Collect some common patterns into methods on `Range`.

3 files changed, 51 insertions, 94 deletions

diff --git a/helix-core/src/movement.rs b/helix-core/src/movement.rs
index 80d19501..4af82a1d 100644
--- a/helix-core/src/movement.rs
+++ b/helix-core/src/movement.rs
@@ -31,15 +31,7 @@ pub fn move_horizontally(
     count: usize,
     behaviour: Movement,
 ) -> Range {
-    use Movement::Extend;
-
-    // Shift back one grapheme if needed, to account for
-    // the cursor being visually 1-width.
-    let pos = if range.head > range.anchor {
-        prev_grapheme_boundary(slice, range.head)
-    } else {
-        range.head
-    };
+    let pos = range.cursor(slice);
 
     // Compute the new position.
     let new_pos = if dir == Direction::Backward {
@@ -49,11 +41,7 @@ pub fn move_horizontally(
     };
 
     // Compute the final new range.
-    if behaviour == Extend {
-        range.move_head(slice, new_pos, true)
-    } else {
-        Range::point(new_pos)
-    }
+    range.put_cursor(slice, new_pos, behaviour == Movement::Extend)
 }
 
 pub fn move_vertically(
@@ -63,13 +51,7 @@ pub fn move_vertically(
     count: usize,
     behaviour: Movement,
 ) -> Range {
-    // Shift back one grapheme if needed, to account for
-    // the cursor being visually 1-width.
-    let pos = if range.head > range.anchor {
-        prev_grapheme_boundary(slice, range.head)
-    } else {
-        range.head
-    };
+    let pos = range.cursor(slice);
 
     // Compute the current position's 2d coordinates.
     let Position { row, col } = coords_at_pos(slice, pos);
@@ -89,24 +71,14 @@ pub fn move_vertically(
         )
     };
 
-    // Compute the new range according to the type of movement.
-    match behaviour {
-        Movement::Move => Range {
-            anchor: new_pos,
-            head: new_pos,
-            horiz: Some(horiz),
-        },
-
-        Movement::Extend => {
-            if slice.line(new_row).len_chars() > 0 {
-                let mut new_range = range.move_head(slice, new_pos, true);
-                new_range.horiz = Some(horiz);
-                new_range
-            } else {
-                range
-            }
-        }
+    // Special-case to avoid moving to the end of the last non-empty line.
+    if behaviour == Movement::Extend && slice.line(new_row).len_chars() == 0 {
+        return range;
     }
+
+    let mut new_range = range.put_cursor(slice, new_pos, behaviour == Movement::Extend);
+    new_range.horiz = Some(horiz);
+    new_range
 }
 
 pub fn move_next_word_start(slice: RopeSlice, range: Range, count: usize) -> Range {
@@ -153,7 +125,7 @@ fn word_move(slice: RopeSlice, range: Range, count: usize, target: WordMotionTar
     // Prepare the range appropriately based on the target movement
     // direction.  This is addressing two things at once:
     //
-    //   1. 1-width range sementics.
+    //   1. Block-cursor semantics.
     //   2. The anchor position being irrelevant to the output result.
     #[allow(clippy::collapsible_else_if)] // Makes the structure clearer in this case.
     let start_range = if is_prev {
diff --git a/helix-core/src/selection.rs b/helix-core/src/selection.rs
index cef68212..247a69fe 100644
--- a/helix-core/src/selection.rs
+++ b/helix-core/src/selection.rs
@@ -73,16 +73,11 @@ impl Range {
         std::cmp::max(self.anchor, self.head)
     }
 
-    /// The line number that the head is on (using 1-width semantics).
+    /// The line number that the block-cursor is on.
     #[inline]
     #[must_use]
-    pub fn head_line(&self, text: RopeSlice) -> usize {
-        let head = if self.anchor < self.head {
-            prev_grapheme_boundary(text, self.head)
-        } else {
-            self.head
-        };
-        text.char_to_line(head)
+    pub fn cursor_line(&self, text: RopeSlice) -> usize {
+        text.char_to_line(self.cursor(text))
     }
 
     /// The (inclusive) range of lines that the range overlaps.
@@ -248,29 +243,44 @@ impl Range {
         }
     }
 
