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(* some parts (AdjustBalance...) of this unit are based on the AVLTree unit *)
(* TODO: Implement node.eof / node.bof *)
unit SynEditFoldedView;

{$mode objfpc}{$H+}
{$coperators on}
{$IFDEF CPUPOWERPC} {$INLINE OFF} {$ENDIF} (* Workaround for bug 12576 (fpc) see bugs.freepascal.org/view.php?id=12576 *)

{$IFOPT C+}
  {$DEFINE SynAssertFold}
{$ENDIF}
{$IFDEF SynAssert}
  {$DEFINE SynAssertFold}
{$ENDIF}

{$IFDEF SynFoldDebug}
  {$DEFINE SynDebug}
  {$DEFINE SynFoldSaveDebug}
{$ENDIF}
{$IFDEF SynFoldSaveDebug}
  {$DEFINE SynDebug}
{$ENDIF}

interface

uses
  LCLProc, LazLoggerBase, LazClasses, Graphics,
  Classes, SysUtils, LazSynEditText, SynEditTypes, SynEditMiscClasses,
  SynEditMiscProcs, SynEditPointClasses,
  SynEditHighlighter, SynEditHighlighterFoldBase;

type

  TFoldNodeClassification = (fncInvalid, fncHighlighter, fncHighlighterEx, fncBlockSelection);
  TFoldNodeClassifications = set of TFoldNodeClassification;

  { TSynTextFoldAVLNodeData }

  TSynTextFoldAVLNodeData = class(TSynSizedDifferentialAVLNode)
  protected
    function Left: TSynTextFoldAVLNodeData;
    function Parent: TSynTextFoldAVLNodeData;
    function Right: TSynTextFoldAVLNodeData;
    procedure FreeAllChildrenAndNested;
  public    (* Position / Size *)
    (* FullCount:  Amount of lines in source for this fold only
                   (excluding overlaps) *)
    FullCount : Integer;
    (* LineOffset: Line-Number Offset to parent node
                   All line numbers are stored as offsets,
                   for faster updates if lines are inserted/deleted *)
    property LineOffset: Integer read FPositionOffset write FPositionOffset;
    (* LeftCount:  Lines folded in left tree.
                   Used to calculate how many lines are folded up to a specified line *)
    property LeftCount: Integer read FLeftSizeSum write FLeftSizeSum;
    (* MergedLineCount: Amount of lines folded away by this fold,
                        FullCount + Lines covered by overlaps *)
    property MergedLineCount: Integer read FSize write FSize;
  public
    (* Sub-Tree  *)
    Nested : TSynTextFoldAVLNodeData; (* Nested folds (folds within this fold) do not need to be part of the searchable tree
                             They will be restored, if the outer fold (this fold) is unfolded
                             Nested points to a standalone tree, the root node in the nested tree, does *not* point back to this node *)


    (* Source Info *)
    FoldIndex: Integer;    (* Index of fold in line; if a line has more than one fold starting *)
    FoldColumn, FoldColumnLen: Integer; (* The column (1-based) and len of the keywordm which starts this fold *)
    FoldTypeCompatible: Pointer; (* help identifying in FixFolding *)
    Classification: TFoldNodeClassification;
    VisibleLines: Integer; (* Visible Source lines, containing the "fold keyword"
                              0: Hiden block (the fold-keyword is inside the fold)
                              1: Normal fold (There is *1* visible line with the fold-keyword)
                            *)


    function RecursiveFoldCount : Integer; (* Amount of lines covered by this and all child nodes *)
    function Precessor : TSynTextFoldAVLNodeData; reintroduce;
    function Successor : TSynTextFoldAVLNodeData; reintroduce;
    function Precessor(var aStartPosition, aSizesBeforeSum : Integer) : TSynTextFoldAVLNodeData; reintroduce;
    function Successor(var aStartPosition, aSizesBeforeSum : Integer) : TSynTextFoldAVLNodeData; reintroduce;
  end;

  { TSynTextFoldAVLNode }

  TSynTextFoldAVLNode = object
  private
    function GetClassification: TFoldNodeClassification;
    function GetFoldColumn: Integer;
    function GetFoldColumnLen: Integer;
    function GetFoldIndex: Integer;
    function GetMergedLineCount : Integer;
    function GetFullCount : Integer;
    function GetSourceLine: integer;
    function GetSourceLineOffset: integer;
    procedure SetFoldColumn(const AValue: Integer);
  protected
    fData : TSynTextFoldAVLNodeData; // nil if unfolded
    fStartLine : Integer;            // start of folded
    fFoldedBefore : Integer;
  public
    procedure Init(aData : TSynTextFoldAVLNodeData; aStartLine, aFoldedBefore: Integer);
    function IsInFold : Boolean;
    function Next : TSynTextFoldAVLNode;
    function Prev : TSynTextFoldAVLNode;

    property MergedLineCount: Integer read GetMergedLineCount; // Zero, if Not in a fold
    property FullCount: Integer read GetFullCount; // Zero, if Not in a fold
    property StartLine: Integer read fStartLine;   // 1st Line of Current Fold
    property FoldedBefore: Integer read fFoldedBefore;  // Count of Lines folded before Startline

    function IsHide: Boolean;
    property FoldIndex: Integer read GetFoldIndex;
    property FoldColumn: Integer read GetFoldColumn write SetFoldColumn;
    property FoldColumnLen: Integer read GetFoldColumnLen;
    property SourceLine: integer read GetSourceLine;    // The SourceLine with the fold-keyword
    property SourceLineOffset: integer read GetSourceLineOffset;    // The SourceLine with the fold-keyword
    property Classification: TFoldNodeClassification read GetClassification;
  end;

  { TSynTextFoldAVLNodeNestedIterator:
    Iterates included nested nodes
    FoldedBefore is not valid in nested nodes
  }

  TSynTextFoldAVLNodeNestedIterator = class
  private
    FCurrentNode: TSynTextFoldAVLNode;
    FOuterNodes: Array of TSynTextFoldAVLNode;
  public
    constructor Create(ANode: TSynTextFoldAVLNode);
    destructor Destroy; override;
    function Next: TSynTextFoldAVLNode;
    function Prev: TSynTextFoldAVLNode;
    function EOF: Boolean;
    function BOF: Boolean;
    function IsInFold: Boolean;
    property Node: TSynTextFoldAVLNode read FCurrentNode;
  end;

  { TSynTextFoldAVLTree
    - Nodes in the tree cover the folded lines only.
      The (visible) cfCollapsed line at the start of a fold, is *not* part of a node.
    - In the public methods "ALine" indicates the first invisible/hidden line
    - TSynEditFoldedView uses this with 1-based lines (ToDo: make 0-based)
  }

  TSynTextFoldAVLTree = class(TSynSizedDifferentialAVLTree)
  protected
    fNestParent: TSynTextFoldAVLNodeData;
    fNestedNodesTree: TSynTextFoldAVLTree; // FlyWeight Tree used for any nested subtree.

    function NewNode : TSynTextFoldAVLNodeData; inline;
    Function RemoveFoldForNodeAtLine(ANode: TSynTextFoldAVLNode;
                                     ALine : Integer) : Integer; overload; // Line is for Nested Nodes

