{  $Id$  }
{
 /***************************************************************************
                               LDockTree.pas
                             -----------------

 ***************************************************************************/

 *****************************************************************************
 *                                                                           *
 *  This file is part of the Lazarus Component Library (LCL)                 *
 *                                                                           *
 *  See the file COPYING.modifiedLGPL, included in this distribution,        *
 *  for details about the copyright.                                         *
 *                                                                           *
 *  This program is distributed in the hope that it will be useful,          *
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of           *
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.                     *
 *                                                                           *
 *****************************************************************************

  Author: Mattias Gaertner

  Abstract:
    This unit contains TLazDockTree, the default TDockTree for the LCL.
}
unit LDockTree;

{$mode objfpc}{$H+}

interface

uses
  Types, Classes, SysUtils, LCLProc, LCLType, LCLStrConsts,
  Graphics, Controls, ExtCtrls, Forms, Menus, Themes
  {$IFDEF VER2_0}
  // needed for 2.0.4
  ,LCLIntf
  {$ENDIF};
  
type
  TLazDockPages = class;
  TLazDockPage = class;
  TLazDockSplitter = class;

  { TLazDockZone }

  TLazDockZone = class(TDockZone)
  private
    FPage: TLazDockPage;
    FPages: TLazDockPages;
    FSplitter: TLazDockSplitter;
  public
    destructor Destroy; override;
    function GetCaption: string;
    function GetParentControl: TWinControl;
    property Splitter: TLazDockSplitter read FSplitter write FSplitter;
    property Pages: TLazDockPages read FPages write FPages;
    property Page: TLazDockPage read FPage write FPage;
  end;

  { TLazDockTree }

  TLazDockTree = class(TDockTree)
  private
    FAutoFreeDockSite: boolean;
  protected
    procedure AdjustDockRect(AControl: TControl; var ARect: TRect); override;
    procedure AnchorDockLayout(Zone: TLazDockZone);
    procedure CreateDockLayoutHelperControls(Zone: TLazDockZone);
    procedure BreakAnchors(Zone: TDockZone);
    procedure PaintDockFrame(ACanvas: TCanvas; AControl: TControl;
                             const ARect: TRect); override;
    procedure UndockControlForDocking(AControl: TControl);
    function DefaultDockGrabberSize: Integer;
  public
    constructor Create(TheDockSite: TWinControl); override;
    destructor Destroy; override;
    procedure InsertControl(AControl: TControl; InsertAt: TAlign;
                            DropControl: TControl); override;
    procedure RemoveControl(AControl: TControl); override;
    procedure BuildDockLayout(Zone: TLazDockZone);
    procedure FindBorderControls(Zone: TLazDockZone; Side: TAnchorKind;
                                 var List: TFPList);
    function FindBorderControl(Zone: TLazDockZone; Side: TAnchorKind): TControl;
    function GetAnchorControl(Zone: TLazDockZone; Side: TAnchorKind;
                              OutSide: boolean): TControl;
    procedure PaintSite(DC: HDC); override;
  public
    property AutoFreeDockSite: boolean read FAutoFreeDockSite write FAutoFreeDockSite;
  end;
  
  { TLazDockForm
    The default DockSite for a TLazDockTree
    
    Note: AnchorDocking does not use DockZone.

    if DockZone<>nil then
      If DockZone is a leaf (DockZone.ChildCount=0) then
        Only child control is DockZone.ChildControl
      else
        if DockZone.Orientation in [doHorizontal,doVertical] then
          Child controls are TLazDockForm and TSplitter
        else if DockZone.Orientation=doPages then
          Child control is a TLazDockPages
  }

  TLazDockForm = class(TCustomForm)
  private
    FDockZone: TDockZone;
    FMainControl: TControl;
    FPageControl: TLazDockPages;
    procedure SetMainControl(const AValue: TControl);
  protected
    procedure Notification(AComponent: TComponent; Operation: TOperation); override;
    procedure InsertControl(AControl: TControl; Index: integer); override;
    function CloseQuery: boolean; override;
  public
    procedure UpdateCaption; virtual;
    function FindMainControlCandidate: TControl;
    property DockZone: TDockZone read FDockZone;
    property PageControl: TLazDockPages read FPageControl;
    property MainControl: TControl read FMainControl write SetMainControl;
  end;
  
  { TLazDockPage
    Pretty the same as a TLazDockForm but as page of a TLazDockPages }

  TLazDockPage = class(TCustomPage)
  private
    FDockZone: TDockZone;
    function GetPageControl: TLazDockPages;
  public
    property DockZone: TDockZone read FDockZone;
    property PageControl: TLazDockPages read GetPageControl;
  end;
  
  { TLazDockPages }

  TLazDockPages = class(TCustomNotebook)
  private
    function GetActiveNotebookPageComponent: TLazDockPage;
    function GetNoteBookPage(Index: Integer): TLazDockPage;
    procedure SetActiveNotebookPageComponent(const AValue: TLazDockPage);
  protected
    function GetFloatingDockSiteClass: TWinControlClass; override;
  public
    constructor Create(TheOwner: TComponent); override;
    property Page[Index: Integer]: TLazDockPage read GetNoteBookPage;
    property ActivePageComponent: TLazDockPage read GetActiveNotebookPageComponent
                                           write SetActiveNotebookPageComponent;
    property Pages;
  end;
  
  TLazDockSplitter = class(TCustomSplitter)
  end;
  
  //----------------------------------------------------------------------------
  
  { TCustomAnchoredDockManager
    This class implements an LCL TDockManager via anchoring.
    The TCustomLazDockingManager component uses this docking manager
    and extends it by layout that can be stored/restored. }

  TCustomAnchoredDockManager = class(TDockManager)
  private
    FSplitterSize: integer;
    FUpdateCount: integer;
  protected
    procedure DeleteSideSplitter(Splitter: TLazDockSplitter; Side: TAnchorKind;
                                 NewAnchorControl: TControl);
    procedure CombineSpiralSplitterPair(Splitter1, Splitter2: TLazDockSplitter);
    procedure DeletePage(Page: TLazDockPage);
    procedure DeletePages(Pages: TLazDockPages);
    procedure DeleteDockForm(ADockForm: TLazDockForm);
    function GetAnchorDepth(AControl: TControl; Side: TAnchorKind): Integer;
  public
    constructor Create;
    procedure BeginUpdate; override;
    procedure EndUpdate; override;
    procedure GetControlBounds(Control: TControl;
                               out AControlBounds: TRect); override;
    procedure DisableLayout(Control: TControl); virtual;
    procedure EnableLayout(Control: TControl); virtual;
    procedure DockControl(Control: TControl; InsertAt: TAlign;
                          DropCtl: TControl);
    procedure UndockControl(Control: TControl; Float: boolean);
    procedure InsertControl(Control: TControl; InsertAt: TAlign;
                            DropCtl: TControl); override;
    function EnlargeControl(Control: TControl; Side: TAnchorKind;
                            Simulate: boolean = false): boolean;
    procedure RemoveControl(Control: TControl); override;
    procedure ReplaceAnchoredControl(OldControl, NewControl: TControl);
    function GetSplitterWidth(Splitter: TControl): integer;
    function GetSplitterHeight(Splitter: TControl): integer;
    property SplitterSize: integer read FSplitterSize write FSplitterSize default 5;

    procedure LoadFromStream(Stream: TStream); override;// not implemented
    procedure PaintSite(DC: HDC); override;// not implemented
    procedure PositionDockRect(Client, DropCtl: TControl; DropAlign: TAlign;
                               var DockRect: TRect); override;// not implemented
    procedure ResetBounds(Force: Boolean); override;// not implemented
    procedure SaveToStream(Stream: TStream); override;// not implemented
    procedure SetReplacingControl(Control: TControl); override;// not implemented
  end;
  
  
const
  DockAlignOrientations: array[TAlign] of TDockOrientation = (
    doPages,     //alNone,
    doVertical,  //alTop,
    doVertical,  //alBottom,
    doHorizontal,//alLeft,
    doHorizontal,//alRight,
    doPages,     //alClient,
    doPages      //alCustom
    );

type
  TAnchorControlsRect = array[TAnchorKind] of TControl;

function GetLazDockSplitter(Control: TControl; Side: TAnchorKind;
                            out Splitter: TLazDockSplitter): boolean;
function GetLazDockSplitterOrParent(Control: TControl; Side: TAnchorKind;
                                    out AnchorControl: TControl): boolean;
function CountAnchoredControls(Control: TControl; Side: TAnchorKind
                               ): Integer;
function NeighbourCanBeShrinked(EnlargeControl, Neighbour: TControl;
                                Side: TAnchorKind): boolean;
function ControlIsAnchoredIndirectly(StartControl: TControl; Side: TAnchorKind;
                                     DestControl: TControl): boolean;
procedure GetAnchorControlsRect(Control: TControl;
                                out ARect: TAnchorControlsRect);
function GetEnclosingControlRect(ControlList: TFPlist;
                                 out ARect: TAnchorControlsRect): boolean;
function GetEnclosedControls(const ARect: TAnchorControlsRect): TFPList;


implementation


function GetLazDockSplitter(Control: TControl; Side: TAnchorKind; out
  Splitter: TLazDockSplitter): boolean;
begin
  Result:=false;
  Splitter:=nil;
  if not (Side in Control.Anchors) then exit;
  Splitter:=TLazDockSplitter(Control.AnchorSide[Side].Control);
  if not (Splitter is TLazDockSplitter) then begin
    Splitter:=nil;
    exit;
  end;
  if Splitter.Parent<>Control.Parent then exit;
  Result:=true;
end;

function GetLazDockSplitterOrParent(Control: TControl; Side: TAnchorKind; out
  AnchorControl: TControl): boolean;
begin
  Result:=false;
  AnchorControl:=nil;
  if not (Side in Control.Anchors) then exit;
  AnchorControl:=Control.AnchorSide[Side].Control;
  if (AnchorControl is TLazDockSplitter)
  and (AnchorControl.Parent=Control.Parent)
  then
    Result:=true
  else if AnchorControl=Control.Parent then
    Result:=true;
end;

function CountAnchoredControls(Control: TControl; Side: TAnchorKind): Integer;
{ return the number of siblings, that are anchored on Side of Control
  For example: if Side=akLeft it will return the number of controls, which
  right side is anchored to the left of Control }
var
  i: Integer;
  Neighbour: TControl;
begin
  Result:=0;
  for i:=0 to Control.Parent.ControlCount-1 do begin
    Neighbour:=Control.Parent.Controls[i];
    if Neighbour=Control then continue;
    if (OppositeAnchor[Side] in Neighbour.Anchors)
    and (Neighbour.AnchorSide[OppositeAnchor[Side]].Control=Control) then
      inc(Result);
  end;
end;

function NeighbourCanBeShrinked(EnlargeControl, Neighbour: TControl;
  Side: TAnchorKind): boolean;
const
  MinControlSize = 20;
var
  Splitter: TLazDockSplitter;
begin
  Result:=false;
  if not GetLazDockSplitter(EnlargeControl,OppositeAnchor[Side],Splitter) then
    exit;
  case Side of
  akLeft: // check if left side of Neighbour can be moved
    Result:=Neighbour.Left+Neighbour.Width
        >EnlargeControl.Left+EnlargeControl.Width+Splitter.Width+MinControlSize;
  akRight: // check if right side of Neighbour can be moved
    Result:=Neighbour.Left+MinControlSize+Splitter.Width<EnlargeControl.Left;
  akTop: // check if top side of Neighbour can be moved
    Result:=Neighbour.Top+Neighbour.Height
       >EnlargeControl.Top+EnlargeControl.Height+Splitter.Height+MinControlSize;
  akBottom: // check if bottom side of Neighbour can be moved
    Result:=Neighbour.Top+MinControlSize+Splitter.Height<EnlargeControl.Top;
  end;
end;

function ControlIsAnchoredIndirectly(StartControl: TControl; Side: TAnchorKind;
  DestControl: TControl): boolean;
{ true if there is an Anchor way from StartControl to DestControl over Side.
  For example:
  
