VirtualTreeview Example for Lazarus/fr

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Voici quelques exemples sur la façon d'utiliser VirtualTreeview pour Lazarus (testé sur win32). Ceci sont essentiellement collectés à partir du web écrit pour delphi, et à partir des tutoriels/documents par Philipp Frenzel et Mike Lischke. Les tutoriels/documents peuvent être téléchargé à partir de l'adresse http://www.soft-gems.net . Ci dessous quelqu'un trouverait seulement la manière rapide d'utiliser VirtualTreeview avec Lazarus, pas une explication. Pour des explications et de nombreuses autres fonctions/méthodes obtenir les documents officiels et le didacticiel.

Arbre de base Listview avec trois Colonnes

1. Installez le composant. Exécutez lazarus.

2. Déposez un composant TVirtualStringTree (Sous l'onglet Virtual Controls).

3. Aller à l'éditeur de source (Appuyez sur F12). Sous la clause Uses ajoutez une unité - appelée VirtualTrees (si elle n'est pas déjà là et que ce n'est pas VirtualStringTree). Ainsi, il peut ressembler à: 

uses
  Classes, SysUtils, LResources, Forms, Controls, Graphics, Dialogs,
  VirtualStringTree, VirtualTrees;

4. Aller à l'éditeur de fiches (Appuyez sur F12). Sélectionnez le composant Virtual Tree. Sur l'inspecteur d'objet cliquez sur Name, tapez VST et appuyez sur entrer. Cliquez sur Header (augmentez-le) -> Columns, cliquez sur le petit bouton situé à côté de "0 items". Cliquez 3 fois sur Add button pour ajouter 3 colonnes. Ne pas fermer cette fenêtre.

5. Sur la fenêtre d'édition de la colonne maintenant la 3ième colonne est sélectionnée. Aller à l'inspecteur d'objet. Cliquez sur Options (augmentez-le) -> fixez coAllowClicks à False.

6. Cliquez sur Text. Tapez Column2.

7. Cliquez sur Width, tapez 100 et appuyez sur enter.

8. Allez à la fenêtre d'édition de la colonne, selectionnez la 1ère et la 2ieme colonne, et fixez leur propriété comme ci-dessus (pour le champ Text, utiliser des noms différents, c'est à dire Column0, Column1).

9. Fermez la fenêtre d'édition de colonnes. Sélectionnez le composant Virtual Tree de la fiche. Sur l'inspecteur d'objet allez à Header -> Options (augmentez-le). Fixez hoVisible à True.

10. Faites défiler la liste jusqu'à Style fixez le à hsFlatButtons.

ExempleVirtualtreeView1.jpg

11. Faites défiler la liste jusqu'à TreeOptions(augmentez-le) -> MiscOption(augmentez-le), fixez toEditable à True. Fixez toGridExtensions à True.

12. Faites défiler la liste jusqu'à SelectionOptions(augmentez-le) -> fixez le toExtendedFocus à True. Fixez toMultiSelect à True. Sur le concepteur de fiche redimensionnez VST (composant Virtual Tree) pour obtenir le visuel de toutes les colonnes, si nécessaire.

13. Maintenant ajoutez 3 boutons sur la fiche. Obtenez les à partir de la palette de composants - Onglet standard (Label "OK" ).

14. CLiquez sur Button1, sur l'inspecteur d'object changez Caption avec AddRoot. Cliquez sur Button2, changez le caption avec AddChild. Changez le caption du Button3 avec Delete.

ExempleVirtualtreeView2.jpg

15. Gardez ceci ici et allez à l'éditeur de source(appuyez sur F12). Dans l'éditeur de source remplacez la ligne:

{$mode objfpc}{$H+} par {$MODE DELPHI}

16. Sous "implementation" coller les lignes suivantes: 

type
  PTreeData = ^TTreeData;
  TTreeData = record
    Column0: String;
    Column1: String;
    Column2: String;
  end;

17. Get to the Form Designer (press F12). Select VST. Go to Object Inspector, select Events tab, scroll down to onChange. Double click on the combobox. Paste the follwings: 

procedure TForm1.VSTChange(Sender: TBaseVirtualTree; Node: PVirtualNode);
begin
 VST.Refresh;
end;