-    /// Moves the head of the `Range` to `char_idx`, adjusting the anchor
-    /// as needed to preserve 1-width range semantics.
+    /// Gets the left-side position of the block cursor.
+    #[must_use]
+    #[inline]
+    pub fn cursor(self, text: RopeSlice) -> usize {
+        if self.head > self.anchor {
+            prev_grapheme_boundary(text, self.head)
+        } else {
+            self.head
+        }
+    }
+
+    /// Puts the left side of the block cursor at `char_idx`, optionally extending.
     ///
-    /// `block_cursor` specifies whether it should treat `char_idx` as a block
-    /// cursor position or as a range-end position.
+    /// This follows "1-width" semantics, and therefore does a combination of anchor
+    /// and head moves to behave as if both the front and back of the range are 1-width
+    /// blocks
     ///
     /// This method assumes that the range and `char_idx` are already properly
     /// grapheme-aligned.
     #[must_use]
     #[inline]
-    pub fn move_head(self, text: RopeSlice, char_idx: usize, block_cursor: bool) -> Range {
-        let anchor = if self.head >= self.anchor && char_idx < self.anchor {
-            next_grapheme_boundary(text, self.anchor)
-        } else if self.head < self.anchor && char_idx >= self.anchor {
-            prev_grapheme_boundary(text, self.anchor)
-        } else {
-            self.anchor
-        };
+    pub fn put_cursor(self, text: RopeSlice, char_idx: usize, extend: bool) -> Range {
+        if extend {
+            let anchor = if self.head >= self.anchor && char_idx < self.anchor {
+                next_grapheme_boundary(text, self.anchor)
+            } else if self.head < self.anchor && char_idx >= self.anchor {
+                prev_grapheme_boundary(text, self.anchor)
+            } else {
+                self.anchor
+            };
 
-        if block_cursor && anchor <= char_idx {
-            Range::new(anchor, next_grapheme_boundary(text, char_idx))
+            if anchor <= char_idx {
+                Range::new(anchor, next_grapheme_boundary(text, char_idx))
+            } else {
+                Range::new(anchor, char_idx)
+            }
         } else {
-            Range::new(anchor, char_idx)
+            Range::point(char_idx)
         }
     }
 
@@ -309,18 +319,6 @@ impl Selection {
         self.ranges[self.primary_index]
     }
 
-    #[must_use]
-    pub fn cursor(&self, text: RopeSlice) -> usize {
-        let range = self.primary();
-
-        // For 1-width cursor semantics.
-        if range.anchor < range.head {
-            prev_grapheme_boundary(text, range.head).max(range.anchor)
-        } else {
-            range.head
-        }
-    }
-
     /// Ensure selection containing only the primary selection.
     pub fn into_single(self) -> Self {
         if self.ranges.len() == 1 {
@@ -452,17 +450,9 @@ impl Selection {
     }
 
     /// Transforms the selection into all of the left-side head positions,
-    /// using 1-width semantics.
+    /// using block-cursor semantics.
     pub fn cursors(self, text: RopeSlice) -> Self {
-        self.transform(|range| {
-            // For 1-width cursor semantics.
-            let pos = if range.anchor < range.head {
-                prev_grapheme_boundary(text, range.head).max(range.anchor)
-            } else {
-                range.head
-            };
-            Range::new(pos, pos)
-        })
+        self.transform(|range| Range::point(range.cursor(text)))
     }
 
     pub fn fragments<'a>(&'a self, text: RopeSlice<'a>) -> impl Iterator<Item = Cow<str>> + 'a {
diff --git a/helix-core/src/textobject.rs b/helix-core/src/textobject.rs
index ae18d7cf..e011c912 100644
--- a/helix-core/src/textobject.rs
+++ b/helix-core/src/textobject.rs
@@ -59,17 +59,12 @@ pub fn textobject_word(
     textobject: TextObject,
     _count: usize,
 ) -> Range {
-    // For 1-width cursor semantics.
-    let head = if range.head > range.anchor {
-        prev_grapheme_boundary(slice, range.head)
-    } else {
-        range.head
-    };
+    let pos = range.cursor(slice);
 
-    let word_start = find_word_boundary(slice, head, Direction::Backward);
-    let word_end = match slice.get_char(head).map(categorize_char) {
-        None | Some(CharCategory::Whitespace | CharCategory::Eol) => head,
-        _ => find_word_boundary(slice, head + 1, Direction::Forward),
+    let word_start = find_word_boundary(slice, pos, Direction::Backward);
+    let word_end = match slice.get_char(pos).map(categorize_char) {
+        None | Some(CharCategory::Whitespace | CharCategory::Eol) => pos,
+        _ => find_word_boundary(slice, pos + 1, Direction::Forward),
     };
 
     // Special case.