AnimationCurveDrawer.cs

using UnityEditor;
using UnityEngine;

[CustomPropertyDrawer( typeof( AnimationCurve ) )]
public sealed class AnimationCurveDrawer : PropertyDrawer
{
    private static AnimationCurve m_copiedCurve;

    public override void OnGUI( Rect position, SerializedProperty property, GUIContent label )
    {
        var curveFieldPos = position;
        curveFieldPos.width -= 18;

        label = EditorGUI.BeginProperty( position, label, property );
        EditorGUI.CurveField( curveFieldPos, property, Color.green, Rect.zero );

        var menuPos = position;
        menuPos.xMin = menuPos.xMax - 13;

        if ( GUI.Button( menuPos, GUIContent.none, "ShurikenDropdown" ) )
        {
            var content1 = new GUIContent( "Copy" );
            var content2 = new GUIContent( "Paste" );

            var genericMenu = new GenericMenu();
            genericMenu.AddItem( content1, false, OnCopy, property );
            genericMenu.AddItem( content2, false, OnPaste, property );

            if ( m_copiedCurve == null )
            {
                genericMenu.AddDisabledItem( content2 );
            }
            genericMenu.DropDown( menuPos );
        }

        EditorGUI.EndProperty();
    }

    private static void OnCopy( object data )
    {
        var property = data as SerializedProperty;
        m_copiedCurve = property.animationCurveValue;
    }

    private static void OnPaste( object data )
    {
        if ( m_copiedCurve == null ) return;

        var property = data as SerializedProperty;
        property.serializedObject.Update();
        property.animationCurveValue = m_copiedCurve;
        property.serializedObject.ApplyModifiedProperties();
    }
}