18. Scroll to onFocusChanged. Double click and paste the follwings: 

procedure TForm1.VSTFocusChanged(Sender: TBaseVirtualTree; Node: PVirtualNode;
  Column: TColumnIndex);
begin
  VST.Refresh;
end;

19. Scroll to onFreeNode. Double click and paste the follwings: 

procedure TForm1.VSTFreeNode(Sender: TBaseVirtualTree; Node: PVirtualNode);
var
 Data: PTreeData;
begin
 Data:=VST.GetNodeData(Node);
 if Assigned(Data) then begin
   Data^.Column0 := '';
   Data^.Column1 := '';
   Data^.Column2 := '';
 end;
end;

20. Scroll down to onGetNodeDataSize. Double click & paste the follwings: 

procedure TForm1.VSTGetNodeDataSize(Sender: TBaseVirtualTree; var NodeDataSize: Integer);
begin
    NodeDataSize := SizeOf(TTreeData);
end;

21. Scroll to onGetText. Double click & paste the follwings: 

procedure TForm1.VSTGetText(Sender: TBaseVirtualTree; Node: PVirtualNode;
 Column: TColumnIndex; TextType: TVSTTextType; var CellText: WideString);
var
  Data: PTreeData;
begin
  Data := VST.GetNodeData(Node);
  case Column of
    0: CellText := Data^.Column0;
    1: CellText := Data^.Column1;
    2: CellText := Data^.Column2;
  end;
end;

22. Press F12 to get Form Designer. Double click AddRoot button. Paste the followings: 

procedure TForm1.Button1Click(Sender: TObject);
Var
Data: PTreeData;
XNode: PVirtualNode;
Rand: Integer;
Begin
  Randomize;
  Rand := Random(99);
  XNode:=VST.AddChild(nil);
  
  if VST.AbsoluteIndex(XNode) > -1 then
  Begin
   Data := VST.GetNodeData(Xnode);
   Data^.Column0:= 'One ' + IntToStr(Rand);
   Data^.Column1:= 'Two ' + IntToStr(Rand + 10);
   Data^.Column2:= 'Three ' + IntToStr(Rand - 10);
  End; 
End;

23. Press F9 to Run the project to check. Click on AddRoot to add node. If it is ok, node will be added on VST.

ExempleVirtualtreeView3.jpg

24. Stop execution. On the Form Designer double click the AddChild captioned button. Paste the followings: 

procedure TForm1.Button2Click(Sender: TObject);
var
  XNode: PVirtualNode;
  Data: PTreeData;
begin
  if not Assigned(VST.FocusedNode) then
    Exit;
    
    XNode := VST.AddChild(VST.FocusedNode);
    Data := VST.GetNodeData(Xnode);
    
    Data^.Column0:= 'Ch 1';
    Data^.Column1:= 'Ch 2';
    Data^.Column2:= 'Ch 3';

   VST.Expanded[VST.FocusedNode]:=True;
end;

25. On the Form Designer double click the Delete captioned button. Paste the followings: 

procedure TForm1.Button3Click(Sender: TObject);
begin
  VST.DeleteSelectedNodes;
end;

26. Run the project by pressing F9 to check. Add some node, child and delete them.

27. Try to edit a node. Select a node and press F2, write new value. If you can see what you are typing then it is OK. Else, read bellow "If Cell Editing Can't Be Seen".

28. To get VST show the new value entered after editing, go to the Form Designer, select VST. On Object Inspector -> Events -> OnNewText combobox double click. Paste the followings: 

procedure TForm1.VSTNewText(Sender: TBaseVirtualTree; Node: PVirtualNode;
  Column: TColumnIndex; NewText: WideString);
Var
 Data: PTreeData;
begin
 Data := VST.GetNodeData(Node);
 Case Column of
  0: Data^.Column0:= NewText;
  1: Data^.Column1:= NewText;
  2: Data^.Column2:= NewText;
 End;
end;

So far, example for basic use ends here. You may drop few more buttons on the form to test few more commands given bellow. Next would be, showing checkbox, image, font colour and adding combobox on node.


