Metal: add config to abandon frame if drawable cannot be acquired (#8397)

filament/backend/CMakeLists.txt

@@ -139,11 +139,11 @@ if (FILAMENT_SUPPORTS_METAL)
             src/metal/MetalEnums.mm
             src/metal/MetalExternalImage.mm
             src/metal/MetalHandles.mm
-            src/metal/MetalPlatform.mm
             src/metal/MetalShaderCompiler.mm
             src/metal/MetalState.mm
             src/metal/MetalTimerQuery.mm
             src/metal/MetalUtils.mm
+            src/metal/PlatformMetal.mm
     )
 
     set(METAL_CPP_SRCS

filament/backend/include/backend/platforms/PlatformMetal.h

@@ -14,8 +14,8 @@
  * limitations under the License.
  */
 
-#ifndef TNT_FILAMENT_BACKEND_PRIVATE_METALPLATFORM_H
-#define TNT_FILAMENT_BACKEND_PRIVATE_METALPLATFORM_H
+#ifndef TNT_FILAMENT_BACKEND_PRIVATE_PLATFORMMETAL_H
+#define TNT_FILAMENT_BACKEND_PRIVATE_PLATFORMMETAL_H
 
 #include <backend/DriverEnums.h>
 #include <backend/Platform.h>
@@ -24,9 +24,12 @@
 
 namespace filament::backend {
 
-class MetalPlatform final : public Platform {
+struct PlatformMetalImpl;
+
+class PlatformMetal final : public Platform {
 public:
-    ~MetalPlatform() override;
+    PlatformMetal();
+    ~PlatformMetal() noexcept override;
 
     Driver* createDriver(void* sharedContext, const Platform::DriverConfig& driverConfig) noexcept override;
     int getOSVersion() const noexcept override { return 0; }
@@ -54,11 +57,30 @@ public:
      */
     id<MTLCommandBuffer> createAndEnqueueCommandBuffer() noexcept;
 
-private:
-    id<MTLCommandQueue> mCommandQueue = nil;
+    /**
+     * The action to take if a Drawable cannot be acquired.
+     *
+     * Each frame rendered requires a CAMetalDrawable texture, which is presented on-screen at the
+     * completion of each frame. These are limited and provided round-robin style by the system.
+     */
+    enum class DrawableFailureBehavior : uint8_t {
+        /**
+         * Terminates the application and reports an error message (default).
+         */
+        PANIC,
+        /*
+         * Aborts execution of the current frame. The Metal backend will attempt to acquire a new
+         * drawable at the next frame.
+         */
+        ABORT_FRAME
+    };
+    void setDrawableFailureBehavior(DrawableFailureBehavior behavior) noexcept;
+    DrawableFailureBehavior getDrawableFailureBehavior() const noexcept;
 
+private:
+    PlatformMetalImpl* pImpl = nullptr;
 };
 
 } // namespace filament::backend
 
-#endif // TNT_FILAMENT_BACKEND_PRIVATE_METALPLATFORM_H
+#endif // TNT_FILAMENT_BACKEND_PRIVATE_PLATFORMMETAL_H

filament/backend/src/metal/MetalBuffer.h

@@ -18,9 +18,9 @@
 #define TNT_FILAMENT_DRIVER_METALBUFFER_H
 
 #include "MetalContext.h"
-#include "MetalPlatform.h"
 
 #include <backend/DriverEnums.h>
+#include <backend/platforms/PlatformMetal.h>
 
 #include <Metal/Metal.h>
 
@@ -54,12 +54,12 @@ public:
         }
     }
 
-    static void setPlatform(MetalPlatform* p) { platform = p; }
+    static void setPlatform(PlatformMetal* p) { platform = p; }
 
 private:
     typedef std::chrono::steady_clock clock_t;
 
-    static MetalPlatform* platform;
+    static PlatformMetal* platform;
 
     std::chrono::time_point<clock_t> mBeginning;
     const char* mName;
@@ -141,7 +141,7 @@ public:
         assert_invariant(type != Type::NONE);
         return aliveBuffers[toIndex(type)];
     }
-    static void setPlatform(MetalPlatform* p) { platform = p; }
+    static void setPlatform(PlatformMetal* p) { platform = p; }
 
 private:
     void swap(TrackedMetalBuffer& other) noexcept {
@@ -152,7 +152,7 @@ private:
     id<MTLBuffer> mBuffer;
     Type mType = Type::NONE;
 
