Browse Prior Art Database

Efficient Display of Tree-form Data on VDU or Printer

IP.com Disclosure Number: IPCOM000121571D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 3 page(s) / 82K

Publishing Venue

IBM

Related People

Jewson, MA: AUTHOR

Abstract

Disclosed is an algorithm to produce tree-form diagrams that can be used with both fixed and proportionally spaced character fonts. It avoids recourse to Graphics Techniques with their high code overheads. The tree-based application advantage is that it gives users an immediate impression of the structure of objects being edited and so passes on more information in a clearer way. The user program can be unaware of whether the font spacing on the target system is fixed or proportional.

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Efficient Display of Tree-form Data on VDU or Printer

      Disclosed is an algorithm to produce tree-form diagrams
that can be used with both fixed and proportionally spaced character
fonts.  It avoids recourse to Graphics Techniques with their high
code overheads.  The tree-based application advantage is that it
gives users an immediate impression of the structure of objects being
edited and so passes on more information in a clearer way.  The user
program can be unaware of whether the font spacing on the target
system is fixed or proportional.

      A useful method for displaying information on a VDU or Printer
is to present it in the form of a tree.  It works well with
fixed-font characters but presents problems with modern
variable-pitch proportional fonts.  Characters in fixed fonts all
have the same width and height.  Producing a tree diagram such as
that in Fig. 1 using the fixed font characters defined in Fig. 2 is
easy because all the characters line up correctly.  Note the position
of a large dot character to indicate to the user that a sub-tree is
available under a particular item.  An application can expand or
contract the tree under an item marked with the dot character,
conveniently achieved by selecting a menu item.

      Characters in proportional fonts have the same height, but
differing widths.  So using the same characters as in Fig. 1 but
instead using a proportional font would produce the effect depicted
in Fig. 3, caused by the vertical bar and the space characters having
much smaller widths than the branch or corner characters.  The effect
is not pleasing to the eye.  The conventional avoidence of the
problem is to change from using characters (i.e., text mode) to using
graphics, where th...