lavfi/metal: fix build with pre-10.11 deployment targets

- Ensure the yadif .metal compiles when targeting any Metal runtime version
- Use some preprocessor awkwardness to ensure Core Video's Metal-specific
  functionality is exposed regardless of our deployment target (this works
  around what seems to be an SDK header bug, filed as FB9816002)
- Ensure all direct references to Metal functions and classes are gated
  behind runtime version checks (this satisfies clang's deployment-target
  violation warnings provided by -Wunguarded-availability).

2 files changed, 36 insertions, 3 deletions

diff --git a/libavfilter/metal/utils.h b/libavfilter/metal/utils.h
index bd0319f63c..7350d42a35 100644
--- a/libavfilter/metal/utils.h
+++ b/libavfilter/metal/utils.h
@@ -20,16 +20,40 @@
 #define AVFILTER_METAL_UTILS_H
 
 #include <Metal/Metal.h>
+
+#include <AvailabilityMacros.h>
+
+// CoreVideo accidentally(?) preprocessor-gates Metal functionality
+// on MAC_OS_X_VERSION_MIN_REQUIRED >= 101100 (FB9816002).
+// There doesn't seem to be any particular reason for this,
+// so here we temporarily redefine it to at least that value
+// so CV will give us CVMetalTextureRef and the related functions.
+
+#if defined(MAC_OS_X_VERSION_MIN_REQUIRED) && (MAC_OS_X_VERSION_MIN_REQUIRED < 101100)
+#define ORIG_MAC_OS_X_VERSION_MIN_REQUIRED MAC_OS_X_VERSION_MIN_REQUIRED
+#undef MAC_OS_X_VERSION_MIN_REQUIRED
+#define MAC_OS_X_VERSION_MIN_REQUIRED 101100
+#endif
+
 #include <CoreVideo/CoreVideo.h>
 
+#ifdef ORIG_MAC_OS_X_VERSION_MIN_REQUIRED
+#undef MAC_OS_X_VERSION_MIN_REQUIRED
+#define MAC_OS_X_VERSION_MIN_REQUIRED ORIG_MAC_OS_X_VERSION_MIN_REQUIRED
+#undef ORIG_MAC_OS_X_VERSION_MIN_REQUIRED
+#endif
+
 void ff_metal_compute_encoder_dispatch(id<MTLDevice> device,
                                        id<MTLComputePipelineState> pipeline,
                                        id<MTLComputeCommandEncoder> encoder,
-                                       NSUInteger width, NSUInteger height);
+                                       NSUInteger width, NSUInteger height)
+                                       API_AVAILABLE(macos(10.11), ios(8.0));
 
 CVMetalTextureRef ff_metal_texture_from_pixbuf(void *avclass,
                                                CVMetalTextureCacheRef textureCache,
                                                CVPixelBufferRef pixbuf,
                                                int plane,
-                                               MTLPixelFormat format);
+                                               MTLPixelFormat format)
+                                               API_AVAILABLE(macos(10.11), ios(8.0));
+
 #endif /* AVFILTER_METAL_UTILS_H */
diff --git a/libavfilter/metal/vf_yadif_videotoolbox.metal b/libavfilter/metal/vf_yadif_videotoolbox.metal
index 50783f2ffe..8a3d41a30f 100644
--- a/libavfilter/metal/vf_yadif_videotoolbox.metal
+++ b/libavfilter/metal/vf_yadif_videotoolbox.metal
@@ -27,6 +27,15 @@
 using namespace metal;
 
 /*
+ * Version compat shims
+ */
+
+#if __METAL_VERSION__ < 210
+#define max3(x, y, z) max(x, max(y, z))
+#define min3(x, y, z) min(x, min(y, z))
+#endif
+
+/*
  * Parameters
  */
 
@@ -44,7 +53,7 @@ struct deintParams {
  */
 
 #define accesstype access::sample
-const sampler s(coord::pixel);
+constexpr sampler s(coord::pixel);
 
 template <typename T>
 T tex2D(texture2d<float, access::sample> tex, uint x, uint y)