From afe00aa90f9ae6b8ee8acf07bf4ff0969c364108 Mon Sep 17 00:00:00 2001
From: Dzmitry Malyshau <kvarkus@gmail.com>
Date: Fri, 1 Feb 2019 09:59:51 -0500
Subject: [PATCH] Borrow temporary queus and frames on Rust side

---
 examples/hello_triangle_rust/main.rs |  9 +++---
 wgpu-native/src/swap_chain.rs        | 10 +++---
 wgpu-rs/src/lib.rs                   | 46 ++++++++++++++++------------
 3 files changed, 35 insertions(+), 30 deletions(-)

diff --git a/examples/hello_triangle_rust/main.rs b/examples/hello_triangle_rust/main.rs
index ba6ed735c2..b1c800cc4a 100644
--- a/examples/hello_triangle_rust/main.rs
+++ b/examples/hello_triangle_rust/main.rs
@@ -9,7 +9,7 @@ fn main() {
     let adapter = instance.get_adapter(&wgpu::AdapterDescriptor {
         power_preference: wgpu::PowerPreference::LowPower,
     });
-    let device = adapter.create_device(&wgpu::DeviceDescriptor {
+    let mut device = adapter.create_device(&wgpu::DeviceDescriptor {
         extensions: wgpu::Extensions {
             anisotropic_filtering: false,
         },
@@ -68,7 +68,7 @@ fn main() {
             .to_physical(window.get_hidpi_factor());
 
         let surface = instance.create_surface(&window);
-        let swap_chain = device.create_swap_chain(&surface, &wgpu::SwapChainDescriptor {
+        let mut swap_chain = device.create_swap_chain(&surface, &wgpu::SwapChainDescriptor {
             usage: wgpu::TextureUsageFlags::OUTPUT_ATTACHMENT,
             format: wgpu::TextureFormat::B8g8r8a8Unorm,
             width: size.width as u32,
@@ -95,12 +95,12 @@ fn main() {
                 _ => {}
             }
 
-            let (_, view) = swap_chain.get_next_texture();
+            let frame = swap_chain.get_next_texture();
             let mut cmd_buf = device.create_command_buffer(&wgpu::CommandBufferDescriptor { todo: 0 });
             {
                 let mut rpass = cmd_buf.begin_render_pass(&wgpu::RenderPassDescriptor {
                     color_attachments: &[wgpu::RenderPassColorAttachmentDescriptor {
-                        attachment: &view,
+                        attachment: &frame.view,
                         load_op: wgpu::LoadOp::Clear,
                         store_op: wgpu::StoreOp::Store,
                         clear_color: wgpu::Color::GREEN,
@@ -116,7 +116,6 @@ fn main() {
                 .get_queue()
                 .submit(&[cmd_buf]);
 
-            swap_chain.present();
             ControlFlow::Continue
         });
     }
diff --git a/wgpu-native/src/swap_chain.rs b/wgpu-native/src/swap_chain.rs
index e9cabeb948..1ad3e3c7a8 100644
--- a/wgpu-native/src/swap_chain.rs
+++ b/wgpu-native/src/swap_chain.rs
@@ -154,13 +154,11 @@ pub extern "C" fn wgpu_swap_chain_present(
         };
 
         device.raw.reset_fence(&frame.fence).unwrap();
-        device.queue_group.queues[0]
-            .submit(submission, Some(&frame.fence));
-
-        swap_chain.raw
+        let queue = &mut device.queue_group.queues[0];
+        queue.submit(submission, Some(&frame.fence));
+        queue
             .present(
-                &mut device.queue_group.queues[0],
-                image_index,
+                iter::once((&swap_chain.raw, image_index)),
                 iter::once(&frame.sem_present),
             )
             .unwrap();
diff --git a/wgpu-rs/src/lib.rs b/wgpu-rs/src/lib.rs
index 09defc2ebf..b2dc5b4e4b 100644
--- a/wgpu-rs/src/lib.rs
+++ b/wgpu-rs/src/lib.rs
@@ -4,6 +4,7 @@ extern crate wgpu_native as wgn;
 use arrayvec::ArrayVec;
 
 use std::ffi::CString;
+use std::marker::PhantomData;
 use std::ops::Range;
 use std::ptr;
 
@@ -112,8 +113,9 @@ pub struct ComputePass<'a> {
     parent: &'a mut CommandBuffer,
 }
 
-pub struct Queue {
+pub struct Queue<'a> {
     id: wgn::QueueId,
+    _marker: PhantomData<&'a Self>,
 }
 
 pub struct BindGroupLayoutDescriptor<'a> {
@@ -155,6 +157,12 @@ pub struct RenderPassDescriptor<'a> {
         Option<RenderPassDepthStencilAttachmentDescriptor<&'a TextureView>>,
 }
 
+pub struct SwapChainOutput<'a> {
+    pub texture: Texture,
+    pub view: TextureView,
+    swap_chain_id: &'a wgn::SwapChainId,
+}
+
 impl Instance {
     pub fn new() -> Self {
         Instance {
@@ -197,10 +205,10 @@ impl Device {
         }
     }
 
-    //TODO: borrow instead of new object?
-    pub fn get_queue(&self) -> Queue {
+    pub fn get_queue(&mut self) -> Queue {
         Queue {
             id: wgn::wgpu_device_get_queue(self.id),
+            _marker: PhantomData,
         }
     }
 
@@ -476,8 +484,8 @@ impl<'a> ComputePass<'a> {
     }
 }
 
-impl Queue {
-    pub fn submit(&self, command_buffers: &[CommandBuffer]) {
+impl<'a> Queue<'a> {
+    pub fn submit(&mut self, command_buffers: &[CommandBuffer]) {
         wgn::wgpu_queue_submit(
             self.id,
             command_buffers.as_ptr() as *const _,
@@ -486,19 +494,19 @@ impl Queue {
     }
 }
 
-impl SwapChain {
-    //TODO: borrow instead of new object?
-    pub fn get_next_texture(&self) -> (Texture, TextureView) {
-        let output = wgn::wgpu_swap_chain_get_next_texture(self.id);
-        (
-            Texture {
-                id: output.texture_id,
-            },
-            TextureView { id: output.view_id },
-        )
-    }
-
-    pub fn present(&self) {
-        wgn::wgpu_swap_chain_present(self.id);
+impl<'a> Drop for SwapChainOutput<'a> {
+    fn drop(&mut self) {
+        wgn::wgpu_swap_chain_present(*self.swap_chain_id);
+    }
+}
+
+impl SwapChain {
+    pub fn get_next_texture(&mut self) -> SwapChainOutput {
+        let output = wgn::wgpu_swap_chain_get_next_texture(self.id);
+        SwapChainOutput {
+            texture: Texture { id: output.texture_id },
+            view: TextureView { id: output.view_id },
+            swap_chain_id: &self.id,
+        }
     }
 }