  • Another Way To Add Root Node
procedure TForm1.Button8Click(Sender: TObject);
begin
  with VST do
  RootNodeCount:=RootNodeCount+1;
end;
  • Another Way To Add Child
procedure TForm1.Button9Click(Sender: TObject);
begin
  if Assigned(VST.FocusedNode) Then
  VST.ChildCount[VST.FocusedNode]:=VST.ChildCount[VST.FocusedNode]+1;
end;
  • Determine & Delete Children Of A Node
procedure TForm1.Button4Click(Sender: TObject);
Var
 c: Integer;
begin
   if not Assigned(VST.FocusedNode) then
    Exit;
   If VST.HasChildren[VST.FocusedNode] then
   Begin
   c := VST.ChildCount[VST.FocusedNode];
   VST.DeleteChildren(VST.FocusedNode);
   ShowMessage('Number of deleted child:' + #13#10 + IntToStr(c));
   End;
end;
  • Delete Node
procedure TForm1.Button5Click(Sender: TObject);
begin
{VST.Clear;  //Delete All Nodes}
   if not Assigned(VST.FocusedNode) then
    Exit;
   VST.DeleteNode(VST.FocusedNode);
end;
  • Search And Select Node
procedure TForm1.Button6Click(Sender: TObject);
Var
 XNode: PVirtualNode;
 Data: PTreeData;
begin
 XNode:= VST.GetFirst;

 while XNode <> nil do
 begin
  Data:=VST.GetNodeData(XNode);
   if Data^.Column0  = '1' then
    Begin
     VST.ClearSelection;
     VST.Selected[XNode]:=True;
     VST.SetFocus;
     break;
    End
    Else
    XNode:= VST.GetNextSibling(XNode);
 End;
End;
  • Determine Parent
procedure TForm1.Button13Click(Sender: TObject);
var
  XNode: PVirtualNode;
begin
  if not Assigned(VST.FocusedNode) then
    Exit;
  XNode:=VST.FocusedNode;
  while VST.GetNodeLevel(XNode) > 0 do
    Begin
    XNode := XNode.Parent;
    VST.Selected[XNode]:= True;
    End;
   VST.Refresh;
   VST.SetFocus;
end;
  • Search All
procedure TForm1.Button7Click(Sender: TObject);
Var
 XNode: PVirtualNode;
 Data: PTreeData;
begin
 If VST.GetFirst = nil then Exit;
 XNode:=nil;
 Repeat
 if XNode = nil then XNode:=VST.GetFirst Else XNode:=VST.GetNext(XNode);
  Data:=VST.GetNodeData(XNode);
   If (Data^.Column0 = '1') OR (Data^.Column1 = '1') OR (Data^.Column2 = '1') then
    Begin
     ShowMessage('Found at Node Level : ' + IntToStr(VST.GetNodeLevel(XNode)) );
     break;
    End;
  Until XNode = VST.GetLast();
end;
  • Insert Node
procedure TForm1.Button12Click(Sender: TObject);
var
XNode: PVirtualNode;
begin
  If Assigned(VST.FocusedNode) then
  begin
      XNode := VST.InsertNode(VST.FocusedNode,amInsertBefore);
      // To Insert After Selected Node.
      {XNode := VST.InsertNode(VST.FocusedNode,amInsertAfter);}
      VST.Refresh;
  end;
end;
  • Set Node Height
procedure TForm1.Button14Click(Sender: TObject);
begin
   If Assigned(VST.FocusedNode) then
   VST.NodeHeight[VST.FocusedNode] := 32;
end;
  • Save And Load

Simple tree (without column) can be saved and loaded as: 

VST.SaveToFile('filename.dat');
VST.LoadFromFile('filename.dat');


To save and load the above mentioned example, place 2 buttons on the form, rename caption to "Save" and "Load". Select VST, on Object Inspector -> TreeOptions -> StringOptions make sure toSaveCaptions is set to True. Go to Object Inspector's Events tab. Scroll down to OnLoadNode, double click and then paste: 

procedure TForm1.VSTLoadNode(Sender: TBaseVirtualTree; Node: PVirtualNode;
  Stream: TStream);
Var
 Data: PTreeData;
 Len: Integer;
begin
 Data := VST.GetNodeData(Node);
 Stream.read(Len, SizeOf(Len));
 SetLength(Data^.Column0, Len);
 Stream.read(PChar(Data^.Column0)^, Len);