    +-+|+-+
    |A|||B|
    +-+|+-+
    
  A is akLeft to B.
  B is akRight to A.
  The splitter is akLeft to B.
  The splitter is akRight to A.
  All other are false.
}
var
  Checked: array of Boolean;
  Parent: TWinControl;
  
  function Check(ControlIndex: integer): boolean;
  var
    AControl: TControl;
    SideControl: TControl;
    i: Integer;
  begin
    if Checked[ControlIndex] then
      exit(false);
    Checked[ControlIndex]:=true;
    AControl:=Parent.Controls[ControlIndex];
    if AControl=DestControl then exit(true);
    
    if (Side in AControl.Anchors) then begin
      SideControl:=AControl.AnchorSide[Side].Control;
      if (SideControl<>nil) and Check(Parent.GetControlIndex(SideControl)) then
        exit(true);
    end;
    for i:=0 to Parent.ControlCount-1 do begin
      if Checked[i] then continue;
      SideControl:=Parent.Controls[i];
      if OppositeAnchor[Side] in SideControl.Anchors then begin
        if (SideControl.AnchorSide[OppositeAnchor[Side]].Control=AControl)
        and Check(i) then
          exit(true);
      end;
    end;
    Result:=false;
  end;
  
var
  i: Integer;
begin
  if (StartControl=nil) or (DestControl=nil)
  or (StartControl.Parent=nil)
  or (StartControl.Parent<>DestControl.Parent)
  or (StartControl=DestControl) then
    exit(false);
  Parent:=StartControl.Parent;
  SetLength(Checked,Parent.ControlCount);
  for i:=0 to length(Checked)-1 do Checked[i]:=false;
  Result:=Check(Parent.GetControlIndex(StartControl));
end;

procedure GetAnchorControlsRect(Control: TControl;
  out ARect: TAnchorControlsRect);
var
  a: TAnchorKind;
begin
  for a:=Low(TAnchorKind) to High(TAnchorKind) do
    ARect[a]:=Control.AnchorSide[a].Control;
end;

function GetEnclosingControlRect(ControlList: TFPlist; out
  ARect: TAnchorControlsRect): boolean;
{ ARect will be the minimum TAnchorControlsRect around the controls in the list
  returns true, if there is such a TAnchorControlsRect.
  
  The controls in ARect will either be the Parent or a TLazDockSplitter
}
var
  Parent: TWinControl;
  
  function ControlIsValidAnchor(Control: TControl; Side: TAnchorKind): boolean;
  var
    i: Integer;
  begin
    Result:=false;
    if (Control=ARect[Side]) then exit(true);// this allows Parent at the beginning
    
    if not (Control is TLazDockSplitter) then
      exit;// not a splitter
    if (TLazDockSplitter(Control).ResizeAnchor in [akLeft,akRight])
      <>(Side in [akLeft,akRight]) then
        exit;// wrong alignment
    if ControlList.IndexOf(Control)>=0 then
      exit;// is an inner control
    if ControlIsAnchoredIndirectly(Control,Side,ARect[Side]) then
      exit; // this anchor would be worse than the current maximum
    for i:=0 to ControlList.Count-1 do begin
      if not ControlIsAnchoredIndirectly(Control,Side,TControl(ControlList[i]))
      then begin
        // this anchor is not above (below, ...) the inner controls
        exit;
      end;
    end;
    Result:=true;
  end;
  
var
  TopIndex: Integer;
  TopControl: TControl;
  RightIndex: Integer;
  RightControl: TControl;
  BottomIndex: Integer;
  BottomControl: TControl;
  LeftIndex: Integer;
  LeftControl: TControl;
  Candidates: TFPList;
  i: Integer;
  a: TAnchorKind;
begin
  Result:=false;
  if (ControlList=nil) or (ControlList.Count=0) then exit;

  // get Parent
  Parent:=TControl(ControlList[0]).Parent;
  if Parent=nil then exit;
  for i:=0 to ControlList.Count-1 do
    if TControl(ControlList[i]).Parent<>Parent then exit;
    
  // set the default rect: the Parent
  Result:=true;
  for a:=Low(TAnchorKind) to High(TAnchorKind) do
    ARect[a]:=Parent;

  // find all possible Candidates
  Candidates:=TFPList.Create;
  Candidates.Add(Parent);
  for i:=0 to Parent.ControlCount-1 do
    if Parent.Controls[i] is TLazDockSplitter then
      Candidates.Add(Parent.Controls[i]);

  // now check every possible rectangle
  // Note: four loops seems to be dog slow, but the checks
  //       avoid most possibilities early
  for TopIndex:=0 to Candidates.Count-1 do begin
    TopControl:=TControl(Candidates[TopIndex]);
    if not ControlIsValidAnchor(TopControl,akTop) then continue;
    
    for RightIndex:=0 to Candidates.Count-1 do begin
      RightControl:=TControl(Candidates[RightIndex]);
      if (TopControl.AnchorSide[akRight].Control<>RightControl)
      and (RightControl.AnchorSide[akTop].Control<>TopControl) then
        continue; // not touching / not a corner
      if not ControlIsValidAnchor(RightControl,akRight) then continue;
      
      for BottomIndex:=0 to Candidates.Count-1 do begin
        BottomControl:=TControl(Candidates[BottomIndex]);
        if (RightControl.AnchorSide[akBottom].Control<>BottomControl)
        and (BottomControl.AnchorSide[akRight].Control<>RightControl) then
          continue; // not touching / not a corner
        if not ControlIsValidAnchor(BottomControl,akBottom) then continue;
        
        for LeftIndex:=0 to Candidates.Count-1 do begin
          LeftControl:=TControl(Candidates[LeftIndex]);
          if (BottomControl.AnchorSide[akLeft].Control<>LeftControl)
          and (LeftControl.AnchorSide[akBottom].Control<>BottomControl) then
            continue; // not touching / not a corner
          if (TopControl.AnchorSide[akLeft].Control<>LeftControl)
          and (LeftControl.AnchorSide[akTop].Control<>LeftControl) then
            continue; // not touching / not a corner
          if not ControlIsValidAnchor(LeftControl,akLeft) then continue;

          // found a better rectangle
          ARect[akLeft]  :=LeftControl;
          ARect[akRight] :=RightControl;
          ARect[akTop]   :=TopControl;
          ARect[akBottom]:=BottomControl;
        end;
      end;
    end;
  end;
  
  Candidates.Free;
end;

function GetEnclosedControls(const ARect: TAnchorControlsRect): TFPList;
{ return a list of all controls bounded by the anchors in ARect }
var
  Parent: TWinControl;
  
  procedure Fill(AControl: TControl);
  var
    a: TAnchorKind;
    SideControl: TControl;
    i: Integer;
  begin
    if AControl=nil then exit;
    if AControl=Parent then exit;// do not add Parent
    for a:=Low(TAnchorKind) to High(TAnchorKind) do
      if ARect[a]=AControl then exit;// do not add boundary
      
    if Result.IndexOf(AControl)>=0 then exit;// already added
    Result.Add(AControl);
    
    for a:=Low(TAnchorKind) to High(TAnchorKind) do
      Fill(AControl.AnchorSide[a].Control);
    for i:=0 to Parent.ControlCount-1 do begin
      SideControl:=Parent.Controls[i];
      for a:=Low(TAnchorKind) to High(TAnchorKind) do
        if SideControl.AnchorSide[a].Control=AControl then
          Fill(SideControl);
    end;
  end;
  
var
  i: Integer;
  AControl: TControl;
  LeftTopControl: TControl;
begin
  Result:=TFPList.Create;

  // find the Parent
  if (ARect[akLeft]=ARect[akRight]) and (ARect[akLeft] is TWinControl) then
    Parent:=TWinControl(ARect[akLeft])
  else
    Parent:=ARect[akLeft].Parent;
    
  // find the left, top most control
  for i:=0 to Parent.ControlCount-1 do begin
    AControl:=Parent.Controls[i];
    if (AControl.AnchorSide[akLeft].Control=ARect[akLeft])
    and (AControl.AnchorSide[akTop].Control=ARect[akTop]) then begin
      LeftTopControl:=AControl;
      break;
    end;
  end;
  if Result.Count=0 then exit;
  
  // use flood fill to find the rest
  Fill(LeftTopControl);
end;

{ TLazDockPages }

function TLazDockPages.GetActiveNotebookPageComponent: TLazDockPage;
begin
  Result:=TLazDockPage(ActivePageComponent);
end;

function TLazDockPages.GetNoteBookPage(Index: Integer): TLazDockPage;
begin
  Result:=TLazDockPage(inherited Page[Index]);
end;

procedure TLazDockPages.SetActiveNotebookPageComponent(
  const AValue: TLazDockPage);
begin
  ActivePageComponent:=AValue;
end;

function TLazDockPages.GetFloatingDockSiteClass: TWinControlClass;
begin
  Result:=TLazDockForm;
end;

constructor TLazDockPages.Create(TheOwner: TComponent);
begin
  PageClass:=TLazDockPage;
  inherited Create(TheOwner);
end;

{ TLazDockTree }

procedure TLazDockTree.UndockControlForDocking(AControl: TControl);
var
  AWinControl: TWinControl;
  Sibling: TControl;
  a: TAnchorKind;
  i: Integer;
begin
  DebugLn(['TLazDockTree.UndockControlForDocking AControl=',DbgSName(AControl),' AControl.Parent=',DbgSName(AControl.Parent)]);
  // undock AControl
  if AControl is TWinControl then begin
    AWinControl:=TWinControl(AControl);
    if AWinControl.DockManager<>nil then begin
      // anything to do here?
    end;
  end;
  if AControl.Parent<>nil then begin
    AControl.Parent:=nil;
  end;
  for i:=AControl.AnchoredControlCount-1 downto 0 do begin
    Sibling:=AControl.AnchoredControls[i];
    if (Sibling<>AControl.Parent) and (Sibling.Parent<>AControl) then begin
      for a:=low(TAnchorKind) to high(TAnchorKind) do
        if Sibling.AnchorSide[a].Control=AControl then
          Sibling.AnchorSide[a].Control:=nil;
    end;
  end;
end;

function TLazDockTree.DefaultDockGrabberSize: Integer;
begin
  Result := {Abs(DockSite.Font.Height) + 4} 20;
end;

procedure TLazDockTree.BreakAnchors(Zone: TDockZone);
begin
  if Zone=nil then exit;
  if (Zone.ChildControl<>nil) and (Zone.ChildControl<>DockSite) then begin
    Zone.ChildControl.AnchorSide[akLeft].Control:=nil;
    Zone.ChildControl.AnchorSide[akTop].Control:=nil;
    Zone.ChildControl.Anchors:=[akLeft,akTop];
  end;
  BreakAnchors(Zone.FirstChild);
  BreakAnchors(Zone.NextSibling);
end;

procedure TLazDockTree.PaintDockFrame(ACanvas: TCanvas; AControl: TControl;
  const ARect: TRect);
var
  Details: TThemedElementDetails;
  BtnRect: TRect;
  DrawRect: TRect;
  d: integer;
  DockCaption: String;
  TextStyle: TTextStyle;
begin
  DockCaption := DockSite.GetDockCaption(AControl);
  TextStyle.Alignment := taLeftJustify;
  TextStyle.Layout := tlCenter;
  TextStyle.SingleLine := True;
  TextStyle.Clipping := True;
  TextStyle.Opaque := False;
  TextStyle.Wordbreak := False;
  TextStyle.SystemFont := False;
  TextStyle.RightToLeft := AControl.UseRightToLeftAlignment;