-    static MetalPlatform* platform;
+    static PlatformMetal* platform;
     static std::array<uint64_t, TypeCount> aliveBuffers;
 };
 

filament/backend/src/metal/MetalBuffer.mm

@@ -23,8 +23,8 @@ namespace filament {
 namespace backend {
 
 std::array<uint64_t, TrackedMetalBuffer::TypeCount> TrackedMetalBuffer::aliveBuffers = { 0 };
-MetalPlatform* TrackedMetalBuffer::platform = nullptr;
-MetalPlatform* ScopedAllocationTimer::platform = nullptr;
+PlatformMetal* TrackedMetalBuffer::platform = nullptr;
+PlatformMetal* ScopedAllocationTimer::platform = nullptr;
 
 MetalBuffer::MetalBuffer(MetalContext& context, BufferObjectBinding bindingType, BufferUsage usage,
         size_t size, bool forceGpuBuffer)

filament/backend/src/metal/MetalContext.h

@@ -128,6 +128,7 @@ struct MetalContext {
     std::atomic<uint64_t> latestCompletedCommandBufferId = 0;
     id<MTLCommandBuffer> pendingCommandBuffer = nil;
     id<MTLRenderCommandEncoder> currentRenderPassEncoder = nil;
+    uint32_t currentFrame = 0;
 
     std::atomic<bool> memorylessLimitsReached = false;
 
@@ -156,6 +157,7 @@ struct MetalContext {
     RenderPassFlags currentRenderPassFlags;
     MetalRenderTarget* currentRenderTarget = nullptr;
     bool validPipelineBound = false;
+    bool currentRenderPassAbandoned = false;
 
     // State trackers.
     PipelineStateTracker pipelineState;

filament/backend/src/metal/MetalDriver.h

@@ -37,7 +37,7 @@
 namespace filament {
 namespace backend {
 
-class MetalPlatform;
+class PlatformMetal;
 
 class MetalBuffer;
 class MetalProgram;
@@ -51,19 +51,19 @@ struct BufferState;
 #endif
 
 class MetalDriver final : public DriverBase {
-    explicit MetalDriver(MetalPlatform* platform, const Platform::DriverConfig& driverConfig) noexcept;
+    explicit MetalDriver(PlatformMetal* platform, const Platform::DriverConfig& driverConfig) noexcept;
     ~MetalDriver() noexcept override;
     Dispatcher getDispatcher() const noexcept final;
 
 public:
-    static Driver* create(MetalPlatform* platform, const Platform::DriverConfig& driverConfig);
+    static Driver* create(PlatformMetal* platform, const Platform::DriverConfig& driverConfig);
 
 private:
 
     friend class MetalSwapChain;
     friend struct MetalDescriptorSet;
 
-    MetalPlatform& mPlatform;
+    PlatformMetal& mPlatform;
     MetalContext* mContext;
 
     ShaderModel getShaderModel() const noexcept final;

filament/backend/src/metal/MetalDriver.mm

@@ -30,7 +30,7 @@
 #include "MetalState.h"
 #include "MetalTimerQuery.h"
 
-#include "MetalPlatform.h"
+#include <backend/platforms/PlatformMetal.h>
 
 #include <CoreVideo/CVMetalTexture.h>
 #include <CoreVideo/CVPixelBuffer.h>
@@ -57,7 +57,7 @@
 namespace filament {
 namespace backend {
 
-Driver* MetalDriverFactory::create(MetalPlatform* const platform, const Platform::DriverConfig& driverConfig) {
+Driver* MetalDriverFactory::create(PlatformMetal* const platform, const Platform::DriverConfig& driverConfig) {
 #if 0
     // this is useful for development, but too verbose even for debug builds
     // For reference on a 64-bits machine in Release mode:
@@ -96,7 +96,7 @@ Driver* MetalDriverFactory::create(MetalPlatform* const platform, const Platform
 }
 