    // SetRoot, does not obbey fRootOffset => use SetRoot(node, -fRootOffset)
    procedure SetRoot(ANode : TSynSizedDifferentialAVLNode); overload; override;
    procedure SetRoot(ANode : TSynSizedDifferentialAVLNode; anAdjustChildLineOffset : Integer); overload; override;

    Function  InsertNode(ANode : TSynTextFoldAVLNodeData) : Integer; reintroduce; // returns FoldedBefore // ANode may not have children
    function TreeForNestedNode(ANode: TSynTextFoldAVLNodeData; aOffset : Integer) : TSynTextFoldAVLTree;
  public
    constructor Create;
    destructor Destroy; override;
    procedure Clear; override;

    (* Find Fold by Line in Real Text *)
    Function FindFoldForLine(ALine : Integer; FindNextNode : Boolean = False) : TSynTextFoldAVLNode;
    (* Find Fold by Line in Folded Text // always returns unfolded, unless next=true *)
    Function FindFoldForFoldedLine(ALine : Integer; FindNextNode: Boolean = False) : TSynTextFoldAVLNode;
    Function InsertNewFold(ALine, AFoldIndex, AColumn, AColumnLen, ACount, AVisibleLines: Integer;
                           AClassification: TFoldNodeClassification;
                           AFoldTypeCompatible: Pointer
                          ) : TSynTextFoldAVLNode;
    (* This will unfold the block which either contains tALine, or has Aline as its cgColapsed line
       If IgnoreFirst, the cfCollapsed will *not* unfold => Hint: IgnoreFirst = Make folded visible
       Returns the pos(1-based) of the cfCollapsed Line that was expanded; or ALine, if nothing was done
    *)
    Function RemoveFoldForLine(ALine : Integer; OnlyCol: Integer = -1) : Integer; overload;
    Procedure AdjustForLinesInserted(AStartLine, ALineCount, ABytePos: Integer);
    Procedure AdjustForLinesDeleted(AStartLine, ALineCount, ABytePos: Integer);
    procedure AdjustColumn(ALine, ABytePos, ACount: Integer; InLineBreak: boolean = False);
    Function FindLastFold : TSynTextFoldAVLNode;
    Function FindFirstFold : TSynTextFoldAVLNode;
    Function LastFoldedLine : integer; // The actual line; LastNode.StartLine + LastNode.LineCount - 1
    {$IFDEF SynDebug}
    procedure Debug; reintroduce;
    {$ENDIF}
  end;

  { TSynFoldNodeInfoHelper }

  TSynFoldNodeInfoHelper = class
    FCurInfo: TSynFoldNodeInfo;
    FActions: TSynFoldActions;
    FHighlighter: TSynCustomFoldHighlighter;
  protected
    procedure Invalidate;
  public
    constructor Create(AHighlighter: TSynCustomFoldHighlighter);

    function FirstOpen: TSynFoldNodeInfo;
    function Next: TSynFoldNodeInfo;
    function Prev: TSynFoldNodeInfo;
    function FindClose: TSynFoldNodeInfo;
    function GotoOpenPos(aLineIdx, aNodeIdx: integer): TSynFoldNodeInfo;
    function GotoOpenAtChar(aLineIdx, aXPos: integer): TSynFoldNodeInfo;
    function GotoNodeOpenPos(ANode : TSynTextFoldAVLNode): TSynFoldNodeInfo;
    function GotoNodeClosePos(ANode : TSynTextFoldAVLNode): TSynFoldNodeInfo;
    function IsAtNodeOpenPos(ANode : TSynTextFoldAVLNode): Boolean;
    function IsValid: Boolean;
    function Equals(AnInfo: TSynFoldNodeInfo): Boolean;
    function Equals(AHelper: TSynFoldNodeInfoHelper): Boolean;

    property Info: TSynFoldNodeInfo read FCurInfo write FCurInfo;
    property Actions: TSynFoldActions read FActions write FActions;
  end;

  TFoldChangedEvent = procedure(aLine: Integer) of object;
  TInvalidateLineProc = procedure(FirstLine, LastLine: integer) of object;

  TFoldViewNodeInfo = record
    HNode: TSynFoldNodeInfo;    // Highlighter Node
    FNode: TSynTextFoldAVLNode; // AvlFoldNode
    Text, Keyword: String;
    LineNum, ColIndex: Integer;
    OpenCount: Integer; // Highlighter-Nodes opening on this line (limited to the FoldGroup requested)
  end;

  TSynEditFoldLineCapability = (
    // Capabilities of Line
    cfFoldStart, cfHideStart,
    cfFoldBody,
    cfFoldEnd,
    // State indicators
    cfCollapsedFold,
    cfCollapsedHide,   // lines hidden, after this line
    // Special flags
    cfSingleLineHide,
    cfNone
  );
  TSynEditFoldLineCapabilities = set of TSynEditFoldLineCapability;
  TSynEditFoldType = (scftOpen, scftFold, scftHide, scftAll, scftInvalid);

  TSynEditFoldLineMapInfo = record
    Capability: TSynEditFoldLineCapabilities;
    Classifications :TFoldNodeClassifications;
  end;

  {$IFDEF SynFoldSaveDebug}
const
  SynEditFoldTypeNames: Array [TSynEditFoldType] of string =
    ('scftOpen', 'scftFold', 'scftHide', 'scftAll', 'scftInvalid');
type
  {$ENDIF}

  { TSynEditFoldProvider }
  TSynEditFoldProviderNodeInfo = record
    LineCount: Integer;
    Column, ColumnLen: Integer;
    DefaultCollapsed: Boolean;
    FoldTypeCompatible: Pointer;  // eg begin, var, procedure
    FoldGroup: Integer; // eg.: pas, region, ifdef
    Classification: TFoldNodeClassification;
  end;

  TSynEditFoldProviderNodeInfoList = array of TSynEditFoldProviderNodeInfo;
  TSynEditFoldProvider = class;

  TSynEditFoldProvider = class
  private
    FHighlighter: TSynCustomFoldHighlighter;
    FLines : TSynEditStrings;
    FSelection: TSynEditSelection;
    FFoldTree : TSynTextFoldAVLTree;
    FNestedFoldsList: TLazSynEditNestedFoldsList;
    function GetFoldsAvailable: Boolean;
    function GetHighLighterWithLines: TSynCustomFoldHighlighter;
    function GetLineCapabilities(ALineIdx: Integer): TSynEditFoldLineCapabilities;
    function GetLineClassification(ALineIdx: Integer): TFoldNodeClassifications;
    function GetNestedFoldsList: TLazSynEditNestedFoldsList;
    procedure SetHighLighter(const AValue: TSynCustomFoldHighlighter);
    procedure SetLines(AValue: TSynEditStrings);
  protected
    property HighLighterWithLines: TSynCustomFoldHighlighter read GetHighLighterWithLines;
  public
    constructor Create(aTextView : TSynEditStrings; AFoldTree : TSynTextFoldAVLTree);
    destructor Destroy; override;

