in PR 9593.
BLT is an extension to Tcl/Tk. It adds plotting widgets (X-Y graph,
barchart, stripchart), a powerful geometry manager, a new canvas item,
and several new commands to Tk.
Plotting widgets: graph, barchart, stripchart
Hierarchical list box: hierbox
Tab set: tabset
Geometry Manager: table
Vector Data Object: vector
Background Program Execution: bgexec
Busy Command: busy
New Canvas Item: eps
Drag & Drop Facility: drag&drop
Bitmap Command: bitmap
Miscellaneous Commands: winop, bltdebug, watch, spline, htext