From 1a0306c50e56cb35b823553715176aad5e898602 Mon Sep 17 00:00:00 2001
From: Richard Knight <rich@funkypixels.com>
Date: Sat, 3 Oct 2020 14:09:11 +0100
Subject: [PATCH] Add native API to allow access to Metal surface on Mac

---
 include/GLFW/glfw3native.h | 14 ++++++
 src/cocoa_window.m         | 88 ++++++++++++++++++++++++--------------
 2 files changed, 71 insertions(+), 31 deletions(-)

diff --git a/include/GLFW/glfw3native.h b/include/GLFW/glfw3native.h
index e680c1e3..bc0376cc 100644
--- a/include/GLFW/glfw3native.h
+++ b/include/GLFW/glfw3native.h
@@ -215,6 +215,20 @@ GLFWAPI CGDirectDisplayID glfwGetCocoaMonitor(GLFWmonitor* monitor);
  *  @ingroup native
  */
 GLFWAPI id glfwGetCocoaWindow(GLFWwindow* window);
+
+/*! @brief Returns the `CAMetalLayer` for the specified window.
+ *
+ *  @return The `CAMetalLayer` of the specified window, or `nil` if an
+ *  [error](@ref error_handling) occurred.
+ *
+ *  @thread_safety This function may be called from any thread.  Access is not
+ *  synchronized.
+ *
+ *  @since Added in version 3.0.
+ *
+ *  @ingroup native
+ */
+GLFWAPI id glfwGetMetalLayer(GLFWwindow* window);
 #endif
 
 #if defined(GLFW_EXPOSE_NATIVE_NSGL)
diff --git a/src/cocoa_window.m b/src/cocoa_window.m
index 81b22e2f..4e17f622 100644
--- a/src/cocoa_window.m
+++ b/src/cocoa_window.m
@@ -878,6 +878,48 @@ static GLFWbool createNativeWindow(_GLFWwindow* window,
     return GLFW_TRUE;
 }
 
+static GLFWbool createMetalLayer(_GLFWwindow* window)
+{
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 101100
+
+    @autoreleasepool {
+
+    // HACK: Dynamically load Core Animation to avoid adding an extra
+    //       dependency for the majority who don't use MoltenVK
+    NSBundle* bundle = [NSBundle bundleWithPath:@"/System/Library/Frameworks/QuartzCore.framework"];
+    if (!bundle)
+    {
+        _glfwInputError(GLFW_PLATFORM_ERROR,
+                        "Cocoa: Failed to find QuartzCore.framework");
+        return GLFW_FALSE;
+    }
+
+    // NOTE: Create the layer here as makeBackingLayer should not return nil
+    window->ns.layer = [[bundle classNamed:@"CAMetalLayer"] layer];
+    if (!window->ns.layer)
+    {
+        _glfwInputError(GLFW_PLATFORM_ERROR,
+                        "Cocoa: Failed to create layer for view");
+        return GLFW_FALSE;
+    }
+
+    if (window->ns.retina)
+        [window->ns.layer setContentsScale:[window->ns.object backingScaleFactor]];
+
+    [window->ns.view setLayer:window->ns.layer];
+    [window->ns.view setWantsLayer:YES];
+
+    } // autoreleasepool
+
+    return GLFW_TRUE;
+
+#else
+
+    return GLFW_FALSE;
+
+#endif
+}
+
 
 //////////////////////////////////////////////////////////////////////////
 //////                       GLFW internal API                      //////
@@ -1805,33 +1847,8 @@ VkResult _glfwPlatformCreateWindowSurface(VkInstance instance,
                                           const VkAllocationCallbacks* allocator,
                                           VkSurfaceKHR* surface)
 {
-    @autoreleasepool {
-
-#if MAC_OS_X_VERSION_MAX_ALLOWED >= 101100
-    // HACK: Dynamically load Core Animation to avoid adding an extra
-    //       dependency for the majority who don't use MoltenVK
-    NSBundle* bundle = [NSBundle bundleWithPath:@"/System/Library/Frameworks/QuartzCore.framework"];
-    if (!bundle)
-    {
-        _glfwInputError(GLFW_PLATFORM_ERROR,
-                        "Cocoa: Failed to find QuartzCore.framework");
+    if (!createMetalLayer(window))
         return VK_ERROR_EXTENSION_NOT_PRESENT;
-    }
-
-    // NOTE: Create the layer here as makeBackingLayer should not return nil
-    window->ns.layer = [[bundle classNamed:@"CAMetalLayer"] layer];
-    if (!window->ns.layer)
-    {
-        _glfwInputError(GLFW_PLATFORM_ERROR,
-                        "Cocoa: Failed to create layer for view");
-        return VK_ERROR_EXTENSION_NOT_PRESENT;
-    }
-
-    if (window->ns.retina)
-        [window->ns.layer setContentsScale:[window->ns.object backingScaleFactor]];
-
-    [window->ns.view setLayer:window->ns.layer];
-    [window->ns.view setWantsLayer:YES];
 
     VkResult err;
 
@@ -1884,11 +1901,6 @@ VkResult _glfwPlatformCreateWindowSurface(VkInstance instance,
     }
 
     return err;
-#else
-    return VK_ERROR_EXTENSION_NOT_PRESENT;
-#endif
-
-    } // autoreleasepool
 }
 
 
@@ -1903,3 +1915,17 @@ GLFWAPI id glfwGetCocoaWindow(GLFWwindow* handle)
     return window->ns.object;
 }
 
+GLFWAPI id glfwGetMetalLayer(GLFWwindow* handle)
+{
+    _GLFWwindow* window = (_GLFWwindow*) handle;
+    _GLFW_REQUIRE_INIT_OR_RETURN(nil);
+
+    if (!window->ns.layer)
+    {
+        if (!createMetalLayer(window))
+            return nil;
+    }
+
+    return window->ns.layer;
+}
+