From 1acd9d627cf109605582a1bec90df6ff129a1082 Mon Sep 17 00:00:00 2001
From: Dan Balasescu <smoogipoo@smgi.me>
Date: Tue, 8 Jul 2025 21:09:34 +0900
Subject: [PATCH] Support tearing in VK swapchain

---
 src/Veldrid/Vk/VkGraphicsDevice.cs |  6 ++++++
 src/Veldrid/Vk/VkSwapchain.cs      | 31 +++++++++++++++++++++++-------
 2 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/src/Veldrid/Vk/VkGraphicsDevice.cs b/src/Veldrid/Vk/VkGraphicsDevice.cs
index 7271e02b0..825da5fda 100644
--- a/src/Veldrid/Vk/VkGraphicsDevice.cs
+++ b/src/Veldrid/Vk/VkGraphicsDevice.cs
@@ -27,6 +27,12 @@ internal unsafe class VkGraphicsDevice : GraphicsDevice
 
         public override bool IsClipSpaceYInverted => !standardClipYDirection;
 
+        public override bool AllowTearing
+        {
+            get => mainSwapchain.AllowTearing;
+            set => mainSwapchain.AllowTearing = value;
+        }
+
         public override Swapchain MainSwapchain => mainSwapchain;
 
         public override GraphicsDeviceFeatures Features { get; }
diff --git a/src/Veldrid/Vk/VkSwapchain.cs b/src/Veldrid/Vk/VkSwapchain.cs
index b92b4acf0..e4db95fc5 100644
--- a/src/Veldrid/Vk/VkSwapchain.cs
+++ b/src/Veldrid/Vk/VkSwapchain.cs
@@ -40,6 +40,22 @@ public override bool SyncToVerticalBlank
             }
         }
 
+        private bool allowTearing;
+
+        public bool AllowTearing
+        {
+            get => allowTearing;
+            set
+            {
+                if (allowTearing == value)
+                    return;
+
+                allowTearing = value;
+
+                recreateAndReacquire(framebuffer.Width, framebuffer.Height);
+            }
+        }
+
         private readonly VkGraphicsDevice gd;
         private readonly VkSwapchainFramebuffer framebuffer;
         private readonly uint presentQueueIndex;
@@ -203,14 +219,15 @@ private bool createSwapchain(uint width, uint height)
 
             if (syncToVBlank)
             {
-                if (presentModes.Contains(VkPresentModeKHR.FifoRelaxedKHR)) presentMode = VkPresentModeKHR.FifoRelaxedKHR;
-            }
-            else
-            {
-                if (presentModes.Contains(VkPresentModeKHR.MailboxKHR))
-                    presentMode = VkPresentModeKHR.MailboxKHR;
-                else if (presentModes.Contains(VkPresentModeKHR.ImmediateKHR)) presentMode = VkPresentModeKHR.ImmediateKHR;
+                if (presentModes.Contains(VkPresentModeKHR.FifoRelaxedKHR))
+                    presentMode = VkPresentModeKHR.FifoRelaxedKHR;
             }
+            else if (allowTearing && presentModes.Contains(VkPresentModeKHR.ImmediateKHR))
+                presentMode = VkPresentModeKHR.ImmediateKHR;
+            else if (presentModes.Contains(VkPresentModeKHR.MailboxKHR))
+                presentMode = VkPresentModeKHR.MailboxKHR;
+            else if (presentModes.Contains(VkPresentModeKHR.ImmediateKHR))
+                presentMode = VkPresentModeKHR.ImmediateKHR;
 
             uint maxImageCount = surfaceCapabilities.maxImageCount == 0 ? uint.MaxValue : surfaceCapabilities.maxImageCount;
             uint imageCount = Math.Min(maxImageCount, surfaceCapabilities.minImageCount + 1);