    // Info about Folds opening on ALineIdx
    function  FoldOpenCount(ALineIdx: Integer; AType: Integer = 0): Integer;
    function  FoldOpenInfo(ALineIdx, AFoldIdx: Integer; AType: Integer = 0): TSynFoldNodeInfo;
    //property FoldOpenInfo[ALineIdx, AColumnIdx: Integer]: Integer read GetFoldOpenInfo;

    function  FoldLineLength(ALine, AFoldIndex: Integer): integer;
    function  InfoForFoldAtTextIndex(ALine, AFoldIndex : Integer;
                                     HideLen: Boolean = False;
                                     NeedLen: Boolean = True): TSynEditFoldProviderNodeInfo;
    function  InfoListForFoldsAtTextIndex(ALine: Integer; NeedLen: Boolean = False): TSynEditFoldProviderNodeInfoList;

    property LineCapabilities[ALineIdx: Integer]: TSynEditFoldLineCapabilities
             read GetLineCapabilities;
    property LineClassification[ALineIdx: Integer]: TFoldNodeClassifications
             read GetLineClassification;
    property Lines: TSynEditStrings read FLines write SetLines;
    property HighLighter: TSynCustomFoldHighlighter read FHighlighter write SetHighLighter;
    property FoldsAvailable: Boolean read GetFoldsAvailable;
    property NestedFoldsList: TLazSynEditNestedFoldsList read GetNestedFoldsList;
  end;

  { TFoldChangedHandlerList }

  TFoldChangedHandlerList = class(TMethodList)
  public
    procedure CallFoldChangedEvents(AnIndex: Integer);
  end;

  TSynEditFoldedView = class;

  { TLazSynDisplayFold }

  TLazSynDisplayFold = class(TLazSynDisplayViewEx)
  private
    FFoldView: TSynEditFoldedView;
    FLineState: integer;
    FTokenAttr: TSynHighlighterAttributesModifier;
    FMarkupLine: TSynSelectedColorMergeResult;
    FLineFlags, FLineFlags2: TSynEditFoldLineCapabilities;
  public
    constructor Create(AFoldView: TSynEditFoldedView);
    destructor Destroy; override;
    procedure SetHighlighterTokensLine(ALine: TLineIdx; out ARealLine: TLineIdx); override;
    function GetNextHighlighterToken(out ATokenInfo: TLazSynDisplayTokenInfo): Boolean; override;
    function GetLinesCount: Integer; override;

    function TextToViewIndex(AIndex: TLineIdx): TLineRange; override;
    function ViewToTextIndex(AIndex: TLineIdx): TLineIdx; override;
  end;

  { TSynTextFoldedView
      *Line      = Line (0-based) on Screen (except TopLine which should be TopViewPos)
      *ViewPos   = Line (1-based) in the array of viewable/visible lines
      *TextIndex = Line (0-based) in the complete text(folded and unfolded)
  }

  TSynEditFoldedViewFlag = (fvfNeedCaretCheck, fvfNeedCalcMaps);
  TSynEditFoldedViewFlags = set of TSynEditFoldedViewFlag;

  { TSynEditFoldedView }

  TSynEditFoldedView = class
  private
    fCaret: TSynEditCaret;
    FBlockSelection: TSynEditSelection;
    FFoldProvider: TSynEditFoldProvider;
    fLines : TSynEditStrings;
    fFoldTree : TSynTextFoldAVLTree;   // Folds are stored 1-based (the 1st line is 1)
    FMarkupInfoFoldedCode: TSynSelectedColor;
    FMarkupInfoFoldedCodeLine: TSynSelectedColor;
    FMarkupInfoHiddenCodeLine: TSynSelectedColor;
    FOnLineInvalidate: TInvalidateLineProc;
    fTopLine : Integer;
    fLinesInWindow : Integer;          // there may be an additional part visible line
    fTextIndexList : Array of integer;   (* Map each Screen line into a line in textbuffer *)
    fFoldTypeList : Array of TSynEditFoldLineMapInfo;
    fOnFoldChanged : TFoldChangedEvent;
    fLockCount : Integer;
    fNeedFixFrom, fNeedFixMinEnd : Integer;
    FFlags: TSynEditFoldedViewFlags;
    FInTopLineChanged: Boolean;
    FDisplayView: TLazSynDisplayFold;
    FFoldChangedHandlerList: TFoldChangedHandlerList;

    function GetCount : integer;
    function GetDisplayView: TLazSynDisplayView;
    function GetFoldClasifications(index : Integer): TFoldNodeClassifications;
    function GetHighLighter: TSynCustomHighlighter;
    function GetLines(index : Integer) : String;
    function GetDisplayNumber(index : Integer) : Integer;
    function GetTextIndex(index : Integer) : Integer;
    function GetFoldType(index : Integer) : TSynEditFoldLineCapabilities;
    function IsFolded(index : integer) : Boolean;  // TextIndex
    procedure SetBlockSelection(const AValue: TSynEditSelection);
    procedure SetHighLighter(AValue: TSynCustomHighlighter);
    procedure SetTopLine(const ALine : integer);
    function  GetTopTextIndex : integer;
    procedure SetTopTextIndex(const AIndex : integer);
    procedure SetLinesInWindow(const AValue : integer);
    procedure DoFoldChanged(AnIndex: Integer);
  protected
    procedure DoBlockSelChanged(Sender: TObject);
    Procedure CalculateMaps;
    function  FoldNodeAtTextIndex(AStartIndex, ColIndex: Integer): TSynTextFoldAVLNode; (* Returns xth Fold at nth TextIndex (all lines in buffer) / 1-based *)
    function  FixFolding(AStart : Integer; AMinEnd : Integer; aFoldTree : TSynTextFoldAVLTree) : Boolean;

    procedure DoCaretChanged(Sender : TObject);
    Procedure LineCountChanged(Sender: TSynEditStrings; AIndex, ACount : Integer);
    Procedure LinesCleared(Sender: TObject);
    Procedure LineEdited(Sender: TSynEditStrings; aLinePos, aBytePos, aCount,
                            aLineBrkCnt: Integer; aText: String);
    Procedure LinesInsertedAtTextIndex(AStartIndex, ALineCount, ABytePos: Integer;
                                       SkipFixFolding : Boolean = False);
    //Procedure LinesInsertedAtViewPos(AStartPos, ALineCount : Integer;
    //                                 SkipFixFolding : Boolean = False);
    Procedure LinesDeletedAtTextIndex(AStartIndex, ALineCount, ABytePos: Integer;
                                      SkipFixFolding : Boolean = False);
    //Procedure LinesDeletedAtViewPos(AStartPos, ALineCount : Integer;
    //                                SkipFixFolding : Boolean = False);
    property FoldTree: TSynTextFoldAVLTree read fFoldTree;
  public
    constructor Create(aTextView : TSynEditStrings; ACaret: TSynEditCaret);
    destructor Destroy; override;
    
