LazNodeEditor — Powerful visual node graph editor component for Lazarus (Free Pascal)

A full-featured, cross-platform node-based visual programming / dataflow editor component for Lazarus IDE (works on Windows and Linux).

Perfect for creating visual scripting tools, shader editors, game logic editors, automation tools, or any application that needs a node graph UI.

• Modern node UI with customizable header/body colors
• Two pin types: pkExec (flow) and pkData (values)
• Rich inspector — edit node properties, pins, values (float, int, string, boolean, JSON)
• Full undo/redo system with command pattern
• Save / Load as JSON (compatible with custom nodes)
• Snap to grid, zoom, pan, frame all, fit to selection
• Copy / Paste / Duplicate nodes (with links)
• Reroute nodes, Comment / Frame nodes
• Drag & drop node creation from context menu or toolbar
• Validation system
• Highly extensible — easy to register your own node classes
• Cross-platform (Windows + Linux tested)

• Lazarus 2.2+ or 3.0+
• Free Pascal 3.2.2+
• No external dependencies (pure LCL)

1. Clone or download the repository
2. Just add laznodeeditor.pas to your project.

uses LazNodeEditor;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Editor := TLazNodeEditor.Create(Self);
  Editor.Parent := Self;
  Editor.Align := alClient;

  // Optional: connect inspector
  Inspector.Editor := Editor;

  // Register custom nodes
  Editor.Graph.Registry.RegisterNodeEx(
    'my_custom_node', 'My Node', 'Category',
    'Description here', 'tag1,tag2', TMyCustomNode, $00FF8000);
end;

type
  TMyCustomNode = class(TCustomNode)
  public
    constructor Create(ATitle: string; AX, AY: Single;
      AWidth: Integer = 200; AHeight: Integer = 160); override;
    procedure SetupPins; override;
  end;

constructor TMyCustomNode.Create(ATitle: string; AX, AY: Single; ...);
begin
  inherited;
  NodeType := 'my_custom_node';
  HeaderColor := $00FF4080;
  BodyColor   := $00FFF0F8;

  // Add values shown in inspector
  AddValue('threshold', nvkFloat).FloatValue := 0.5;
  AddValue('enabled', nvkBoolean).BooleanValue := True;
end;

procedure TMyCustomNode.SetupPins;
begin
  ClearPins;

  // Exec pins
  AddInput ('▶ Exec In',  'exec', pkExec, 35);
  AddOutput('▶ Exec Out', 'exec', pkExec, 35);

  // Data pins
  AddInput ('Value', 'float', pkData, 75);
  AddOutput('Result', 'float', pkData, 110);
end;

TLazNodeEditor

• SnapToGrid, GridSize
• Zoom, OffsetX, OffsetY
• SaveToFile / LoadFromFile
• Undo, Redo
• CopySelectionToClipboard, PasteFromClipboard
• FrameAll, FitToSelection
• ValidateGraphToStrings

TLazNodeInspector

• Automatically shows selected node properties, pins, and values
• Color pickers, editors, grids for pins/values

• Windows 10/11 (Lazarus 3.0)
• Linux (Ubuntu 22.04/24.04, GTK2/GTK3/Qt5/Qt6)

MIT License.

Contributions are welcome!

• Report bugs
• Add new example nodes
• Improve documentation
• Add more features (pin colors per type, sub-graphs, etc.)