{
 *****************************************************************************
  See the file COPYING.modifiedLGPL.txt, included in this distribution,
  for details about the license.
 *****************************************************************************

  Author: Mattias Gaertner

  Abstract:
    TComponentTreeView is a component to show the child components of a
    TComponent. TControls are shown in a hierachic view.
    It supports
      - multi selecting components
      - editing the creation order
      - editing the TControl.Parent hierachy
    For an usage example, see the object inspector.
}
unit ComponentTreeView;

{$mode objfpc}{$H+}

{off $DEFINE VerboseComponentTVWalker}

interface

uses
  Classes, SysUtils, TypInfo, Laz_AVL_Tree,
  // LazUtils
  LazLoggerBase,
  // LCL
  LCLProc, Dialogs, Controls, ComCtrls, Graphics,
  // IdeIntf
  ObjInspStrConsts, PropEdits, PropEditUtils, IDEImagesIntf;
  
type
  TCTVGetImageIndexEvent = procedure(APersistent: TPersistent;
    var AIndex: integer) of object;

  { TComponentTreeView }

  TComponentTreeView = class(TCustomTreeView)
  private
    FComponentList: TBackupComponentList;
    FOnComponentGetImageIndex: TCTVGetImageIndexEvent;
    FOnModified: TNotifyEvent;
    FPropertyEditorHook: TPropertyEditorHook;
    function CollectionCaption(ACollection: TCollection; DefaultName: string): string;
    function CollectionItemCaption(ACollItem: TCollectionItem): string;
    function ComponentCaption(AComponent: TComponent): String;
    function GetSelection: TPersistentSelectionList;
    procedure SetPropertyEditorHook(AValue: TPropertyEditorHook);
    procedure SetSelection(NewSelection: TPersistentSelectionList);
    procedure UpdateSelected;
    function CreateNodeCaption(APersistent: TPersistent; DefaultName: string = ''): string;
  protected
    procedure DoSelectionChanged; override;
    function GetImageFor(APersistent: TPersistent):integer;
    procedure DragOver(Source: TObject; X, Y: Integer; State: TDragState;
                       var Accept: Boolean); override;
    procedure DragCanceled; override;
    procedure MouseLeave; override;
    procedure GetComponentInsertMarkAt(X, Y: Integer;
                              out AnInsertMarkNode: TTreeNode;
                              out AnInsertMarkType: TTreeViewInsertMarkType);
    procedure DoModified;
  public
    constructor Create(TheOwner: TComponent); override;
    destructor Destroy; override;
    procedure DragDrop(Source: TObject; X, Y: Integer); override;
    procedure RebuildComponentNodes; virtual;
    procedure UpdateComponentNodesValues; virtual;
  public
    ImgIndexForm: Integer;
    ImgIndexComponent: Integer;
    ImgIndexControl: Integer;
    ImgIndexBox: Integer;
    ImgIndexCollection: Integer;
    ImgIndexItem: Integer;
    property Selection: TPersistentSelectionList read GetSelection
                                                 write SetSelection;
    property PropertyEditorHook: TPropertyEditorHook
                           read FPropertyEditorHook write SetPropertyEditorHook;
    property OnSelectionChanged;
    property OnModified: TNotifyEvent read FOnModified write FOnModified;
    property OnComponentGetImageIndex : TCTVGetImageIndexEvent
                           read FOnComponentGetImageIndex write FOnComponentGetImageIndex;
  end;

implementation

{$R ../../images/componenttreeview.res}

type
  TCollectionAccess = class(TCollection);

  TComponentCandidate = class
  public
    APersistent: TPersistent;
    Parent: TComponent;
    Added: boolean;
  end;

  { TComponentWalker }

  TComponentWalker = class
  private
    FComponentTV: TComponentTreeView;
    FCandidates: TAvlTree;
    FLookupRoot: TComponent;
    FNode: TTreeNode;
    procedure AddCollection(AColl: TCollection; AParentNode: TTreeNode);
    procedure AddOwnedPersistent(APers: TPersistent; APropName: String;
      AParentNode: TTreeNode);
    procedure GetOwnedPersistents(APers: TPersistent; AParentNode: TTreeNode);
    function PersistentFoundInNode(APers: TPersistent): Boolean;
    procedure Walk(AComponent: TComponent);
  public
    constructor Create(
      ATreeView: TComponentTreeView; ACandidates: TAvlTree;
      ALookupRoot: TComponent; ANode: TTreeNode);
  end;

