From 4f07ce8248c7b6a77e23379fb8ab0e830f7abc54 Mon Sep 17 00:00:00 2001
From: Dzmitry Malyshau <dmalyshau@mozilla.com>
Date: Tue, 30 Oct 2018 21:23:22 -0400
Subject: [PATCH] Cache framebuffers by the Device

---
 wgpu-native/src/command/mod.rs | 37 ++++++++++++++++++++++++----------
 wgpu-native/src/device.rs      |  8 ++++++++
 2 files changed, 34 insertions(+), 11 deletions(-)

diff --git a/wgpu-native/src/command/mod.rs b/wgpu-native/src/command/mod.rs
index 967f0a391b..ec348ee93c 100644
--- a/wgpu-native/src/command/mod.rs
+++ b/wgpu-native/src/command/mod.rs
@@ -14,7 +14,7 @@ use {
     BufferId, CommandBufferId, ComputePassId, DeviceId, RenderPassId, TextureId, TextureViewId,
 };
 use conv;
-use device::RenderPassKey;
+use device::{FramebufferKey, RenderPassKey};
 use registry::{HUB, Items, Registry};
 use track::{BufferTracker, TextureTracker};
 
@@ -230,15 +230,30 @@ pub extern "C" fn wgpu_command_buffer_begin_render_pass(
         }
     };
 
-    let framebuffer = {
-        let attachments = desc.color_attachments
+    let mut framebuffer_cache = device.framebuffers.lock().unwrap();
+    let fb_key = FramebufferKey {
+        attachments: desc.color_attachments
             .iter()
-            .map(|at| at.attachment)
-            .chain(desc.depth_stencil_attachment.as_ref().map(|at| at.attachment))
-            .map(|id| &view_guard.get(id).raw);
-        device.raw
-            .create_framebuffer(&render_pass, attachments, extent.unwrap())
-            .unwrap()
+            .map(|at| Stored(at.attachment))
+            .chain(desc.depth_stencil_attachment.as_ref().map(|at| Stored(at.attachment)))
+            .collect(),
+    };
+    let framebuffer = match framebuffer_cache.entry(fb_key) {
+        Entry::Occupied(e) => e.into_mut(),
+        Entry::Vacant(e) => {
+            let fb = {
+                let attachments = e
+                    .key()
+                    .attachments
+                    .iter()
+                    .map(|&Stored(id)| &view_guard.get(id).raw);
+
+                device.raw
+                    .create_framebuffer(&render_pass, attachments, extent.unwrap())
+                    .unwrap()
+            };
+            e.insert(fb)
+        }
     };
 
     let rect = {
@@ -263,8 +278,8 @@ pub extern "C" fn wgpu_command_buffer_begin_render_pass(
         }));
 
     current_comb.begin_render_pass(
-        &render_pass,
-        &framebuffer,
+        render_pass,
+        framebuffer,
         rect,
         clear_values,
         hal::command::SubpassContents::Inline,
diff --git a/wgpu-native/src/device.rs b/wgpu-native/src/device.rs
index 8ab1661dfd..ee53e951cd 100644
--- a/wgpu-native/src/device.rs
+++ b/wgpu-native/src/device.rs
@@ -24,6 +24,12 @@ pub(crate) struct RenderPassKey {
 }
 impl Eq for RenderPassKey {}
 
+#[derive(Hash, PartialEq)]
+pub(crate) struct FramebufferKey {
+    pub attachments: Vec<Stored<TextureViewId>>,
+}
+impl Eq for FramebufferKey {}
+
 
 pub struct Device<B: hal::Backend> {
     pub(crate) raw: B::Device,
@@ -34,6 +40,7 @@ pub struct Device<B: hal::Backend> {
     texture_tracker: Mutex<TextureTracker>,
     mem_props: hal::MemoryProperties,
     pub(crate) render_passes: Mutex<HashMap<RenderPassKey, B::RenderPass>>,
+    pub(crate) framebuffers: Mutex<HashMap<FramebufferKey, B::Framebuffer>>,
 }
 
 impl<B: hal::Backend> Device<B> {
@@ -72,6 +79,7 @@ impl<B: hal::Backend> Device<B> {
             texture_tracker: Mutex::new(TextureTracker::new()),
             mem_props,
             render_passes: Mutex::new(HashMap::new()),
+            framebuffers: Mutex::new(HashMap::new()),
         }
     }
 }