  DrawRect := ARect;
  InflateRect(DrawRect, -1, -1);
  ACanvas.Brush.Color := clBtnShadow;
  ACanvas.FrameRect(DrawRect);
  InflateRect(DrawRect, -1, -1);
  case AControl.DockOrientation of
    doHorizontal:
      begin
        d := DrawRect.Bottom - DrawRect.Top;
        BtnRect := DrawRect;
        BtnRect.Left := BtnRect.Right - d;
        Details := ThemeServices.GetElementDetails(twMDICloseButtonNormal);
        ThemeServices.DrawElement(ACanvas.Handle, Details, BtnRect);

        DrawRect.Right := BtnRect.Left;
        BtnRect := DrawRect;
        Dec(BtnRect.Right);
        BtnRect.Left := BtnRect.Right - d;
        Details := ThemeServices.GetElementDetails(twMDIRestoreButtonNormal);
        ThemeServices.DrawElement(ACanvas.Handle, Details, BtnRect);

        DrawRect.Right := BtnRect.Left;
        InflateRect(DrawRect, -4, 0);

        ACanvas.TextRect(DrawRect, DrawRect.Left, DrawRect.Top, DockCaption, TextStyle);
      end;
    doVertical:
      begin
        d := DrawRect.Right - DrawRect.Left;
        BtnRect := DrawRect;
        BtnRect.Bottom := BtnRect.Top + d;
        Details := ThemeServices.GetElementDetails(twMDICloseButtonNormal);
        ThemeServices.DrawElement(ACanvas.Handle, Details, BtnRect);

        DrawRect.Top := BtnRect.Bottom;
        BtnRect := DrawRect;
        Inc(BtnRect.Top);
        BtnRect.Bottom := BtnRect.Top + d;
        Details := ThemeServices.GetElementDetails(twMDIRestoreButtonNormal);
        ThemeServices.DrawElement(ACanvas.Handle, Details, BtnRect);

        DrawRect.Top := BtnRect.Bottom;
        InflateRect(DrawRect, 0, -4);

        ACanvas.TextRect(DrawRect, DrawRect.Left, DrawRect.Bottom, DockCaption, TextStyle);
      end;
  end;
end;

procedure TLazDockTree.CreateDockLayoutHelperControls(Zone: TLazDockZone);
var
  ParentPages: TLazDockPages;
  ZoneIndex: LongInt;
begin
  if Zone=nil then exit;

  // create needed TLazDockSplitter
  if (Zone.Parent<>nil)
  and (Zone.Parent.Orientation in [doVertical,doHorizontal])
  and (Zone.PrevSibling<>nil) then begin
    // a zone with a side sibling -> needs a TLazDockSplitter
    if Zone.Splitter=nil then begin
      Zone.Splitter:=TLazDockSplitter.Create(nil);
    end;
  end else if Zone.Splitter<>nil then begin
    // zone no longer needs the splitter
    Zone.Splitter.Free;
    Zone.Splitter:=nil;
  end;

  // create needed TLazDockPages
  if (Zone.Orientation=doPages) then begin
    // a zone of pages -> needs a TLazDockPages
    if Zone.FirstChild=nil then
      RaiseGDBException('TLazDockTree.CreateDockLayoutHelperControls Inconsistency: doPages without childs');
    if (Zone.Pages=nil) then begin
      Zone.Pages:=TLazDockPages.Create(nil);
    end;
  end else if Zone.Pages<>nil then begin
    // zone no longer needs the pages
    Zone.Pages.Free;
    Zone.Pages:=nil;
  end;

  // create needed TLazDockPage
  if (Zone.Parent<>nil)
  and (Zone.Parent.Orientation=doPages) then begin
    // a zone as page -> needs a TLazDockPage
    if (Zone.Page=nil) then begin
      ParentPages:=TLazDockZone(Zone.Parent).Pages;
      ZoneIndex:=Zone.GetIndex;
      ParentPages.Pages.Insert(ZoneIndex,Zone.GetCaption);
      Zone.Page:=ParentPages.Page[ZoneIndex];
    end;
  end else if Zone.Page<>nil then begin
    // zone no longer needs the page
    Zone.Page.Free;
    Zone.Page:=nil;
  end;

  // create controls for childs and siblings
  CreateDockLayoutHelperControls(Zone.FirstChild as TLazDockZone);
  CreateDockLayoutHelperControls(Zone.NextSibling as TLazDockZone);
end;

procedure TLazDockTree.AdjustDockRect(AControl: TControl; var ARect: TRect);
begin
  // offset one of the borders of control rect in order to get space for frame
  case AControl.DockOrientation of
    doHorizontal:
      Inc(ARect.Top, DefaultDockGrabberSize);
    doVertical:
      Inc(ARect.Left, DefaultDockGrabberSize);
  end;
end;

procedure TLazDockTree.AnchorDockLayout(Zone: TLazDockZone);
// setup all anchors between all docked controls and helper controls
var
  AnchorControls: array[TAnchorKind] of TControl;
  a: TAnchorKind;
  SplitterSide: TAnchorKind;
  CurControl: TControl;
  NewSplitterAnchors: TAnchors;
  NewAnchors: TAnchors;
begin
  if Zone=nil then exit;

  if Zone.Pages<>nil then
    CurControl:=Zone.Pages
  else
    CurControl:=Zone.ChildControl;
  //DebugLn(['TLazDockTree.AnchorDockLayout CurControl=',DbgSName(CurControl),' DockSite=',DbgSName(DockSite)]);
  if (CurControl<>nil) and (CurControl<>DockSite) then begin
    // get outside anchor controls
    NewAnchors:=[akLeft,akRight,akTop,akBottom];
    for a:=Low(TAnchorKind) to High(TAnchorKind) do
      AnchorControls[a]:=GetAnchorControl(Zone,a,true);

    // anchor splitter
    if (Zone.Splitter<>nil) then begin
      if Zone.Parent.Orientation=doHorizontal then
        SplitterSide:=akLeft
      else
        SplitterSide:=akTop;
      // IMPORTANT: first set the AnchorSide, then set the Anchors
      NewSplitterAnchors:=[akLeft,akRight,akTop,akBottom]-[SplitterSide];
      for a:=Low(TAnchorKind) to High(TAnchorKind) do
        if a in NewSplitterAnchors then
          Zone.Splitter.AnchorSide[a].Control:=AnchorControls[a]
        else
          Zone.Splitter.AnchorSide[a].Control:=nil;
      Zone.Splitter.Anchors:=NewSplitterAnchors;
      AnchorControls[SplitterSide]:=Zone.Splitter;
    end;

    // anchor pages
    // IMPORTANT: first set the AnchorSide, then set the Anchors
    //DebugLn(['TLazDockTree.AnchorDockLayout CurControl.Parent=',DbgSName(CurControl.Parent),' ',CurControl.Visible]);
    for a := Low(TAnchorKind) to High(TAnchorKind) do
    begin
      CurControl.AnchorSide[a].Control := AnchorControls[a];
      if (AnchorControls[a] <> nil) and (AnchorControls[a].Parent = CurControl.Parent) then
        CurControl.AnchorSide[a].Side := DefaultSideForAnchorKind[a]
      else
        CurControl.AnchorSide[a].Side := DefaultSideForAnchorKind[OppositeAnchor[a]];
    end;
    CurControl.Anchors := NewAnchors;
    // how to set space for header?
    //CurControl.BorderSpacing.Top := CurControl.BoundsRect.Top;
    //CurControl.BorderSpacing.Left := CurControl.BoundsRect.Left;
  end;

  // anchor controls for childs and siblings
  AnchorDockLayout(Zone.FirstChild as TLazDockZone);
  AnchorDockLayout(Zone.NextSibling as TLazDockZone);
end;

constructor TLazDockTree.Create(TheDockSite: TWinControl);
begin
  SetDockZoneClass(TLazDockZone);
  if TheDockSite=nil then begin
    TheDockSite:=TLazDockForm.Create(nil);
    TheDockSite.DockManager:=Self;
    FAutoFreeDockSite:=true;
  end;
  inherited Create(TheDockSite);
end;

destructor TLazDockTree.Destroy;
begin
  if FAutoFreeDockSite then begin
    if DockSite.DockManager=Self then
      DockSite.DockManager:=nil;
    DockSite.Free;
    DockSite:=nil;
  end;
  inherited Destroy;
end;

procedure TLazDockTree.InsertControl(AControl: TControl; InsertAt: TAlign;
  DropControl: TControl);
{ undocks AControl and docks it into the tree
  It creates a new TDockZone for AControl and inserts it as a new leaf.
  It automatically changes the tree, so that the parent of the new TDockZone
  will have the Orientation for InsertAt.
  
  Example 1:

    A newly created TLazDockTree has only a DockSite (TLazDockForm) and a single
    TDockZone - the RootZone, which has as ChildControl the DockSite.
    
