making default event handler for TLazVirtualStringTree

[egsuh]

Hello,

VirtualStringTree seems a little complex at first glance. I'm looking for ways to make it more easily accessible, using helpers etc.
The following example works fine with assigning methods to event handlers.

I'm wondering there are any ways to directly change the default behavior of this TLazVirtualStringTree as in HVStr. The key is I do not have to assign event handling methods at form designer.

Code: Pascal  [Select][+][-]

1. type
2.   { TTreeData -- an object  }
3.  
4.   TTreeData = class
5.     Field0: String;
6.     Field1: String;
7.     Field2: String;
8.     Field3: String;
9.     Field4: String;
10.     Field5: String;
11.     Field6: String;
12.  
13.   public
14.      constructor Create(AValue:integer);
15.   end;
16.  
17.  
18.   { HVStr }
19.  
20.   HVStr = class helper for TLazVirtualStringTree
21.     procedure GetText(Sender: TBaseVirtualTree; Node: PVirtualNode; // want to make this procedure as default,
22.       Column: TColumnIndex; TextType: TVSTTextType; var CellText: String);
23.   end;
24.  
25.  
26.   { Tfrvst }
27.  
28.   Tfrvst = class(TFrame)
29.     vst: TLazVirtualStringTree;
30.  
31.     procedure vstEditing(Sender: TBaseVirtualTree; Node: PVirtualNode;
32.       Column: TColumnIndex; var Allowed: Boolean);
33.     procedure vstFreeNode(Sender: TBaseVirtualTree; Node: PVirtualNode);
34.     procedure vstGetNodeDataSize(Sender: TBaseVirtualTree;
35.       var NodeDataSize: Integer);
36.     procedure vstGetText(Sender: TBaseVirtualTree; Node: PVirtualNode;
37.        Column: TColumnIndex; TextType: TVSTTextType; var CellText: String);
38.     procedure vstNewText(Sender: TBaseVirtualTree; Node: PVirtualNode;
39.       Column: TColumnIndex; const NewText: String);
40.   end;
41.  
42. implementation
43.  
44. {$R *.lfm}
45.  
46. { TTreeData }
47.  
48. constructor TTreeData.Create(AValue: integer);
49. begin
50.    inherited Create;
51.  
52.    Field0 := IntToStr(AValue);
53.    Field1 := 'Col 1 ' + IntToStr(Avalue);
54.    Field2 := 'Col 2 ' + IntToStr(Avalue);
55.    Field3 := '(col 3)';
56.    Field4 := '(col 4)';
57.    Field5 := '(col 5)';
58.    Field6 := '(col 6)';
59. end;
60.  
61. { HVStr }
62.  
63. // like following way
64.  
65. procedure HVStr.GetText(Sender: TBaseVirtualTree; Node: PVirtualNode;
66.    Column: TColumnIndex; TextType: TVSTTextType; var CellText: String);
67. begin
68.    with TTreeData(Sender.GetNodeData(Node)^) do begin
69.        case Column of
70.          0: CellText := Field0;
71.          1: CellText := Field1;
72.          ......
73.          6: CellText := Field6;
74.        end;
75.    end;
76. end;
77.  
78. { Tfrvst }
79.  
80.  
81. { -------- mapping text & column --------------- }
82.  
83.  
84. // ---------- current this is fine, but must be assigned to OnGetText event.
85.  
86. procedure Tfrvst.vstGetText(Sender: TBaseVirtualTree; Node: PVirtualNode;
87.   Column: TColumnIndex; TextType: TVSTTextType; var CellText: String);
88. begin
89.   with TTreeData(Sender.GetNodeData(Node)^) do begin
90.      case Column of
91.        0: CellText := Field0;
92.        1: CellText := Field1;
93.        ......
94.        6: CellText := Field6;
95.      end;
96.   end;
97. end;
98. // -------- }
99.  
100.  
101.  
102. procedure Tfrvst.vstNewText(Sender: TBaseVirtualTree; Node: PVirtualNode;
103.   Column: TColumnIndex; const NewText: String);
104. var
105.   Data: TTreeData;
106. begin
107.   with TTreeData(Sender.GetNodeData(Node)^) do begin
108.      case Column of
109.        0: Data.Field0 := NewText;
110.        1: Data.Field1 := NewText;
111.        .....
112.        6: Data.Field6 := NewText;
113.      end;
114.   end;
115. end;
116.