EM_Task/UnrealEd/Public/MouseDeltaTracker.h

// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include "CoreMinimal.h"
#include "InputCoreTypes.h"
#include "UnrealWidget.h"

class FCanvas;
class FDragTool;
class FEditorViewportClient;
class FPrimitiveDrawInterface;
class FSceneView;
struct FInputEventState;

/**
 * Keeps track of mouse movement deltas in the viewports.
 */
class UNREALED_API FMouseDeltaTracker
{
public:
    FMouseDeltaTracker();
    ~FMouseDeltaTracker();

    /**
     * Begin tracking at the specified location for the specified viewport.
     */
    void StartTracking(FEditorViewportClient* InViewportClient, const int32 InX, const int32 InY, const FInputEventState& InInputState, bool bNudge = false, bool bResetDragToolState = true);

    /**
     * Called when a mouse button has been released.  If there are no other
     * mouse buttons being held down, the internal information is reset.
     */
    bool EndTracking(FEditorViewportClient* InViewportClient);

    /**
     * Adds delta movement into the tracker.
     */
    void AddDelta(FEditorViewportClient* InViewportClient, FKey InKey, const int32 InDelta, bool InNudge);

    /**
     * Returns the current delta.
     */
    const FVector GetDelta() const;

    /**
     * Returns the current snapped delta.
     */
    const FVector GetDeltaSnapped() const;

    /**
     * Returns the absolute delta since dragging started.
     */
    const FVector GetAbsoluteDelta() const;

    /**
     * Returns the absolute snapped delta since dragging started.
     */
    const FVector GetAbsoluteDeltaSnapped() const;

    /**
     * Returns the screen space delta since dragging started.
     */
    const FVector GetScreenDelta() const;

    /**
     * Returns the raw mouse delta in pixels since dragging started.
     */
    const FVector GetRawDelta() const;

    /**
     * Returns the unsnapped start position of the current mouse drag. (This will be zero if there is no drag in progress)
     */
    const FVector GetDragStartPos() const;

    /**
     * Returns if the user used a modifier to drag a selected item. (Rather than using a widget handle)
     */
    const bool GetUsedDragModifier() const;

    /**
     * Resets the UsedDragModifier flag
     */
    void ResetUsedDragModifier();

    /**
     * Converts the delta movement to drag/rotation/scale based on the viewport type or widget axis.
     */
    void ConvertMovementDeltaToDragRot(FSceneView* InView, FEditorViewportClient* InViewportClient, FVector& InDragDelta, FVector& OutDrag, FRotator& OutRotation, FVector& OutScale) const;
    /**
     * Absolute Translation conversion from mouse position on the screen to widget axis movement/rotation.
     */
    void AbsoluteTranslationConvertMouseToDragRot(FSceneView* InView, FEditorViewportClient* InViewportClient, FVector& OutDrag, FRotator& OutRotation, FVector& OutScale) const;

    /**
     * Subtracts the specified value from End and EndSnapped.
     */
    void ReduceBy(const FVector& In);

    /**
     * @return		true if a drag tool is being used by the tracker, false otherwise.
     */
    bool UsingDragTool() const;

    /**
     * @return True if any mouse movement has happened since tracking started
     */
    bool HasReceivedDelta() const { return bHasReceivedAddDelta; }

    /**
     * Marks that something caused the equivalent of mouse dragging, but with other means (keyboard short cut, mouse wheel).  Allows suppression of context menus with flight camera, etc
     */
    void SetExternalMovement(void) { bExternalMovement = true; };
    /**
     * @return		true if something caused external movement of the mouse (keyboard, mouse wheel)
     */
    bool WasExternalMovement(void) const { return bExternalMovement; }

    /**
     * Renders the drag tool.  Does nothing if no drag tool exists.
     */
    void Render3DDragTool(const FSceneView* View, FPrimitiveDrawInterface* PDI);

    /**
     * Renders the drag tool.  Does nothing if no drag tool exists.
     */
    void RenderDragTool(const FSceneView* View, FCanvas* Canvas);

    /**
     * @return 		the widget mode last time this tracker object started tracking
     */
    FWidget::EWidgetMode GetTrackingWidgetMode() const { return TrackingWidgetMode; }

private:
    /**
     * Starts using a drag tool if needed
     */
    void ConditionalBeginUsingDragTool(FEditorViewportClient* InViewportClient);

private:
    /** The unsnapped start position of the current mouse drag. */
    FVector Start;
    /** The snapped start position of the current mouse drag. */
    FVector StartSnapped;
    /** The screen space start position of the current mouse drag (may be scaled or rotated according to the ortho zoom or view). */
    FVector StartScreen;
    /** The unsnapped end position of the current mouse drag. */
    FVector End;
    /** The snapped end position of the current mouse drag. */
    FVector EndSnapped;
    /** The screen space end position of the current mouse drag (may be scaled or rotated according to the ortho zoom or view). */
    FVector EndScreen;
    /** The raw unscaled mouse delta in pixels */
    FVector RawDelta;

    /** The amount that the End vectors have been reduced by since dragging started, this is added to the deltas to get an absolute delta. */
    FVector ReductionAmount;

    /**
     * If there is a dragging tool being used, this will point to it.
     * Gets newed/deleted in StartTracking/EndTracking.
     */
    TSharedPtr<FDragTool> DragTool;

    /** Keeps track of whether AddDelta has been called since StartTracking. */
    bool bHasReceivedAddDelta;

    /** True if we attempted to use a drag tool since StartTracking was called */
    bool bHasAttemptedDragTool;

    /** Tracks whether keyboard/mouse wheel/etc have caused simulated mouse movement.  Reset on StartTracking */
    bool bExternalMovement;

    /** Tracks if the user used a modifier to drag a selected item. (Rather than using a widget handle).Reset on StartTracking */
    bool bUsedDragModifier;

    /** Tracks whether the drag tool is in the process of being deleted (to protect against reentrancy) */
    bool bIsDeletingDragTool;

    /** Stores the widget mode active when the tracker begins tracking to help stop it change mid-track */
    FWidget::EWidgetMode TrackingWidgetMode;

    /**
     * Sets the current axis of the widget for the specified viewport.
     *
     * @param	InViewportClient		The viewport whose widget axis is to be set.
     */
    void DetermineCurrentAxis(FEditorViewportClient* InViewportClient);
};

static const float MOUSE_CLICK_DRAG_DELTA = 4.0f * 4.0f;