    Visual:
      +-DockSite--+
      |           |
      +-----------+
    Tree of TDockZone:
      RootZone (DockSite,doNoOrient)


  Inserting the first control:  InsertControl(Form1,alLeft,nil);
    Visual:
      +-DockSite---+
      |+--Form1---+|
      ||          ||
      |+----------+|
      +------------+
    Tree of TDockZone:
      RootZone (DockSite,doHorizontal)
       +-Zone2 (Form1,doNoOrient)


  Dock Form2 right of Form1:  InsertControl(Form2,alLeft,Form1);
    Visual:
      +-DockSite----------+
      |+-Form1-+|+-Form2-+|
      ||        ||       ||
      |+-------+|+-------+|
      +-------------------+
    Tree of TDockZone:
      RootZone (DockSite,doHorizontal)
       +-Zone2 (Form1,doNoOrient)
       +-Zone3 (Form2,doNoOrient)
}

  procedure PrepareControlForResize(AControl: TControl); inline;
  var
    a: TAnchorKind;
  begin
    AControl.Align := alNone;
    AControl.Anchors := [akLeft, akTop];
    for a := Low(TAnchorKind) to High(TAnchorKind) do
      AControl.AnchorSide[a].Control := nil;
    AControl.AutoSize := False;
  end;

const
  SplitterWidth = 5;
  SplitterHeight = 5;
var
  DropZone: TDockZone;
  NewZone: TLazDockZone;
  NewOrientation: TDockOrientation;
  NeedNewParentZone: Boolean;
  NewParentZone: TDockZone;
  OldParentZone: TDockZone;
  NewBounds: TRect;
  ASibling: TDockZone;
begin
  if DropControl=nil then
    DropControl:=DockSite;
  DropZone:=RootZone.FindZone(DropControl);
  if DropZone=nil then
    raise Exception.Create('TLazDockTree.InsertControl DropControl is not part of this TDockTree');

  NewOrientation:=DockAlignOrientations[InsertAt];

  // undock
  UndockControlForDocking(AControl);
  
  // dock
  // create a new zone for AControl
  NewZone:=DockZoneClass.Create(Self,AControl) as TLazDockZone;
  
  // insert new zone into tree
  if (DropZone=RootZone) and (RootZone.FirstChild=nil) then begin
    // this is the first child
    debugln('TLazDockTree.InsertControl First Child');
    RootZone.Orientation := NewOrientation;
    RootZone.AddAsFirstChild(NewZone);
    AControl.DockOrientation := NewOrientation;
    if not AControl.Visible then
      DockSite.Visible := False;

    NewBounds := AControl.BoundsRect;
    AdjustDockRect(AControl, NewBounds);
    DockSite.BoundsRect := NewBounds;
    
    PrepareControlForResize(AControl);
    AControl.BoundsRect := NewBounds;
    AControl.Parent := DockSite;
    
    if AControl.Visible then
      DockSite.Visible := True;
  end else begin
    // there are already other childs

    // optimize DropZone
    if (DropZone.ChildCount>0)
    and (NewOrientation in [doHorizontal,doVertical])
    and ((DropZone.Orientation=NewOrientation)
         or (DropZone.Orientation=doNoOrient))
    then begin
      // docking on a side of an inner node is the same as docking to a side of
      // a child
      if InsertAt in [alLeft,alTop] then
        DropZone:=DropZone.FirstChild
      else
        DropZone:=DropZone.GetLastChild;
    end;
    
    // insert a new Parent Zone if needed
    NeedNewParentZone:=true;
    if (DropZone.Parent<>nil) then begin
      if (DropZone.Orientation=doNoOrient) then
        NeedNewParentZone:=false;
      if (DropZone.Orientation=NewOrientation) then
        NeedNewParentZone:=false;
    end;
    if NeedNewParentZone then begin
      // insert a new zone between current DropZone.Parent and DropZone
      // this new zone will become the new DropZone.Parent
      OldParentZone:=DropZone.Parent;
      NewParentZone:=DockZoneClass.Create(Self,nil);
      if OldParentZone<>nil then
        OldParentZone.ReplaceChild(DropZone,NewParentZone);
      NewParentZone.AddAsFirstChild(DropZone);
    end;
    
    // adjust Orientation in tree
    if DropZone.Parent.Orientation=doNoOrient then
      DropZone.Parent.Orientation:=NewOrientation;
    if DropZone.Parent.Orientation<>NewOrientation then
      RaiseGDBException('TLazDockTree.InsertControl Inconsistency DropZone.Orientation<>NewOrientation');

    // insert new node
    if DropZone.Parent=nil then
      RaiseGDBException('TLazDockTree.InsertControl Inconsistency DropZone.Parent=nil');
    if InsertAt in [alLeft,alTop] then
      DropZone.Parent.AddAsFirstChild(NewZone)
    else
      DropZone.Parent.AddAsLastChild(NewZone);
      
    // break anchors and resize DockSite
    BreakAnchors(RootZone);
    NewBounds := DockSite.BoundsRect;
    case InsertAt of
      alLeft:  dec(NewBounds.Left,SplitterWidth+AControl.Width);
      alRight: inc(NewBounds.Right,SplitterWidth+AControl.Width);
      alTop:   dec(NewBounds.Top,SplitterHeight+AControl.Height);
      alBottom:inc(NewBounds.Bottom,SplitterHeight+AControl.Height);
    else     // no change
    end;
    DockSite.BoundsRect := NewBounds;
    
    // add AControl to DockSite
    AControl.Visible := False;
    AControl.Parent := nil;
    PrepareControlForResize(AControl);
    // resize control
    DebugLn('TLazDockTree.InsertControl TODO resize control');
    if NewOrientation in [doHorizontal,doVertical] then begin
      ASibling:=NewZone.PrevSibling;
      if ASibling=nil then ASibling:=NewZone.NextSibling;
      if ASibling<>nil then begin
        if NewOrientation=doHorizontal then
          AControl.Height:=ASibling.Height
        else
          AControl.Width:=ASibling.Width;
      end;
    end;
    AControl.DockOrientation := NewOrientation;
    AControl.Parent := NewZone.GetParentControl;
  end;
  
  // Build dock layout (anchors, splitters, pages)
  BuildDockLayout(RootZone as TLazDockZone);
end;

procedure TLazDockTree.RemoveControl(AControl: TControl);
var
  RemoveZone: TLazDockZone;
begin
  RemoveZone:=RootZone.FindZone(AControl) as TLazDockZone;
  if RemoveZone.ChildCount>0 then
    raise Exception.Create('TLazDockTree.RemoveControl RemoveZone.ChildCount>0');
  FreeAndNil(RemoveZone.Splitter);
  FreeAndNil(RemoveZone.Page);
  FreeAndNil(RemoveZone.Pages);
  if RemoveZone.Parent<>nil then
    RemoveZone.Parent.Remove(RemoveZone);
  RemoveZone.Free;

  // Build dock layout (anchors, splitters, pages)
  BuildDockLayout(RootZone as TLazDockZone);
  DockSite.Invalidate; // to redraw dock headers
end;

procedure TLazDockTree.BuildDockLayout(Zone: TLazDockZone);
begin
  if DockSite<>nil then
    DockSite.DisableAlign;
  try
    BreakAnchors(Zone);
    CreateDockLayoutHelperControls(Zone);
    AnchorDockLayout(Zone);
  finally
    if DockSite<>nil then
      DockSite.EnableAlign;
  end;
end;

procedure TLazDockTree.FindBorderControls(Zone: TLazDockZone; Side: TAnchorKind;
  var List: TFPList);
begin
  if List=nil then List:=TFPList.Create;
  if Zone=nil then exit;
  
  if (Zone.Splitter<>nil) and (Zone.Parent<>nil)
  and (Zone.Orientation=doVertical) then begin
    // this splitter is leftmost, topmost, bottommost
    if Side in [akLeft,akTop,akBottom] then
      List.Add(Zone.Splitter);
    if Side=akLeft then begin
      // the splitter fills the whole left side => no more controls
      exit;
    end;
  end;
  if (Zone.Splitter<>nil) and (Zone.Parent<>nil)
  and (Zone.Orientation=doHorizontal) then begin
    // this splitter is topmost, leftmost, rightmost
    if Side in [akTop,akLeft,akRight] then
      List.Add(Zone.Splitter);
    if Side=akTop then begin
      // the splitter fills the whole top side => no more controls
      exit;
    end;
  end;
  if Zone.ChildControl<>nil then begin
    // the ChildControl fills the whole zone (except for the splitter)
    List.Add(Zone.ChildControl);
    exit;
  end;
  if Zone.Pages<>nil then begin
    // the pages fills the whole zone (except for the splitter)
    List.Add(Zone.Pages);
    exit;
  end;

  // go recursively through all child zones
  if (Zone.Parent<>nil) and (Zone.Orientation in [doVertical,doHorizontal])
  and (Zone.FirstChild<>nil) then
  begin
    if Side in [akLeft,akTop] then
      FindBorderControls(Zone.FirstChild as TLazDockZone,Side,List)
    else
      FindBorderControls(Zone.GetLastChild as TLazDockZone,Side,List);
  end;
end;

function TLazDockTree.FindBorderControl(Zone: TLazDockZone; Side: TAnchorKind
  ): TControl;
var
  List: TFPList;
begin
  Result:=nil;
  if Zone=nil then exit;
  List:=nil;
  FindBorderControls(Zone,Side,List);
  if (List=nil) or (List.Count=0) then
    Result:=DockSite
  else
    Result:=TControl(List[0]);
  List.Free;
end;

function TLazDockTree.GetAnchorControl(Zone: TLazDockZone; Side: TAnchorKind;
  OutSide: boolean): TControl;
// find a control to anchor the Zone's Side
begin
  if Zone=nil then begin
    Result:=DockSite;
    exit;
  end;

  if not OutSide then begin
    // also check the Splitter and the Page
    if (Side=akLeft)
    and (Zone.Parent<>nil) and (Zone.Parent.Orientation=doHorizontal)
    and (Zone.Splitter<>nil) then begin
      Result:=Zone.Splitter;
      exit;
    end;
    if (Side=akTop)
    and (Zone.Parent<>nil) and (Zone.Parent.Orientation=doVertical)
    and (Zone.Splitter<>nil) then begin
      Result:=Zone.Splitter;
      exit;
    end;
    if (Zone.Page<>nil) then begin
      Result:=Zone.Page;
      exit;
    end;
  end;

  // search the neighbour zones:
  Result:=DockSite;
  if (Zone.Parent=nil) then exit;
  case Zone.Parent.Orientation of
  doHorizontal:
    if (Side=akLeft) and (Zone.PrevSibling<>nil) then
      Result:=FindBorderControl(Zone.PrevSibling as TLazDockZone,akRight)
    else if (Side=akRight) and (Zone.NextSibling<>nil) then
      Result:=FindBorderControl(Zone.NextSibling as TLazDockZone,akLeft)
    else
      Result:=GetAnchorControl(Zone.Parent as TLazDockZone,Side,false);
  doVertical:
    if (Side=akTop) and (Zone.PrevSibling<>nil) then
      Result:=FindBorderControl(Zone.PrevSibling as TLazDockZone,akBottom)
    else if (Side=akBottom) and (Zone.NextSibling<>nil) then
      Result:=FindBorderControl(Zone.NextSibling as TLazDockZone,akTop)
    else
      Result:=GetAnchorControl(Zone.Parent as TLazDockZone,Side,false);
  doPages:
    Result:=GetAnchorControl(Zone.Parent as TLazDockZone,Side,false);
  end;
end;

procedure TLazDockTree.PaintSite(DC: HDC);
var
  ACanvas: TCanvas;
  ARect: TRect;
  i: integer;
begin
  // paint bounds for each control and close button
  if DockSite.ControlCount > 0 then
  begin
    ACanvas := TCanvas.Create;
    ACanvas.Handle := DC;
    try
      for i := 0 to DockSite.ControlCount - 1 do
      begin
        if DockSite.Controls[i].HostDockSite = DockSite then
        begin
          ARect := DockSite.Controls[i].BoundsRect;
          case DockSite.Controls[i].DockOrientation of
            doHorizontal:
              begin
                ARect.Bottom := ARect.Top;
                Dec(ARect.Top, DefaultDockGrabberSize);
              end;
            doVertical:
              begin
                ARect.Right := ARect.Left;
                Dec(ARect.Left, DefaultDockGrabberSize);
              end;
          end;
          PaintDockFrame(ACanvas, DockSite.Controls[i], ARect);
        end;
      end;
    finally
      ACanvas.Free;
    end;
  end;
end;