 UTILS_NOINLINE
-Driver* MetalDriver::create(MetalPlatform* const platform, const Platform::DriverConfig& driverConfig) {
+Driver* MetalDriver::create(PlatformMetal* const platform, const Platform::DriverConfig& driverConfig) {
     assert_invariant(platform);
     size_t defaultSize = FILAMENT_METAL_HANDLE_ARENA_SIZE_IN_MB * 1024U * 1024U;
     Platform::DriverConfig validConfig {driverConfig};
@@ -109,7 +109,7 @@ Dispatcher MetalDriver::getDispatcher() const noexcept {
 }
 
 MetalDriver::MetalDriver(
-        MetalPlatform* platform, const Platform::DriverConfig& driverConfig) noexcept
+        PlatformMetal* platform, const Platform::DriverConfig& driverConfig) noexcept
     : mPlatform(*platform),
       mContext(new MetalContext),
       mHandleAllocator(
@@ -246,6 +246,7 @@ void MetalDriver::tick(int) {
 
 void MetalDriver::beginFrame(int64_t monotonic_clock_ns,
         int64_t refreshIntervalNs, uint32_t frameId) {
+    mContext->currentFrame = frameId;
     DEBUG_LOG("beginFrame(monotonic_clock_ns = %lld, refreshIntervalNs = %lld, frameId = %d)\n",
             monotonic_clock_ns, refreshIntervalNs, frameId);
 #if defined(FILAMENT_METAL_PROFILING)
@@ -631,19 +632,19 @@ void MetalDriver::createFenceR(Handle<HwFence> fh, int dummy) {
 void MetalDriver::createSwapChainR(Handle<HwSwapChain> sch, void* nativeWindow, uint64_t flags) {
     if (UTILS_UNLIKELY(flags & SWAP_CHAIN_CONFIG_APPLE_CVPIXELBUFFER)) {
         CVPixelBufferRef pixelBuffer = (CVPixelBufferRef) nativeWindow;
-        construct_handle<MetalSwapChain>(sch, *mContext, pixelBuffer, flags);
+        construct_handle<MetalSwapChain>(sch, *mContext, mPlatform, pixelBuffer, flags);
         // This release matches the retain call in setupExternalImage. The MetalSwapchain will have
         // retained the buffer by now.
         CVPixelBufferRelease((CVPixelBufferRef)pixelBuffer);
     } else {
         auto* metalLayer = (__bridge CAMetalLayer*) nativeWindow;
-        construct_handle<MetalSwapChain>(sch, *mContext, metalLayer, flags);
+        construct_handle<MetalSwapChain>(sch, *mContext, mPlatform, metalLayer, flags);
     }
 }
 
 void MetalDriver::createSwapChainHeadlessR(Handle<HwSwapChain> sch,
         uint32_t width, uint32_t height, uint64_t flags) {
-    construct_handle<MetalSwapChain>(sch, *mContext, width, height, flags);
+    construct_handle<MetalSwapChain>(sch, *mContext, mPlatform, width, height, flags);
 }
 
 void MetalDriver::createTimerQueryR(Handle<HwTimerQuery> tqh, int) {
@@ -1272,6 +1273,13 @@ void MetalDriver::beginRenderPass(Handle<HwRenderTarget> rth,
     MTLRenderPassDescriptor* descriptor = [MTLRenderPassDescriptor renderPassDescriptor];
     renderTarget->setUpRenderPassAttachments(descriptor, params);
 
+    if (renderTarget->involvesAbandonedSwapChain()) {
+        mContext->currentRenderPassAbandoned = true;
+        return;
+    } else {
+        mContext->currentRenderPassAbandoned = false;
+    }
+
     mContext->currentRenderPassEncoder =
             [getPendingCommandBuffer(mContext) renderCommandEncoderWithDescriptor:descriptor];
     if (!mContext->groupMarkers.empty()) {
@@ -1333,6 +1341,10 @@ void MetalDriver::endRenderPass(int dummy) {
     os_signpost_interval_end(mContext->log, OS_SIGNPOST_ID_EXCLUSIVE, "Render pass");
 #endif
 
+    if (UTILS_UNLIKELY(mContext->currentRenderPassAbandoned)) {
+        return;
+    }
+
     [mContext->currentRenderPassEncoder endEncoding];
 
     // Command encoders are one time use. Set it to nil to release the encoder and ensure we don't
@@ -1633,6 +1645,11 @@ void MetalDriver::blitDEPRECATED(TargetBufferFlags buffers,
     auto srcTarget = handle_cast<MetalRenderTarget>(src);
     auto dstTarget = handle_cast<MetalRenderTarget>(dst);
 
