Impl From<Encoding> for Scene.

This allows creating a `Scene` with a pre-existing `Encoding`.

Fixes #530.

src/scene.rs

@@ -14,8 +14,12 @@ use vello_encoding::{Encoding, Glyph, GlyphRun, Patch, Transform};
 
 /// The main datatype for rendering graphics.
 ///
-/// A Scene stores a sequence of drawing commands, their context, and the
+/// A `Scene` stores a sequence of drawing commands, their context, and the
 /// associated resources, which can later be rendered.
+///
+/// A `Scene` can be created in a default (empty) state via `Scene::new()`
+/// or via `Default`. It can also be created from a pre-existing [`Encoding`]
+/// using `From`.
 #[derive(Clone, Default)]
 pub struct Scene {
     encoding: Encoding,
@@ -219,6 +223,17 @@ impl Scene {
     }
 }
 
+impl From<Encoding> for Scene {
+    fn from(encoding: Encoding) -> Self {
+        // TODO: Properly update the estimator for the encoding.
+        Self {
+            encoding,
+            #[cfg(feature = "bump_estimate")]
+            estimator: vello_encoding::BumpEstimator::default(),
+        }
+    }
+}
+
 /// Builder for encoding a glyph run.
 pub struct DrawGlyphs<'a> {
     encoding: &'a mut Encoding,