 Stream.read(Len, SizeOf(Len));
 SetLength(Data^.Column1, Len);
 Stream.read(PChar(Data^.Column1)^, Len);

 Stream.read(Len, SizeOf(Len));
 SetLength(Data^.Column2, Len);
 Stream.read(PChar(Data^.Column2)^, Len);
end;

Again on Object Inspector's Events tab - scroll down to OnSaveNode, double click and then paste: 

procedure TForm1.VSTSaveNode(Sender: TBaseVirtualTree; Node: PVirtualNode;
  Stream: TStream);
Var
 Data: PTreeData;
 Len: Integer;
begin
 Data := VST.GetNodeData(Node);
 Len := Length(Data^.Column0);
 Stream.write(Len, SizeOf(Len));
 Stream.write(PChar(Data^.Column0)^, Len);

 Len := Length(Data^.Column1);
 Stream.write(Len, SizeOf(Len));
 Stream.write(PChar(Data^.Column1)^, Len);

 Len := Length(Data^.Column2);
 Stream.write(Len, SizeOf(Len));
 Stream.write(PChar(Data^.Column2)^, Len);
end;

On Form Designer double click Save captioned button, paste: 

procedure TForm1.Button10Click(Sender: TObject);
begin
 VST.SaveToFile('C:\vst.dat');
end;

On Form Designer double click Load captioned button, paste: 

procedure TForm1.Button11Click(Sender: TObject);
begin
  VST.LoadFromFile('C:\vst.dat');
end;

Now test to save and load tree.

  • Scroll Problem

The header of the treeview disappears fully or partially when scrolling. I could not find a good solution for this. One way to overcome this is to set the header height to 0, then using general label for columns. This is good while there are few columns, and all are visible without horizontal scrolling. Or, the header height can be set to a higher value like 25 or 30. VST.Refresh can be added to the OnScroll event.

  • Column Resize

It was not possible to resize column by dragging mouse on VST header. May be it is for the header bug or I have missed something. If it is for the header, probably will be fixed on next version of Lazarus. See this link: http://bugs.freepascal.org/view.php?id=11209
Anyway, it is possible to resize column from code. When you press down right mouse button and move mouse-wheel up, the width of the selected column increases and press down the right mouse button and move mouse-wheel down, to decrease the width of the selected column. To do this:

1. Add a variable in the source editor named as CurCol: Integer; So it looks like: 

var
  Form1: TForm1; 
  CurCol: Integer; // <- Add this line only.

implementation

{ TForm1 }

2. On the Form Designer double click the form to generate an event OnCreate. Inside the OnCreate procedure type Form1.OnMouseWheelUp:= and press Ctrl+Shift+C, this will complete the code and make skeleton of the MouseWheelUp event. Now get back to procedure TForm1.FormCreate(Sender: TObject); And add another event for MouseWheelDown. Type Form1.OnMouseWheelDown:= and press Ctrl+Shift+C, to generate the MouseWheelDown event. FormCreate procedure now looks like: 

procedure TForm1.FormCreate(Sender: TObject);
begin
    Form1.OnMouseWheelUp:=@Form1MouseWheelUp;
    Form1.OnMouseWheelDown:=@Form1MouseWheelDown;
end;

3. Fill the TForm1.Form1MouseWheelUp procedure as: 

procedure TForm1.Form1MouseWheelUp(Sender: TObject; Shift: TShiftState;
  MousePos: TPoint; var Handled: Boolean);
begin
 If VST.Focused then
   if ssRight in Shift then
 VST.Header.Columns[CurCol].Width:= VST.Header.Columns[CurCol].Width + 10;
end;

