lefty - A Programmable Graphics Editor


   lefty [ options ] [ file ]


   lefty is a two-view graphics editor for technical pictures. This editor
   has no hardwired knowledge about specific picture  layouts  or  editing
   operations.   Each  picture  is  described  by  a program that contains
   functions  to  draw  the  picture  and  functions  to  perform  editing
   operations  that  are  appropriate  for the specific picture. Primitive
   user actions, like  mouse  and  keyboard  events,  are  also  bound  to
   functions  in  this  program. Besides the graphical view of the picture
   itself, the  editor  presents  a  textual  view  of  the  program  that
   describes the picture. Programmability and the two-view interface allow
   the editor to handle a variety of pictures, but are particularly useful
   for  pictures used in technical contexts, e.g., graphs and trees. Also,
   lefty can communicate with other processes. This feature allows  it  to
   use  existing  tools  to  compute  specific  picture layouts and allows
   external processes to use the editor as a front end  to  display  their
   data structures graphically.


   The  file  name  is  optional.  It  may be -, for reading from standard
   input.   lefty  uses   two   environment   variables,   LEFTYPATH   and
   LEFTYOPTIONS.  LEFTYPATH is a colon separated list of directories. When
   lefty tries to open a file, it searches that path for  the  file.  When
   lefty  tries  to start up another process, it searches LEFTYPATH first,
   then the standard PATH variable.   LEFTYOPTIONS  can  be  used  to  set
   specific  options.  Options  specified  on  the  command  line override
   options set through this variable.


   -x     Instructs the editor to exit after processing file.

   -e <expression>
          <expression> is parsed and executed.

   -el <num>
          Set error reporting level. The default  value  is  0.   0  never
          prints  any messages.  1 prints severe errors, such as trying to
          return from a non function.  2 is the most  useful:  it  reports
          function  calls that cannot be executed, either because there is
          no function, or because of argument mismatches.   3  also  warns
          about  bad  variable  names.  4,5 warn about expressions that do
          not return a value. Only level 1 messages are real  errors.  The
          rest  arise  from  legal  lefty statements, but may be caused by
          some logic errors.

   -sd <num>
          Specifies how much of the stack to show, when an  error  message
          is  to  be  printed. The default value is 2.  With 0, no part of
          the stack is shown. With 1, only the top stack frame is printed.
          With 2, the full stack is printed.

   -sb <num>
          Specifies  how  much of each function in the stack to show, when
          an error message is to be printed. The default value is 2.  With
          0,  no  part  of  the  function  is shown. With 1, only the line
          around the error is printed. With 2, the full function  body  is

   -df <string>
          Sets  the  default  font. This font is used whenever a requested
          font cannot be found. The string must be  a  legal  X  font.  If
          string is '', lefty will draw small boxes instead of text.

   -ps <file>
          Specifies a default file name for postscript files. This name is
          used when no name is specified in  the  createwidget  call.  The
          default file name is out.ps.

   -V     Prints the version.

   -?     Prints the usage and exits.


   lefty user guide.



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