    // Converting between Folded and Unfolded Lines/Indexes
    function TextIndexToViewPos(aTextIndex : Integer) : Integer;    (* Convert TextIndex (0-based) to ViewPos (1-based) *)
    function TextIndexToScreenLine(aTextIndex : Integer) : Integer; (* Convert TextIndex (0-based) to Screen (0-based) *)
    function ViewPosToTextIndex(aViewPos : Integer) : Integer;      (* Convert ViewPos (1-based) to TextIndex (0-based) *)
    function ScreenLineToTextIndex(aLine : Integer) : Integer;      (* Convert Screen (0-based) to TextIndex (0-based) *)

    function TextIndexAddLines(aTextIndex, LineOffset : Integer) : Integer;     (* Add/Sub to/from TextIndex (0-based) skipping folded *)
    function TextPosAddLines(aTextpos, LineOffset : Integer) : Integer;     (* Add/Sub to/from TextPos (1-based) skipping folded *)

    property BlockSelection: TSynEditSelection write SetBlockSelection;
    // Attributes for Visible-Lines-On-screen
    property Lines[index : Integer] : String            (* Lines on screen / 0 = TopLine *)
      read GetLines; default;
    property DisplayNumber[index : Integer] : Integer   (* LineNumber for display in Gutter / result is 1-based *)
      read GetDisplayNumber;
    property FoldType[index : Integer] : TSynEditFoldLineCapabilities (* FoldIcon / State *)
      read GetFoldType;
    property FoldClasifications[index : Integer] : TFoldNodeClassifications (* FoldIcon / State *)
      read GetFoldClasifications;
    property TextIndex[index : Integer] : Integer       (* Position in SynTextBuffer / result is 0-based *)
      read GetTextIndex; // maybe writable

    // Define Visible Area
    property TopLine : integer                          (* refers to visible (unfolded) lines / 1-based *)
      read fTopLine write SetTopLine;
    property TopTextIndex : integer                     (* refers to TextIndex (folded + unfolded lines) / 1-based *)
      read GetTopTextIndex write SetTopTextIndex;
    property LinesInWindow : integer                    (* Fully Visible lines in Window; There may be one half visible line *)
      read fLinesInWindow write SetLinesInWindow;

    property Count : integer read GetCount;             (* refers to visible (unfolded) lines *)

    property MarkupInfoFoldedCode: TSynSelectedColor read FMarkupInfoFoldedCode;
    property MarkupInfoFoldedCodeLine: TSynSelectedColor read FMarkupInfoFoldedCodeLine;
    property MarkupInfoHiddenCodeLine: TSynSelectedColor read FMarkupInfoHiddenCodeLine;
  public
    procedure Lock;
    procedure UnLock;
    {$IFDEF SynDebug}
    procedure debug;
    {$ENDIF}
    (* Arguments for (Un)FoldAt* (Line, ViewPos, TextIndex):
       - ColumnIndex (0-based)
           Can be negative, to access the highest(-1) available, 2nd highest(-2) ...
           If negative, count points downward
       - ColCount = 0 => all
       - Skip => Do not count nodes that are already in the desired state
           (or can not archive the desired state: e.g. can not hide)
       - AVisibleLines: 0 = Hide / 1 = Fold
    *)
    procedure FoldAtLine(AStartLine: Integer; ColIndex : Integer = -1;          (* Folds at ScreenLine / 0-based *)
                         ColCount : Integer = 1; Skip: Boolean = False;
                         AVisibleLines: Integer = 1);
    procedure FoldAtViewPos(AStartPos: Integer; ColIndex : Integer = -1;        (* Folds at nth visible/unfolded Line / 1-based *)
                            ColCount : Integer = 1; Skip: Boolean = False;
                            AVisibleLines: Integer = 1);
    procedure FoldAtTextIndex(AStartIndex: Integer; ColIndex : Integer = -1;    (* Folds at nth TextIndex (all lines in buffer) / 1-based *)
                              ColCount : Integer = 1; Skip: Boolean = False;
                              AVisibleLines: Integer = 1);
    procedure UnFoldAtLine(AStartLine: Integer; ColIndex : Integer = -1;        (* UnFolds at ScreenLine / 0-based *)
                         ColCount : Integer = 0; Skip: Boolean = False;
                         AVisibleLines: Integer = 1);
    procedure UnFoldAtViewPos(AStartPos: Integer; ColIndex : Integer = -1;      (* UnFolds at nth visible/unfolded Line / 1-based *)
                         ColCount : Integer = 0; Skip: Boolean = False;
                         AVisibleLines: Integer = 1);
    procedure UnFoldAtTextIndex(AStartIndex: Integer; ColIndex : Integer = -1;  (* UnFolds at nth TextIndex (all lines in buffer) / 1-based *)
                         ColCount : Integer = 0; Skip: Boolean = False;
                         AVisibleLines: Integer = 1);
    procedure UnFoldAtTextIndexCollapsed(AStartIndex: Integer);   (* UnFolds only if Index is in the fold, ignores cfcollapsed line, if unfolded / 1-based *)

    function LogicalPosToNodeIndex(AStartIndex: Integer; LogX: Integer;         (* Returns the index of the node, at the logical char pos *)
                                   Previous: Boolean = False): Integer;

    procedure CollapseDefaultFolds;
    // Load/Save folds to string
    // AStartIndex, AEndIndex: (0 based) First/last line (EndIndex = -1 = open end)
    // AStartCol, AEndCol: (1 based) Logical text pos in Line. (AEndCol = -1 = full line)
    function  GetFoldDescription(AStartIndex, AStartCol, AEndIndex,
                                 AEndCol: Integer; AsText: Boolean = False;
                                 Extended: Boolean = False) :String;
    procedure ApplyFoldDescription(AStartIndex, AStartCol, AEndIndex,
                                   AEndCol: Integer; FoldDesc: PChar;
                                   FoldDescLen: Integer; IsText: Boolean = False);

    procedure UnfoldAll;
    procedure FoldAll(StartLevel : Integer = 0; IgnoreNested : Boolean = False);
    procedure FixFoldingAtTextIndex(AStartIndex: Integer; AMinEndLine: Integer = 0); // Real/All lines
  public
    function OpenFoldCount(aStartIndex: Integer; AType: Integer = 0): Integer;
    function OpenFoldInfo(aStartIndex, ColIndex: Integer; AType: Integer = 0): TFoldViewNodeInfo;

  public
    // Find the visible first line of the fold at ALine. Returns -1 if Aline is not folded
    function CollapsedLineForFoldAtLine(ALine : Integer) : Integer;
    function ExpandedLineForBlockAtLine(ALine : Integer; HalfExpanded: Boolean = True) : Integer;

    procedure AddFoldChangedHandler(AHandler: TFoldChangedEvent);
    procedure RemoveFoldChangedHandler(AHandler: TFoldChangedEvent);

    function GetPhysicalCharWidths(Index: Integer): TPhysicalCharWidths;

    function  IsFoldedAtTextIndex(AStartIndex, ColIndex: Integer): Boolean;      (* Checks xth Fold at nth TextIndex (all lines in buffer) / 1-based *)
    property FoldedAtTextIndex [index : integer] : Boolean read IsFolded;

    property OnFoldChanged: TFoldChangedEvent  (* reports 1-based line *) {TODO: synedit expects 0 based }
      read fOnFoldChanged write fOnFoldChanged;
    property OnLineInvalidate: TInvalidateLineProc(* reports 1-based line *) {TODO: synedit expects 0 based }
      read FOnLineInvalidate write FOnLineInvalidate;
    property HighLighter: TSynCustomHighlighter read GetHighLighter
                                                write SetHighLighter;
    property FoldProvider: TSynEditFoldProvider read FFoldProvider;

    property DisplayView: TLazSynDisplayView read GetDisplayView;
  end;

function dbgs(AClassification: TFoldNodeClassification): String; overload;

implementation

//var
//  SYN_FOLD_DEBUG: PLazLoggerLogGroup;

type
  TFoldExportEntry = Record
    // Lines and Pos (o 1st line) are relative to Scan-Start
    Line, LogX, LogX2: Integer;     // StartLine and Pos
    ELine, ELogX, ELogX2: Integer;  // EndLine and pos
    FType: Integer;                 // e.g ord(cfbtBeginEnd)
    LinesFolded: Integer;          // Lines Folded according to AVL-Node
  end;

