn mode(&self) -> Mode {
         self.mode