The BLT toolkit is simply an extension available for the Tcl Tk toolkit allowing developers to add new widgets, geometry managers and all sorts of commands to the Tcl interpreter. You don’t need to perform any patching of the Tcl Tk source files for using BLT in an effective manner. The last known release of BLT works efficiently with the Tk versions 8.4, 8.3, 8.2, 8.1 and 8.0. You can even use the binary releases that are available for the Windows XP, Windows 2000, Windows NT, Windows 98 and Windows 95 environments. Please keep in mind that you can only install either of the 8.4, 8.3, 8.2, 8.1 and 8.0 BLT versions.

Following are some commands that the BLT library adds to the Tk:

busy – This command helps in easy handling of the user interactions at a time when the application is in busy mode. It creates and manages an invisible busy window that prevents any further interaction with the user devices like mouse buttons, keyboard etc. It also provides a distinct type of cursor that supersedes the normal application cursors.

barchart – This is a bar chart wizard which allows you to plot 2-variable data, making use of bars. You’re provided support for 2 sets of y and x, custom axis layout and inverted axes.

watch – It allows you to specify different Tcl procedures, which can be run prior to and/or after any Tcl command. You can even use it for easy debugging, profiling, tracing or logging of the Tcl code/s.

vector – It helps in easy creation of a vector with floating point values. The components of the vector can be manipulated and altered in three different ways: via C API, some Tcl command or a Tcl array variable.

spline – This command computes a spline that accommodates or fits a set of y and x vector data points, resulting in production of a vector of interpolated images (on the y-coordinates) at some given set of x-coordinates.

table – This a table-based geometry manager that can be used in Tk. You’re required to specify the widget layout in the form of column and row positions of the table. It has various options for constraining the window resizing.

bgexec – This is just like the Tcl’s ‘exec….&’ command but it collects the status, error and output of the detached or disconnected UNIX sub-processes. It leads to the setting of a particular Tcl variable post its completion. What’s interesting is that you can even use bgexec along with the ‘tkwait’ variable for easy handling of the expose events and more, while waiting for the sub-processes to conclude.

drag & drop – It’s a command that adds the drag-and-drop capabilities to the Tk interface. You’re provided with a ‘send’ style communication with the drag-and-drop targets and sources. The result – a very powerful drag-and-drop mechanism which is available with both Motif or OpenLook.

htext – This is a simple and basic hypertext widget which allows the Tk and text widgets to be integrated into a scrollable text window. You can embed any Tk widget and use it for creation of hyperlinks. Other options provide for easy text searches and selections.

graph – This is a x-y graph widget which allows you to plot 2-variable data. It provides support for 2 sets of y and x axes, custom axis layout and inverted axes.

winop – Low level Xlib calls that allow you to unmap, map, lower or raise any window.

bitmap – This is the basic command for creation and manipulation of bitmaps from the Tcl language. It allows you to read and write bitmaps via Tcl. You can also input definitions of X bitmaps and create the bitmaps using text strings. Other options provide for rotation and scalability of bitmaps too.

bltdebug – This command allows you to take a printout of every Tcl command, prior to its execution.