Add ts_tree_cursor_goto_first_child_for_point function

This function (and the similar `ts_tree_cursor_goto_first_child_for_byte`)
allows you to efficiently seek the tree cursor to a given position,
exploiting the tree's internal balancing, without having to visit
all of the preceding siblings of each node.

lib/binding_rust/bindings.rs

@@ -586,12 +586,16 @@ extern "C" {
 }
 extern "C" {
     #[doc = " Move the cursor to the first child of its current node that extends beyond"]
-    #[doc = " the given byte offset."]
+    #[doc = " the given byte offset or point."]
     #[doc = ""]
     #[doc = " This returns the index of the child node if one was found, and returns -1"]
     #[doc = " if no such child was found."]
     pub fn ts_tree_cursor_goto_first_child_for_byte(arg1: *mut TSTreeCursor, arg2: u32) -> i64;
 }
+extern "C" {
+    pub fn ts_tree_cursor_goto_first_child_for_point(arg1: *mut TSTreeCursor, arg2: TSPoint)
+        -> i64;
+}
 extern "C" {
     pub fn ts_tree_cursor_copy(arg1: *const TSTreeCursor) -> TSTreeCursor;
 }

lib/binding_rust/lib.rs

@@ -1172,6 +1172,21 @@ impl<'a> TreeCursor<'a> {
         }
     }
 
+    /// Move this cursor to the first child of its current node that extends beyond
+    /// the given byte offset.
+    ///
+    /// This returns the index of the child node if one was found, and returns `None`
+    /// if no such child was found.
+    pub fn goto_first_child_for_point(&mut self, point: Point) -> Option<usize> {
+        let result =
+            unsafe { ffi::ts_tree_cursor_goto_first_child_for_point(&mut self.0, point.into()) };
+        if result < 0 {
+            None
+        } else {
+            Some(result as usize)
+        }
+    }
+
     /// Re-initialize this tree cursor to start at a different node.
     pub fn reset(&mut self, node: Node<'a>) {
         unsafe { ffi::ts_tree_cursor_reset(&mut self.0, node.0) };