  TComponentAccessor = class(TComponent);

function CompareComponentCandidates(
  Candidate1, Candidate2: TComponentCandidate): integer;
begin
  Result := ComparePointers(Candidate1.APersistent, Candidate2.APersistent);
end;

function ComparePersistentWithComponentCandidate(
  APersistent: TPersistent; Candidate: TComponentCandidate): integer;
begin
  Result := ComparePointers(APersistent, Candidate.APersistent);
end;

{ TComponentWalker }

constructor TComponentWalker.Create(ATreeView: TComponentTreeView;
  ACandidates: TAvlTree; ALookupRoot: TComponent; ANode: TTreeNode);
begin
  {$IFDEF VerboseComponentTVWalker}
  DebugLn(['TComponentWalker.Create ALookupRoot=',DbgSName(ALookupRoot)]);
  {$ENDIF}
  FComponentTV := ATreeView;
  FCandidates := ACandidates;
  FLookupRoot := ALookupRoot;
  FNode := ANode;
end;

procedure TComponentWalker.AddCollection(AColl: TCollection; AParentNode: TTreeNode);
var
  ItemNode: TTreeNode;
  Item: TCollectionItem;
  i: integer;
begin
  for i := 0 to AColl.Count - 1 do
  begin
    Item := AColl.Items[i];
    {$IFDEF VerboseComponentTVWalker}
    DebugLn(['TComponentWalker.AddCollection, Adding CollectionItem ',
             Item.DisplayName, ':', Item.ClassName]);
    {$ENDIF}
    ItemNode := FComponentTV.Items.AddChild(AParentNode,
                                       FComponentTV.CollectionItemCaption(Item));
    ItemNode.Data := Item;
    ItemNode.ImageIndex := FComponentTV.GetImageFor(Item);
    ItemNode.SelectedIndex := ItemNode.ImageIndex;
    ItemNode.MultiSelected := FComponentTV.Selection.IndexOf(Item) >= 0;
    // Collections can be nested. Add possible Collections under a CollectionItem.
    GetOwnedPersistents(Item, ItemNode);
  end;
end;

procedure TComponentWalker.AddOwnedPersistent(APers: TPersistent;
  APropName: String; AParentNode: TTreeNode);
var
  TVNode: TTreeNode;
  TheRoot: TPersistent;
begin
  if (APers is TComponent)
  and (csDestroying in TComponent(APers).ComponentState) then Exit;
  TheRoot := GetLookupRootForComponent(APers);
  {$IFDEF VerboseComponentTVWalker}
  DebugLn(['TComponentWalker.AddOwnedPersistent'+
           ' PropName=',APropName,' Persistent=',DbgSName(APers),
           ' its root=',DbgSName(TheRoot),' FLookupRoot=',DbgSName(FLookupRoot)]);
  {$ENDIF}
  if TheRoot <> FLookupRoot then Exit;
  if PersistentFoundInNode(APers) then Exit;
  TVNode := FComponentTV.Items.AddChild(AParentNode,
                          FComponentTV.CreateNodeCaption(APers, APropName));
  TVNode.Data := APers;
  TVNode.ImageIndex := FComponentTV.GetImageFor(APers);
  TVNode.SelectedIndex := TVNode.ImageIndex;
  TVNode.MultiSelected := FComponentTV.Selection.IndexOf(APers) >= 0;
  if APers is TCollection then
    AddCollection(TCollection(APers), TVNode);
  //AParentNode.Expanded := True;
end;

procedure TComponentWalker.GetOwnedPersistents(APers: TPersistent; AParentNode: TTreeNode);
var
  PropList: PPropList;
  PropCount, i: Integer;
  PropInfo: PPropInfo;
  PropPers: TPersistent;
begin
  PropCount := GetPropList(APers, PropList);
  try
    for i := 0 to PropCount - 1 do begin
      PropInfo:=PropList^[i];
      if (PropInfo^.PropType^.Kind <> tkClass) then Continue;
      {$IFDEF ShowOwnedObjectsOI}
      PropPers := TPersistent(GetObjectProp(APers, PropInfo, TPersistent));
      {$ELSE}
      PropPers := TPersistent(GetObjectProp(APers, PropInfo, TCollection));
      {$ENDIF}
      if PropPers=nil then Continue;
      if GetEditorClass(PropInfo, APers)=nil then Continue;
      {$IFDEF VerboseComponentTVWalker}
      DebugLn(['TComponentWalker.GetOwnedPersistents Persistent=',DbgSName(APers),
               ' PropName=',PropInfo^.Name,' FLookupRoot=',DbgSName(FLookupRoot)]);
      {$ENDIF}
      AddOwnedPersistent(PropPers, PropInfo^.Name, AParentNode);
    end;
  finally
    FreeMem(PropList);
  end;
end;

