Add a ToPointUtf16 trait in text and multibuffer

Co-Authored-By: Nathan Sobo <nathan@zed.dev>

crates/text/src/rope.rs

@@ -179,6 +179,19 @@ impl Rope {
             })
     }
 
+    pub fn point_to_point_utf16(&self, point: Point) -> PointUtf16 {
+        if point >= self.summary().lines {
+            return self.summary().lines_utf16;
+        }
+        let mut cursor = self.chunks.cursor::<(Point, PointUtf16)>();
+        cursor.seek(&point, Bias::Left, &());
+        let overshoot = point - cursor.start().0;
+        cursor.start().1
+            + cursor.item().map_or(PointUtf16::zero(), |chunk| {
+                chunk.point_to_point_utf16(overshoot)
+            })
+    }
+
     pub fn point_to_offset(&self, point: Point) -> usize {
         if point >= self.summary().lines {
             return self.summary().bytes;
@@ -580,6 +593,27 @@ impl Chunk {
         offset
     }
 
+    fn point_to_point_utf16(&self, target: Point) -> PointUtf16 {
+        let mut point = Point::zero();
+        let mut point_utf16 = PointUtf16::new(0, 0);
+        for ch in self.0.chars() {
+            if point >= target {
+                break;
+            }
+
+            if ch == '\n' {
+                point_utf16.row += 1;
+                point_utf16.column = 0;
+                point.row += 1;
+                point.column = 0;
+            } else {
+                point_utf16.column += ch.len_utf16() as u32;
+                point.column += ch.len_utf8() as u32;
+            }
+        }
+        point_utf16
+    }
+
     fn point_utf16_to_offset(&self, target: PointUtf16) -> usize {
         let mut offset = 0;
         let mut point = PointUtf16::new(0, 0);

crates/text/src/text.rs

@@ -1512,6 +1512,10 @@ impl BufferSnapshot {
         self.visible_text.offset_to_point_utf16(offset)
     }
 
+    pub fn point_to_point_utf16(&self, point: Point) -> PointUtf16 {
+        self.visible_text.point_to_point_utf16(point)
+    }
+
     pub fn version(&self) -> &clock::Global {
         &self.version
     }
@@ -2260,6 +2264,34 @@ impl ToPoint for Point {
     }
 }
 
+pub trait ToPointUtf16 {
+    fn to_point_utf16<'a>(&self, snapshot: &BufferSnapshot) -> PointUtf16;
+}
+
+impl ToPointUtf16 for Anchor {
+    fn to_point_utf16<'a>(&self, snapshot: &BufferSnapshot) -> PointUtf16 {
+        snapshot.summary_for_anchor(self)
+    }
+}
+
+impl ToPointUtf16 for usize {
+    fn to_point_utf16<'a>(&self, snapshot: &BufferSnapshot) -> PointUtf16 {
+        snapshot.offset_to_point_utf16(*self)
+    }
+}
+
+impl ToPointUtf16 for PointUtf16 {
+    fn to_point_utf16<'a>(&self, _: &BufferSnapshot) -> PointUtf16 {
+        *self
+    }
+}
+
+impl ToPointUtf16 for Point {
+    fn to_point_utf16<'a>(&self, snapshot: &BufferSnapshot) -> PointUtf16 {
+        snapshot.point_to_point_utf16(*self)
+    }
+}
+
 pub trait Clip {
     fn clip(&self, bias: Bias, snapshot: &BufferSnapshot) -> Self;
 }