intro(BLT 2.4) intro(BLT 2.4)
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BLT - Introduction to the BLT library
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BLT is a library of extensions to the Tk library. It adds new commands
and variables to the application's interpreter.
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 ycoordinate
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.
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.
ADDING BLT TO YOUR APPLICATIONS [Toc] [Back] 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.
Send bug reports, requests, suggestions, etc. to [email protected] or
[email protected]
BLT
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