function TComponentWalker.PersistentFoundInNode(APers: TPersistent): Boolean;
var
  i: Integer;
begin
  for i:=0 to FNode.Count-1 do
    if TObject(FNode[i].Data) = APers then
      Exit(True);
  Result := False;
end;

procedure TComponentWalker.Walk(AComponent: TComponent);
var
  OldNode: TTreeNode;
  Candidate: TComponentCandidate;
  AVLNode: TAvlTreeNode;
  Root: TComponent;
begin
  if csDestroying in AComponent.ComponentState then exit;
  if GetLookupRootForComponent(AComponent) <> FLookupRoot then Exit;

  AVLNode := FCandidates.FindKey(AComponent, TListSortCompare(@ComparePersistentWithComponentCandidate));
  if AVLNode = nil then Exit;

  Candidate := TComponentCandidate(AVLNode.Data);
  if Candidate.Added then Exit;
  Candidate.Added := True;

  OldNode := FNode;
  FNode := FComponentTV.Items.AddChild(FNode, FComponentTV.ComponentCaption(AComponent));
  FNode.Data := AComponent;
  FNode.ImageIndex := FComponentTV.GetImageFor(AComponent);
  FNode.SelectedIndex := FNode.ImageIndex;
  FNode.MultiSelected := FComponentTV.Selection.IndexOf(AComponent) >= 0;

  GetOwnedPersistents(AComponent, FNode);

  if (csInline in AComponent.ComponentState) or (AComponent.Owner = nil) then
    Root := AComponent
  else
    Root := AComponent.Owner;

  if not ( (Root is TControl)
       and (csOwnedChildrenNotSelectable in TControl(Root).ControlStyle) )
  then
    TComponentAccessor(AComponent).GetChildren(@Walk, Root);
  FNode := OldNode;
  FNode.Expanded := True;
end;

{ TComponentTreeView }

procedure TComponentTreeView.SetSelection(NewSelection: TPersistentSelectionList);
begin
  if (PropertyEditorHook = nil) then
  begin
    if (FComponentList.LookupRoot = nil) then
      Exit;
    FComponentList.Clear;
  end
  else if not NewSelection.ForceUpdate
     and FComponentList.IsEqual(PropertyEditorHook.LookupRoot, NewSelection) then
  begin
    // nodes ok, but maybe node values need update
    DebugLn('TComponentTreeView.SetSelection: Updating component node values.');
    UpdateComponentNodesValues;
    Exit;
  end;
  FComponentList.LookupRoot := PropertyEditorHook.LookupRoot;
  FComponentList.Selection.Assign(NewSelection);
  if NewSelection.ForceUpdate then
  begin
    DebugLn('TComponentTreeView.SetSelection: Selection.ForceUpdate encountered.');
    NewSelection.ForceUpdate:=false;
  end;
  UpdateSelected;
end;

procedure TComponentTreeView.DoSelectionChanged;
var
  ANode: TTreeNode;
  APersistent: TPersistent;
  NewSelection: TPersistentSelectionList;
begin
  NewSelection := TPersistentSelectionList.Create;
  try
    if (PropertyEditorHook<>nil) and
       (PropertyEditorHook.LookupRoot<>nil) and
       (not (csDestroying in ComponentState)) then
    begin
      ANode := GetFirstMultiSelected;
      while ANode <> nil do
      begin
        APersistent := TPersistent(ANode.Data);
        if APersistent = nil then
          RaiseGDBException('TComponentTreeView.DoSelectionChanged ANode.Data=nil');
        if GetLookupRootForComponent(APersistent) = PropertyEditorHook.LookupRoot then
          NewSelection.Add(APersistent);
        ANode := ANode.GetNextMultiSelected;
      end;
      NewSelection.SortLike(FComponentList.Selection);
    end;
    if NewSelection.IsEqual(FComponentList.Selection) then
      Exit;
    FComponentList.Selection.Assign(NewSelection);