  { TSynEditFoldExportStream }

  TSynEditFoldExportStream = class
  private
    FData: String;
    FLen, FPos: Integer;
    FMem: PChar;
    function  GetLen: Integer;
    procedure SetLen(const AValue: Integer);
    function  GetMem: PChar;
    procedure SetMem(const AValue: PChar);
    function  GetText: String;
    procedure SetText(const AValue: String);
  protected
    function GrowData(AppendSize: Integer): PChar;
    function EncodeIntEx(Anum: Integer): String;  // base 43, with leading continue bit
    function EncodeIntEx2(Anum: Integer): String; // for numbers expected below 467; specially 0..80
    function InternalReadNum(var APos: Integer): Integer;
    function InternalReadNumEx(var APos: Integer): Integer;
  public
    constructor Create;
    procedure Compress;
    procedure Decompress;

    procedure AddChecksum;
    function  VerifyChecksum: Boolean;

    // see notes for Compression
    Procedure AppendMem(AMem: Pointer; ALen: Integer);
    Procedure AppendString(ATxt: String);
    Procedure AppendNum(ANum: Integer);
    Procedure AppendNumEx(ANum: Integer);

    Procedure Reset;
    Procedure Clear;
    function ReadMem(AMem: Pointer; ALen: Integer): Boolean;
    function PeakString(ALen: Integer): String;
    function FindChar(AChar: Char): Integer; // 0 based
    function ReadString(ALen: Integer): String;
    function ReadNum: Integer;
    function ReadNumEx: Integer;
    function EOF: Boolean;

    property Text: String read GetText write SetText;
    property Mem: PChar read GetMem write SetMem;
    property Len: Integer read GetLen write SetLen;
    property Pos: Integer read FPos;
  end;

  TSynEditFoldExportCoderEntry = record
    aX, aY, aLen: Integer;
    aFoldType: TSynEditFoldType;
  end;
  TSynEditFoldExportCoderStates =
    (sfecAtBegin, sfecAtPoint, sfecInRepeatCount, sfecInvalid, sfecAtEOF);
  {$IFDEF SynFoldSaveDebug}
const
  SynEditFoldExportCoderStates: Array [TSynEditFoldExportCoderStates] of String =
    ('sfecAtBegin', 'sfecAtPoint', 'sfecInRepeatCount', 'sfecInvalid', 'sfecAtEOF');
type
  {$ENDIF}

  { TSynEditFoldExportCoder }

  TSynEditFoldExportCoder = class
  private
    FExportStream: TSynEditFoldExportStream;
    FFoldType: Pointer;

    FReadY, FReadLastY, FReadX, FReadSumLen, FReadCount: Integer;
    FReadType: TSynEditFoldType;
    FReadDefaultType: TSynEditFoldType;
    FReadState: TSynEditFoldExportCoderStates;

    FWriteCache: Array of TSynEditFoldExportCoderEntry;
    FWriteCacheLen: Integer;
    FWriteCacheTypes: set of TSynEditFoldType;
    function GetReadIsValid: Boolean;
  public
    constructor Create(AFoldType: Pointer);
    constructor Create(AStream: TSynEditFoldExportStream);
    destructor Destroy; override;

    procedure AddNode(aX, aY, aLen: Integer; aFoldType: TSynEditFoldType);
    procedure Finish;

    function ReadNode(aX, aY: Integer; aLen: Integer): TSynEditFoldType;
    function EOF: Boolean;
    procedure Reset;
    property ReadIsValid: Boolean read GetReadIsValid;

    property FoldType: Pointer read FFoldType;
    property Stream: TSynEditFoldExportStream read FExportStream;
  end;

const
  // use only xml encode-able ascii
  // do not use [ or ], they are reserved for compression
  // space can be used a special indicator
  NumEncode86Chars: string[86] = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-+;:,.@=*/\!?$%()''^{}~_#';

  NumEncodeAsOneMax = 80;                        // Maximum Value to encode as 1 char
  NumEncodeAsTwoMax = 81 + 4*86 + 43;            // =  467; Maximum Value to encode as 2 char
  NumEncodeAsThreeMax = 81 + 4*86 + 43 * 43 - 1; // = 2273  Maximum Value to encode as 3 char


  SEQMaxNodeCount     = 75;  // New Full entry at least every 75 folds
  SEQMaxLineDistEach  = 500;  //  New Full entry, if folds startlines are more than 500 appart
  SEQMaxLineDistTotal = 2500; // New Full entry at least every 2500; check position

var
  NumEncode86Values: Array [Char] of integer;

procedure InitNumEncodeValues;
var
  i: integer;
  c : Char;
begin
  for c := low(Char) to high(Char) do begin
    NumEncode86Values[c] := -1;
  end;
  for i := 1 to length(NumEncode86Chars) do
    NumEncode86Values[NumEncode86Chars[i]] := i - 1;
end;

{ TFoldChangedHandlerList }

procedure TFoldChangedHandlerList.CallFoldChangedEvents(AnIndex: Integer);
var
  i: LongInt;
begin
  i:=Count;
  while NextDownIndex(i) do
    TFoldChangedEvent(Items[i])(AnIndex);
end;

{ TLazSynDisplayFold }

constructor TLazSynDisplayFold.Create(AFoldView: TSynEditFoldedView);
begin
  inherited Create;
  FFoldView := AFoldView;
  FTokenAttr := TSynHighlighterAttributesModifier.Create(nil);
  FMarkupLine := TSynSelectedColorMergeResult.Create(nil);
end;

destructor TLazSynDisplayFold.Destroy;
begin
  FreeAndNil(FTokenAttr);
  FreeAndNil(FMarkupLine);
  inherited Destroy;
end;

procedure TLazSynDisplayFold.SetHighlighterTokensLine(ALine: TLineIdx; out ARealLine: TLineIdx);
begin
  FLineState := 0;
  CurrentTokenLine := ALine;
  FLineFlags := FFoldView.FoldType[CurrentTokenLine + 1 - FFoldView.TopLine] * [cfCollapsedFold, cfCollapsedHide];
  FLineFlags2 := FLineFlags;

  if not FFoldView.MarkupInfoFoldedCodeLine.IsEnabled then
    Exclude(FLineFlags2, cfCollapsedFold);
  if not FFoldView.MarkupInfoHiddenCodeLine.IsEnabled then
    Exclude(FLineFlags2, cfCollapsedHide);

