#toc
Table of Contents
#toc0
Name
BLT - Introduction to the BLT library
#toc1
Description
BLT
is a library of extensions to the Tk library.  It adds new commands and
variables to the application's interpreter.
#toc2
Commands
The following commands
are added to the interpreter from the BLT library:
table
A table geometry
manager for Tk.  You specify window placements as table  row,column positions
and windows can also span multiple rows or columns.  It also has many options
for setting and/or bounding window sizes.
graph
A 2D plotting widget.  Plots
two variable data in a window with an optional  legend and annotations.
It has of several components; coordinate axes,  crosshairs, a legend,
and a collection of elements and tags.
barchart
A barchart widget.  Plots
two-variable data as rectangular bars in a  window.  The x-coordinate values
designate the position of the bar along  the x-axis, while the y-coordinate
values designate the magnitude. The
barchart
widget has of several components;
coordinate axes,  crosshairs, a legend, and a collection of elements and
tags.
vector
Creates a vector of floating point values.  The vector's components
can be manipulated in three ways: through a Tcl array variable, a Tcl command,
or the C API.
spline
Computes a spline fitting a set of data points (x and
y vectors) and produces a vector of the interpolated images (y-coordinates)
at a given set of x-coordinates.
bgexec
Like Tcl's
exec
command,
bgexec
runs
a pipeline of Unix  commands in the background.  Unlike
exec
, the output
of the last process is collected and a global Tcl variable is set upon
its completion.
bgexec
can be used with
tkwait
to wait for Unix commands
to finish while still handling expose events.  Intermediate output is also
available while the pipeline is active.
busy
Creates a "busy window" which
prevents user-interaction when an application is busy.  The busy window also
provides an easy way  to have temporary busy cursors (such as a watch or
hourglass).
bitmap
Reads and writes bitmaps from Tcl.  New X bitmaps can
be defined on-the-fly from Tcl, obviating the need to copy around bitmap
files.   Other options query loaded X bitmap's dimensions and data.
drag&drop
Provides a drag-and-drop facility for Tk.  Information (represented by a
token window) can be dragged to and from any Tk window, including those
of another Tk application.
drag&drop
acts as a  coordinator, directing Tk
send
commands between (or within) TCL/Tk  applications.
htext
A simple
hypertext widget.  Combines text and Tk widgets into a single scroll-able
window.  Tcl commands can be embedded into text, which are invoked as the
text is parsed.  In addition, Tk widgets can be appended to the window at
the current point in the text.
Htext
can be also used to create scrolled
windows of Tk widgets.
winop
Raise, lower, map, or, unmap any window.  The
raise and lower functions are useful for stacking windows above or below
"busy windows".
watch
Arranges for Tcl procedures to be called before and/or
after the execution of every Tcl command. This command may be used in the
logging, profiling, or tracing of Tcl code.
bltdebug
A simple Tcl command
tracing facility useful for debugging Tcl code.   Displays each Tcl command
before and after substitution along its level  in the interpreter on standard
error.
#toc3
Variables
The following Tcl variables are either set or used by BLT
at various times in its execution:
blt_library
This variable contains the
name of a directory containing a library of Tcl scripts and other files
related to BLT.  Currently, this  directory contains the
drag&drop
protocol
scripts and the  PostScript prolog used by
graph
and
barchart
. The value
of this variable is taken from the BLT_LIBRARY environment variable, if
one exists, or else from a default value compiled into the
BLT
library.
blt_versions
This variable is set in the interpreter for each application.
It is an  array of the current version numbers for each  of the BLT commands
in the form
major
.
minor
.
Major
and
minor
are integers.  The major version
number increases in any command that includes changes that are not backward
compatible (i.e. whenever existing applications and scripts may have to change
to work with the new release).  The minor version number increases with
each new release of a command, except that it resets to zero whenever the
major version number changes.  The array is indexed by the individual  command
name.
#toc4
Adding Blt to Your Applications
It's easy to add BLT to an existing
Tk application.  BLT requires no  patches or edits to the Tcl or Tk libraries.
To add BLT, simply add the  following code snippet to your application's
tkAppInit.c file.
if (Blt_Init(interp) != TCL_OK) {
return TCL_ERROR;
}
Recompile and link with the BLT library (libBLT.a) and that's it.
Alternately,
you can dynamically load BLT, simply by invoking the command
package require BLT
from your Tcl script.
#toc5
Bugs
Send bug reports, requests, suggestions, etc. to
gah@siliconmetrics.com or gah@myfirstlink.net
#toc6
Keywords
BLT
Table of Contents
#sect0
Name
#sect1
Description
#sect2
Commands
#sect3
Variables
#sect4
Adding Blt to Your Applications
#sect5
Bugs
#sect6
Keywords