    inherited DoSelectionChanged;
  finally
    NewSelection.Free;
  end;
end;

procedure TComponentTreeView.DragDrop(Source: TObject; X, Y: Integer);
var
  Node, SelNode: TTreeNode;
  ACollection: TCollection;
  AContainer: TWinControl;
  AControl: TControl;
  ParentNode: TTreeNode;
  InsertType: TTreeViewInsertMarkType;
  NewIndex, AIndex: Integer;
  ok: Boolean;
begin
  GetComponentInsertMarkAt(X, Y, Node, InsertType);
  SetInsertMark(nil, tvimNone);
  ParentNode := Node;
  if InsertType in [tvimAsNextSibling, tvimAsPrevSibling] then
    ParentNode := ParentNode.Parent;
  if Assigned(ParentNode) then
  begin
    if TObject(ParentNode.Data) is TWinControl then
    begin
      AContainer := TWinControl(ParentNode.Data);
      SelNode := GetFirstMultiSelected;
      while Assigned(SelNode) do
      begin
        if TObject(SelNode.Data) is TControl then
        begin
          AControl := TControl(SelNode.Data);
          ok:=false;
          try
            AControl.Parent := AContainer;
            ok:=true;
            DoModified;
          except
            on E: Exception do
              MessageDlg(oisError,
                Format(oisUnableToChangeParentOfControlToNewParent,
                       [DbgSName(AControl), DbgSName(AContainer), LineEnding, E.Message]),
                mtError, [mbOk], 0);
          end;
          if not ok then break;
        end;
        SelNode := SelNode.GetNextMultiSelected;
      end;
    end
    else
    if TObject(Node.Data) is TCollectionItem then
    begin
      ACollection := TCollectionItem(Node.Data).Collection;
      ACollection.BeginUpdate;
      case InsertType of
        tvimAsNextSibling:
          NewIndex := TCollectionItem(Node.Data).Index + 1;
        tvimAsPrevSibling:
          NewIndex := TCollectionItem(Node.Data).Index;
      end;
      SelNode := GetLastMultiSelected;
      while Assigned(SelNode) do
      begin
        if (TObject(SelNode.Data) is TCollectionItem) and
           (TCollectionItem(SelNode.Data).Collection = ACollection) then
        begin
          ok := False;
          try
            AIndex := TCollectionItem(SelNode.Data).Index;
            if AIndex < NewIndex then
              TCollectionItem(SelNode.Data).Index := NewIndex - 1
            else
              TCollectionItem(SelNode.Data).Index := NewIndex;
            ok := True;
            DoModified;
          except
            on E: Exception do
              MessageDlg(E.Message, mtError, [mbOk], 0);
          end;
          if not ok then break;
        end;
        SelNode := SelNode.GetPrevMultiSelected;
      end;
      ACollection.EndUpdate;
    end;
    RebuildComponentNodes;
  end;
  inherited DragDrop(Source, X, Y);
end;

procedure TComponentTreeView.DragOver(Source: TObject; X, Y: Integer;
  State: TDragState; var Accept: Boolean);
var
  Node: TTreeNode;
  AnObject: TObject;
  AControl: TControl absolute AnObject;
  AContainer: TPersistent;
  AcceptControl, AcceptContainer: Boolean;
  InsertType: TTreeViewInsertMarkType;
  ParentNode: TTreeNode;
  aLookupRoot: TPersistent;
begin
  //debugln('TComponentTreeView.DragOver START ',dbgs(Accept));

  AcceptContainer := False;
  AcceptControl := True;

  GetComponentInsertMarkAt(X, Y, Node, InsertType);
  SetInsertMark(Node, InsertType);

  if PropertyEditorHook<>nil then
    aLookupRoot := PropertyEditorHook.LookupRoot
  else
    aLookupRoot := nil;