4. Fill the TForm1.Form1MouseWheelDown procedure as: 

procedure TForm1.Form1MouseWheelDown(Sender: TObject; Shift: TShiftState;
  MousePos: TPoint; var Handled: Boolean);
begin
  If VST.Focused then
   if ssRight in Shift then
 VST.Header.Columns[CurCol].Width:= VST.Header.Columns[CurCol].Width - 10;
end;

5. Go to the Form Designer (press F12), select VST, on Object Inspector's Events tab scroll to OnFocusChanged, double click & paste: 

procedure TForm1.VSTFocusChanged(Sender: TBaseVirtualTree;
  Node: PVirtualNode; Column: TColumnIndex);
begin
  CurCol:=Column;
end;

When you run, click on a column then hold down right mouse button and move wheel up to increase width, wheel down to decrease. You may tune-up the above procedures if needed. Or, add keyboard event with something like "if (key=187) and (ssShift in Shift) then" to watch for Shift + "+".

Checkbox

On Form Designer select VST. Go to:

  1. Object Inspector -> Properties -> CheckImageKind and select ckDarkCheck.
  2. Object Inspector -> Properties -> TreeOptions -> MiscOptions -> toCheckSupport and set it to True.

Now switch to Events tab.

  • Scroll to OnInitNode. Double click and paste the followings:
procedure TForm1.VSTInitNode(Sender: TBaseVirtualTree; ParentNode,
  Node: PVirtualNode; var InitialStates: TVirtualNodeInitStates);
Var
 Level: Integer;
begin
    Level := VST.GetNodeLevel(Node);
    if Level = 0 then
    Node.CheckType:=ctCheckBox;

    if Level = 2 then
    Node.CheckType:=ctRadioButton;

    if Level = 1 then
    begin
    Node.CheckType:=ctTriStateCheckBox;
    Node.CheckState := csCheckedNormal;
    end;

    if Level = 3 then
    Node.CheckType:=ctButton;
end;

Run the program, add rootnode and child then child of the child, and check if you can check and uncheck properly. If not, close the program. Go to the Object Inspector's Events tab.

  • Scroll to OnChecked, double click and paste:
procedure TForm1.VSTChecked(Sender: TBaseVirtualTree; Node: PVirtualNode);
begin
   vst.Refresh;
end;
  • Scroll to OnChecking, double click and paste:
procedure TForm1.VSTChecking(Sender: TBaseVirtualTree; Node: PVirtualNode;
  var NewState: TCheckState; var Allowed: Boolean);
begin
 VST.Refresh;
end;

Hope now it is ok. To determine checkbox state use like:

If XNode.CheckState = csCheckedNormal then
ShowMessage('Checked.');

Other states are:

csUncheckedNormal = unchecked and not pressed
csUncheckedPressed = unchecked and pressed
csCheckedNormal = checked and not pressed
csCheckedPressed = checked and pressed
csMixedNormal = 3-state check box and not pressed
csMixedPressed = 3-state check box and pressed

Other types are:

ctNone
ctTriStateCheckBox
ctCheckBox
ctRadioButton
ctButton
  • To Catch Checkbox's Button (ctButton) Click

Go to Object Inspector's Events tab. Scroll to OnChecked, double click and paste: 

procedure TForm1.VSTChecked(Sender: TBaseVirtualTree; Node: PVirtualNode);
begin
 if Node.CheckType = ctButton then
 ShowMessage('Ok.');
 VST.Refresh;
end;

End of checkbox.

Image & Font Colour

To show image on VST nodes, a list of image should be created.

  • Go to the Component Palette -> Common Controls. Select and drop a TImageList component on the form. Right click on the component icon and select ImageList Editor. Click on Add button and and select some images (at least 3 for now), then click on tick button to accept and close the ImageList Editor. By the way, there are some nice images you can download from http://www.famfamfam.com/lab/icons/silk/
  • Now on the Form Designer select VST, and on Object Inspector's Properties tab, scroll to Images and select ImageList1
  • On Object Inspector's Events tab scroll to OnGetImageIndex, double click and paste:
procedure TForm1.VSTGetImageIndex(Sender: TBaseVirtualTree; Node: PVirtualNode;
  Kind: TVTImageKind; Column: TColumnIndex; var Ghosted: Boolean;
  var ImageIndex: Integer);
begin
if Kind in [ikNormal , ikSelected] then // Either Selected or not
 begin
  if Column = 0 then                    // if 1st Column
    ImageIndex:=0;                      // 1st Image of the ImageList1

