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lefty - Online in the Cloud

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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


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 printed.

-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.

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