Implement textual hit testing

core/src/hit_test.rs

@@ -0,0 +1,28 @@
+use crate::Vector;
+
+/// The result of hit testing on text.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum HitTestResult {
+    /// The point was within the bounds of the returned character index.
+    CharOffset(usize),
+    /// The provided point was not within the bounds of a glyph. The index
+    /// of the character with the closest centeroid position is returned,
+    /// as well as its delta.
+    NearestCharOffset(usize, Vector),
+}
+
+impl HitTestResult {
+    /// Computes the cursor position corresponding to this [`HitTestResult`] .
+    pub fn cursor(&self) -> usize {
+        match self {
+            HitTestResult::CharOffset(i) => *i,
+            HitTestResult::NearestCharOffset(i, delta) => {
+                if delta.x > f32::EPSILON {
+                    i + 1
+                } else {
+                    *i
+                }
+            }
+        }
+    }
+}

core/src/lib.rs

@@ -22,6 +22,7 @@ mod align;
 mod background;
 mod color;
 mod font;
+mod hit_test;
 mod length;
 mod padding;
 mod point;
@@ -33,6 +34,7 @@ pub use align::{Align, HorizontalAlignment, VerticalAlignment};
 pub use background::Background;
 pub use color::Color;
 pub use font::Font;
+pub use hit_test::HitTestResult;
 pub use length::Length;
 pub use menu::Menu;
 pub use padding::Padding;