From 56939df615af8726906718e2888aea1841a51d54 Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Thu, 9 Feb 2023 09:34:53 +0000
Subject: [PATCH] Re-use render context in headless

---
 examples/headless/src/main.rs | 28 ++++++++++------------------
 examples/scenes/src/svg.rs    |  1 +
 src/util.rs                   |  2 +-
 3 files changed, 12 insertions(+), 19 deletions(-)

diff --git a/examples/headless/src/main.rs b/examples/headless/src/main.rs
index b5c258e..c82318e 100644
--- a/examples/headless/src/main.rs
+++ b/examples/headless/src/main.rs
@@ -10,11 +10,11 @@ use scenes::{SceneParams, SceneSet, SimpleText};
 use vello::{
     block_on_wgpu,
     kurbo::{Affine, Vec2},
+    util::RenderContext,
     Scene, SceneBuilder, SceneFragment,
 };
 use wgpu::{
-    util::initialize_adapter_from_env_or_default, Backends, BufferDescriptor, BufferUsages,
-    CommandEncoderDescriptor, DeviceDescriptor, Extent3d, ImageCopyBuffer, Instance, Limits,
+    BufferDescriptor, BufferUsages, CommandEncoderDescriptor, Extent3d, ImageCopyBuffer,
     TextureDescriptor, TextureFormat, TextureUsages,
 };
 
@@ -77,23 +77,15 @@ fn main() -> Result<()> {
 }
 
 async fn render(mut scenes: SceneSet, index: usize, args: &Args) -> Result<()> {
-    let instance = Instance::new(wgpu::InstanceDescriptor {
-        backends: wgpu::Backends::PRIMARY,
-        dx12_shader_compiler: wgpu::Dx12Compiler::Fxc,
-    });
-    let adapter = initialize_adapter_from_env_or_default(&instance, Backends::PRIMARY, None)
+    let mut context = RenderContext::new()
+        .or_else(|_| bail!("Got non-Send/Sync error from creating render context"))?;
+    let device_id = context
+        .device(None)
         .await
-        .ok_or_else(|| anyhow!("Failed to intiialise adapter"))?;
-    let (device, queue) = adapter
-        .request_device(
-            &DeviceDescriptor {
-                label: Some("Vello Headless"),
-                features: wgpu::Features::TIMESTAMP_QUERY | wgpu::Features::CLEAR_TEXTURE,
-                limits: Limits::default(),
-            },
-            None,
-        )
-        .await?;
+        .ok_or_else(|| anyhow!("No compatible device found"))?;
+    let device_handle = &mut context.devices[device_id];
+    let device = &device_handle.device;
+    let queue = &device_handle.queue;
     let mut renderer = vello::Renderer::new(&device)
         .or_else(|_| bail!("Got non-Send/Sync error from creating renderer"))?;
     let mut fragment = SceneFragment::new();
diff --git a/examples/scenes/src/svg.rs b/examples/scenes/src/svg.rs
index 56d7f1c..9f4f5c0 100644
--- a/examples/scenes/src/svg.rs
+++ b/examples/scenes/src/svg.rs
@@ -90,6 +90,7 @@ fn example_scene_of(file: PathBuf) -> ExampleScene {
                 let mut builder = SceneBuilder::for_fragment(&mut new_scene);
                 vello_svg::render_tree(&mut builder, &svg);
                 let resolution = Vec2::new(svg.size.width(), svg.size.height());
+                // TODO: Handle svg.view_box
                 (new_scene, resolution)
             });
             builder.append(&scene_frag, None);
diff --git a/src/util.rs b/src/util.rs
index 4d5b09c..ac1070e 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -84,7 +84,7 @@ impl RenderContext {
     }
 
     /// Finds or creates a compatible device handle id.
-    async fn device(&mut self, compatible_surface: Option<&Surface>) -> Option<usize> {
+    pub async fn device(&mut self, compatible_surface: Option<&Surface>) -> Option<usize> {
         let compatible = match compatible_surface {
             Some(s) => self
                 .devices