feat: implement double-click + drag by-word selection

1 files changed, 73 insertions, 0 deletions

diff --git a/src/selection.rs b/src/selection.rs
index 9be01dd..375072c 100644
--- a/src/selection.rs
+++ b/src/selection.rs
@@ -213,6 +213,78 @@ impl Selection {
         self.select_range(start, end);
     }
 
+    /// Updates the current selection by setting a new end point, either to the start of the
+    /// previous word, or to the next one's end.
+    pub fn change_selection_by_word(
+        &mut self,
+        new_end: SelectionEnd,
+        paragraph: &Paragraph,
+    ) {
+        let (base_word_start, base_word_end) = {
+            if self.direction == Direction::Right {
+                let value = Value::new(
+                    paragraph.buffer().lines[self.start.line].text(),
+                );
+
+                let end = SelectionEnd::new(
+                    self.start.line,
+                    value.next_end_of_word(self.start.index),
+                );
+
+                (self.start, end)
+            } else {
+                let value =
+                    Value::new(paragraph.buffer().lines[self.end.line].text());
+
+                let start = SelectionEnd::new(
+                    self.end.line,
+                    value.previous_start_of_word(self.end.index),
+                );
+
+                (start, self.end)
+            }
+        };
+
+        let value = Value::new(paragraph.buffer().lines[new_end.line].text());
+
+        let (start, end) = if new_end < self.start {
+            self.direction = Direction::Left;
+
+            let start = SelectionEnd::new(
+                new_end.line,
+                value.previous_start_of_word(new_end.index),
+            );
+
+            (start, base_word_end)
+        } else if new_end > self.end {
+            self.direction = Direction::Right;
+
+            let end = SelectionEnd::new(
+                new_end.line,
+                value.next_end_of_word(new_end.index),
+            );
+
+            (base_word_start, end)
+        } else if self.direction == Direction::Right {
+            let end = SelectionEnd::new(
+                new_end.line,
+                value.next_end_of_word(new_end.index),
+            );
+
+            (base_word_start, end.max(base_word_end))
+        } else {
+            let start = SelectionEnd::new(
+                new_end.line,
+                value.previous_start_of_word(new_end.index),
+            );
+
+            (start.min(base_word_start), base_word_end)
+        };
+
+        self.moving_line_index = None;
+        self.select_range(start, end);
+    }
+
     /// Updates the current selection by setting a new end point, either to the end of a following
     /// line, or the beginning of a previous one.
     pub fn change_selection_by_line(
@@ -246,6 +318,7 @@ impl Selection {
             (start, end)
         } else {
             let start = SelectionEnd::new(new_line, 0);
+
             let end = if self.direction == old_direction {
                 self.end
             } else {