  if (FLineFlags2 <> []) then begin
    FFoldView.MarkupInfoFoldedCodeLine.SetFrameBoundsLog(1, MaxInt, 0);
    FFoldView.MarkupInfoHiddenCodeLine.SetFrameBoundsLog(1, MaxInt, 0);
  end;

  inherited SetHighlighterTokensLine(FFoldView.ViewPosToTextIndex(ALine + 1), ARealLine);
end;

function TLazSynDisplayFold.GetNextHighlighterToken(out ATokenInfo: TLazSynDisplayTokenInfo): Boolean;
const
  MarkSpaces: string = '   ';
  MarkDots: string = '...';
  LSTATE_BOL       = 0; // at BOL
  LSTATE_TEXT      = 1; // in text
  LSTATE_BOL_GAP   = 2; // BOL and in Gap (empty line)         // must be LSTATE_BOL + 2
  LSTATE_GAP       = 3; // In Gap betwen txt and dots          // must be LSTATE_TEXT + 2
  LSTATE_DOTS      = 4; // In Dots
  LSTATE_EOL       = 5; // at start of EOL
var
  EolAttr: TSynHighlighterAttributes;
  MergeStartX, MergeEndX: TLazSynDisplayTokenBound;
begin
  case FLineState of
    LSTATE_BOL, LSTATE_TEXT: begin
        Result := inherited GetNextHighlighterToken(ATokenInfo);
        if ( (not Result) or (ATokenInfo.TokenStart = nil)) and (FLineFlags <> [])
        then begin
          inc(FLineState, 2); // LSTATE_BOL_GAP(2), if was at bol // LSTATE_GAP(3) otherwise
          ATokenInfo.TokenStart := PChar(MarkSpaces);
          ATokenInfo.TokenLength := 3;
          if Assigned(CurrentTokenHighlighter)
          then EolAttr := CurrentTokenHighlighter.GetEndOfLineAttribute
          else EolAttr := nil;
          if EolAttr <> nil then begin
            FTokenAttr.Assign(EolAttr);
            ATokenInfo.TokenAttr := FTokenAttr;
          end
          else begin
            ATokenInfo.TokenAttr := nil;
          end;
          Result := True;
        end;
      end;
    LSTATE_GAP: begin
        FLineState := LSTATE_DOTS;
        FTokenAttr.Assign(FFoldView.MarkupInfoFoldedCode);
        FTokenAttr.SetAllPriorities(MaxInt);
        ATokenInfo.TokenStart := PChar(MarkDots);
        ATokenInfo.TokenLength := 3;
        ATokenInfo.TokenAttr := FTokenAttr;
        Result := True;
      end;
    else begin
      Result := inherited GetNextHighlighterToken(ATokenInfo);
    end;
  end;

  if (FLineFlags2 <> []) then begin
    FMarkupLine.Clear;
    if ATokenInfo.TokenAttr = nil then begin
      // Text Area does not expect StartX/Endx
      // So we must merge, to eliminate unwanted borders
      //  if (cfCollapsedFold in FLineFlags2)
      //  then ATokenInfo.TokenAttr := FFoldView.MarkupInfoFoldedCodeLine
      //  else ATokenInfo.TokenAttr := FFoldView.MarkupInfoHiddenCodeLine;
      //  exit;
      FMarkupLine.Clear;
    end //;
    else
      FMarkupLine.Assign(ATokenInfo.TokenAttr);

    MergeStartX.Physical := -1;
    MergeStartX.Logical := -1;
    MergeEndX.Physical := -1;
    MergeEndX.Logical := -1;
    if FLineState in [LSTATE_BOL, LSTATE_BOL_GAP] then
      MergeStartX := FFoldView.MarkupInfoFoldedCodeLine.StartX;
    if FLineState = LSTATE_EOL then // LSTATE_GAP; // or result := true
      MergeEndX := FFoldView.MarkupInfoFoldedCodeLine.EndX;

    // fully expand all frames
    //FMarkupLine.SetFrameBoundsLog(0,0,0);
    //FMarkupLine.CurrentStartX := FMarkupLine.StartX;
    //FMarkupLine.CurrentEndX := FMarkupLine.EndX;

    if (cfCollapsedFold in FLineFlags2) then
      FMarkupLine.Merge(FFoldView.MarkupInfoFoldedCodeLine, MergeStartX, MergeEndX)
    else
      FMarkupLine.Merge(FFoldView.MarkupInfoHiddenCodeLine, MergeStartX, MergeEndX);

    ATokenInfo.TokenAttr := FMarkupLine;
  end;

  if FLineState in [LSTATE_BOL, LSTATE_BOL_GAP, LSTATE_DOTS, LSTATE_EOL] then
    inc(FLineState);
end;

function TLazSynDisplayFold.GetLinesCount: Integer;
begin
  Result := FFoldView.Count;
end;

function TLazSynDisplayFold.TextToViewIndex(AIndex: TLineIdx): TLineRange;
begin
  Result := inherited TextToViewIndex(AIndex);
  if Result.Top = Result.Bottom then begin
    Result.Top    := FFoldView.TextIndexToViewPos(Result.Top) - 1;
    Result.Bottom := Result.Top;
  end
  else begin;
    Result.Top    := FFoldView.TextIndexToViewPos(Result.Top) - 1;
    Result.Bottom := FFoldView.TextIndexToViewPos(Result.Bottom) - 1;
  end;
end;

function TLazSynDisplayFold.ViewToTextIndex(AIndex: TLineIdx): TLineIdx;
begin
  Result := FFoldView.ViewPosToTextIndex(inherited ViewToTextIndex(AIndex)+1);
end;

{ TSynEditFoldExportStream }

constructor TSynEditFoldExportStream.Create;
begin
  inherited;
  FPos := 0;
  FLen := 0;
  FMem := nil;
end;


function TSynEditFoldExportStream.GetLen: Integer;
begin
  Result := FLen;
end;

procedure TSynEditFoldExportStream.SetLen(const AValue: Integer);
begin
  FPos := 0;
  FLen:= AValue;
end;

function TSynEditFoldExportStream.GetMem: PChar;
begin
  if FData <> '' then
    Result := @FData[1]
  else
    Result := FMem;
end;

procedure TSynEditFoldExportStream.SetMem(const AValue: PChar);
begin
  FData := '';
  FMem := AValue;
  FPos := 0;
end;

function TSynEditFoldExportStream.GetText: String;
begin
  // only valid for FData
  SetLength(FData, FLen);
  Result := FData;
end;

procedure TSynEditFoldExportStream.SetText(const AValue: String);
begin
  FData := AValue;
  FMem := nil;
  FPos := 0;
end;

function TSynEditFoldExportStream.GrowData(AppendSize: Integer): PChar;
var
  l: integer;
begin
  l := length(FData);
  if l < FLen + AppendSize then
    SetLength(FData, l + AppendSize + Max((l+AppendSize) div 4, 1024));
  Result := @FData[FLen + 1];
  inc(FLen, AppendSize);
end;

