Make anchoring explicit and improve reusability of text pipelines

core/src/rectangle.rs

@@ -1,3 +1,4 @@
+use crate::alignment;
 use crate::{Padding, Point, Radians, Size, Vector};
 
 /// An axis-aligned rectangle.
@@ -303,6 +304,34 @@ impl Rectangle<f32> {
             height: self.height * zoom,
         }
     }
+
+    /// Returns the top-left position to render an object of the given [`Size`].
+    /// inside the [`Rectangle`] that is anchored to the edge or corner
+    /// defined by the alignment arguments.
+    pub fn anchor(
+        &self,
+        size: Size,
+        align_x: impl Into<alignment::Horizontal>,
+        align_y: impl Into<alignment::Vertical>,
+    ) -> Point {
+        let x = match align_x.into() {
+            alignment::Horizontal::Left => self.x,
+            alignment::Horizontal::Center => {
+                self.x + (self.width - size.width) / 2.0
+            }
+            alignment::Horizontal::Right => self.x + self.width - size.width,
+        };
+
+        let y = match align_y.into() {
+            alignment::Vertical::Top => self.y,
+            alignment::Vertical::Center => {
+                self.y + (self.height - size.height) / 2.0
+            }
+            alignment::Vertical::Bottom => self.y + self.height - size.height,
+        };
+
+        Point::new(x, y)
+    }
 }
 
 impl std::ops::Mul<f32> for Rectangle<f32> {