{ TLazDockZone }

destructor TLazDockZone.Destroy;
begin
  inherited Destroy;
  FreeAndNil(FSplitter);
  FreeAndNil(FPage);
  FreeAndNil(FPages);
end;

function TLazDockZone.GetCaption: string;
begin
  if ChildControl<>nil then
    Result:=ChildControl.Caption
  else
    Result:=IntToStr(GetIndex);
end;

function TLazDockZone.GetParentControl: TWinControl;
var
  Zone: TDockZone;
begin
  Result:=nil;
  Zone:=Parent;
  while Zone<>nil do begin
    if Zone.Orientation=doPages then begin
      Result:=(Zone as TLazDockZone).Pages;
      exit;
    end;
    if (Zone.Parent=nil) then begin
      if Zone.ChildControl is TWinControl then
        Result:=TWinControl(Zone.ChildControl);
      exit;
    end;
    Zone:=Zone.Parent;
  end;
end;

{ TCustomAnchoredDockManager }

procedure TCustomAnchoredDockManager.DeleteSideSplitter(Splitter: TLazDockSplitter;
  Side: TAnchorKind; NewAnchorControl: TControl);
var
  SplitterParent: TWinControl;
  i: Integer;
  CurControl: TControl;
  NewSideRef: TAnchorSideReference;
begin
  //DebugLn('TCustomAnchoredDockManager.DeleteSideSplitter Splitter=',DbgSName(Splitter),' Side=',dbgs(Side),' NewAnchorControl=',DbgSName(NewAnchorControl));
  SplitterParent:=Splitter.Parent;
  SplitterParent.DisableAlign;
  try
    for i:=0 to SplitterParent.ControlCount-1 do begin
      CurControl:=SplitterParent.Controls[i];
      if CurControl.AnchorSide[Side].Control=Splitter then begin
        CurControl.AnchorSide[Side].Control:=NewAnchorControl;
        if NewAnchorControl=CurControl.Parent then
          NewSideRef:=DefaultSideForAnchorKind[OppositeAnchor[Side]]
        else
          NewSideRef:=DefaultSideForAnchorKind[Side];
        CurControl.AnchorSide[Side].Side:=NewSideRef;
        //DebugLn('TCustomAnchoredDockManager.DeleteSideSplitter Anchor ',DbgSName(CurControl),'(',dbgs(Side),') to ',DbgSName(NewAnchorControl));
      end;
    end;
    Splitter.Free;
  finally
    SplitterParent.EnableAlign;
  end;
end;

procedure TCustomAnchoredDockManager.CombineSpiralSplitterPair(Splitter1,
  Splitter2: TLazDockSplitter);
{  Anchor all controls anchored to Splitter2 to Splitter1,
   extend Splitter1,
   delete Splitter2.

   Example:

   Four spiral splitters:

     Before:
              |
           A  |
     ---------|
       | +--+ |  C
     B | |  | |
       | +--+ |
       | ----------
       |   D

     The left and right splitter will be combined to one.

     After:
              |
           A  |
       -------|
              |  C
            B |
              |
              |------
              |   D
  }
  
  procedure MoveAnchorSide(AControl: TControl; Side: TAnchorKind);
  begin
    if AControl.AnchorSide[Side].Control=Splitter2 then
      AControl.AnchorSide[Side].Control:=Splitter1;
  end;
  
  procedure EnlargeSplitter(Side: TAnchorKind);
  begin
    if GetAnchorDepth(Splitter1,Side)<GetAnchorDepth(Splitter2,Side) then
      Splitter1.AnchorSide[Side].Assign(Splitter2.AnchorSide[Side]);
  end;
  
var
  LeftRightSplitter: boolean;
  ParentControl: TWinControl;
  i: Integer;
  CurControl: TControl;
begin
  DebugLn('TCustomAnchoredDockManager.CombineSpiralSplitterPair Splitter1=',DbgSName(Splitter1),dbgs(Splitter1.BoundsRect),' Splitter2=',DbgSName(Splitter2),dbgs(Splitter2.BoundsRect));
  // check splitters have the same Parent
  ParentControl:=Splitter1.Parent;
  if (ParentControl=nil) then
    RaiseGDBException('TCustomAnchoredDockManager.CombineSpiralSplitterPair Inconsistency: Parent=nil');
  if (ParentControl<>Splitter2.Parent) then
    RaiseGDBException('TCustomAnchoredDockManager.CombineSpiralSplitterPair Inconsistency: Splitters not siblings');
  // check splitters have same orientation
  LeftRightSplitter:=(Splitter1.ResizeAnchor in [akLeft,akRight]);
  if LeftRightSplitter<>(Splitter2.ResizeAnchor in [akLeft,akRight]) then
    RaiseGDBException('TCustomAnchoredDockManager.CombineSpiralSplitterPair Inconsistency: different orientation');

  ParentControl.DisableAlign;
  try
    // move incident anchors from Splitter2 to Splitter1
    for i:=0 to ParentControl.ControlCount-1 do begin
      CurControl:=ParentControl.Controls[i];
      if CurControl=Splitter1 then continue;
      if CurControl=Splitter2 then continue;
      if LeftRightSplitter then begin
        MoveAnchorSide(CurControl,akLeft);
        MoveAnchorSide(CurControl,akRight);
      end else begin
        MoveAnchorSide(CurControl,akTop);
        MoveAnchorSide(CurControl,akBottom);
      end;
    end;
    
    // enlarge Splitter1
    if LeftRightSplitter then begin
      // enlarge Splitter1 to top and bottom
      EnlargeSplitter(akTop);
      EnlargeSplitter(akBottom);
    end else begin
      // enlarge Splitter1 to left and right
      EnlargeSplitter(akLeft);
      EnlargeSplitter(akRight);
    end;
    
    // delete Splitter2
    Splitter2.Free;
  finally
    ParentControl.EnableAlign;
  end;
end;

procedure TCustomAnchoredDockManager.DeletePage(Page: TLazDockPage);
var
  Pages: TLazDockPages;
begin
  DebugLn('TCustomAnchoredDockManager.DeletePage Page=',DbgSName(Page));
  Pages:=Page.PageControl;
  Page.Free;
  if Pages.PageCount=0 then
    DeletePages(Pages);
end;

procedure TCustomAnchoredDockManager.DeletePages(Pages: TLazDockPages);
begin
  DebugLn('TCustomAnchoredDockManager.DeletePages Pages=',DbgSName(Pages));
  if Pages.Parent<>nil then
    UndockControl(Pages,false);
  Pages.Free;
end;

procedure TCustomAnchoredDockManager.DeleteDockForm(ADockForm: TLazDockForm);
begin
  DebugLn('TCustomAnchoredDockManager.DeleteDockForm ADockForm=',DbgSName(ADockForm));
  if ADockForm.Parent<>nil then
    UndockControl(ADockForm,false);
  ADockForm.Free;
end;

function TCustomAnchoredDockManager.GetAnchorDepth(AControl: TControl;
  Side: TAnchorKind): Integer;
var
  NewControl: TControl;
begin
  Result:=0;
  while (AControl<>nil) do begin
    inc(Result);
    if not (Side in AControl.Anchors) then break; // loose end
    NewControl:=AControl.AnchorSide[Side].Control;
    if NewControl=nil then break; // loose end
    if NewControl.Parent<>AControl.Parent then break; // parent end
    if Result>AControl.Parent.ControlCount then break; // circle
    AControl:=NewControl;
  end;
end;

constructor TCustomAnchoredDockManager.Create;
begin
  FSplitterSize:=5;
end;

procedure TCustomAnchoredDockManager.BeginUpdate;
begin
  inc(FUpdateCount);
end;

procedure TCustomAnchoredDockManager.EndUpdate;
begin
  if FUpdateCount<=0 then
    RaiseGDBException('TCustomAnchoredDockManager.EndUpdate');
  dec(FUpdateCount);
  if FUpdateCount=0 then begin

  end;
end;

procedure TCustomAnchoredDockManager.GetControlBounds(Control: TControl;
  out AControlBounds: TRect);
begin
  AControlBounds:=Control.BoundsRect;
end;

procedure TCustomAnchoredDockManager.DisableLayout(Control: TControl);
begin

end;

procedure TCustomAnchoredDockManager.EnableLayout(Control: TControl);
begin

end;

{-------------------------------------------------------------------------------
  procedure TCustomAnchoredDockManager.DockControl(Control: TControl;
    InsertAt: TAlign; DropCtl: TControl);

  Docks Control to or into DropCtl.
  Control.Parent must be nil.

  If InsertAt in [alLeft,alTop,alRight,alBottom] then Control will be docked to
  the side of DropCtl.
  Otherwise it is docked as Page to a TLazDockPages.

  Docking to a side:
    If DockCtl.Parent=nil then a parent will be created via
    DropCtl.ManualFloat.
    Then Control is added as child to DockCtl.Parent.
    Then a Splitter is added.
    Then all three are anchored.

  Docking as page:
    if DropCtl.Parent is not a TLazDockPage then a new TLazDockPages is created
    and replaces DropCtl and DropCtl is added as page.
    Then Control is added as page.
-------------------------------------------------------------------------------}
procedure TCustomAnchoredDockManager.DockControl(Control: TControl;
  InsertAt: TAlign; DropCtl: TControl);
var
  Splitter: TLazDockSplitter;
  NewDropCtlBounds: TRect;
  NewControlBounds: TRect;
  NewDropCtlWidth: Integer;
  SplitterBounds: TRect;
  a: TAnchorKind;
  ControlAnchor: TAnchorKind;
  DropCtlAnchor: TAnchorKind;
  NewDropCtlHeight: Integer;
  SplitterWidth: LongInt;
  SplitterHeight: LongInt;
  DockPages: TLazDockPages;
  DropCtlPage: TLazDockPage;
  NewPageIndex: Integer;
  NewPage: TLazDockPage;
  NewParent: TLazDockForm;
  ParentDisabledAlign: Boolean;
begin
  if Control.Parent<>nil then
    RaiseGDBException('TCustomAnchoredDockManager.InsertControl Control.Parent<>nil');
  if Control=DropCtl then
    RaiseGDBException('TCustomAnchoredDockManager.InsertControl Control=DropCtl');
  DisableLayout(Control);
  DisableLayout(DropCtl);
  try

    // dock Control to DropCtl
    case InsertAt of
    alLeft,alTop,alRight,alBottom:
      begin
        // dock Control to a side of DropCtl
        // e.g. alLeft: insert Control to the left of DropCtl

        DropCtlAnchor:=MainAlignAnchor[InsertAt];
        ControlAnchor:=OppositeAnchor[DropCtlAnchor];

        ParentDisabledAlign:=false;
        try
          NewDropCtlBounds:=DropCtl.BoundsRect;

