render: effectively rename Display to Output, push remaining common code into Renderer task

src/buffers.rs

@@ -1,5 +1,6 @@
 use crate::geometry::*;
-use crate::render::{Surface, Shader, Surfaces};
+use crate::lib8::interpolate::Fract8Ops;
+use crate::render::{PixelView, Sample, Shader, Surface, Surfaces};
 
 use std::fmt::Debug;
 use std::rc::Rc;
@@ -158,11 +159,27 @@ impl<S: Surface + Default> SurfacePool<S> {
     }
 }
 
-impl<S: Surface + Default> Surfaces<S> for SurfacePool<S> {
+impl<S: Surface + Default> Surfaces for SurfacePool<S> {
+    type Surface = S;
     fn new_surface(&mut self, area: &Rectangle<Virtual>) -> Result<S, io::Error> {
         let mut surface = S::default();
         surface.set_rect(area);
         self.surfaces.push(surface.clone());
         return Ok(surface);
     }
+
+    fn render_to<Sampler: Sample>(&self, output: &mut Sampler, frame: usize) {
+        for surface in self.iter() {
+            let opacity = surface.opacity();
+            if opacity > 0 {
+                let rect = surface.rect();
+                let mut sample = output.sample(&rect);
+                surface.with_shader(|shader| {
+                    while let Some((virt_coords, pixel)) = sample.next() {
+                        *pixel = pixel.blend8(shader.draw(&virt_coords, frame).into(), opacity);
+                    }
+                })
+            }
+        }
+    }
 }