function TSynEditFoldExportStream.EncodeIntEx(Anum: Integer): String;
var
  n: integer;
begin
  //    0 -   42 => 1 byte
  //   43 - 1848 => 2 byte
  // 1849 - .... => 3 and more
  Result := '';
  if ANum = 0 then Result := NumEncode86Chars[1];
  n := 0;
  while ANum > 0 do begin
    Result := NumEncode86Chars[1 + (Anum mod 43) + n] + Result;
    ANum := ANum div 43;
    n := 43;
  end;
end;

function TSynEditFoldExportStream.EncodeIntEx2(Anum: Integer): String;
var
  n: Integer;
begin
  //   0 -   80 => 1 char
  //  81 -  424 => 2 char   (80 + 4 * 86)
  // 425 -  467 => 2 char (len(EncodeIntEx) = 1)
  // 468 - 2272 => 3 and more char
  //2273 - .... => 4 and more char
  Result := '';
  if Anum <= 80 then
    Result := NumEncode86Chars[1 + Anum]
  else
  begin
    n := (Anum-81) div 86;
    if n <= 3 then
      Result := NumEncode86Chars[1 + 81 + n] + NumEncode86Chars[1 + (Anum - 81) mod 86]
    else
      Result := NumEncode86Chars[1 + 85] + EncodeIntEx(Anum - 81 - 4*86);
  end;
end;

function TSynEditFoldExportStream.InternalReadNum(var APos: Integer): Integer;
var
  n: Integer;
begin
  Result := 0;
  while True do begin
    if FPos >= FLen then exit(-1);
    n := NumEncode86Values[(FMem + APos)^];
    if n < 43 then break;
    dec(n, 43);
    Result := Result * 43 + n;
    inc(APos);
  end;
  Result := Result * 43 + n;
  inc(APos);
end;

function TSynEditFoldExportStream.InternalReadNumEx(var APos: Integer): Integer;
begin
  if FPos >= FLen then exit(-1);
  Result := NumEncode86Values[(FMem + APos)^];
  inc(APos);
  if Result <= 80 then
    exit;
  if FPos >= FLen then exit(-1);
  if Result < 85 then begin
    Result := 81 + (Result-81)*86 +  NumEncode86Values[(FMem + APos)^];
    inc(APos);
    exit;
  end;
  Result := 81 + 4*86 + InternalReadNum(APos);
end;

procedure TSynEditFoldExportStream.Compress;
(* Known Sequences: XX = Enc64Num (copy sequence from XX chars before)
                    NN = ENc22 Num / n = enc22digit (copy n bytes)
     [XXn     (up to 21 bytes, from up to 64*64 back)
     [NNXX[   (more then 21 bytes, from up to 64*64 back)
     ]X       (3 bytes from max 64 back)
     ]nx      ( reocurring space,x times, ever n pos)
const
  max_single_len = 22 - 1;
  *)
var
  CurPos, EndPos, SearchPos: Integer;
  FndLen, FndPos, FndPos2: Integer;
  BestLen, BestPos, BestPos2: Integer;
  s: string;
begin
  AppendString(#0);
  dec(FLen);

  EndPos := FLen;
  CurPos := FLen - 3;
  while CurPos >= 4 do begin
    SearchPos := CurPos - 3;
    BestLen := 0;
    while (SearchPos >= 1) do begin
      if CompareMem(@FData[CurPos], @FData[SearchPos], 3) then begin
        FndLen := 3;
        FndPos := SearchPos;
        FndPos2 := CurPos;
        while (SearchPos + FndLen < FndPos2) and
              (FndPos2 + FndLen < EndPos - 1) and
              (FData[SearchPos + FndLen] = FData[CurPos + FndLen])
        do
          inc(FndLen);
        while (FndPos > 1) and (FndPos + FndLen < FndPos2) and
              (FData[FndPos - 1] = FData[FndPos2 - 1]) do
        begin
          dec(FndPos);
          dec(FndPos2);
          inc(FndLen);
        end;

        if (FndLen > BestLen) and
           ((FndPos2 - FndPos <= NumEncodeAsOneMax) or (FndLen >= 4)) and
           ((FndPos2 - FndPos <= NumEncodeAsTwoMax) or (FndLen >= 5)) and
           ((FndPos2 - FndPos <= NumEncodeAsThreeMax) or (FndLen >= 6))
        then begin
          BestLen := FndLen;
          BestPos := FndPos;
          BestPos2 := FndPos2;
        end;
      end;
      dec(SearchPos);
    end;

    s := '';
    if (BestLen >= 4) then
      s := '[' + EncodeIntEx2(BestPos2 - BestPos) + EncodeIntEx2(BestLen)
    else
    if (BestLen = 3) and (BestPos2 - BestPos <= NumEncodeAsOneMax) then
      s := ']' + EncodeIntEx2(BestPos2 - BestPos);
    if (s<>'') and (length(s) < BestLen) then begin
      System.Move(s[1], FData[BestPos2], length(s));
      System.Move(FData[BestPos2 + BestLen], FData[BestPos2 + length(s)], FLen + 1 - (BestPos2 + BestLen));
      dec(FLen, BestLen - length(s));
      EndPos := BestPos;
      CurPos := BestPos2 - 3;
    end
    else
      dec(CurPos);
  end;
end;

procedure TSynEditFoldExportStream.Decompress;
var
  i, j, n: Integer;
  p, p2: PChar;
  NewLen: Integer;
begin
  // curently assumes that FMem points NOT at FData
  if FLen = 0 then
    exit;
  NewLen := 0;
  i := 0;
  while i < Flen do begin
    case (FMem+i)^ of
      '[' :
        begin
          inc(i);
          j := InternalReadNumEx(i);
          n := InternalReadNumEx(i);
          if (j < n) or (j > NewLen) then raise ESynEditError.Create('fold format error');
          inc(NewLen, n);
        end;
      ']' :
        begin
          inc(i, 1);
          j := InternalReadNumEx(i);
          if (j < 3) or (j > NewLen) then raise ESynEditError.Create('fold format error');
          inc(NewLen, 3);
        end;
      else
        begin
          inc(NewLen);
          inc(i);
        end;
    end;
  end;
  SetLength(FData, NewLen);

  i := 0;
  p := PChar(FData);
  while i < Flen do begin
    case (FMem+i)^ of
      '[' :
        begin
          inc(i);
          j := InternalReadNumEx(i);
          n := InternalReadNumEx(i);
          p2 := p;
          while n > 0 do begin
            p^ := (p2 - j)^;
            inc(p);
            dec(j);
            dec(n);
          end;
        end;
      ']' :
        begin
          inc(i);
          j := InternalReadNumEx(i);
          p2 := p;
          for n := 0 to 2 do begin
            p^ := (p2 - j)^;
            inc(p);
            dec(j);
          end;
        end;
      else
        begin
          p^ := (FMem + i)^;
          inc(p);
          inc(i);
        end;
    end;
  end;