  // check new parent
  ParentNode := Node;
  if InsertType in [tvimAsNextSibling, tvimAsPrevSibling] then
    ParentNode := ParentNode.Parent;
  if Assigned(ParentNode) and Assigned(ParentNode.Data) then
  begin
    AnObject := TObject(ParentNode.Data);
    if (AnObject is TWinControl) then
    begin
      if ControlAcceptsStreamableChildComponent(TWinControl(AControl),
         TComponentClass(AnObject.ClassType),aLookupRoot)
      then begin
        AContainer := TPersistent(AnObject);
        //DebugLn(['TComponentTreeView.DragOver AContainer=',DbgSName(AContainer)]);
        AcceptContainer := True;
      end;
    end
    else
    if (AnObject is TCollection) then
    begin
      // it is allowed to move container items inside the container
      AContainer := TPersistent(AnObject);
      AcceptContainer := True;
    end;
  end;

  if AcceptContainer then 
  begin
    Node := GetFirstMultiSelected;
    while Assigned(Node) and AcceptControl do
    begin
      AnObject := TObject(Node.Data);
      // don't allow to move ancestor components
      if (AnObject is TComponent) and
         (csAncestor in TComponent(AnObject).ComponentState) then break;
      if (AnObject is TControl) then
      begin
        if AnObject = AContainer then break;
        if not (AContainer is TWinControl) then break;
        //DebugLn(['TComponentTreeView.DragOver AControl=',DbgSName(AControl),' Parent=',DbgSName(AControl.Parent),' OldAccepts=',csAcceptsControls in AControl.Parent.ControlStyle]);
        // check if new parent allows this control class
        if not TWinControl(AContainer).CheckChildClassAllowed(AnObject.ClassType, False) then
          break;
        // check if one of the parent of the container is the control itself
        if AControl.IsParentOf(TWinControl(AContainer)) then break;
        // do not move children of a restricted parent to another parent
        // e.g. TPage of TPageControl
        if (AControl.Parent <> nil) and (AControl.Parent <> AContainer) and
            (not (csAcceptsControls in AControl.Parent.ControlStyle)) then
          break;
      end
      else
      if (AnObject is TCollectionItem) then
      begin
        if AnObject = AContainer then break;
        if not (AContainer is TCollection) then
          break;
        if TCollectionItem(AnObject).Collection <> TCollection(AContainer) then
          break;
      end;
      Node := Node.GetNextMultiSelected;
    end;
    AcceptControl := (Node = nil);
  end;

  Accept := AcceptContainer and AcceptControl;
  //debugln('TComponentTreeView.DragOver A ',dbgs(Accept));
  inherited DragOver(Source, X, Y, State, Accept);
  //debugln('TComponentTreeView.DragOver B ',dbgs(Accept));

  Accept := AcceptContainer and AcceptControl and ((OnDragOver=nil) or Accept);
end;

procedure TComponentTreeView.DragCanceled;
begin
  SetInsertMark(nil, tvimNone);
  inherited DragCanceled;
end;

procedure TComponentTreeView.MouseLeave;
begin
  SetInsertMark(nil,tvimNone);
  inherited MouseLeave;
end;

procedure TComponentTreeView.GetComponentInsertMarkAt(X, Y: Integer; out
  AnInsertMarkNode: TTreeNode; out AnInsertMarkType: TTreeViewInsertMarkType);
var
  Node: TTreeNode;
begin
  Node := GetFirstMultiSelected;
  if (Node <> nil) and (TObject(Node.Data) is TControl) then
  begin
    // TWinControl allows only to add/remove children, but not at a specific position
    AnInsertMarkNode := GetNodeAt(X,Y);
    AnInsertMarkType := tvimAsFirstChild;
  end
  else
  begin
    GetInsertMarkAt(X, Y, AnInsertMarkNode, AnInsertMarkType);
    if (Node <> nil) and (TObject(Node.Data) is TCollectionItem) then
      if AnInsertMarkType = tvimAsFirstChild then
        AnInsertMarkType := tvimAsPrevSibling;
  end;
end;

procedure TComponentTreeView.DoModified;
begin
  if Assigned(PropertyEditorHook) then
    PropertyEditorHook.RefreshPropertyValues;
  if Assigned(FOnModified) then
    OnModified(Self);
end;

function TComponentTreeView.GetImageFor(APersistent: TPersistent): integer;
begin
  Result := -1;
  if Assigned(APersistent) then
  begin
    if (APersistent is TControl)
    and (csAcceptsControls in TControl(APersistent).ControlStyle) then
      Result := ImgIndexBox
    else
    if (APersistent is TControl) then
      Result := ImgIndexControl
    else
    if (APersistent is TComponent) then
      Result := ImgIndexComponent
    else
    if (APersistent is TCollection) then
      Result := ImgIndexCollection
    else
    if (APersistent is TCollectionItem) then
      Result := ImgIndexItem;
  end;
  // finally, ask the designer such as TDesignerMediator to override it, if any
  if Assigned(OnComponentGetImageIndex) then
    OnComponentGetImageIndex(APersistent, Result);
end;

