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       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 cased 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

       -V     Prints the version.


       lefty user guide.