TAtlasDiagram

Create constructor

constructor Create(AOwner: TComponent); override;

Creates a 900 x 600 white diagram without a graph, with TabStop = True and double buffering.

Destroy destructor

destructor Destroy; override;

Detaches from the graph (the graph itself is not freed).

SelectedID property

property SelectedID: Integer read FSelected;

ID of the selected node, 0 when none. Only user input changes it; it is cleared when that node is deleted or the graph is replaced.

if Diagram.SelectedID <> 0 then Graph.DeleteNode(Diagram.SelectedID);

Graph property

property Graph: TAtlasGraph read FGraph write SetGraph;

The model to show and edit. Assigning it registers a listener and clears the selection; nil detaches. Freeing the graph detaches it automatically.

Diagram.Graph := Graph;

ConnectMode property

property ConnectMode: Boolean read FConnectMode write FConnectMode default False;

When True, the next click on a node other than the selected one adds an edge from the selected node to it and resets ConnectMode to False. With no node selected, the first click selects the source. Connecting an already connected pair raises EAtlasGraphError (Duplicate edge).

Diagram.ConnectMode := True;

NodeColor property

property NodeColor: TColor read FNodeColor write SetNodeColor default $00F3E8DC;

Fill colour of unselected nodes.

NodeTextColor property

property NodeTextColor: TColor read FNodeTextColor write SetNodeTextColor default clBlack;

Border and caption colour of unselected nodes.

Align property

property Align;

Standard VCL alignment in the parent.

Anchors property

property Anchors;

Standard VCL anchors.

Color property

property Color;

Background; clWhite by default.

Font property

property Font;

Caption font; Font.Color is also the colour of the edges and arrowheads.

ParentFont property

property ParentFont;

Standard VCL property: use the parent's font.

TabStop property

property TabStop;

True by default. The diagram takes the focus when clicked, so Delete works.

Render method

procedure Render(Target: TCanvas);

Draws the diagram on any canvas, over the rectangle of the control's client area, so size a bitmap to ClientWidth x ClientHeight. Paint calls it.

Bitmap.SetSize(Diagram.ClientWidth, Diagram.ClientHeight);
Diagram.Render(Bitmap.Canvas);

NodeAt method

function NodeAt(X, Y: Integer): Integer;

ID of the topmost node (the last in Nodes order) containing client point X, Y, or 0 when there is none or no graph.

ID := Diagram.NodeAt(120, 60);

Show a graph

Connects a diagram to an existing graph; it repaints on every change to the graph.

uses System.Classes, Vcl.Controls, Atlas.Graph, Atlas.Diagram;

function AddDiagram(Owner: TComponent; Parent: TWinControl; Graph: TAtlasGraph): TAtlasDiagram;
begin
  Result := TAtlasDiagram.Create(Owner);
  Result.Parent := Parent;
  Result.Align := alClient;
  Result.Graph := Graph;
end;

Connect command

For a Connect button: the user then clicks the source node and the target node.

uses Atlas.Diagram;

procedure StartConnecting(Diagram: TAtlasDiagram);
begin
  Diagram.ConnectMode := True;
  if Diagram.CanFocus then Diagram.SetFocus;
end;

Save the diagram as PNG

Renders the current view into a bitmap of the control's size.

uses Vcl.Graphics, Vcl.Imaging.pngimage, Atlas.Diagram;

procedure SaveDiagram(Diagram: TAtlasDiagram; const FileName: string);
var
  Bitmap: TBitmap;
  Png: TPngImage;
begin
  Bitmap := TBitmap.Create;
  Png := TPngImage.Create;
  try
    Bitmap.SetSize(Diagram.ClientWidth, Diagram.ClientHeight);
    Diagram.Render(Bitmap.Canvas);
    Png.Assign(Bitmap);
    Png.SaveToFile(FileName);
  finally
    Png.Free;
    Bitmap.Free;
  end;
end;