[graphite] Fix some Viewer issues

There are two issues fixed here:
* In Viewer we don't have a GraphiteTestContext, so check for that.

* When running in Xcode with validation enabled, sometimes we get
asserts that we're trying to delete an resource used by a
MTLCommandBuffer. However, that MTLCommandBuffer is the one we're
trying to clean up. Because MTLCommandBuffer objects are assigned
to an AutoreleasePool, there may be a second ref on the command buffer object, which won't be released until its pool is drained at some future time. The solution for that is to create a temporary pool at object creation, which will get drained immediately when it leaves scope, releasing that dangling ref. We also have to do this for the CommandEncoders, which apparently have refs to their CommandBuffer.
While this doesn't 100% fix the issue it does seem to help some.

Change-Id: Ic8684ce05a116389dd9cbadfd7d5128ce8023475
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/836116
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>

gm/asyncrescaleandread.cpp

@@ -166,7 +166,9 @@ class AsyncReadGMBase : public skiagm::GM {
             graphiteContext->submit();
             while (!asyncContext->fCalled) {
                 graphiteContext->checkAsyncWorkCompletion();
-                this->graphiteTestContext()->tick();
+                if (this->graphiteTestContext()) {
+                    this->graphiteTestContext()->tick();
+                }
             }
 #endif
         } else {
@@ -254,7 +256,9 @@ class AsyncReadGMBase : public skiagm::GM {
             graphiteContext->submit();
             while (!asyncContext.fCalled) {
                 graphiteContext->checkAsyncWorkCompletion();
-                this->graphiteTestContext()->tick();
+                if (this->graphiteTestContext()) {
+                    this->graphiteTestContext()->tick();
+                }
             }
 #endif
         } else {

src/gpu/graphite/mtl/MtlBlitCommandEncoder.h

@@ -24,11 +24,13 @@ class MtlBlitCommandEncoder : public Resource {
 public:
     static sk_sp<MtlBlitCommandEncoder> Make(const SharedContext* sharedContext,
                                              id<MTLCommandBuffer> commandBuffer) {
-        // Adding a retain here to keep our own ref separate from the autorelease pool
-        sk_cfp<id<MTLBlitCommandEncoder>> encoder =
-                sk_ret_cfp<id<MTLBlitCommandEncoder>>([commandBuffer blitCommandEncoder]);
-        return sk_sp<MtlBlitCommandEncoder>(new MtlBlitCommandEncoder(sharedContext,
-                                                                      std::move(encoder)));
+        @autoreleasepool {
+            // Adding a retain here to keep our own ref separate from the autorelease pool
+            sk_cfp<id<MTLBlitCommandEncoder>> encoder =
+                    sk_ret_cfp<id<MTLBlitCommandEncoder>>([commandBuffer blitCommandEncoder]);
+            return sk_sp<MtlBlitCommandEncoder>(new MtlBlitCommandEncoder(sharedContext,
+                                                                          std::move(encoder)));
+        }
     }
 
     const char* getResourceType() const override { return "Metal Blit Command Encoder"; }