+    if (UTILS_UNLIKELY(srcTarget->involvesAbandonedSwapChain() ||
+                dstTarget->involvesAbandonedSwapChain())) {
+        return;
+    }
+
     FILAMENT_CHECK_PRECONDITION(buffers == TargetBufferFlags::COLOR0)
             << "blitDEPRECATED only supports COLOR0";
 
@@ -1917,6 +1934,10 @@ void MetalDriver::bindDescriptorSet(
 }
 
 void MetalDriver::draw2(uint32_t indexOffset, uint32_t indexCount, uint32_t instanceCount) {
+    if (UTILS_UNLIKELY(mContext->currentRenderPassAbandoned)) {
+        return;
+    }
+
     FILAMENT_CHECK_PRECONDITION(mContext->currentRenderPassEncoder != nullptr)
             << "draw() without a valid command encoder.";
     DEBUG_LOG("draw2(...)\n");
@@ -1960,6 +1981,9 @@ void MetalDriver::draw2(uint32_t indexOffset, uint32_t indexCount, uint32_t inst
 
 void MetalDriver::draw(PipelineState ps, Handle<HwRenderPrimitive> rph,
         uint32_t const indexOffset, uint32_t const indexCount, uint32_t const instanceCount) {
+    if (UTILS_UNLIKELY(mContext->currentRenderPassAbandoned)) {
+        return;
+    }
     MetalRenderPrimitive const* const rp = handle_cast<MetalRenderPrimitive>(rph);
     ps.primitiveType = rp->type;
     ps.vertexBufferInfo = rp->vertexBuffer->vbih;

filament/backend/src/metal/MetalDriverFactory.h

@@ -21,12 +21,12 @@
 
 namespace filament {
 namespace backend {
-class MetalPlatform;
+class PlatformMetal;
 class Driver;
 
 class MetalDriverFactory {
 public:
-    static Driver* create(MetalPlatform* platform, const Platform::DriverConfig& driverConfig);
+    static Driver* create(PlatformMetal* platform, const Platform::DriverConfig& driverConfig);
 };
 
 } // namespace backend

filament/backend/src/metal/MetalHandles.h

@@ -30,6 +30,7 @@
 #include "MetalState.h" // for MetalState::VertexDescription
 
 #include <backend/DriverEnums.h>
+#include <backend/platforms/PlatformMetal.h>
 
 #include <utils/bitset.h>
 #include <utils/CString.h>
@@ -51,13 +52,16 @@ class MetalSwapChain : public HwSwapChain {
 public:
 
     // Instantiate a SwapChain from a CAMetalLayer
-    MetalSwapChain(MetalContext& context, CAMetalLayer* nativeWindow, uint64_t flags);
+    MetalSwapChain(MetalContext& context, PlatformMetal& platform, CAMetalLayer* nativeWindow,
+            uint64_t flags);
 
     // Instantiate a SwapChain from a CVPixelBuffer
-    MetalSwapChain(MetalContext& context, CVPixelBufferRef pixelBuffer, uint64_t flags);
+    MetalSwapChain(MetalContext& context, PlatformMetal& platform, CVPixelBufferRef pixelBuffer,
+            uint64_t flags);
 
     // Instantiate a headless SwapChain.
-    MetalSwapChain(MetalContext& context, int32_t width, int32_t height, uint64_t flags);
+    MetalSwapChain(MetalContext& context, PlatformMetal& platform, int32_t width, int32_t height,
+            uint64_t flags);
 
     ~MetalSwapChain();
 
@@ -86,6 +90,8 @@ public:
 
     bool isPixelBuffer() const { return type == SwapChainType::CVPIXELBUFFERREF; }
 
+    bool isAbandoned() const;
+
 private:
 
     enum class SwapChainType {
@@ -103,6 +109,7 @@ private:
     void ensureDepthStencilTexture();
 
     MetalContext& context;
+    PlatformMetal& platform;
     id<CAMetalDrawable> drawable = nil;
     id<MTLTexture> depthStencilTexture = nil;
     id<MTLTexture> headlessDrawable = nil;
@@ -114,6 +121,8 @@ private:
     MetalExternalImage externalImage;
     SwapChainType type;
 
