1 files changed, 159 insertions, 0 deletions
diff --git a/third_party/rust/metal/examples/headless-render/main.rs b/third_party/rust/metal/examples/headless-render/main.rs
new file mode 100644
index 0000000000..ed68da1a53
--- /dev/null
+++ b/third_party/rust/metal/examples/headless-render/main.rs
@@ -0,0 +1,159 @@
+use std::mem;
+use std::path::PathBuf;
+
+use std::fs::File;
+use std::io::BufWriter;
+
+use metal::{
+    Buffer, Device, DeviceRef, LibraryRef, MTLClearColor, MTLLoadAction, MTLOrigin, MTLPixelFormat,
+    MTLPrimitiveType, MTLRegion, MTLResourceOptions, MTLSize, MTLStoreAction, RenderPassDescriptor,
+    RenderPassDescriptorRef, RenderPipelineDescriptor, RenderPipelineState, Texture,
+    TextureDescriptor, TextureRef,
+};
+use png::ColorType;
+
+const VIEW_WIDTH: u64 = 512;
+const VIEW_HEIGHT: u64 = 512;
+const TOTAL_BYTES: usize = (VIEW_WIDTH * VIEW_HEIGHT * 4) as usize;
+
+const VERTEX_SHADER: &'static str = "triangle_vertex";
+const FRAGMENT_SHADER: &'static str = "triangle_fragment";
+
+// [2 bytes position, 3 bytes color] * 3
+#[rustfmt::skip]
+const VERTEX_ATTRIBS: [f32; 15] = [
+    0.0, 0.5, 1.0, 0.0, 0.0,
+    -0.5, -0.5, 0.0, 1.0, 0.0,
+    0.5, -0.5, 0.0, 0.0, 1.0,
+];
+
+/// This example shows how to render headlessly by:
+///
+/// 1. Rendering a triangle to an MtlDrawable
+///
+/// 2. Waiting for the render to complete and the color texture to be synchronized with the CPU
+///    by using a blit command encoder
+///
+/// 3. Reading the texture bytes from the MtlTexture
+///
+/// 4. Saving the texture to a PNG file
+fn main() {
+    let device = Device::system_default().expect("No device found");
+
+    let texture = create_texture(&device);
+
+    let library_path = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+        .join("examples/window/shaders.metallib");
+
+    let library = device.new_library_with_file(library_path).unwrap();
+
+    let pipeline_state = prepare_pipeline_state(&device, &library);
+
+    let command_queue = device.new_command_queue();
+
+    let vertex_buffer = create_vertex_buffer(&device);
+
+    let render_pass_descriptor = RenderPassDescriptor::new();
+    initialize_color_attachment(&render_pass_descriptor, &texture);
+
+    let command_buffer = command_queue.new_command_buffer();
+    let rc_encoder = command_buffer.new_render_command_encoder(&render_pass_descriptor);
+    rc_encoder.set_render_pipeline_state(&pipeline_state);
+    rc_encoder.set_vertex_buffer(0, Some(&vertex_buffer), 0);
+    rc_encoder.draw_primitives(MTLPrimitiveType::Triangle, 0, 3);
+    rc_encoder.end_encoding();
+
+    render_pass_descriptor
+        .color_attachments()
+        .object_at(0)
+        .unwrap()
+        .set_load_action(MTLLoadAction::DontCare);
+
+    let blit_encoder = command_buffer.new_blit_command_encoder();
+    blit_encoder.synchronize_resource(&texture);
+    blit_encoder.end_encoding();
+
+    command_buffer.commit();
+
+    command_buffer.wait_until_completed();
+
+    save_image(&texture);
+}
+
+fn save_image(texture: &TextureRef) {
+    let mut image = vec![0; TOTAL_BYTES];
+
+    texture.get_bytes(
+        image.as_mut_ptr() as *mut std::ffi::c_void,
+        VIEW_WIDTH * 4,
+        MTLRegion {
+            origin: MTLOrigin { x: 0, y: 0, z: 0 },
+            size: MTLSize {
+                width: VIEW_WIDTH,
+                height: VIEW_HEIGHT,
+                depth: 1,
+            },
+        },
+        0,
+    );
+
+    let out_file =
+        PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("examples/headless-render/out.png");
+    let file = File::create(&out_file).unwrap();
+    let ref mut w = BufWriter::new(file);
+
+    let mut encoder = png::Encoder::new(w, VIEW_WIDTH as u32, VIEW_HEIGHT as u32);
+    encoder.set_color(ColorType::RGBA);
+    encoder.set_depth(png::BitDepth::Eight);
+    let mut writer = encoder.write_header().unwrap();
+
+    writer.write_image_data(&image).unwrap();
+
+    println!("Image saved to {:?}", out_file);
+}
+
+fn create_texture(device: &Device) -> Texture {
+    let texture = TextureDescriptor::new();
+    texture.set_width(VIEW_WIDTH);
+    texture.set_height(VIEW_HEIGHT);
+    texture.set_pixel_format(MTLPixelFormat::RGBA8Unorm);
+
+    device.new_texture(&texture)
+}
+
+fn prepare_pipeline_state(device: &DeviceRef, library: &LibraryRef) -> RenderPipelineState {
+    let vert = library.get_function(VERTEX_SHADER, None).unwrap();
+    let frag = library.get_function(FRAGMENT_SHADER, None).unwrap();
+
+    let pipeline_state_descriptor = RenderPipelineDescriptor::new();
+
+    pipeline_state_descriptor.set_vertex_function(Some(&vert));
+    pipeline_state_descriptor.set_fragment_function(Some(&frag));
+
+    pipeline_state_descriptor
+        .color_attachments()
+        .object_at(0)
+        .unwrap()
+        .set_pixel_format(MTLPixelFormat::RGBA8Unorm);
+
+    device
+        .new_render_pipeline_state(&pipeline_state_descriptor)
+        .unwrap()
+}
+
+fn create_vertex_buffer(device: &DeviceRef) -> Buffer {
+    device.new_buffer_with_data(
+        VERTEX_ATTRIBS.as_ptr() as *const _,
+        (VERTEX_ATTRIBS.len() * mem::size_of::<f32>()) as u64,
+        MTLResourceOptions::CPUCacheModeDefaultCache | MTLResourceOptions::StorageModeManaged,
+    )
+}
+
+fn initialize_color_attachment(descriptor: &RenderPassDescriptorRef, texture: &TextureRef) {
+    let color_attachment = descriptor.color_attachments().object_at(0).unwrap();
+
+    color_attachment.set_texture(Some(texture));
+    color_attachment.set_load_action(MTLLoadAction::Clear);
+    color_attachment.set_clear_color(MTLClearColor::new(0.5, 0.2, 0.2, 1.0));
+    color_attachment.set_store_action(MTLStoreAction::Store);
+}