feat: Add rtl support to text input

widget/src/text_input/cursor.rs

@@ -1,10 +1,12 @@
 //! Track the cursor of a text input.
+use crate::core::text::Affinity;
 use crate::text_input::Value;
 
 /// The cursor of a text input.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub struct Cursor {
     state: State,
+    affinity: Affinity,
 }
 
 /// The state of a [`Cursor`].
@@ -26,6 +28,7 @@ impl Default for Cursor {
     fn default() -> Self {
         Cursor {
             state: State::Index(0),
+            affinity: Affinity::Before,
         }
     }
 }
@@ -186,4 +189,52 @@ impl Cursor {
             State::Selection { start, end } => start.max(end),
         }
     }
+
+    /// Returns the current cursor [`Affinity`].
+    pub fn affinity(&self) -> Affinity {
+        self.affinity
+    }
+
+    /// Sets the cursor [`Affinity`].
+    pub fn set_affinity(&mut self, affinity: Affinity) {
+        self.affinity = affinity;
+    }
+
+    /// Moves the cursor in a visual direction, accounting for RTL text.
+    ///
+    /// `forward` = `true` is visually rightward
+    /// RTL text flips the logical direction so that pressing the right-arrow key
+    /// still moves the caret forward visually.
+    pub fn move_visual(
+        &mut self,
+        forward: bool,
+        by_words: bool,
+        rtl: bool,
+        value: &Value,
+    ) {
+        match (forward ^ rtl, by_words) {
+            (true, false) => self.move_right(value),
+            (true, true) => self.move_right_by_words(value),
+            (false, false) => self.move_left(value),
+            (false, true) => self.move_left_by_words(value),
+        }
+    }
+
+    /// Extends the selection in a visual direction, accounting for RTL text.
+    ///
+    /// See [`Cursor::move_visual`] for the `forward` / `rtl` semantics.
+    pub fn select_visual(
+        &mut self,
+        forward: bool,
+        by_words: bool,
+        rtl: bool,
+        value: &Value,
+    ) {
+        match (forward ^ rtl, by_words) {
+            (true, false) => self.select_right(value),
+            (true, true) => self.select_right_by_words(value),
+            (false, false) => self.select_left(value),
+            (false, true) => self.select_left_by_words(value),
+        }
+    }
 }

widget/src/text_input/value.rs

@@ -127,6 +127,26 @@ impl Value {
             .collect(),
         }
     }
+
+    /// Converts a grapheme index to a byte index in the underlying string.
+    pub fn byte_index_at_grapheme(&self, grapheme_index: usize) -> usize {
+        self.graphemes[..grapheme_index.min(self.graphemes.len())]
+            .iter()
+            .map(|g| g.len())
+            .sum()
+    }
+
+    /// Converts a byte index to a grapheme index.
+    pub fn grapheme_index_at_byte(&self, byte_index: usize) -> usize {
+        let mut bytes = 0;
+        for (i, g) in self.graphemes.iter().enumerate() {
+            if bytes >= byte_index {
+                return i;
+            }
+            bytes += g.len();
+        }
+        self.graphemes.len()
+    }
 }
 
 impl std::fmt::Display for Value {