          // make sure, there is a parent HostSite
          if DropCtl.Parent=nil then begin
            // remember bounds
            NewDropCtlBounds:=Rect(0,0,DropCtl.ClientWidth,DropCtl.ClientHeight);
            // create a TLazDockForm as new parent with the size of DropCtl
            NewParent:=TLazDockForm.Create(Application);// starts with Visible=false
            NewParent.DisableAlign;
            ParentDisabledAlign:=true;
            NewParent.BoundsRect:=DropCtl.BoundsRect;
            // move the WindowState to the new parent
            if DropCtl is TCustomForm then begin
              NewParent.WindowState:=TCustomForm(DropCtl).WindowState;
              TCustomForm(DropCtl).WindowState:=wsNormal;
              TCustomForm(DropCtl).BorderStyle:=bsNone;
            end;
            // first move DropCtl to the invsible parent, so changes do not cause flicker
            DropCtl.Parent:=NewParent;
            // init anchors of DropCtl
            DropCtl.Align:=alNone;
            DropCtl.AnchorClient(0);
            DropCtl.Anchors:=[akLeft,akTop,akRight,akBottom];
            DropCtl.Visible:=true;
            NewParent.Visible:=true;
            //DebugLn('TCustomAnchoredDockManager.DockControl DropCtl=',DbgSName(DropCtl),' NewParent.BoundsRect=',dbgs(NewParent.BoundsRect));
          end else begin
            if (DropCtl.Parent is TLazDockForm) then begin
              // ok
            end else if (DropCtl.Parent is TLazDockPage) then begin
              // ok
            end else begin
              RaiseGDBException('TCustomAnchoredDockManager.InsertControl DropCtl has invalid parent');
            end;
          end;

          if not ParentDisabledAlign then begin
            DropCtl.Parent.DisableAlign;
            ParentDisabledAlign:=true;
          end;
          // create a splitter
          Splitter:=TLazDockSplitter.Create(Control);
          Splitter.Align:=alNone;
          Splitter.Beveled:=true;
          Splitter.ResizeAnchor:=ControlAnchor;
          //debugln('TCustomAnchoredDockManager.InsertControl A Control.Bounds=',DbgSName(Control),dbgs(Control.BoundsRect),' DropCtl.Bounds=',DbgSName(DropCtl),dbgs(DropCtl.BoundsRect),' Splitter.Bounds=',DbgSName(Splitter),dbgs(Splitter.BoundsRect));

          // calculate new bounds
          NewControlBounds:=NewDropCtlBounds;
          if InsertAt in [alLeft,alRight] then begin
            SplitterWidth:=Splitter.Constraints.MinMaxWidth(SplitterSize);
            NewDropCtlWidth:=NewDropCtlBounds.Right-NewDropCtlBounds.Left;
            dec(NewDropCtlWidth,Control.Width+SplitterWidth);
            NewDropCtlWidth:=DropCtl.Constraints.MinMaxWidth(NewDropCtlWidth);
            if InsertAt=alLeft then begin
              // alLeft: insert Control to the left of DropCtl
              NewDropCtlBounds.Left:=NewDropCtlBounds.Right-NewDropCtlWidth;
              NewControlBounds.Right:=NewDropCtlBounds.Left-SplitterWidth;
              SplitterBounds:=Rect(NewControlBounds.Right,NewDropCtlBounds.Top,
                                   NewDropCtlBounds.Left,NewDropCtlBounds.Bottom);
            end else begin
              // alRight: insert Control to the right of DropCtl
              NewDropCtlBounds.Right:=NewDropCtlBounds.Left+NewDropCtlWidth;
              NewControlBounds.Left:=NewDropCtlBounds.Right+SplitterWidth;
              SplitterBounds:=Rect(NewDropCtlBounds.Right,NewDropCtlBounds.Top,
                                   NewControlBounds.Left,NewDropCtlBounds.Bottom);
              //debugln('TCustomAnchoredDockManager.InsertControl A NewDropCtlBounds=',dbgs(NewDropCtlBounds),' NewControlBounds=',dbgs(NewControlBounds),' SplitterBounds=',dbgs(SplitterBounds));
            end;
          end else begin
            SplitterHeight:=Splitter.Constraints.MinMaxHeight(SplitterSize);
            NewDropCtlHeight:=NewDropCtlBounds.Bottom-NewDropCtlBounds.Top;
            dec(NewDropCtlHeight,Control.Height+SplitterHeight);
            NewDropCtlHeight:=DropCtl.Constraints.MinMaxHeight(NewDropCtlHeight);
            if InsertAt=alTop then begin
              // alTop: insert Control to the top of DropCtl
              NewDropCtlBounds.Top:=NewDropCtlBounds.Bottom-NewDropCtlHeight;
              NewControlBounds.Bottom:=NewDropCtlBounds.Top-SplitterHeight;
              SplitterBounds:=Rect(NewDropCtlBounds.Left,NewControlBounds.Bottom,
                                   NewDropCtlBounds.Right,NewDropCtlBounds.Top);
            end else begin
              // alBottom: insert Control to the bottom of DropCtl
              NewDropCtlBounds.Bottom:=NewDropCtlBounds.Top+NewDropCtlHeight;
              NewControlBounds.Top:=NewDropCtlBounds.Bottom+SplitterHeight;
              SplitterBounds:=Rect(NewDropCtlBounds.Left,NewDropCtlBounds.Bottom,
                                   NewDropCtlBounds.Right,NewControlBounds.Top);
            end;
            //debugln('TCustomAnchoredDockManager.InsertControl A NewDropCtlBounds=',dbgs(NewDropCtlBounds),' NewControlBounds=',dbgs(NewControlBounds),' SplitterBounds=',dbgs(SplitterBounds));
          end;

          // position splitter
          Splitter.BoundsRect:=SplitterBounds;
          if InsertAt in [alLeft,alRight] then begin
            Splitter.AnchorSide[akTop].Assign(DropCtl.AnchorSide[akTop]);
            Splitter.AnchorSide[akBottom].Assign(DropCtl.AnchorSide[akBottom]);
            Splitter.Anchors:=[akLeft,akTop,akBottom];
          end else begin
            Splitter.AnchorSide[akLeft].Assign(DropCtl.AnchorSide[akLeft]);
            Splitter.AnchorSide[akRight].Assign(DropCtl.AnchorSide[akRight]);
            Splitter.Anchors:=[akLeft,akTop,akRight];
          end;
          Splitter.Parent:=DropCtl.Parent;

          // position Control
          Control.Align:=alNone;
          for a:=Low(TAnchorKind) to High(TAnchorKind) do
            Control.AnchorSide[a].Control:=nil;
          Control.AnchorSide[DropCtlAnchor].Assign(DropCtl.AnchorSide[DropCtlAnchor]);
          Control.AnchorToNeighbour(ControlAnchor,0,Splitter);
          if InsertAt in [alLeft,alRight] then begin
            Control.AnchorSide[akTop].Assign(DropCtl.AnchorSide[akTop]);
            Control.AnchorSide[akBottom].Assign(DropCtl.AnchorSide[akBottom]);
          end else begin
            Control.AnchorSide[akLeft].Assign(DropCtl.AnchorSide[akLeft]);
            Control.AnchorSide[akRight].Assign(DropCtl.AnchorSide[akRight]);
          end;
          Control.Anchors:=[akLeft,akTop,akRight,akBottom];
          Control.Parent:=DropCtl.Parent;
          Control.Visible:=true;

          // position DropCtl
          DropCtl.AnchorToNeighbour(DropCtlAnchor,0,Splitter);

          //debugln('TCustomAnchoredDockManager.InsertControl BEFORE ALIGNING Control.Bounds=',DbgSName(Control),dbgs(Control.BoundsRect),' DropCtl.Bounds=',DbgSName(DropCtl),dbgs(DropCtl.BoundsRect),' Splitter.Bounds=',DbgSName(Splitter),dbgs(Splitter.BoundsRect));
        finally
          if ParentDisabledAlign then
            DropCtl.Parent.EnableAlign;
        end;
        //debugln('TCustomAnchoredDockManager.InsertControl END Control.Bounds=',DbgSName(Control),dbgs(Control.BoundsRect),' DropCtl.Bounds=',DbgSName(DropCtl),dbgs(DropCtl.BoundsRect),' Splitter.Bounds=',DbgSName(Splitter),dbgs(Splitter.BoundsRect));
      end;

    alClient:
      begin
        // docking as page
        DebugLn('TCustomAnchoredDockManager.InsertControl alClient DropCtl=',DbgSName(DropCtl),' Control=',DbgSName(Control));

        if not (DropCtl.Parent is TLazDockPage) then begin
          // create a new TLazDockPages
          //DebugLn('TCustomAnchoredDockManager.InsertControl Create TLazDockPages');
          DockPages:=TLazDockPages.Create(nil);
          if DropCtl.Parent<>nil then begin
            // DockCtl is a child control
            // => replace the anchors to and from DockCtl with the new DockPages
            ReplaceAnchoredControl(DropCtl,DockPages);
          end else begin
            // DockCtl has no parent
            // => float DockPages
            DockPages.ManualFloat(DropCtl.BoundsRect);
          end;
          // add DockCtl as page to DockPages
          DockPages.Pages.Add(DropCtl.Caption);
          DropCtlPage:=DockPages.Page[0];
          DropCtlPage.DisableAlign;
          try
            DropCtl.Parent:=DropCtlPage;
            DropCtl.AnchorClient(0);
          finally
            DropCtlPage.EnableAlign;
          end;
        end;
        // add Control as new page behind the page of DockCtl
        DropCtlPage:=DropCtl.Parent as TLazDockPage;
        DockPages:=DropCtlPage.PageControl as TLazDockPages;
        NewPageIndex:=DropCtlPage.PageIndex+1;
        DockPages.Pages.Insert(NewPageIndex,Control.Caption);
        NewPage:=DockPages.Page[NewPageIndex];
        NewPage.DisableAlign;
        try
          Control.Parent:=NewPage;
          if Control is TCustomForm then
            TCustomForm(Control).WindowState:=wsNormal;
          Control.AnchorClient(0);
        finally
          NewPage.EnableAlign;
        end;
      end;
    else
      RaiseGDBException('TCustomAnchoredDockManager.InsertControl TODO');
    end;
  finally
    EnableLayout(Control);
    EnableLayout(DropCtl);
  end;
end;

{-------------------------------------------------------------------------------
  procedure TCustomAnchoredDockManager.UndockControl(Control: TControl);

  Removes a control from a docking form.
  It breaks all anchors and cleans up.
  
  The created gap will be tried to fill up.
  It removes TLazDockSplitter, TLazDockPage and TLazDockPages if they are no
  longer needed.
-------------------------------------------------------------------------------}
procedure TCustomAnchoredDockManager.UndockControl(Control: TControl; Float: boolean);
{

  Examples:

  Search Order:

  1. A TLazDockSplitter dividing only two controls:

     Before:
     |-------------
     | +--+ | +---
     | |  | | | B
     | +--+ | +---
     |-------------

     The splitter will be deleted and the right control will be anchored to the
     left.

     After:
     |-------------
     | +---
     | | B
     | +---
     |-------------


  2. Four spiral splitters:
  
     Before:
              |
           A  |
     ---------|
       | +--+ |  C
     B | |  | |
       | +--+ |
       | ----------
       |   D

     The left and right splitter will be combined to one.
     
     After:
              |
           A  |
       -------|
              |  C
            B |
              |
              |------
              |   D


  3. No TLazDockSplitter. Control is the only child of a TLazDockPage
     In this case the page will be deleted.
     If the TLazDockPages has no childs left, it is recursively undocked.
  
  4. No TLazDockSplitter, Control is the only child of a TLazDockForm.
     The TLazDockForm is deleted and the Control is floated.
     This normally means: A form will simply be placed on the desktop, other
     controls will be docked into their DockSite.
     
