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intro(n) BLT Built-In Commands intro(n)
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NAME
BLT - Introduction to the BLT library
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DESCRIPTION
BLT is a library of extensions to the Tk library. It adds new commands and variables to
the application's interpreter.
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 win-
dow. The x-coordinate values designate the position of the bar along the
x-axis, while the y-coordinate values designate the magnitude. The bar-
chart widget has of several components; coordinate axes, crosshairs, a leg-
end, 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 pro-
duces 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. Dis-
plays each Tcl command before and after substitution along its level in the
interpreter on standard error.
VARIABLES
The following Tcl variables are either set or used by BLT at various times in its execu-
tion:
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 envi-
ronment 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 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 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 appli-
cation'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 AT siliconmetrics.com or
ghowlett AT grandecom.net
KEYWORDS
BLT
BLT 2.4 intro(n)
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On Apache
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