Merge #1145

1145: Support trailing render passes after the swapchain rendering r=kvark a=kvark

**Connections**
Discussed on the matrix.

**Description**
Fixes a case where we have any other render pass in a command encoder that draws to the swapchain (after the pass that draws to the swapchain).

**Testing**
Tested on a modified hello-triangle example.

Co-authored-by: Dzmitry Malyshau <kvarkus@gmail.com>

wgpu-core/src/command/allocator.rs

@@ -115,7 +115,7 @@ impl<B: GfxBackend> CommandAllocator<B> {
             recorded_thread_id: thread_id,
             device_id,
             trackers: TrackerSet::new(B::VARIANT),
-            used_swap_chain: None,
+            used_swap_chains: Default::default(),
             limits,
             private_features,
             has_labels: label.is_some(),

wgpu-core/src/command/mod.rs

@@ -29,6 +29,7 @@ use crate::{
 };
 
 use hal::command::CommandBuffer as _;
+use smallvec::SmallVec;
 use thiserror::Error;
 
 use std::thread::ThreadId;
@@ -42,7 +43,7 @@ pub struct CommandBuffer<B: hal::Backend> {
     recorded_thread_id: ThreadId,
     pub(crate) device_id: Stored<id::DeviceId>,
     pub(crate) trackers: TrackerSet,
-    pub(crate) used_swap_chain: Option<(Stored<id::SwapChainId>, B::Framebuffer)>,
+    pub(crate) used_swap_chains: SmallVec<[(Stored<id::SwapChainId>, B::Framebuffer); 1]>,
     limits: wgt::Limits,
     private_features: PrivateFeatures,
     has_labels: bool,
@@ -216,7 +217,7 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
             Ok(cmd_buf) => {
                 cmd_buf.is_recording = false;
                 // stop tracking the swapchain image, if used
-                if let Some((ref sc_id, _)) = cmd_buf.used_swap_chain {
+                for (ref sc_id, _) in cmd_buf.used_swap_chains.iter() {
                     let view_id = swap_chain_guard[sc_id.value]
                         .acquired_view_id
                         .as_ref()

wgpu-core/src/command/render.rs

@@ -420,8 +420,6 @@ pub enum RenderPassErrorInner {
     InvalidStencilOps,
     #[error("all attachments must have the same sample count, found {actual} != {expected}")]
     SampleCountMismatch { actual: u8, expected: u8 },
-    #[error("texture view's swap chain must match swap chain in use")]
-    SwapChainMismatch,
     #[error("setting `values_offset` to be `None` is only for internal use in render bundles")]
     InvalidValuesOffset,
     #[error("required device features not enabled: {0:?}")]
@@ -696,14 +694,8 @@ impl<'a, B: GfxBackend> RenderPassInfo<'a, B> {
                         old_layout..new_layout
                     }
                     TextureViewInner::SwapChain { ref source_id, .. } => {
-                        if let Some((ref sc_id, _)) = cmd_buf.used_swap_chain {
-                            if source_id.value != sc_id.value {
-                                return Err(RenderPassErrorInner::SwapChainMismatch);
-                            }
-                        } else {
-                            assert!(used_swap_chain.is_none());
-                            used_swap_chain = Some(source_id.clone());
-                        }
+                        assert!(used_swap_chain.is_none());
+                        used_swap_chain = Some(source_id.clone());
 
                         let end = hal::image::Layout::Present;
                         let start = match at.channel.load_op {
@@ -786,14 +778,8 @@ impl<'a, B: GfxBackend> RenderPassInfo<'a, B> {
                         old_layout..new_layout
                     }
                     TextureViewInner::SwapChain { ref source_id, .. } => {
-                        if let Some((ref sc_id, _)) = cmd_buf.used_swap_chain {
-                            if source_id.value != sc_id.value {
-                                return Err(RenderPassErrorInner::SwapChainMismatch);
-                            }
-                        } else {
-                            assert!(used_swap_chain.is_none());
-                            used_swap_chain = Some(source_id.clone());
-                        }
+                        assert!(used_swap_chain.is_none());
+                        used_swap_chain = Some(source_id.clone());
                         hal::image::Layout::Undefined..hal::image::Layout::Present
                     }
                 };
@@ -919,7 +905,6 @@ impl<'a, B: GfxBackend> RenderPassInfo<'a, B> {
 
         let framebuffer = match used_swap_chain.take() {
             Some(sc_id) => {
-                assert!(cmd_buf.used_swap_chain.is_none());
                 // Always create a new framebuffer and delete it after presentation.
                 let attachments = fb_key
                     .all()
@@ -1886,7 +1871,9 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
         let cmd_buf =
             CommandBuffer::get_encoder_mut(&mut *cmb_guard, encoder_id).map_pass_err(scope)?;
         cmd_buf.has_labels |= base.label.is_some();
-        cmd_buf.used_swap_chain = used_swapchain_with_framebuffer;
+        cmd_buf
+            .used_swap_chains
+            .extend(used_swapchain_with_framebuffer);
 
         #[cfg(feature = "trace")]
         if let Some(ref mut list) = cmd_buf.commands {

wgpu-core/src/device/queue.rs

@@ -514,7 +514,7 @@ impl<G: GlobalIdentityHandlerFactory> Global<G> {
                             ));
                         }
 
-                        if let Some((sc_id, fbo)) = cmdbuf.used_swap_chain.take() {
+                        for (sc_id, fbo) in cmdbuf.used_swap_chains.drain(..) {
                             let sc = &mut swap_chain_guard[sc_id.value];
                             sc.active_submission_index = submit_index;
                             if sc.acquired_view_id.is_none() {