src/gpu/graphite/mtl/MtlCommandBuffer.mm

@@ -59,17 +59,22 @@
 
 bool MtlCommandBuffer::createNewMTLCommandBuffer() {
     SkASSERT(fCommandBuffer == nil);
-    if (@available(macOS 11.0, iOS 14.0, tvOS 14.0, *)) {
-        sk_cfp<MTLCommandBufferDescriptor*> desc([[MTLCommandBufferDescriptor alloc] init]);
-        (*desc).retainedReferences = NO;
+
+    // Inserting a pool here so the autorelease occurs when we return and the
+    // only remaining ref is the retain below.
+    @autoreleasepool {
+        if (@available(macOS 11.0, iOS 14.0, tvOS 14.0, *)) {
+            sk_cfp<MTLCommandBufferDescriptor*> desc([[MTLCommandBufferDescriptor alloc] init]);
+            (*desc).retainedReferences = NO;
 #ifdef SK_ENABLE_MTL_DEBUG_INFO
-        (*desc).errorOptions = MTLCommandBufferErrorOptionEncoderExecutionStatus;
+            (*desc).errorOptions = MTLCommandBufferErrorOptionEncoderExecutionStatus;
 #endif
-        // We add a retain here because the command buffer is set to autorelease (not alloc or copy)
-        fCommandBuffer.reset([[fQueue commandBufferWithDescriptor:desc.get()] retain]);
-    } else {
-        // We add a retain here because the command buffer is set to autorelease (not alloc or copy)
-        fCommandBuffer.reset([[fQueue commandBufferWithUnretainedReferences] retain]);
+            // We add a retain here because the command buffer is set to autorelease (not alloc or copy)
+            fCommandBuffer.reset([[fQueue commandBufferWithDescriptor:desc.get()] retain]);
+        } else {
+            // We add a retain here because the command buffer is set to autorelease (not alloc or copy)
+            fCommandBuffer.reset([[fQueue commandBufferWithUnretainedReferences] retain]);
+        }
     }
     return fCommandBuffer != nil;
 }

src/gpu/graphite/mtl/MtlComputeCommandEncoder.h

@@ -24,14 +24,18 @@ class MtlComputeCommandEncoder : public Resource {
 public:
     static sk_sp<MtlComputeCommandEncoder> Make(const SharedContext* sharedContext,
                                                 id<MTLCommandBuffer> commandBuffer) {
-        // Adding a retain here to keep our own ref separate from the autorelease pool
-        sk_cfp<id<MTLComputeCommandEncoder>> encoder =
-                sk_ret_cfp([commandBuffer computeCommandEncoder]);
-
-        // TODO(armansito): Support concurrent dispatch of compute passes using
-        // MTLDispatchTypeConcurrent on macOS 10.14+ and iOS 12.0+.
-        return sk_sp<MtlComputeCommandEncoder>(
-                new MtlComputeCommandEncoder(sharedContext, std::move(encoder)));
+        // Inserting a pool here so the autorelease occurs when we return and the
+        // only remaining ref is the retain below.
+        @autoreleasepool {
+            // Adding a retain here to keep our own ref separate from the autorelease pool
+            sk_cfp<id<MTLComputeCommandEncoder>> encoder =
+                    sk_ret_cfp([commandBuffer computeCommandEncoder]);
+
+            // TODO(armansito): Support concurrent dispatch of compute passes using
+            // MTLDispatchTypeConcurrent on macOS 10.14+ and iOS 12.0+.
+            return sk_sp<MtlComputeCommandEncoder>(
+                    new MtlComputeCommandEncoder(sharedContext, std::move(encoder)));
+        }
     }
 
     const char* getResourceType() const override { return "Metal Compute Command Encoder"; }

src/gpu/graphite/mtl/MtlRenderCommandEncoder.h

@@ -24,11 +24,15 @@ class MtlRenderCommandEncoder : public Resource {
     static sk_sp<MtlRenderCommandEncoder> Make(const SharedContext* sharedContext,
                                                id<MTLCommandBuffer> commandBuffer,
                                                MTLRenderPassDescriptor* descriptor) {
-        // Adding a retain here to keep our own ref separate from the autorelease pool
-        sk_cfp<id<MTLRenderCommandEncoder>> encoder =
-                 sk_ret_cfp([commandBuffer renderCommandEncoderWithDescriptor:descriptor]);
-        return sk_sp<MtlRenderCommandEncoder>(new MtlRenderCommandEncoder(sharedContext,
-                                                                          std::move(encoder)));
+        // Inserting a pool here so the autorelease occurs when we return and the
+        // only remaining ref is the retain below.
+        @autoreleasepool {
+            // Adding a retain here to keep our own ref separate from the autorelease pool
+            sk_cfp<id<MTLRenderCommandEncoder>> encoder =
+                    sk_ret_cfp([commandBuffer renderCommandEncoderWithDescriptor:descriptor]);
+            return sk_sp<MtlRenderCommandEncoder>(new MtlRenderCommandEncoder(sharedContext,
+                                                                              std::move(encoder)));
+        }
     }
 
     const char* getResourceType() const override { return "Metal Render Command Encoder"; }