  FLen := NewLen;
  FMem := PChar(FData);
  FPos := 0;
end;

procedure TSynEditFoldExportStream.AddChecksum;
var
  i, c: Integer;
begin
  if FLen = 0 then
    exit;
  if FMem = nil then
    FMem := @FData[1];
  c := 0;
  for i := 0 to FLen - 1 do
    c := c xor (ord((FMem + i)^) * (i+1));
  c := (c mod 256) xor ((c div 256) mod 256) xor ((c div 65536) mod 256);
  AppendString(NumEncode86Chars[1 + (c mod 86)]);
end;

function TSynEditFoldExportStream.VerifyChecksum: Boolean;
var
  i, c: Integer;
begin
  if FLen = 0 then
    exit(True);
  if FMem = nil then
    FMem := @FData[1];
  dec(Flen);
  c := 0;
  for i := 0 to FLen - 1 do
    c := c xor (ord((FMem + i)^) * (i+1));
  c := (c mod 256) xor ((c div 256) mod 256) xor ((c div 65536) mod 256);
  Result := (FMem + FLen)^ = NumEncode86Chars[1 + (c mod 86)];
end;

procedure TSynEditFoldExportStream.AppendMem(AMem: Pointer; ALen: Integer);
begin
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportStream.AppendMem len=', ALen]);
  {$ENDIF}
  FMem := nil;
  if ALen > 0 then
    System.Move(AMem^, GrowData(ALen)^, ALen);
end;

procedure TSynEditFoldExportStream.AppendString(ATxt: String);
var
  l: Integer;
begin
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportStream.AppendString ', ATxt]);
  {$ENDIF}
  FMem := nil;
  l := length(ATxt);
  if l > 0 then
    System.Move(ATxt[1], GrowData(l)^, l);
end;

procedure TSynEditFoldExportStream.AppendNum(ANum: Integer);
begin
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportStream.AppendNum ', ANum]);
  {$ENDIF}
  FMem := nil;
  AppendString(EncodeIntEx(ANum));
end;

procedure TSynEditFoldExportStream.AppendNumEx(ANum: Integer);
begin
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportStream.AppendNumEx ', ANum]);
  {$ENDIF}
  FMem := nil;
  AppendString(EncodeIntEx2(ANum));
end;

procedure TSynEditFoldExportStream.Reset;
begin
  FPos := 0;
  if (FMem = nil) and (FData <> '') then
    FMem := @FData[1];
end;

procedure TSynEditFoldExportStream.Clear;
begin
  FLen := 0;
  FMem := nil;
  FPos := 0;
  SetLength(FData, 0);
end;

function TSynEditFoldExportStream.ReadMem(AMem: Pointer; ALen: Integer): Boolean;
begin
  Result := FPos+ ALen <= FLen;
  If not Result then
    exit;
  System.Move((FMem + FPos)^, AMem^, ALen);
  inc(FPos, ALen);
end;

function TSynEditFoldExportStream.PeakString(ALen: Integer): String;
begin
  If not(FPos+ ALen <= FLen) then
    exit('');
  SetLength(Result, ALen);
  if ALen > 0 then
    System.Move((FMem + FPos)^, Result[1], ALen);
end;

function TSynEditFoldExportStream.FindChar(AChar: Char): Integer;
begin
  Result := 0;
  While (FPos + Result < FLen) and ((FMem + FPos + Result)^ <> AChar) do
    inc(Result);
  if FPos + Result = FLen then
    Result := -1;
end;

function TSynEditFoldExportStream.ReadString(ALen: Integer): String;
begin
  If not(FPos+ ALen <= FLen) then
    exit('');
  SetLength(Result, ALen);
  if ALen > 0 then
    System.Move((FMem + FPos)^, Result[1], ALen);
  inc(FPos, ALen);
end;

function TSynEditFoldExportStream.ReadNum: Integer;
begin
  Result := InternalReadNum(FPos);
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportStream.ReadNum ', Result]);
  {$ENDIF}
end;

function TSynEditFoldExportStream.ReadNumEx: Integer;
begin
  Result := InternalReadNumEx(FPos);
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportStream.ReadNumEx ', Result]);
  {$ENDIF}
end;

function TSynEditFoldExportStream.EOF: Boolean;
begin
  Result := FPos >= FLen;
end;

{ TSynEditFoldExportCoder }

function TSynEditFoldExportCoder.GetReadIsValid: Boolean;
begin
  Result := FReadState <> sfecInvalid;
end;

constructor TSynEditFoldExportCoder.Create(AFoldType: Pointer);
begin
  inherited Create;
  FExportStream := TSynEditFoldExportStream.Create;
  FExportStream.AppendString(' T');                // Type Marker
  FExportStream.AppendNum(PtrUInt(AFoldType));
  FFoldType := AFoldType;
  FWriteCacheLen := 0;
  FWriteCache := nil;
  FWriteCacheTypes := [];
end;

constructor TSynEditFoldExportCoder.Create(AStream: TSynEditFoldExportStream);
var
  i: Integer;
begin
  inherited Create;
  FExportStream := TSynEditFoldExportStream.Create;
  FReadState := sfecInvalid;
  if AStream.PeakString(2) <> ' T' then exit;

  AStream.ReadString(2);

  FFoldType := Pointer(PtrUInt(AStream.ReadNum));
  while(true) do begin
    i := AStream.FindChar(' ');
    if i < 0 then i := AStream.Len - AStream.Pos;
    FExportStream.AppendString(AStream.ReadString(i));
    if AStream.EOF or (AStream.PeakString(2) = ' T') then
      break;
    FExportStream.AppendString(AStream.ReadString(2));
  end;
  {$IFDEF SynFoldSaveDebug}
  DebugLn(['TSynEditFoldExportCoder.Create(<from input-stream> FType=', dbgs(FFoldType), '  txtLen=', FExportStream.Len, ' Txt="', FExportStream.Text, '"']);
  {$ENDIF}
  Reset;
end;

destructor TSynEditFoldExportCoder.Destroy;
begin
  FreeAndNil(FExportStream);
  Inherited;
end;

procedure TSynEditFoldExportCoder.AddNode(aX, aY, aLen: Integer; aFoldType: TSynEditFoldType);
(* Format:  [Num] <NumEX>
  ' T' [type] [yo] <X> <len> ( <c>* ' p' [sum]  [yo] <X> <len> )* <c>* (' P' [sum] [yo] <X> <len>)?

  //////////////////////////
  // Version info
  V1 - no entries
  V2  July 2010  0.9.29
     - added fold-hide <HideInfo>

  //////////////////////////

  <Stream> = { <TypeStream> };

  <TypeStream> = " T" <TypeId>  <TypeData>;        [* Stores all folds for the given type (eg cfbtBeginEnd) *]

  <TypeId>   = ord(cfbtBeginEnd) or similar
  <TypeData> = [<HideInfo>],
               <NodePos>,
               [ [<FoldList>,]  [{ <FoldListEndCont>, <NodePos>, [<FoldList>] }] ],
               [ <FoldListEnd> ];


  <FoldList> = [{ <ConsecutiveFoldedCount>,  <ConsecutiveUnFoldedCount> }],
               <ConsecutiveFoldedCount>,
               ;
  [* NodePos: is the  position of a folded node (of the type matching the current stream)
     ConsecutiveFoldedCount: more folded nodes of the same type, without any
                             unfolded node (of this type) inbetween.
     ConsecutiveUnFoldedCount: amount of unfolded nodes (of this type) before the next folded node.
  *]

  <NodePos> =  <YOffset> <XPos> <len>;
  <YOffset>…