Table of Contents

Lines and linking

Lines are the connectors of a diagram. A line (TTMSFNCBloxLine) draws a path between two points and, in most diagrams, anchors those points to block link points so the connection follows the blocks as they move. This chapter covers creating and anchoring lines, choosing a line style, configuring arrows, forcing connections, and labelling a line.

Connecting two blocks

To connect blocks, create a TTMSFNCBloxLine, anchor its SourceLinkPoint and TargetLinkPoint to link points on each block, and add it to the collection. The line then tracks both blocks: move a block and the connector follows.

function TForm1.ConnectBlocks(ASource, ATarget: TTMSFNCBloxBlock): TTMSFNCBloxLine;
begin
  Result := TTMSFNCBloxLine.Create;
  Result.SourceLinkPoint.AnchorLink := ASource.LinkPoints[1]; { bottom }
  Result.TargetLinkPoint.AnchorLink := ATarget.LinkPoints[0]; { top }
  Result.StrokeColor := MakeGraphicsColor(120, 120, 120);
  Result.StrokeWidth := 2;
  Result.TargetArrow.Shape := asSolidArrow;
  BloxControl1.Blox.Add(Result);
end;
Note

The endpoints anchor to link points, not to blocks directly. Use a TTMSFNCBloxLinkableBlock (four built-in points) or add points to a plain block first — see Working with blocks.

Line styles

LineStyle selects how the path between the endpoints is drawn:

TTMSFNCBloxLineStyle Path
lsLine A single straight segment (the default).
lsSideLine Perpendicular (orthogonal) segments — the flowchart "elbow" connector.
lsParabolicArc A parabolic arc.
lsCircularArc A circular arc.
lsBezier A bezier curve. 
procedure TForm1.AddStyledLine(ASource, ATarget: TTMSFNCBloxBlock;
  AStyle: TTMSFNCBloxLineStyle);
var
  LLine: TTMSFNCBloxLine;
begin
  LLine := TTMSFNCBloxLine.Create;
  LLine.LineStyle := AStyle;            { lsLine, lsSideLine, lsCircularArc, lsBezier, ... }
  LLine.SourceLinkPoint.AnchorLink := ASource.LinkPoints[3]; { right }
  LLine.TargetLinkPoint.AnchorLink := ATarget.LinkPoints[2]; { left }
  LLine.TargetArrow.Shape := asLineArrow;
  BloxControl1.Blox.Add(LLine);
end;
Lines drawn with straight, side-line, arc, and bezier styles Lines drawn with straight, side-line, arc, and bezier styles

Arrows

Each end has an arrow (SourceArrow and TargetArrow, both TTMSFNCBloxLineArrow). Set Shape to choose the head and Width / Height to size it:

TTMSFNCBloxArrowShape Head
asNone No arrowhead.
asSolidArrow Filled triangle.
asLineArrow Open (line) arrow.
asDiamond / asAngledDiamond Diamond heads.
asRectangle / asEllipse Block and round terminators.
asHalfLine Half-barb.

Mandatory anchoring and labels

Set RequiresConnections := True to forbid a line whose ends are not both anchored to a block — the user cannot insert, move, or resize it until it is fully connected, which keeps flow diagrams valid. A line also carries text: assign Text for the centre label, or index the TextCells collection for finer control over the individual cells along the line.

Putting it together

The example below combines a styled side-line, a solid arrow, a centre label, and a required connection in one connector:

function TForm1.AddLabeledConnection(ASource, ATarget: TTMSFNCBloxBlock;
  const ALabel: string): TTMSFNCBloxLine;
begin
  Result := TTMSFNCBloxLine.Create;
  Result.LineStyle := lsSideLine;             { orthogonal elbow connector }
  Result.SourceLinkPoint.AnchorLink := ASource.LinkPoints[1];
  Result.TargetLinkPoint.AnchorLink := ATarget.LinkPoints[0];
  Result.TargetArrow.Shape := asSolidArrow;
  Result.TargetArrow.Width := 14;
  Result.TargetArrow.Height := 14;
  Result.Text := ALabel;                       { label shown at the line centre }
  Result.RequiresConnections := True;          { both ends must stay connected }
  BloxControl1.Blox.Add(Result);
end;

Pitfalls

  • Anchoring to a block with no link points fails silently — the endpoint has nothing to attach to. Ensure the block has link points first.
  • RequiresConnections blocks interactive editing of unconnected lines. Set it only after both endpoints are anchored, or the user cannot manipulate the line at all.
  • Link-point indices are layout-specific. For the default four points the order is top, bottom, left, right (0–3); verify the order for library blocks that define their own.

See also