From 051d08424c0bcdf8f9792519b4e0fb6e70737918 Mon Sep 17 00:00:00 2001
From: Aaron Loucks <aloucks@cofront.net>
Date: Thu, 5 Mar 2020 18:19:18 -0500
Subject: [PATCH 1/2] Add PresentMode::Mailbox

---
 ffi/wgpu.h                  | 1 +
 wgpu-core/src/swap_chain.rs | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/ffi/wgpu.h b/ffi/wgpu.h
index 06ee444f6b..0c6a89018c 100644
--- a/ffi/wgpu.h
+++ b/ffi/wgpu.h
@@ -128,6 +128,7 @@ typedef enum {
 typedef enum {
   WGPUPresentMode_NoVsync = 0,
   WGPUPresentMode_Vsync = 1,
+  WGPUPresentMode_Mailbox = 2,
 } WGPUPresentMode;
 
 typedef enum {
diff --git a/wgpu-core/src/swap_chain.rs b/wgpu-core/src/swap_chain.rs
index 90a5e0b535..f914fdc804 100644
--- a/wgpu-core/src/swap_chain.rs
+++ b/wgpu-core/src/swap_chain.rs
@@ -65,6 +65,7 @@ pub struct SwapChain<B: hal::Backend> {
 pub enum PresentMode {
     NoVsync = 0,
     Vsync = 1,
+    Mailbox = 2,
 }
 
 #[repr(C)]
@@ -95,6 +96,7 @@ impl SwapChainDescriptor {
         config.present_mode = match self.present_mode {
             PresentMode::NoVsync => hal::window::PresentMode::IMMEDIATE,
             PresentMode::Vsync => hal::window::PresentMode::FIFO,
+            PresentMode::Mailbox => hal::window::PresentMode::MAILBOX,
         };
         config
     }

From fe95fddf5af4bdad4c3fff17bae5713993954716 Mon Sep 17 00:00:00 2001
From: Aaron Loucks <aloucks@cofront.net>
Date: Fri, 6 Mar 2020 00:48:45 -0500
Subject: [PATCH 2/2] Use vulkan nomenclature for PresentMode variants

https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/VkPresentModeKHR.html
---
 examples/triangle/main.c    |  4 ++--
 ffi/wgpu.h                  |  6 +++---
 wgpu-core/src/swap_chain.rs | 21 ++++++++++++++++-----
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/examples/triangle/main.c b/examples/triangle/main.c
index 05eab3e59a..dd0d8509b7 100644
--- a/examples/triangle/main.c
+++ b/examples/triangle/main.c
@@ -208,7 +208,7 @@ int main() {
             .format = WGPUTextureFormat_Bgra8Unorm,
             .width = prev_width,
             .height = prev_height,
-            .present_mode = WGPUPresentMode_Vsync,
+            .present_mode = WGPUPresentMode_Fifo,
         });
 
     while (!glfwWindowShouldClose(window)) {
@@ -225,7 +225,7 @@ int main() {
                     .format = WGPUTextureFormat_Bgra8Unorm,
                     .width = width,
                     .height = height,
-                    .present_mode = WGPUPresentMode_Vsync,
+                    .present_mode = WGPUPresentMode_Fifo,
                 });
         }
 
diff --git a/ffi/wgpu.h b/ffi/wgpu.h
index 0c6a89018c..9f94162f76 100644
--- a/ffi/wgpu.h
+++ b/ffi/wgpu.h
@@ -126,9 +126,9 @@ typedef enum {
 } WGPUPowerPreference;
 
 typedef enum {
-  WGPUPresentMode_NoVsync = 0,
-  WGPUPresentMode_Vsync = 1,
-  WGPUPresentMode_Mailbox = 2,
+  WGPUPresentMode_Immediate = 0,
+  WGPUPresentMode_Mailbox = 1,
+  WGPUPresentMode_Fifo = 2,
 } WGPUPresentMode;
 
 typedef enum {
diff --git a/wgpu-core/src/swap_chain.rs b/wgpu-core/src/swap_chain.rs
index f914fdc804..3205701b7c 100644
--- a/wgpu-core/src/swap_chain.rs
+++ b/wgpu-core/src/swap_chain.rs
@@ -63,9 +63,20 @@ pub struct SwapChain<B: hal::Backend> {
 #[repr(C)]
 #[derive(Copy, Clone, Debug)]
 pub enum PresentMode {
-    NoVsync = 0,
-    Vsync = 1,
-    Mailbox = 2,
+    /// The presentation engine does **not** wait for a vertical blanking period and 
+    /// the request is presented immediately. This is a low-latency presentation mode,
+    /// but visible tearing may be observed. Will fallback to `Fifo` if unavailable on the
+    /// selected  platform and backend. Not optimal for mobile. 
+    Immediate = 0,
+    /// The presentation engine waits for the next vertical blanking period to update
+    /// the current image, but frames may be submitted without delay. This is a low-latency 
+    /// presentation mode and visible tearing will **not** be observed. Will fallback to `Fifo`
+    /// if unavailable on the selected platform and backend. Not optimal for mobile.
+    Mailbox = 1,
+    /// The presentation engine waits for the next vertical blanking period to update 
+    /// the current image. The framerate will be capped at the display refresh rate, 
+    /// corresponding to the `VSync`. Tearing cannot be observed. Optimal for mobile.
+    Fifo = 2,
 }
 
 #[repr(C)]
@@ -94,9 +105,9 @@ impl SwapChainDescriptor {
         config.image_usage = conv::map_texture_usage(self.usage, hal::format::Aspects::COLOR);
         config.composite_alpha_mode = hal::window::CompositeAlphaMode::OPAQUE;
         config.present_mode = match self.present_mode {
-            PresentMode::NoVsync => hal::window::PresentMode::IMMEDIATE,
-            PresentMode::Vsync => hal::window::PresentMode::FIFO,
+            PresentMode::Immediate => hal::window::PresentMode::IMMEDIATE,
             PresentMode::Mailbox => hal::window::PresentMode::MAILBOX,
+            PresentMode::Fifo => hal::window::PresentMode::FIFO,
         };
         config
     }