procedure TComponentTreeView.SetPropertyEditorHook(AValue: TPropertyEditorHook);
begin
  if FPropertyEditorHook=AValue then exit;
  FPropertyEditorHook:=AValue;
  RebuildComponentNodes;
end;

function TComponentTreeView.GetSelection: TPersistentSelectionList;
begin
  Result:=FComponentList.Selection;
end;

constructor TComponentTreeView.Create(TheOwner: TComponent);
begin
  inherited Create(TheOwner);
  DragMode := dmAutomatic;
  FComponentList:=TBackupComponentList.Create;
  Options := Options + [tvoAllowMultiselect, tvoAutoItemHeight, tvoKeepCollapsedNodes, tvoReadOnly];
  MultiSelectStyle := MultiSelectStyle + [msShiftSelect];
  ImgIndexForm := IDEImages.GetImageIndex('oi_form');
  ImgIndexComponent := IDEImages.GetImageIndex('oi_comp');
  ImgIndexControl := IDEImages.GetImageIndex('oi_control');
  ImgIndexBox := IDEImages.GetImageIndex('oi_box');
  ImgIndexCollection := IDEImages.GetImageIndex('oi_collection');
  ImgIndexItem := IDEImages.GetImageIndex('oi_item');
  Images := IDEImages.Images_16;
end;

destructor TComponentTreeView.Destroy;
begin
  FreeThenNil(FComponentList);
  inherited Destroy;
end;

procedure TComponentTreeView.RebuildComponentNodes;
var
  Candidates: TAvlTree; // tree of TComponentCandidate sorted for aPersistent (CompareComponentCandidates)
  RootObject: TPersistent;
  RootComponent: TComponent absolute RootObject;

  procedure AddChildren(AComponent: TComponent; ANode: TTreeNode);
  var
    Walker: TComponentWalker;
    Root: TComponent;
  begin
    if csDestroying in AComponent.ComponentState then exit;
    //debugln(['AddChildren ',DbgSName(AComponent),' ',AComponent.ComponentCount]);
    Walker := TComponentWalker.Create(Self, Candidates, RootComponent, ANode);
    try
      // add inline components children
      if csInline in AComponent.ComponentState then
        Root := AComponent
      else
        Root := RootComponent;
      TComponentAccessor(AComponent).GetChildren(@Walker.Walk, Root);
    finally
      Walker.Free;
    end;
  end;

  procedure AddCandidates(OwnerComponent: TComponent);
  var
    AComponent: TComponent;
    Candidate: TComponentCandidate;
    i: Integer;
  begin
    //debugln(['AddCandidates OwnerComponent=',DbgSName(OwnerComponent)]);
    if OwnerComponent = nil then Exit;
    if csDestroying in OwnerComponent.ComponentState then exit;
    for i := 0 to OwnerComponent.ComponentCount - 1 do
    begin
      AComponent := OwnerComponent.Components[i];
      if csDestroying in AComponent.ComponentState then continue;
      Candidate := TComponentCandidate.Create;
      Candidate.APersistent := AComponent;
      if Candidates.Find(Candidate)<>nil then
      begin
        DebugLn('WARNING: TComponentTreeView.RebuildComponentNodes doppelganger found ', AComponent.Name);
        Candidate.Free;
      end
      else
      begin
        Candidates.Add(Candidate);
        if csInline in AComponent.ComponentState then
          AddCandidates(AComponent);
      end;
    end;
  end;

var
  RootNode: TTreeNode;
  Candidate: TComponentCandidate;
begin
  BeginUpdate;
  Items.Clear;
  RootObject := nil;
  if PropertyEditorHook<>nil then
    RootObject := PropertyEditorHook.LookupRoot;
  if (RootObject is TComponent)
  and (csDestroying in TComponent(RootObject).ComponentState) then
    RootObject:=nil;
  if RootObject <> nil then
  begin
    Candidates:=TAvlTree.Create(TListSortCompare(@CompareComponentCandidates));
    try
      // first add the lookup root
      RootNode := Items.Add(nil, CreateNodeCaption(RootObject));
      RootNode.Data := RootObject;
      RootNode.ImageIndex := ImgIndexForm;
      RootNode.SelectedIndex := RootNode.ImageIndex;
      RootNode.MultiSelected := Selection.IndexOf(RootObject) >= 0;

