FrameGrabber.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "HAL/ThreadSafeCounter.h"
#include "HAL/ThreadSafeBool.h"
#include "Slate/SceneViewport.h"
 
class SWindow;
 
struct FViewportSurfaceReader
{
    MOVIESCENECAPTURE_API FViewportSurfaceReader(EPixelFormat InPixelFormat, FIntPoint InBufferSize);
 
    MOVIESCENECAPTURE_API ~FViewportSurfaceReader();
 
    MOVIESCENECAPTURE_API void Initialize();
 
    MOVIESCENECAPTURE_API void BlockUntilAvailable();
 
    MOVIESCENECAPTURE_API void Reset();
 
    MOVIESCENECAPTURE_API void ResolveRenderTarget(FViewportSurfaceReader* RenderToReadback, const FTextureRHIRef& BackBuffer, TFunction<void(FColor*, int32, int32)> Callback);
 
    MOVIESCENECAPTURE_API FIntPoint GetCurrentSize() const;
 
    void SetCaptureRect(FIntRect InCaptureRect) { CaptureRect = InCaptureRect; }
 
    void SetWindowSize(FIntPoint InWindowSize) { WindowSize = InWindowSize; }
 
    bool WasEverQueued() const { return bQueuedForCapture; } 
 
protected:
 
    MOVIESCENECAPTURE_API void Resize(uint32 Width, uint32 Height);
 
    FThreadSafeBool bEnabled;
 
    FEvent* AvailableEvent;
 
    FTextureRHIRef ReadbackTexture;
 
    FIntRect CaptureRect;
 
    FIntPoint WindowSize;
 
    EPixelFormat PixelFormat;
 
    bool bIsEnabled;
 
    bool bQueuedForCapture;
};
 
struct IFramePayload
{
    virtual ~IFramePayload() {}
 
    virtual bool OnFrameReady_RenderThread(FColor* ColorBuffer, FIntPoint BufferSize, FIntPoint TargetSize) const { return true; }
};
 
typedef TSharedPtr<IFramePayload, ESPMode::ThreadSafe> FFramePayloadPtr;
 
struct FCapturedFrameData
{
    FCapturedFrameData(FIntPoint InBufferSize, FFramePayloadPtr InPayload) : BufferSize(InBufferSize), Payload(MoveTemp(InPayload)) {}
 
    FCapturedFrameData(FCapturedFrameData&& In) : ColorBuffer(MoveTemp(In.ColorBuffer)), BufferSize(In.BufferSize), Payload(MoveTemp(In.Payload)) {}
    FCapturedFrameData& operator=(FCapturedFrameData&& In){ ColorBuffer = MoveTemp(In.ColorBuffer); BufferSize = In.BufferSize; Payload = MoveTemp(In.Payload); return *this; }
 
    template<typename T>
    T* GetPayload() { return static_cast<T*>(Payload.Get()); }
 
    TArray<FColor> ColorBuffer;
 
    FIntPoint BufferSize;
 
    FFramePayloadPtr Payload;
    
private:
    FCapturedFrameData(const FCapturedFrameData& In);
    FCapturedFrameData& operator=(const FCapturedFrameData& In);
};
 
class FFrameGrabber
{
public:
    MOVIESCENECAPTURE_API FFrameGrabber(TSharedRef<FSceneViewport> Viewport, FIntPoint DesiredBufferSize, EPixelFormat InPixelFormat = PF_B8G8R8A8, uint32 NumSurfaces = 3);
 
    MOVIESCENECAPTURE_API ~FFrameGrabber();
 
public:
 
    MOVIESCENECAPTURE_API void StartCapturingFrames();
 
    MOVIESCENECAPTURE_API bool IsCapturingFrames() const;
 
    MOVIESCENECAPTURE_API void CaptureThisFrame(FFramePayloadPtr Payload);
 
    MOVIESCENECAPTURE_API void StopCapturingFrames();
 
    MOVIESCENECAPTURE_API void Shutdown();
 
public:
 
    MOVIESCENECAPTURE_API bool HasOutstandingFrames() const;
 
    MOVIESCENECAPTURE_API TArray<FCapturedFrameData> GetCapturedFrames();
 
protected:
    
    MOVIESCENECAPTURE_API void OnBackBufferReadyToPresentCallback(SWindow& SlateWindow, const FTextureRHIRef& BackBuffer);
 
    MOVIESCENECAPTURE_API void OnFrameReady(int32 SurfaceIndex, FColor* ColorBuffer, int32 Width, int32 Height);
 
private:
 
    FFrameGrabber(const FFrameGrabber&);
    FFrameGrabber& operator=(const FFrameGrabber&);
 
    void* TargetWindowPtr;
 
    FDelegateHandle OnBackBufferReadyToPresent;
 
    TArray<FCapturedFrameData> CapturedFrames;
 
    mutable FCriticalSection CapturedFramesMutex;
 
    struct FResolveSurface
    {
        FResolveSurface(EPixelFormat InPixelFormat, FIntPoint BufferSize) : Surface(InPixelFormat, BufferSize) {}
 
        FFramePayloadPtr Payload;
        FViewportSurfaceReader Surface;
    };
    TArray<FResolveSurface> Surfaces;
 
    int32 CurrentFrameIndex;
 
    int32 SlateRenderIndex;
 
    FThreadSafeCounter OutstandingFrameCount;
 
    TArray<FFramePayloadPtr> RenderThread_PendingFramePayloads;
 
    int32 FrameGrabLatency;
 
    enum class EFrameGrabberState
    {
        Inactive, Active, PendingShutdown
    };
    EFrameGrabberState State;
 
    FIntPoint TargetSize;
};