  5. Otherwise: this control was not docked.
}
var
  a: TAnchorKind;
  AnchorControl: TControl;
  AnchorSplitter: TLazDockSplitter;
  i: Integer;
  Sibling: TControl;
  OldAnchorControls: array[TAnchorKind] of TControl;
  IsSpiralSplitter: Boolean;
  ParentControl: TWinControl;
  Done: Boolean;

  procedure DoFinallyForParent;
  var
    OldParentControl: TWinControl;
    NewBounds: TRect;
    NewOrigin: TPoint;
  begin
    try
      if Float then begin
        NewBounds:=Control.BoundsRect;
        NewOrigin:=Control.ControlOrigin;
        OffsetRect(NewBounds,NewOrigin.X,NewOrigin.Y);
        Control.ManualFloat(NewBounds);
      end else begin
        Control.Parent:=nil;
      end;
    finally
      if (ParentControl<>nil) then begin
        OldParentControl:=ParentControl;
        ParentControl:=nil;
        //DebugLn('DoFinallyForParent EnableAlign for ',DbgSName(OldParentControl));
        OldParentControl.EnableAlign;
        //OldParentControl.WriteLayoutDebugReport('X  ');
      end;
    end;
  end;
  
begin
  if Control.Parent=nil then begin
    // already undocked
    RaiseGDBException('TCustomAnchoredDockManager.UndockControl Control.Parent=nil');
  end;
  
  ParentControl:=Control.Parent;
  ParentControl.DisableAlign;
  try
    // break anchors
    Control.Align:=alNone;
    for a:=Low(TAnchorKind) to High(TAnchorKind) do begin
      OldAnchorControls[a]:=Control.AnchorSide[a].Control;
      Control.AnchorSide[a].Control:=nil;
    end;
    Control.Anchors:=[akLeft,akTop];

    Done:=false;

    if not Done then begin
      // check if there is a splitter, that has a side with only 'Control'
      // anchored to it.
      for a:=Low(TAnchorKind) to High(TAnchorKind) do begin
        AnchorControl:=OldAnchorControls[a];
        if AnchorControl is TLazDockSplitter then begin
          AnchorSplitter:=TLazDockSplitter(AnchorControl);
          i:=ParentControl.ControlCount-1;
          while i>=0 do begin
            Sibling:=ParentControl.Controls[i];
            if (Sibling.AnchorSide[a].Control=AnchorSplitter) then begin
              // Sibling is anchored with the same side to the splitter
              // => this splitter is needed, can not be deleted.
              //DebugLn('TCustomAnchoredDockManager.UndockControl Splitter still needed: ',DbgSName(AnchorSplitter),'(',dbgs(AnchorSplitter.BoundsRect),') by ',DbgSName(Sibling));
              break;
            end;
            dec(i);
          end;
          if i<0 then begin
            // this splitter is not needed anymore
            //DebugLn('TCustomAnchoredDockManager.UndockControl Splitter not needed: ',DbgSName(AnchorSplitter),'(',dbgs(AnchorSplitter.BoundsRect),')');
            DeleteSideSplitter(AnchorSplitter,OppositeAnchor[a],
                               OldAnchorControls[OppositeAnchor[a]]);
            Done:=true;
          end;
        end;
      end;
    end;

    if not Done then begin
      // check if there are four spiral splitters around Control
      IsSpiralSplitter:=true;
      for a:=Low(TAnchorKind) to High(TAnchorKind) do begin
        AnchorControl:=OldAnchorControls[a];
        if (AnchorControl=nil)
        or (not (AnchorControl is TLazDockSplitter)) then begin
          IsSpiralSplitter:=false;
        end;
      end;
      if IsSpiralSplitter then begin
        CombineSpiralSplitterPair(OldAnchorControls[akLeft] as TLazDockSplitter,
                                OldAnchorControls[akRight] as TLazDockSplitter);
        Done:=true;
      end;
    end;

    if not Done then begin
      // check if Control is the only child of a TLazDockPage
      if (ParentControl.ControlCount=1)
      and (ParentControl is TLazDockPage) then begin
        DoFinallyForParent;
        DeletePage(TLazDockPage(Control.Parent));
      end;
    end;
    
    if not Done then begin
      // check if Control is the only child of a TLazDockForm
      if (ParentControl.ControlCount=1)
      and (ParentControl is TLazDockForm) then begin
        DoFinallyForParent;
        DeleteDockForm(TLazDockForm(ParentControl));
      end;
    end;
    
    if not Done then begin
      // otherwise: keep
    end;
    
  finally
    DoFinallyForParent;
  end;
end;

procedure TCustomAnchoredDockManager.InsertControl(Control: TControl;
  InsertAt: TAlign; DropCtl: TControl);
begin
  DockControl(Control, InsertAt, DropCtl);
end;

function TCustomAnchoredDockManager.EnlargeControl(Control: TControl;
  Side: TAnchorKind; Simulate: boolean): boolean;
{ If Simulate=true then it will only test if control can be enlarged.

  Case A:
  Shrink one neighbour control, enlarge Control. Two splitters are resized.

      |#|         |#         |#|         |#
      |#| Control |#         |#|         |#
    --+#+---------+#   --> --+#| Control |#
    ===============#       ===#|         |#
    --------------+#       --+#|         |#
        A         |#        A|#|         |#
    --------------+#       --+#+---------+#
    ==================     ===================


  Case B:
  Move one neighbour splitter, enlarge Control, resize one splitter,
  rotate the other splitter.

      |#|         |#|          |#|         |#|
      |#| Control |#|          |#|         |#|
    --+#+---------+#+--  --> --+#| Control |#+--
    ===================      ===#|         |#===
    --------+#+--------      --+#|         |#+--
            |#|   B            |#|         |#|B
            |#+--------        |#|         |#+--
        A   |#=========       A|#|         |#===
            |#+--------        |#|         |#+--
            |#|   C            |#|         |#|C
    --------+#+--------      --+#+---------+#+--
    ===================      ===================
}
const
  MinControlSize = 20;
var
  MainSplitter: TLazDockSplitter;
  Side2: TAnchorKind;
  Side3: TAnchorKind;
  Side2Anchor: TControl;
  Side3Anchor: TControl;
  Parent: TWinControl;
  i: Integer;
  Sibling: TControl;
  CurSplitter: TLazDockSplitter;
  Neighbour: TControl;
  ShrinkSide: TAnchorKind;
  ParentDisabledAlign: Boolean;
  EnlargeSplitter: TLazDockSplitter;
  RotateSplitter: TLazDockSplitter;
  
  procedure ParentDisableAlign;
  begin
    if ParentDisabledAlign then exit;
    ParentDisabledAlign:=true;
    Parent.DisableAlign;
  end;
  
begin
  Result:=false;
  if Control=nil then exit;
  DebugLn(['TCustomAnchoredDockManager.EnlargeControl Control=',DbgSName(Control),' Side=',AnchorNames[Side]]);
  if Side in [akLeft,akRight] then
    Side2:=akTop
  else
    Side2:=akLeft;
  Side3:=OppositeAnchor[Side2];
  if not GetLazDockSplitter(Control,Side,MainSplitter) then exit;
  if not GetLazDockSplitterOrParent(Control,Side2,Side2Anchor) then exit;
  if not GetLazDockSplitterOrParent(Control,Side3,Side3Anchor) then exit;
  Parent:=Control.Parent;
  if (Side2Anchor=Parent) and (Side3Anchor=Parent) then exit;
  
  // search controls anchored to the MainSplitter on the other side
  Neighbour:=nil;
  for i:=0 to Parent.ControlCount-1 do begin
    Sibling:=Parent.Controls[i];
    if (not GetLazDockSplitter(Sibling,OppositeAnchor[Side],CurSplitter))
    or (CurSplitter<>MainSplitter) then continue;
    DebugLn(['TCustomAnchoredDockManager.EnlargeControl neighbour Sibling=',DbgSName(Sibling)]);
    // Sibling is anchored to MainSplitter on the other side
    // check if it is at the same height as Control
    if Side in [akTop,akBottom] then begin
      if (Side2Anchor is TLazDockSplitter) then begin
        if (Sibling.Left+Sibling.Width<Side2Anchor.Left) then continue;
      end else begin
        // Side2Anchor is Parent
        if Sibling.Left+Sibling.Width<Control.Left then continue;
      end;
      if (Side3Anchor is TLazDockSplitter) then begin
        if (Sibling.Left>Side3Anchor.Left+Side3Anchor.Width) then continue;
      end else begin
        // Side3Anchor is Parent
        if Sibling.Left>Control.Left+Control.Width then continue;
      end;
    end else begin
      if (Side2Anchor is TLazDockSplitter) then begin
        if (Sibling.Top+Sibling.Height<Side2Anchor.Top) then continue;
      end else begin
        // Side2Anchor is Parent
        if Sibling.Top+Sibling.Height<Control.Top then continue;
      end;
      if (Side3Anchor is TLazDockSplitter) then begin
        if (Sibling.Top>Side3Anchor.Top+Side3Anchor.Height) then continue;
      end else begin
        // Side3Anchor is Parent
        if Sibling.Top>Control.Top+Control.Height then continue;
      end;
    end;
    
    if Neighbour=nil then
      Neighbour:=Sibling
    else if Sibling is TLazDockSplitter then begin
      if Neighbour is TLazDockSplitter then begin
        // two splitters means, there is at least one Neighbour which can not
        // be shrinked
        exit;
      end;
      Neighbour:=Sibling;
    end;
  end;

  if Neighbour=nil then exit; // no neighbour found
  DebugLn(['TCustomAnchoredDockManager.EnlargeControl Neighbour=',DbgSName(Neighbour)]);
  
  ParentDisabledAlign:=false;
  try
    if Neighbour is TLazDockSplitter then begin
      // one splitter as Neighbour
      RotateSplitter:=TLazDockSplitter(Neighbour);
      DebugLn(['TCustomAnchoredDockManager.EnlargeControl rotate splitter RotateSplitter=',DbgSName(RotateSplitter)]);
      // check that all anchored controls of this splitter can be shrinked
      for i:=0 to Parent.ControlCount-1 do begin
        Sibling:=Parent.Controls[i];
        if Sibling=RotateSplitter then continue;
        if GetLazDockSplitter(Sibling,Side2,CurSplitter)
        and (CurSplitter=RotateSplitter)
        and (not NeighbourCanBeShrinked(Control,Sibling,Side2))
        then begin
          // this Sibling is anchored with Side2 at RotateSplitter
          // but can not be shrinked
          exit;
        end;
        if GetLazDockSplitter(Sibling,Side3,CurSplitter)
        and (CurSplitter=RotateSplitter)
        and (not NeighbourCanBeShrinked(Control,Sibling,Side3))
        then begin
          // this Sibling is anchored with Side3 at RotateSplitter
          // but can not be shrinked
          exit;
        end;
      end;

      {   |#|         |#|          |#|         |#|
          |#| Control |#|          |#|         |#|
        --+#+---------+#+--  --> --+#| Control |#+--
        ===================      ===#|         |#===
        --------+#+--------      --+#|         |#+--
                |#|   B            |#|         |#|B
                |#+--------        |#|         |#+--
            A   |#=========       A|#|         |#===
                |#+--------        |#|         |#+--
                |#|   C            |#|         |#|C
        --------+#+--------      --+#+---------+#+--
        ===================      =================== }