+    int64_t abandonedUntilFrame = -1;
+
     // These fields store a callback to notify the client that a frame is ready for presentation. If
     // !frameScheduled.callback, then the Metal backend automatically calls presentDrawable when the
     // frame is committed. Otherwise, the Metal backend will not automatically present the frame.
@@ -341,6 +350,8 @@ public:
 
     void setUpRenderPassAttachments(MTLRenderPassDescriptor* descriptor, const RenderPassParams& params);
 
+    bool involvesAbandonedSwapChain() const noexcept;
+
     MTLViewport getViewportFromClientViewport(
             Viewport rect, float depthRangeNear, float depthRangeFar) {
         const int32_t height = int32_t(getAttachmentSize().y);

filament/backend/src/metal/MetalHandles.mm

@@ -69,8 +69,10 @@ static inline MTLTextureUsage getMetalTextureUsage(TextureUsage usage) {
     return MTLTextureUsage(u);
 }
 
-MetalSwapChain::MetalSwapChain(MetalContext& context, CAMetalLayer* nativeWindow, uint64_t flags)
+MetalSwapChain::MetalSwapChain(
+        MetalContext& context, PlatformMetal& platform, CAMetalLayer* nativeWindow, uint64_t flags)
     : context(context),
+      platform(platform),
       depthStencilFormat(decideDepthStencilFormat(flags)),
       layer(nativeWindow),
       layerDrawableMutex(std::make_shared<std::mutex>()),
@@ -94,15 +96,19 @@ MetalSwapChain::MetalSwapChain(MetalContext& context, CAMetalLayer* nativeWindow
     layer.device = context.device;
 }
 
-MetalSwapChain::MetalSwapChain(MetalContext& context, int32_t width, int32_t height, uint64_t flags)
+MetalSwapChain::MetalSwapChain(MetalContext& context, PlatformMetal& platform, int32_t width,
+        int32_t height, uint64_t flags)
     : context(context),
+      platform(platform),
       depthStencilFormat(decideDepthStencilFormat(flags)),
       headlessWidth(width),
       headlessHeight(height),
       type(SwapChainType::HEADLESS) {}
 
-MetalSwapChain::MetalSwapChain(MetalContext& context, CVPixelBufferRef pixelBuffer, uint64_t flags)
+MetalSwapChain::MetalSwapChain(MetalContext& context, PlatformMetal& platform,
+        CVPixelBufferRef pixelBuffer, uint64_t flags)
     : context(context),
+      platform(platform),
       depthStencilFormat(decideDepthStencilFormat(flags)),
       externalImage(MetalExternalImage::createFromImage(context, pixelBuffer)),
       type(SwapChainType::CVPIXELBUFFERREF) {
@@ -140,6 +146,10 @@ NSUInteger MetalSwapChain::getSurfaceHeight() const {
     return (NSUInteger) layer.drawableSize.height;
 }
 
+bool MetalSwapChain::isAbandoned() const {
+    return context.currentFrame < abandonedUntilFrame;
+}
+
 id<MTLTexture> MetalSwapChain::acquireDrawable() {
     if (drawable) {
         return drawable.texture;
@@ -180,7 +190,18 @@ id<MTLTexture> MetalSwapChain::acquireDrawable() {
         drawable = [layer nextDrawable];
     }
 
-    FILAMENT_CHECK_POSTCONDITION(drawable != nil) << "Could not obtain drawable.";
+    if (UTILS_UNLIKELY(drawable == nil)) {
+        switch (platform.getDrawableFailureBehavior()) {
+            case PlatformMetal::DrawableFailureBehavior::PANIC:
+                FILAMENT_CHECK_POSTCONDITION(drawable != nil) << "Could not obtain drawable.";
+                break;
+
+            case PlatformMetal::DrawableFailureBehavior::ABORT_FRAME:
+                abandonedUntilFrame = context.currentFrame + 1;
+                return nil;
+        }
+    }
+
     return drawable.texture;
 }
 
@@ -1117,12 +1138,20 @@ void MetalRenderTarget::setUpRenderPassAttachments(MTLRenderPassDescriptor* desc
     }
 }
 
