From 2d3271403bb85407f775bd4fe75ccc96542b0244 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Milo=C5=A1=20Markovi=C4=87?= <milos.z.markovic.89@gmail.com>
Date: Wed, 31 Dec 2025 15:11:42 +0100
Subject: [PATCH] Metal backend resource for MacOS fixes (#4020)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 platform/macos/src/MLNMapView+Impl.h   |  7 +++++++
 platform/macos/src/MLNMapView+Metal.h  |  1 +
 platform/macos/src/MLNMapView+Metal.mm | 15 +++++++++++++--
 platform/macos/src/MLNMapView.h        | 11 +++++++++++
 platform/macos/src/MLNMapView.mm       |  7 +++++++
 5 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/platform/macos/src/MLNMapView+Impl.h b/platform/macos/src/MLNMapView+Impl.h
index 07fd08cc2..d314baf9c 100644
--- a/platform/macos/src/MLNMapView+Impl.h
+++ b/platform/macos/src/MLNMapView+Impl.h
@@ -2,6 +2,8 @@
 #import <mbgl/map/map_observer.hpp>
 #import <mbgl/util/image.hpp>
 
+#import "MLNBackendResource.h"
+
 @class MLNMapView;
 
 typedef struct _CGLContextObject* CGLContextObj;
@@ -20,6 +22,11 @@ class MLNMapViewImpl : public mbgl::MapObserver {
 
   virtual CGLContextObj getCGLContextObj() { return nullptr; }
 
+#if MLN_RENDER_BACKEND_METAL
+  // Returns the backend resource for Metal rendering in custom layers
+  virtual MLNBackendResource* getObject() { return nullptr; }
+#endif
+
   // Called by the view delegate when it's time to render.
   void render();
 
diff --git a/platform/macos/src/MLNMapView+Metal.h b/platform/macos/src/MLNMapView+Metal.h
index f6d12e66c..55a6adb43 100644
--- a/platform/macos/src/MLNMapView+Metal.h
+++ b/platform/macos/src/MLNMapView+Metal.h
@@ -36,6 +36,7 @@ class MLNMapViewMetalImpl final : public MLNMapViewImpl,
   mbgl::gfx::RendererBackend& getRendererBackend() override { return *this; }
 
   mbgl::PremultipliedImage readStillImage() override;
+  MLNBackendResource* getObject() override;
 
  private:
   bool presentsWithTransaction = false;
diff --git a/platform/macos/src/MLNMapView+Metal.mm b/platform/macos/src/MLNMapView+Metal.mm
index 5c4759cbd..8513803c6 100644
--- a/platform/macos/src/MLNMapView+Metal.mm
+++ b/platform/macos/src/MLNMapView+Metal.mm
@@ -44,8 +44,10 @@ public:
             commandQueue = [mtlView.device newCommandQueue];
         }
 
-        commandBuffer = [commandQueue commandBuffer];
-        commandBufferPtr = NS::RetainPtr((__bridge MTL::CommandBuffer*)commandBuffer);
+        if (!commandBuffer) {
+            commandBuffer = [commandQueue commandBuffer];
+            commandBufferPtr = NS::RetainPtr((__bridge MTL::CommandBuffer*)commandBuffer);
+        }
     }
 
     const mbgl::mtl::RendererBackend& getBackend() const override { return backend; }
@@ -158,3 +160,12 @@ mbgl::PremultipliedImage MLNMapViewMetalImpl::readStillImage() {
     // return readFramebuffer(mapView.framebufferSize); // TODO: RendererBackend::readFramebuffer
     return {};
 }
+
+MLNBackendResource* MLNMapViewMetalImpl::getObject() {
+    auto& resource = getResource<MLNMapViewMetalRenderableResource>();
+
+    return [[MLNBackendResource alloc] initWithMTKView:resource.mtlView
+                                                device:resource.mtlView.device
+                                  renderPassDescriptor:resource.mtlView.currentRenderPassDescriptor
+                                         commandBuffer:resource.commandBuffer];
+}
diff --git a/platform/macos/src/MLNMapView.h b/platform/macos/src/MLNMapView.h
index 389474131..1f12769fe 100644
--- a/platform/macos/src/MLNMapView.h
+++ b/platform/macos/src/MLNMapView.h
@@ -2,6 +2,7 @@
 #import <CoreLocation/CoreLocation.h>
 #import <QuartzCore/QuartzCore.h>
 
+#import "MLNBackendResource.h"
 #import "MLNFoundation.h"
 #import "MLNGeometry.h"
 #import "MLNMapOptions.h"
@@ -1336,6 +1337,16 @@ around the returned camera object if it were set as the receiver’s camera.
  */
 - (void)clearActionJournalLog;
 
+#if MLN_RENDER_BACKEND_METAL
+/**
+ Returns the Metal backend resource for use in custom style layers.
+
+ This property provides access to the Metal device, command buffer, and other
+ resources needed for custom Metal rendering in MLNCustomStyleLayer subclasses.
+ */
+- (MLNBackendResource *)backendResource;
+#endif
+
 @end
 
 NS_ASSUME_NONNULL_END
diff --git a/platform/macos/src/MLNMapView.mm b/platform/macos/src/MLNMapView.mm
index 6dc79ba88..cb5afa550 100644
--- a/platform/macos/src/MLNMapView.mm
+++ b/platform/macos/src/MLNMapView.mm
@@ -48,6 +48,7 @@
 #import <unordered_set>
 
 #import "MLNMapView+Impl.h"
+#import "MLNBackendResource.h"
 #import "NSBundle+MLNAdditions.h"
 #import "NSDate+MLNAdditions.h"
 #import "NSProcessInfo+MLNAdditions.h"
@@ -3314,4 +3315,10 @@ public:
     actionJournal->clearLog();
 }
 
+#if MLN_RENDER_BACKEND_METAL
+- (MLNBackendResource *)backendResource {
+    return _mbglView->getObject();
+}
+#endif
+
 @end