{-------------------------------------------------------------------------------
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-------------------------------------------------------------------------------}
unit SynEditTextTabExpander;

{$I synedit.inc}

interface

uses
LCLProc,
  Classes, SysUtils, SynEditTextBase;

const
  // Offset to add to LengthOfLine, if Line has no tabs.
  // (Length will still be valid if tab-width changes)
  NoTabLengthOffset = MaxInt div 2;

type

{ TSynEditStringTabExpander }

  TSynEditStringTabExpander = class(TSynEditStringsLinked)
  private
    FTabWidth: integer;
    FIndexOfLongestLine: Integer;
    function GetLengthOfLine(Index: Integer): integer;
    procedure SetLengthOfLine(Index: Integer; const AValue: integer);
    Procedure LineCountChanged(Sender: TSynEditStrings; AIndex, ACount : Integer);
    function ExpandedString(Index: integer): string;
    function ExpandedStringLength(Index: integer): Integer;
  protected
    function  GetTabWidth : integer;
    procedure SetTabWidth(const AValue : integer);
    function  GetExpandedString(Index: integer): string; override;
    function  GetLengthOfLongestLine: integer; override;
    property LengthOfLine[Index: Integer]: integer
      read GetLengthOfLine write SetLengthOfLine;
  public
    constructor Create(ASynStringSource: TSynEditStrings);
    destructor Destroy; override;
    function GetPhysicalCharWidths(const Line: String; Index: Integer): TPhysicalCharWidths; override;

    property LengthOfLongestLine: integer read GetLengthOfLongestLine;
  public
    property TabWidth: integer read GetTabWidth write SetTabWidth;
  end;


implementation

function GetHasTabs(pLine: PChar): boolean;
begin
  if Assigned(pLine) then begin
    while (pLine^ <> #0) do begin
      if (pLine^ = #9) then break;
      Inc(pLine);
    end;
    Result := (pLine^ = #9);
  end else
    Result := FALSE;
end;

{ TSynEditStringTabExpander }

constructor TSynEditStringTabExpander.Create(ASynStringSource: TSynEditStrings);
begin
  FIndexOfLongestLine := -1;
  inherited Create(ASynStringSource);
  fSynStrings.RegisterAttribute(TSynEditStringTabExpander, SizeOf(Integer));
  TabWidth := 8;
  fSynStrings.AddChangeHandler(senrLineCount, {$IFDEF FPC}@{$ENDIF}LineCountChanged);
  fSynStrings.AddChangeHandler(senrLineChange, {$IFDEF FPC}@{$ENDIF}LineCountChanged);
end;

destructor TSynEditStringTabExpander.Destroy;
begin
  fSynStrings.RemoveChangeHandler(senrLineChange, {$IFDEF FPC}@{$ENDIF}LineCountChanged);
  fSynStrings.RemoveChangeHandler(senrLineCount, {$IFDEF FPC}@{$ENDIF}LineCountChanged);
  inherited Destroy;
end;

function TSynEditStringTabExpander.GetLengthOfLine(Index: Integer): integer;
begin
  Result := Integer(PtrUInt(Attribute[TSynEditStringTabExpander, Index]));
end;

procedure TSynEditStringTabExpander.SetLengthOfLine(Index: Integer; const AValue: integer);
begin
   Attribute[TSynEditStringTabExpander, Index] := Pointer(PtrUInt(AValue));
end;

function TSynEditStringTabExpander.GetTabWidth: integer;
begin
  Result := FTabWidth;
end;

procedure TSynEditStringTabExpander.SetTabWidth(const AValue: integer);
var
  i: integer;
begin
  if FTabWidth = AValue then exit;

  FTabWidth := AValue;
  FIndexOfLongestLine := -1;
  for i := 0 to Count - 1 do
    if not(LengthOfLine[i] >= NoTabLengthOffset) then
      LengthOfLine[i] := -1;
end;

procedure TSynEditStringTabExpander.LineCountChanged(Sender: TSynEditStrings; AIndex, ACount: Integer);
var
  i: integer;
begin
  FIndexOfLongestLine := -1;
  for i := AIndex to AIndex + ACount - 1 do
    LengthOfLine[i] := -1;
end;

function TSynEditStringTabExpander.ExpandedString(Index: integer): string;
var
  Line: String;
  CharWidths: TPhysicalCharWidths;
  i, j, l: Integer;
begin
  Line := fSynStrings[Index];
  if (Line = '') or (not GetHasTabs(PChar(Line))) then begin
    Result := Line;
    LengthOfLine[Index] := length(Result) + NoTabLengthOffset;
  end else begin
    CharWidths := GetPhysicalCharWidths(Line, Index);
    l := 0;
    for i := 0 to length(CharWidths)-1 do
      l := l + CharWidths[i];
    SetLength(Result, l);

    l := 1;
    for i := 1 to length(CharWidths) do begin
      if Line[i] <> #9 then begin
        Result[l] := Line[i];
        inc(l);
      end else begin
        for j := 1 to CharWidths[i-1] do begin
          Result[l] := ' ';
          inc(l);
        end;
      end;
    end;
    LengthOfLine[Index] := length(Result);
  end;
end;

function TSynEditStringTabExpander.ExpandedStringLength(Index: integer): Integer;
var
  Line: String;
  CharWidths: TPhysicalCharWidths;
  i: Integer;
begin
  Line := fSynStrings[Index];
  if (Line = '') or (not GetHasTabs(PChar(Line))) then begin
    Result := Length(Line);
    LengthOfLine[Index] := Result + NoTabLengthOffset;
  end else begin
    CharWidths := GetPhysicalCharWidths(Line, Index);
    Result := 0;
    for i := 0 to length(CharWidths)-1 do
      Result := Result + CharWidths[i];

    LengthOfLine[Index] := Result;
  end;
end;

function TSynEditStringTabExpander.GetExpandedString(Index: integer): string;
begin
  if (Index >= 0) and (Index < Count) then begin
    if LengthOfLine[Index] >= NoTabLengthOffset then
      Result := fSynStrings[Index]
    else
      Result := ExpandedString(Index);
  end else
    Result := '';
end;

function TSynEditStringTabExpander.GetPhysicalCharWidths(const Line: String;
  Index: Integer): TPhysicalCharWidths;
var
  i, p: Integer;
begin
  Result := inherited GetPhysicalCharWidths(Line, Index);
  p := 0;
  for i := 0 to length(Line) -1 do begin
    if Result[i] = 0 then continue;
    if Line[i+1] = #9 then
      Result[i] := FTabWidth - p mod FTabWidth;
    p := p + Result[i];
  end
end;

function TSynEditStringTabExpander.GetLengthOfLongestLine: integer;
var
  i, j, MaxLen: integer;
begin
  if fIndexOfLongestLine < 0 then begin
    MaxLen := 0;
    if Count > 0 then begin
      for i := 0 to Count - 1 do begin
        j := LengthOfLine[i];
        if j >= NoTabLengthOffset then j := j -  NoTabLengthOffset;
        if j < 0 then
          j := ExpandedStringLength(i);
        if j > MaxLen then begin
          MaxLen := j;
          fIndexOfLongestLine := i;
        end;
      end;
    end;
    exit(MaxLen);
  end;
  if (fIndexOfLongestLine >= 0) and (fIndexOfLongestLine < Count) then begin
    Result := LengthOfLine[fIndexOfLongestLine];
    if Result >= NoTabLengthOffset then Result := Result -  NoTabLengthOffset;
  end else
    Result := 0;
end;

end.