Subsections

• The Canvas
• The Button-bar

The Tk Widget

The option -tk [[-q Integer] [-xd Dist] [-angle Angle]] File indicates that a finite state automaton is read from File and shown in a Tk Widget. The -xd option can be used to alter the default X distance of nodes (default: 120). The -angle option indicates the angle of edges (default: 0.25). Straight lines can be obtained with a value of 0. The quality option indicates how hard the system should try to obtain a good visualization. Default is 1, which indicates that not much effort is made at reducing the number of crossing branches; larger integers will (dramatically) increase processing time, resulting sometimes in slightly better output.

The Tk Widget offers a graphical user interface to browse finite-state automata. For an illustration, consider figure 3. The use of this widget is explained now as follows.

Figure 3: The FSA Utilities toolbox uses Tcl/Tk for its built-in visualization of finite-state automata. The user can interactively alter the visualization by dragging states of the automaton to different positions. L^ATEX picture output and Postscript output can be generated on the basis of the current view.

The Canvas

The canvas displays the finite-state automaton. The display can be controlled by a number of options to the fsa command, or on-line by using the button-bar.

By default, edges are not drawn as straight lines, but as curves. The angle of the edge is determined by the -angle option or the Edge Angle field on the button-bar.

The default distance between nodes is determined by the -xd option or the X-distance field on the button-bar.

Finally the system provides limited functionality to compute the most suitable geometry. The intent is to minimize the number of crossing edges, as well as the size of the area needed to display an automaton. Since in general such a procedure is much too costly, the -q option or the Quality field on the button-bar can be used to tell the system how much effort should be spent on this. A higher value should imply better quality.

The finite-state automaton can be manipulated manually by dragging states of the automaton to a new place. This possibility implies that you can adapt the visualization of the automaton to your own taste, and to the characteristics of a particular automaton.

The Button-bar

Save

The current geometry of the finite-state automaton is saved in the file from which the current automaton was read. Note that the next time this file is used as input for the fsa -tk command, all geometry options are ignored, and this information is used instead.

SaveAs

As the above, but the user is prompted for a file-name.

SaveAsTeX

The user is prompted for a file-name. In this file the system outputs the current geometry of the automaton as a L^ATEX picture. This can then be used in a L^ATEX file, to give e.g.:

SaveAsPs

The user is prompted for a file-name. In this file the system outputs the current geometry of the automaton as a Postscript picture.

Load

You are prompted for a file-name. The file-name is assumed to contain a finite-state automaton which will be displayed in the canvas.

Redraw

The current automaton is redrawn.

Revert

All changes are discarded and the automaton is redrawn.

Pause

The Tk-Widget is removed from the screen.

Debugging

When this option is set, progress information during the computation of the geometry is shown.

Quit

The application is halted.

Edge Angle

Determines the edge of an angle. When this is set to 0 then straight lines are used. Useful values are between 0 and 1.

X-distance

Determines the distance between nodes.

Quality

Determines the effort that should be spent on the computation of the geometry. If this value is larger than 0, the system tries to minimize the number of crossing edges and the size of the area needed for the automaton. Larger values dramatically increase the time needed to compute this.

Help

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