  if Column = 1 then                    // if 2nd Column
    ImageIndex:=1;                      // 2nd Image of the ImageList1

  if Sender.FocusedNode = Node then     // Only show if Focused
   if Column =2 then                    // if 3rd Column
    ImageIndex:=2;                      // 3rd Image of the ImageList1
  end;
 {Sender.NodeHeight[node]:=40; //If Image is big}
end;
Font Colour

On the Form Designer select VST, and on Object Inspector's Events tab, scroll to OnPaintText, double click and paste: 

procedure TForm1.VSTPaintText(Sender: TBaseVirtualTree;
  const TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex;
  TextType: TVSTTextType);
Var
 Data: PTreeData;
begin
 Data := VST.GetNodeData(Node);
 
 if Data^.Column0 = 'sky' then
  TargetCanvas.Font.Color:=clBlue;
  
 if Column = 1 then
 begin
   TargetCanvas.Font.Color:=clRed;
   TargetCanvas.Font.Style:= Font.Style + [fsItalic];
 end;
 
 if Column = 2 then
 begin
//  ImageList1.Draw(Form1.Canvas,-1,-1,2); {draw top left of form, 3rd image of ImageList1??}
  TargetCanvas.Font.Size:= 9;
  TargetCanvas.Font.Color:=clHighlightText;
 end;
end;

Image & Font Colour ends here.

Adding A Combobox

  • I guess you have an open project on Lazarus IDE having VST on it and can edit the nodes. If not see the "Basic Tree Listview With 3 Columns" above, and atleast complete steps 1 to 21.
  • Bellow there is an unit file named combo. Copy that unit and save as combo.pas inside the project directory. Under your program's uses clause add combo. So it may look like:
uses
  Classes, SysUtils, LResources, Forms, Controls, Graphics, Dialogs,
  VirtualStringTree, VirtualTrees, combo;
  • The combo.pas unit
unit combo;

{$mode delphi}

interface

uses
  Classes, SysUtils, LResources, Forms, Controls, Graphics, Dialogs,
  VirtualStringTree, VirtualTrees, messages, windows, StdCtrls;

type
  TStringEditLink = class(TInterfacedObject, IVTEditLink)
  private
    FEdit: TWinControl;
    FTree: TVirtualStringTree;
    FNode: PVirtualNode;
    FColumn: Integer;
  protected
    procedure EditKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
  public
    destructor Destroy; override;
    function BeginEdit: Boolean; stdcall;
    function CancelEdit: Boolean; stdcall;
    function EndEdit: Boolean; stdcall;
    function GetBounds: TRect; stdcall;
    function PrepareEdit(Tree: TBaseVirtualTree; Node: PVirtualNode; Column: TColumnIndex): Boolean; stdcall;
    procedure ProcessMessage(var Message: TMessage); stdcall;
    procedure SetBounds(R: TRect); stdcall;
  end;

implementation

destructor TStringEditLink.Destroy;
begin
  FEdit.Free;
  inherited;
end;

procedure TStringEditLink.EditKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
    case Key of
    VK_ESCAPE:
      begin
        FTree.CancelEditNode;
        Key := 0;
        FTree.setfocus;
      end;
      VK_RETURN:
      begin
       PostMessage(FTree.Handle, WM_KEYDOWN, VK_DOWN, 0);
       Key := 0;
       FTree.EndEditNode;
       FTree.setfocus;
      end;
     End; //case
end;


function TStringEditLink.BeginEdit: Boolean;
begin
  Result := True;
  //FEdit.Height:=(FTree.DefaultNodeHeight - 1); //Needed for editbox. Not combo
  FEdit.Show;
  TComboBox(FEdit).DroppedDown:=True;
  FEdit.SetFocus;
end;

function TStringEditLink.CancelEdit: Boolean;
begin
  Result := True;
  FEdit.Hide;
end;


function TStringEditLink.EndEdit: Boolean;
var
  S: WideString;
begin
  Result := True;
  S:= TComboBox(FEdit).Text;
  FTree.Text[FNode, FColumn] := S;

