NAME
BLT - Introduction to the BLT library
_________________________________________________________________
DESCRIPTION
BLT is a library of extensions to the Tk library. It adds
new commands and variables to the application's inter
preter.
COMMANDS
The following commands are added to the interpreter from
the BLT library:
table A table geometry manager for Tk. You spec
ify window placements as table row,column
positions and windows can also span multi
ple 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 compo
nents; coordinate axes, crosshairs, a leg
end, 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-coor
dinate 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 vari
able, 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-coor
dinates) at a given set of x-coordinates.
bgexec Like Tcl's exec command, bgexec runs a
pipeline of Unix commands in the back
ground. 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
dling 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 use
ful for debugging Tcl code. Displays each
Tcl command before and after substitution
along its level in the interpreter on stan
dard error.
VARIABLES
The following Tcl variables are either set or used by BLT
at various times in its execution:
tory containing a library of Tcl scripts
and other files related to BLT. Currently,
this directory contains the drag&drop pro
tocol 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 com
patible (i.e. whenever existing applica
tions and scripts may have to change to
work with the new release). The minor ver
sion 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 com
mand name.
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.
BUGS
Send bug reports, requests, suggestions, etc. to gah@bell-
labs.com or ghowlett@fast.net
KEYWORDS
BLT
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