1.4.2. Polygon Fill

  An area between segment handles can be filled with a polygon by clicking the polygon button and then clicking handles to create the connections. The handles will be highlighted in red as they are selected. Finish creating the polygon by clicking the first handle again (highlighted with a black dot in the handle) or by clicking the polygon button again. A minimum of 3 connections is required to create a polygon and the same connection cannot be added more than once. A polygon cannot be created if it has the same connections as an existing polygon.
Polygons are useful for filling large areas and for creating stretchable regions that move with the segments.
It can be tedious to add polygons with a large number of connections by clicking each connecting handle. The process can be performed much more quickly by holding the Ctrl key while clicking a handle to include all connections between the clicked connection and the previous connection. The connections will follow the shortest route between the two points by following a chain of segments.
If you make a mistake while selecting polygon connections, you can undo using the Edit menu option or Ctrl+Z. You can undo any number of connections and if you used Ctrl to add multiple connections at once at any point then undo will remove that whole group of connections.
Some examples of figures containing polygon fill, with the polygon selected
Select a polygon by clicking it anywhere. The connected handles will be highlighted in red. The number of handle connections and the draw order (z-order) will be shown in the status bar at the bottom of the window.
  Delete a polygon by selecting it and clicking the delete button. A polygon will also be deleted if a segment it attaches to is deleted which results in the polygon having fewer than 3 handle connections.
  Setting the colour and changing the draw order (z-order) also works for polygons in the same way as segments. Polygons can be semi transparent by setting the opacity in the colour selector.

Polygons and Bent Line Segments

Line segments can be bent into arcs by dragging the handle at the end of the line using the right mouse button or by selecting the option in the positioning toolbar. If an edge of a polygon coincides with a bent line segment, then the polygon will fill the area inside the arc. This is demonstrated by the cloud example shown above where all segments have been bent and the whole area filled with a polygon. Note that the beginning and end of the bent line must be consecutive connections of the polygon for this to work (using the Ctrl key to add multiple connections will take care of that automatically).

Operations on Branches Containing Polygons

A branch of a figure can be selected by holding down the Shift key


If the connections of a polygon are contained entirely within the selected branch then it is also selected. This means that operations on the branch such as setting the colour, deleting or changing the draw order (z-order) will also be performed on the polygon. However, if at least one of the polygon connections is not part of the branch then this will not be the case.