  FTree.InvalidateNode(FNode);
  FEdit.Hide;
  FTree.SetFocus;
end;


function TStringEditLink.GetBounds: TRect;
begin
  Result := FEdit.BoundsRect;
end;


function TStringEditLink.PrepareEdit(Tree: TBaseVirtualTree; Node: PVirtualNode; Column: TColumnIndex): Boolean;
begin
  Result := True;
  FTree := Tree as TVirtualStringTree;
  FNode := Node;
  FColumn := Column;

  FEdit.Free;
  FEdit := nil;

  FEdit := TComboBox.Create(nil);
   with FEdit as TComboBox do
     begin
          Visible := False;
          Parent := Tree;
          Items.Add('Google');
          Items.Add('Yahoo');
          Items.Add('Altavista');
          OnKeyDown := EditKeyDown;
      end;
end;


procedure TStringEditLink.ProcessMessage(var Message: TMessage);
begin
  FEdit.WindowProc(Message);
end;


procedure TStringEditLink.SetBounds(R: TRect);
var
  Dummy: Integer;

begin
  FTree.Header.Columns.GetColumnBounds(FColumn, Dummy, R.Right);
  FEdit.BoundsRect := R;
end;

End.
  • After saving the file, on the Form Designer select VST and on Object Inspector's Properties, scroll to TreeOptions -> MiscOptions, set toEditable to True. Then get to TreeOptions -> SelectionOptions, set toExtendedFocus to True.
  • Switch to Object Inspector's Events tab. Scroll to OnCreateEditor, double click and paste:
procedure TForm1.VSTCreateEditor(Sender: TBaseVirtualTree;
  Node: PVirtualNode; Column: TColumnIndex; out EditLink: IVTEditLink);
begin
  EditLink:=TStringEditLink.Create;
end;
  • On Object Inspector's Events tab. Scroll to OnNewText, double click and paste:
procedure TForm1.VSTNewText(Sender: TBaseVirtualTree; Node: PVirtualNode;
  Column: TColumnIndex; NewText: WideString);
Var
Data: PTreeData;
begin
Data := VST.GetNodeData(Node);
Case Column of
 0: Data^.Column0:= NewText;
 1: Data^.Column1:= NewText;
 2: Data^.Column2:= NewText;
End;
end;

Run program, select a node and press F2 to get combobox. On pressing Enter new value should appear on the node.

If Cell Editing Can't Be Seen

Open VirtualStringTree.pas unit file (if you are still on the above example project, right click on VirtualStringTree under Uses clause and select Find Declaration. This opens the file on next tab. Go to that file's tab.). Get to the "function TStringEditLink.BeginEdit: Boolean; stdcall;". It looks like: 

    
function TStringEditLink.BeginEdit: Boolean; stdcall;

// Notifies the edit link that editing can start now. Descentants may cancel node edit
// by returning False.

begin
  Result := not FStopping;
  if Result then
  begin
    FEdit.Show;
    FEdit.SelectAll;
    FEdit.SetFocus;
  end;
end;

Now add "FEdit.Height:=18;". It should look like: 

function TStringEditLink.BeginEdit: Boolean; stdcall;

// Notifies the edit link that editing can start now. Descentants may cancel node edit
// by returning False.

begin
  Result := not FStopping;
  if Result then
  begin
    FEdit.Show;
    FEdit.SelectAll;
    FEdit.SetFocus;
    FEdit.Height:=18; // <--- Added this line.
  end;
end;

Save the file (press Ctrl + S). If you are on the example project, close this (Project -> Close Project). Click on Tools -> Configure "Build Lazarus" ... Select Clean Up + Build All and then click on the Build button. After compile Lazarus should be restarted. Now open the example project and try to edit node on VST. This time it should be ok.
Thank you.
--Rabiul 21:37, 20 October 2008 (CEST)
Alhamdulillah.

Programando en Pascal - Spanish tutorial focused on FPC/Lazarus, hosted in Wikibooks.

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