2 files changed, 140 insertions, 0 deletions
diff --git a/src/Platform/Metal/MetalContext.h b/src/Platform/Metal/MetalContext.h
new file mode 100644
index 0000000..5d9eb08
--- /dev/null
+++ b/src/Platform/Metal/MetalContext.h
@@ -0,0 +1,16 @@
+#pragma once
+
+// Pure-C++ interface to the Metal backend (no Objective-C leaks into the rest
+// of the engine). Implemented in MetalContext.mm.
+namespace Donut
+{
+    // Phase 1 bring-up: creates the default Metal device + command queue and
+    // logs its capabilities, proving the Metal toolchain and build integration
+    // work natively on Apple Silicon. This grows into the Metal compute island
+    // that runs the geodesic ray tracer in real time.
+    bool MetalProbe();
+
+    // Compiles + dispatches a trivial compute kernel and validates the read-back,
+    // proving the Metal compute path the geodesic ray tracer will run on.
+    bool MetalComputeSelfTest();
+}
diff --git a/src/Platform/Metal/MetalContext.mm b/src/Platform/Metal/MetalContext.mm
new file mode 100644
index 0000000..1bb9e70
--- /dev/null
+++ b/src/Platform/Metal/MetalContext.mm
@@ -0,0 +1,124 @@
+#import <Metal/Metal.h>
+#import <Foundation/Foundation.h>
+
+#include "MetalContext.h"
+#include "Core/Log.h"
+
+#include <vector>
+
+namespace Donut
+{
+    bool MetalProbe()
+    {
+        @autoreleasepool
+        {
+            id<MTLDevice> device = MTLCreateSystemDefaultDevice();
+            if (device == nil)
+            {
+                DONUT_ERROR("Metal: no default device available");
+                return false;
+            }
+
+            id<MTLCommandQueue> queue = [device newCommandQueue];
+            const char* name = [[device name] UTF8String];
+
+            DONUT_INFO("Metal device: {}", name ? name : "(unknown)");
+            DONUT_INFO("Metal: unified memory = {}, max threads/threadgroup = {}",
+                       device.hasUnifiedMemory ? "yes" : "no",
+                       (unsigned long)device.maxThreadsPerThreadgroup.width);
+
+            if (queue == nil)
+            {
+                DONUT_WARN("Metal: failed to create command queue");
+                return false;
+            }
+
+            return true;
+        }
+    }
+
+    // Compiles a trivial compute kernel, dispatches it over a small texture, and
+    // reads the result back to confirm the full Metal compute path works: source
+    // compilation, pipeline state, command encoding, dispatch, and shared-memory
+    // read-back. This is the mechanism the geodesic ray tracer will run on.
+    bool MetalComputeSelfTest()
+    {
+        @autoreleasepool
+        {
+            id<MTLDevice> device = MTLCreateSystemDefaultDevice();
+            id<MTLCommandQueue> queue = [device newCommandQueue];
+            if (device == nil || queue == nil)
+                return false;
+
+            NSString* src =
+                @"#include <metal_stdlib>\n"
+                 "using namespace metal;\n"
+                 "kernel void selfTest(texture2d<float, access::write> outTex [[texture(0)]],\n"
+                 "                     uint2 gid [[thread_position_in_grid]])\n"
+                 "{\n"
+                 "    uint w = outTex.get_width();\n"
+                 "    uint h = outTex.get_height();\n"
+                 "    if (gid.x >= w || gid.y >= h) return;\n"
+                 "    outTex.write(float4(float(gid.x) / float(w - 1),\n"
+                 "                        float(gid.y) / float(h - 1), 0.5, 1.0), gid);\n"
+                 "}\n";
+
+            NSError* err = nil;
+            id<MTLLibrary> lib = [device newLibraryWithSource:src options:nil error:&err];
+            if (lib == nil)
+            {
+                DONUT_ERROR("Metal self-test: kernel compile failed: {}",
+                            err ? [[err localizedDescription] UTF8String] : "unknown");
+                return false;
+            }
+
+            id<MTLFunction> fn = [lib newFunctionWithName:@"selfTest"];
+            id<MTLComputePipelineState> pipeline =
+                [device newComputePipelineStateWithFunction:fn error:&err];
+            if (pipeline == nil)
+            {
+                DONUT_ERROR("Metal self-test: pipeline creation failed");
+                return false;
+            }
+
+            const uint32_t W = 64, H = 64;
+            MTLTextureDescriptor* desc =
+                [MTLTextureDescriptor texture2DDescriptorWithPixelFormat:MTLPixelFormatRGBA8Unorm
+                                                                   width:W
+                                                                  height:H
+                                                               mipmapped:NO];
+            desc.usage = MTLTextureUsageShaderWrite | MTLTextureUsageShaderRead;
+            desc.storageMode = MTLStorageModeShared;
+            id<MTLTexture> tex = [device newTextureWithDescriptor:desc];
+
+            id<MTLCommandBuffer> cb = [queue commandBuffer];
+            id<MTLComputeCommandEncoder> enc = [cb computeCommandEncoder];
+            [enc setComputePipelineState:pipeline];
+            [enc setTexture:tex atIndex:0];
+
+            MTLSize tg = MTLSizeMake(16, 16, 1);
+            MTLSize grid = MTLSizeMake(W, H, 1);
+            [enc dispatchThreads:grid threadsPerThreadgroup:tg];
+            [enc endEncoding];
+            [cb commit];
+            [cb waitUntilCompleted];
+
+            // Read back the far corner; the kernel writes (~1, ~1, 0.5, 1) there.
+            std::vector<uint8_t> px(W * H * 4);
+            [tex getBytes:px.data()
+              bytesPerRow:W * 4
+               fromRegion:MTLRegionMake2D(0, 0, W, H)
+              mipmapLevel:0];
+
+            size_t corner = ((size_t)(H - 1) * W + (W - 1)) * 4;
+            DONUT_INFO("Metal compute self-test: corner pixel RGBA = ({}, {}, {}, {})",
+                       (int)px[corner + 0], (int)px[corner + 1],
+                       (int)px[corner + 2], (int)px[corner + 3]);
+
+            bool ok = px[corner + 0] > 250 && px[corner + 1] > 250 &&
+                      px[corner + 3] == 255;
+            DONUT_INFO("Metal compute self-test: {}", ok ? "PASS" : "FAIL");
+            return ok;
+        }
+    }
+}