Updates to scene/fragment builder

* Add impl Into<Affine> for pushing transforms.
* Small QOL API changes to Scene and Fragment.
* Add some missing docs.

piet-scene/src/scene/builder.rs

@@ -24,8 +24,8 @@ use core::borrow::Borrow;
 const MAX_BLEND_STACK: usize = 256;
 
 /// Creates a new builder for constructing a scene.
-pub fn build_scene<'a>(scene: &'a mut Scene, resources: &'a mut ResourceContext) -> Builder<'a> {
-    Builder::new(&mut scene.data, ResourceData::Scene(resources))
+pub fn build_scene<'a>(scene: &'a mut Scene, rcx: &'a mut ResourceContext) -> Builder<'a> {
+    Builder::new(&mut scene.data, ResourceData::Scene(rcx))
 }
 
 /// Creates a new builder for construction a scene fragment.
@@ -62,7 +62,8 @@ impl<'a> Builder<'a> {
     }
 
     /// Pushes a transform matrix onto the stack.
-    pub fn push_transform(&mut self, transform: Affine) {
+    pub fn push_transform(&mut self, transform: impl Into<Affine>) {
+        let transform = transform.into();
         self.transform(transform);
         self.transforms.push(transform);
     }

piet-scene/src/scene/mod.rs

@@ -23,11 +23,13 @@ pub use builder::{build_fragment, build_scene, Builder};
 pub use style::*;
 
 use super::brush::*;
-use super::geometry::{Affine, Point, Rect};
+use super::geometry::{Affine, Point};
 use super::path::Element;
+use super::resource::ResourceContext;
 
 use core::ops::Range;
 
+/// Raw data streams describing an encoded scene.
 #[derive(Default)]
 pub struct SceneData {
     pub transform_stream: Vec<Affine>,
@@ -83,6 +85,13 @@ pub struct Scene {
 }
 
 impl Scene {
+    /// Creates a new builder for filling the scene. Any current content in
+    /// the scene is cleared.
+    pub fn build<'a>(&'a mut self, rcx: &'a mut ResourceContext) -> Builder<'a> {
+        build_scene(self, rcx)
+    }
+
+    /// Returns the raw encoded scene data streams.
     pub fn data(&self) -> &SceneData {
         &self.data
     }
@@ -96,9 +105,17 @@ pub struct Fragment {
 }
 
 impl Fragment {
+    /// Returns the underlying stream of points that defined all encoded path
+    /// segments.
     pub fn points(&self) -> &[Point] {
         bytemuck::cast_slice(&self.data.pathseg_stream)
     }
+
+    /// Creates a new builder for filling the fragment. Any current content in
+    /// the fragment is cleared.
+    pub fn build<'a>(&'a mut self) -> Builder<'a> {
+        build_fragment(self)
+    }
 }
 
 #[derive(Default)]