+bool MetalRenderTarget::involvesAbandonedSwapChain() const noexcept {
+    const auto* draw = context->currentDrawSwapChain;
+    const auto* read = context->currentReadSwapChain;
+    return (draw && draw->isAbandoned()) || (read && read->isAbandoned());
+}
+
 MetalRenderTarget::Attachment MetalRenderTarget::getDrawColorAttachment(size_t index) {
     assert_invariant(index < MRT::MAX_SUPPORTED_RENDER_TARGET_COUNT);
     Attachment result = color[index];
     if (index == 0 && defaultRenderTarget) {
         assert_invariant(context->currentDrawSwapChain);
         result.texture = context->currentDrawSwapChain->acquireDrawable();
+        // acquireDrawable may fail to acquire the drawable, in which case result.texture will be
+        // nil, and an invalid attachment
     }
     return result;
 }
@@ -1133,6 +1162,8 @@ MetalRenderTarget::Attachment MetalRenderTarget::getReadColorAttachment(size_t i
     if (index == 0 && defaultRenderTarget) {
         assert_invariant(context->currentReadSwapChain);
         result.texture = context->currentReadSwapChain->acquireDrawable();
+        // acquireDrawable may fail to acquire the drawable, in which case result.texture will be
+        // nil, and an invalid attachment
     }
     return result;
 }

filament/backend/src/metal/PlatformMetal.mm

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include "MetalPlatform.h"
+#include <backend/platforms/PlatformMetal.h>
 
 #include "MetalDriverFactory.h"
 
@@ -22,19 +22,32 @@
 
 #import <Foundation/Foundation.h>
 
+#include <atomic>
+
 namespace filament::backend {
 
+struct PlatformMetalImpl {
+    id<MTLCommandQueue> mCommandQueue = nil;
+    // read form driver thread, read/written to from client thread
+    std::atomic<PlatformMetal::DrawableFailureBehavior> mDrawableFailureBehavior =
+            PlatformMetal::DrawableFailureBehavior::PANIC;
+};
+
 Platform* createDefaultMetalPlatform() {
-    return new MetalPlatform();
+    return new PlatformMetal();
 }
 
-MetalPlatform::~MetalPlatform() = default;
+PlatformMetal::PlatformMetal() : pImpl(new PlatformMetalImpl) {}
 
-Driver* MetalPlatform::createDriver(void* /*sharedContext*/, const Platform::DriverConfig& driverConfig) noexcept {
+PlatformMetal::~PlatformMetal() noexcept {
+    delete pImpl;
+}
+
+Driver* PlatformMetal::createDriver(void* /*sharedContext*/, const Platform::DriverConfig& driverConfig) noexcept {
     return MetalDriverFactory::create(this, driverConfig);
 }
 
-id<MTLDevice> MetalPlatform::createDevice() noexcept {
+id<MTLDevice> PlatformMetal::createDevice() noexcept {
     id<MTLDevice> result;
 
 #if !defined(FILAMENT_IOS)
@@ -62,16 +75,24 @@ id<MTLDevice> MetalPlatform::createDevice() noexcept {
     return result;
 }
 
-id<MTLCommandQueue> MetalPlatform::createCommandQueue(id<MTLDevice> device) noexcept {
-    mCommandQueue = [device newCommandQueue];
-    mCommandQueue.label = @"Filament";
-    return mCommandQueue;
+id<MTLCommandQueue> PlatformMetal::createCommandQueue(id<MTLDevice> device) noexcept {
+    pImpl->mCommandQueue = [device newCommandQueue];
+    pImpl->mCommandQueue.label = @"Filament";
+    return pImpl->mCommandQueue;
 }
 
-id<MTLCommandBuffer> MetalPlatform::createAndEnqueueCommandBuffer() noexcept {
-    id<MTLCommandBuffer> commandBuffer = [mCommandQueue commandBuffer];
+id<MTLCommandBuffer> PlatformMetal::createAndEnqueueCommandBuffer() noexcept {
+    id<MTLCommandBuffer> commandBuffer = [pImpl->mCommandQueue commandBuffer];
     [commandBuffer enqueue];
     return commandBuffer;
 }
 
+void PlatformMetal::setDrawableFailureBehavior(DrawableFailureBehavior behavior) noexcept {
+    pImpl->mDrawableFailureBehavior = behavior;
+}
+
+PlatformMetal::DrawableFailureBehavior PlatformMetal::getDrawableFailureBehavior() const noexcept {
+    return pImpl->mDrawableFailureBehavior;
+}
+
 } // namespace filament