intro(n)						       BLT Built-In Commands							  intro(n)

__________________________________________________________________________________________________________________________________________________

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 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 mul-
		      tiple 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 com-
		      ponents; 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 com-
		      ponents; 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-coordi-
		      nates) 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 bit-
		      map 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 substitu-
		      tion 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 execution:

       blt_library    This variable contains the name of a directory containing a library of Tcl scripts and other files  related  to  BLT.   Cur-
		      rently,  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  com-
		      piled 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

       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@siliconmetrics.com or ghowlett@grandecom.net

KEYWORDS

       BLT

BLT
									2.4								  intro(n)