      Result:=true;
      if not Simulate then begin
        ParentDisableAlign;
        GetLazDockSplitter(Control,OppositeAnchor[Side2],EnlargeSplitter);
        // enlarge Control and its two side splitters
        Control.AnchorSame(Side,RotateSplitter);
        Side2Anchor.AnchorSame(Side,RotateSplitter);
        Side3Anchor.AnchorSame(Side,RotateSplitter);
        // shrink controls anchored to RotateSplitter
        for i:=0 to Parent.ControlCount-1 do begin
          Sibling:=Parent.Controls[i];
          if Sibling=RotateSplitter then continue;
          if GetLazDockSplitter(Sibling,Side2,CurSplitter)
          and (CurSplitter=RotateSplitter) then begin
            // this Sibling is anchored with Side2 at RotateSplitter
            Sibling.AnchorToNeighbour(Side2,0,Side3Anchor);
          end;
          if GetLazDockSplitter(Sibling,Side3,CurSplitter)
          and (CurSplitter=RotateSplitter) then begin
            // this Sibling is anchored with Side3 at RotateSplitter
            Sibling.AnchorToNeighbour(Side3,0,Side2Anchor);
          end;
        end;
        // rotate RotateSplitter
        RotateSplitter.AnchorSide[Side].Control:=nil;
        RotateSplitter.AnchorSide[OppositeAnchor[Side]].Control:=nil;
        RotateSplitter.ResizeAnchor:=Side;
        RotateSplitter.AnchorToNeighbour(Side2,0,Side3Anchor);
        RotateSplitter.AnchorSame(Side3,MainSplitter);
        if Side in [akLeft,akRight] then
          RotateSplitter.Anchors:=RotateSplitter.Anchors-[akRight]+[akLeft]
        else
          RotateSplitter.Anchors:=RotateSplitter.Anchors-[akBottom]+[akTop];
        // shrink MainSplitter
        MainSplitter.AnchorToNeighbour(Side2,0,Side2Anchor);
        // reanchor controls from MainSplitter to RotateSplitter
        for i:=0 to Parent.ControlCount-1 do begin
          Sibling:=Parent.Controls[i];
          if GetLazDockSplitter(Sibling,Side,CurSplitter)
          and (CurSplitter=MainSplitter) then begin
            if Side in [akLeft,akRight] then begin
              if Sibling.Top>Control.Top then
                Sibling.AnchorSide[Side].Control:=RotateSplitter;
            end else begin
              if Sibling.Left>Control.Left then
                Sibling.AnchorSide[Side].Control:=RotateSplitter;
            end;
          end;
        end;
      end;
      
    end else begin
      // shrink a neighbour control
      DebugLn(['TCustomAnchoredDockManager.EnlargeControl Shrink one control: Neighbour=',DbgSName(Neighbour)]);
      // check if Neighbour already shares a side with Control
      if (Neighbour.AnchorSide[Side2].Control<>Side2Anchor)
      and (Neighbour.AnchorSide[Side3].Control<>Side3Anchor) then begin
        { Neighbour is too broad.
            |#|         |#|
            |#| Control |#|
          --+#+---------+#+--
          ===================
          -------------------
               Neighbour
          ------------------- }
        exit;
      end;
      
      // check if the Neighbour can be shrinked
      if NeighbourCanBeShrinked(Control,Neighbour,Side2) then begin
        ShrinkSide:=Side2;
      end else if NeighbourCanBeShrinked(Control,Neighbour,Side3) then begin
        ShrinkSide:=Side3;
      end else begin
        // Neighbour can not be shrinked
        exit;
      end;
      

      {              EnlargeSplitter
                           ^
                          |#|         |#         |#|         |#
                          |#| Control |#         |#|         |#
                        --+#+---------+#   --> --+#| Control |#
       MainSplitter <-- ===============#       ===#|         |#
                        --------------+#       --+#|         |#
                             Neighbour|#        N|#|         |#
                        --------------+#       --+#+---------+#
                        ==================     =================== }
      Result:=true;
      if not Simulate then begin
        ParentDisableAlign;
        GetLazDockSplitter(Control,OppositeAnchor[ShrinkSide],EnlargeSplitter);
        Neighbour.AnchorToNeighbour(ShrinkSide,0,EnlargeSplitter);
        MainSplitter.AnchorToNeighbour(ShrinkSide,0,EnlargeSplitter);
        EnlargeSplitter.AnchorSame(Side,Neighbour);
        Control.AnchorSame(Side,Neighbour);
      end;
    end;
  finally
    if ParentDisabledAlign then
      Parent.EnableAlign;
  end;
end;

procedure TCustomAnchoredDockManager.LoadFromStream(Stream: TStream);
begin
  RaiseGDBException('TCustomAnchoredDockManager.LoadFromStream TODO');
end;

procedure TCustomAnchoredDockManager.PaintSite(DC: HDC);
begin
  RaiseGDBException('TCustomAnchoredDockManager.PaintSite TODO');
end;

procedure TCustomAnchoredDockManager.PositionDockRect(Client, DropCtl: TControl;
  DropAlign: TAlign; var DockRect: TRect);
begin
  RaiseGDBException('TCustomAnchoredDockManager.PositionDockRect TODO');
end;

procedure TCustomAnchoredDockManager.RemoveControl(Control: TControl);
begin
  UndockControl(Control,false);
end;

procedure TCustomAnchoredDockManager.ResetBounds(Force: Boolean);
begin
  RaiseGDBException('TCustomAnchoredDockManager.ResetBounds TODO');
end;

procedure TCustomAnchoredDockManager.SaveToStream(Stream: TStream);
begin
  RaiseGDBException('TCustomAnchoredDockManager.SaveToStream TODO');
end;

procedure TCustomAnchoredDockManager.SetReplacingControl(Control: TControl);
begin
  RaiseGDBException('TCustomAnchoredDockManager.SetReplacingControl TODO');
end;

procedure TCustomAnchoredDockManager.ReplaceAnchoredControl(OldControl,
  NewControl: TControl);
var
  a: TAnchorKind;
  Side: TAnchorSide;
  i: Integer;
  Sibling: TControl;
  CurParent: TWinControl;
begin
  if OldControl.Parent<>nil then begin
    CurParent:=OldControl.Parent;
    CurParent.DisableAlign;
    try
      // put NewControl on the same Parent with the same bounds
      NewControl.Parent:=nil;
      NewControl.Align:=alNone;
      NewControl.BoundsRect:=OldControl.BoundsRect;
      NewControl.Parent:=CurParent;
      // copy all four AnchorSide
      for a:=Low(TAnchorKind) to High(TAnchorKind) do
        NewControl.AnchorSide[a].Assign(OldControl.AnchorSide[a]);
      // bend all Anchors from OldControl to NewControl
      for i:=0 to CurParent.ControlCount-1 do begin
        Sibling:=CurParent.Controls[i];
        if (Sibling=NewControl) or (Sibling=OldControl) then continue;
        for a:=Low(TAnchorKind) to High(TAnchorKind) do begin
          Side:=Sibling.AnchorSide[a];
          if Side.Control=OldControl then begin
            Side.Control:=NewControl;
          end;
        end;
      end;
      // remove OldControl from its Parent
      OldControl.Parent:=nil;
    finally
      CurParent.EnableAlign;
    end;
  end else begin
    NewControl.Parent:=nil;
    NewControl.Align:=alNone;
    NewControl.BoundsRect:=OldControl.BoundsRect;
  end;
end;

function TCustomAnchoredDockManager.GetSplitterWidth(Splitter: TControl): integer;
begin
  Result:=Splitter.Constraints.MinMaxWidth(SplitterSize);
end;

function TCustomAnchoredDockManager.GetSplitterHeight(Splitter: TControl): integer;
begin
  Result:=Splitter.Constraints.MinMaxHeight(SplitterSize);
end;

{ TLazDockPage }

function TLazDockPage.GetPageControl: TLazDockPages;
begin
  Result:=Parent as TLazDockPages;
end;

{ TLazDockForm }

procedure TLazDockForm.SetMainControl(const AValue: TControl);
var
  NewValue: TControl;
begin
  if (AValue<>nil) and (not IsParentOf(AValue)) then
    raise Exception.Create('invalid main control');
  NewValue:=AValue;
  if NewValue=nil then
    NewValue:=FindMainControlCandidate;
  if FMainControl=NewValue then exit;
  FMainControl:=NewValue;
  if FMainControl<>nil then
    FMainControl.FreeNotification(Self);
  UpdateCaption;
end;

procedure TLazDockForm.Notification(AComponent: TComponent;
  Operation: TOperation);
begin
  if (Operation=opRemove) then begin
    if AComponent=FMainControl then
      MainControl:=nil;
  end;
  inherited Notification(AComponent, Operation);
end;

procedure TLazDockForm.InsertControl(AControl: TControl; Index: integer);
var
  NewMainConrtrol: TControl;
begin
  inherited InsertControl(AControl, Index);
  if FMainControl=nil then begin
    NewMainConrtrol:=FindMainControlCandidate;
    if NewMainConrtrol<>nil then
      MainControl:=NewMainConrtrol;
  end;
end;

function TLazDockForm.CloseQuery: boolean;
// query all top level forms, if form can close

  function QueryForms(ParentControl: TWinControl): boolean;
  var
    i: Integer;
    AControl: TControl;
  begin
    for i:=0 to ParentControl.ControlCount-1 do begin
      AControl:=ParentControl.Controls[i];
      if (AControl is TWinControl) then begin
        if (AControl is TCustomForm) then begin
          // a top level form: query and do not ask childs
          if (not TCustomForm(AControl).CloseQuery) then
            exit(false);
        end
        else if not QueryForms(TWinControl(AControl)) then
          // search childs for forms
          exit(false);
      end;
    end;
    Result:=true;
  end;

begin
  Result:=inherited CloseQuery;
  if Result then
    Result:=QueryForms(Self);
end;

procedure TLazDockForm.UpdateCaption;
begin
  if FMainControl<>nil then
    Caption:=FMainControl.Caption
  else
    Caption:='';
end;

function TLazDockForm.FindMainControlCandidate: TControl;
var
  BestLevel: integer;

  procedure FindCandidate(ParentControl: TWinControl; Level: integer);
  var
    i: Integer;
    AControl: TControl;
    ResultIsForm, ControlIsForm: boolean;
  begin
    for i:=0 to ParentControl.ControlCount-1 do begin
      AControl:=ParentControl.Controls[i];
      if (AControl.Name<>'')
      and (not (AControl is TLazDockForm))
      and (not (AControl is TLazDockSplitter))
      and (not (AControl is TLazDockPages))
      and (not (AControl is TLazDockPage))
      then begin
        // this is a candidate
        // prefer forms and top level controls
        if (Application<>nil) and (Application.MainForm=AControl) then begin
          // the MainForm is the best control
          Result:=Application.MainForm;
          BestLevel:=-1;
          exit;
        end;
        ResultIsForm:=Result is TCustomForm;
        ControlIsForm:=AControl is TCustomForm;
        if (Result=nil)
        or ((not ResultIsForm) and ControlIsForm)
        or ((ResultIsForm=ControlIsForm) and (Level<BestLevel))
        then begin
          BestLevel:=Level;
          Result:=AControl;
        end;
      end;
      if AControl is TWinControl then
        FindCandidate(TWinControl(AControl),Level+1);
    end;
  end;

begin
  Result:=nil;
  BestLevel:=High(Integer);
  FindCandidate(Self,0);
end;

initialization
  DefaultDockTreeClass := TLazDockTree;

end.