SlateAccessibleMessageHandler.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#if WITH_ACCESSIBILITY
 
#include "GenericPlatform/Accessibility/GenericAccessibleInterfaces.h"
#include "Misc/Variant.h"
 
class FSlateAccessibleWidget;
class SWidget;
class SWindow;
 
// Used to radically increase the responsiveness of accessibility navigation for debugging pruposes. The implementation is too slow to be feasible for shipping builds. 
#define ACCESSIBILITY_DEBUG_RESPONSIVENESS 0 && !UE_BUILD_SHIPPING
 
class FSlateAccessibleMessageHandler : public FGenericAccessibleMessageHandler
{
public:
    SLATECORE_API FSlateAccessibleMessageHandler();
 
    // FGenericAccessibleMessageHandler
    SLATECORE_API virtual void OnActivate() override;
    SLATECORE_API virtual void OnDeactivate() override;
    SLATECORE_API virtual TSharedPtr<IAccessibleWidget> GetAccessibleWindow(const TSharedRef<FGenericWindow>& InWindow) const override;
    SLATECORE_API virtual AccessibleWidgetId GetAccessibleWindowId(const TSharedRef<FGenericWindow>& InWindow) const override;
    SLATECORE_API virtual TSharedPtr<IAccessibleWidget> GetAccessibleWidgetFromId(AccessibleWidgetId Id) const override;
    SLATECORE_API virtual void RunInThread(const TFunction<void()>& InFunction, bool bWaitForCompletion = true, ENamedThreads::Type InThread = ENamedThreads::GameThread) override;
    SLATECORE_API virtual void MakeAccessibleAnnouncement(const FString& AnnouncementString) override;
    //~
 
    SLATECORE_API void OnWidgetRemoved(SWidget* Widget);
 
    struct FSlateWidgetAccessibleEventArgs
    {
        FSlateWidgetAccessibleEventArgs(TSharedRef<SWidget> InWidget, EAccessibleEvent InEvent, FVariant InOldValue = FVariant(), FVariant InNewValue = FVariant(), FAccessibleUserIndex InSlateUserIndex = 0)
            : Widget(InWidget)
            , Event(InEvent)
            , OldValue(InOldValue)
            , NewValue(InNewValue)
            , SlateUserIndex(InSlateUserIndex)
        {}
            
        TSharedRef<SWidget> Widget;
        EAccessibleEvent Event;
        FVariant OldValue;
        FVariant NewValue;
        FAccessibleUserIndex SlateUserIndex;
    };
    SLATECORE_API void OnWidgetEventRaised(const FSlateWidgetAccessibleEventArgs& Args);
 
    void MarkDirty() { bDirty = true; }
 
    SLATECORE_API void ProcessAccessibleTasks();
 
    SLATECORE_API void Tick();
 
 
private:
    SLATECORE_API void HandleAccessibleWidgetFocusChangeEvent(const TSharedRef<IAccessibleWidget>& FocusWidget, bool bIsWidgetGainingFocus, FAccessibleUserIndex UserIndex);
    class FSlateAccessibleTask
    {
    public:
        FSlateAccessibleTask(const TFunction<void()>& InTask, FEvent* InCompletionEvent = nullptr)
            : Task(InTask)
            , CompletionEvent(InCompletionEvent)
        {
            check(Task);
        }
 
        void DoTask()
        {
            // We should always have a valid task 
            check(Task);
            Task();
            if (CompletionEvent)
            {
                CompletionEvent->Trigger();
            }
        }
    private:
        TFunction<void()> Task;
 
        FEvent* CompletionEvent;
    };
 
    SLATECORE_API void EnqueueAccessibleTask(const FSlateAccessibleTask& InAccessibleTask);
 
    struct FWidgetAndParent {
        FWidgetAndParent(TWeakPtr<SWidget> InWidget, TSharedRef<FSlateAccessibleWidget> InParent)
            : Widget(InWidget), Parent(InParent)
        {
        }
 
        TWeakPtr<SWidget> Widget;
        TSharedRef<FSlateAccessibleWidget> Parent;
    };
 
    TArray<FWidgetAndParent> ToProcess;
 
    TArray<FSlateAccessibleTask> AccessibleTaskStorageQueue;
    TArray<FSlateAccessibleTask> AccessibleTaskProcessingQueue;
 
    FCriticalSection QueueCriticalSection;
 
#if ACCESSIBILITY_DEBUG_RESPONSIVENESS
    FEvent* EnqueueEvent;
#endif
    bool bDirty;
};
 
#endif