      // create candidate nodes for every child
      Candidate := TComponentCandidate.Create;
      Candidate.APersistent := RootObject;
      Candidate.Added := True;
      Candidates.Add(Candidate);

      // add components in creation order and TControl.Parent relationship
      if RootObject is TComponent then
      begin
        AddCandidates(RootComponent);
        AddChildren(RootComponent,RootNode);
      end;
    finally
      Candidates.FreeAndClear;
      Candidates.Free;
    end;

    RootNode.Expand(true);
  end;
  MakeSelectionVisible;
  EndUpdate;
end;

procedure TComponentTreeView.UpdateComponentNodesValues;
// Could be optimised by adding a PropName parameter and searching a node by name.

  procedure UpdateComponentNode(ANode: TTreeNode);
  var
    APersistent: TPersistent;
  begin
    if ANode = nil then Exit;
    APersistent := TPersistent(ANode.Data);
    if APersistent is TComponent then
      ANode.Text := ComponentCaption(TComponent(APersistent))
    else if APersistent is TCollectionItem then
      ANode.Text := CollectionItemCaption(TCollectionItem(APersistent));
    // Note: Collection name does not change, don't update.

    UpdateComponentNode(ANode.GetFirstChild);    // Recursive call.
    UpdateComponentNode(ANode.GetNextSibling);
  end;

begin
  BeginUpdate;
  UpdateComponentNode(Items.GetFirstNode);
  EndUpdate;
end;

procedure TComponentTreeView.UpdateSelected;

  procedure UpdateComponentNode(ANode: TTreeNode);
  var
    APersistent: TPersistent;
  begin
    if ANode = nil then Exit;
    APersistent := TPersistent(ANode.Data);
    ANode.MultiSelected := Selection.IndexOf(APersistent) >= 0;
    UpdateComponentNode(ANode.GetFirstChild);
    UpdateComponentNode(ANode.GetNextSibling);
  end;

begin
  BeginUpdate;
  Selected := Nil;
  UpdateComponentNode(Items.GetFirstNode);
  EndUpdate;
end;

function TComponentTreeView.CollectionCaption(ACollection: TCollection; DefaultName: string): string;
var
  PropList: PPropList;
  i, PropCount: Integer;
begin
  Result := '';
  if Result <> '' then
    Result := TCollectionAccess(ACollection).PropName
  else if DefaultName<>'' then
    Result := DefaultName  // DefaultName is the property name.
  else if ACollection.Owner <> nil then
  begin
    PropCount := GetPropList(ACollection.Owner, PropList);
    try                 // Find the property name where ACollection can be found.
      for i := 0 to PropCount - 1 do
        if (PropList^[i]^.PropType^.Kind = tkClass) then
          if GetObjectProp(ACollection.Owner, PropList^[i], ACollection.ClassType) = ACollection then
          begin
            Result := PropList^[i]^.Name;
            Break;
          end;
    finally
      FreeMem(PropList);
    end;
  end;
  if Result = '' then
    Result := '<unknown collection>';
  Result := Result + ': ' + ACollection.ClassName;
end;

function TComponentTreeView.CollectionItemCaption(ACollItem: TCollectionItem): string;
begin
  Result := IntToStr(ACollItem.Index)+' - '+ACollItem.DisplayName+': '+ACollItem.ClassName;
end;

function TComponentTreeView.ComponentCaption(AComponent: TComponent): String;
begin
  Result := AComponent.Name + ': ' + AComponent.ClassName;
end;

function TComponentTreeView.CreateNodeCaption(APersistent: TPersistent; DefaultName: string): string;
begin
  Result := APersistent.ClassName;
  if APersistent is TComponent then
    Result := ComponentCaption(TComponent(APersistent))
  else if APersistent is TCollection then
    Result := CollectionCaption(TCollection(APersistent), DefaultName)
  else if APersistent is TCollectionItem then
    Result := CollectionItemCaption(TCollectionItem(APersistent))
  else if DefaultName<>'' then
    Result := DefaultName + ':' + Result;
end;

end.