Swarm FAQ:BLT

Q: What is this BLT thing?

A: BLT is a required library. It provides graphs, such as time plots and histograms. BLT is an extension of the tcl/tk libraries. At one time, in order to build BLT, one had to integrate its source code into the code tree from tcl/tk, but that is no longer necessary. If you have the development headers for tcl/tk, you can build BLT in the normal GNU way--configure, make, make install.

Over the years, the BLT project has had variable amounts of interest and upkeep. At one time, the original author appeared to have dropped from the face of the earth and a team of volunteers started to announce updates with a package called "blt-unofficial". Then the original author said, in a rather Monty Python-esque way, "I'm not dead yet" and development on the original channel continued.

There is now a Sourceforge page for blt: http://blt.sourceforge.net.

The versioning on blt has been in this style: 2.4a, 2.4b, and so forth. The current version, 2.4z is now more than two years old. A lot of work has been done by the author towards version 3.0 which seems to include MacOS X code. However, as of May 2005, some files are missing from the cvs and the package will not build from cvs code. Hopefully version 3.0 will get finished at some point.

Q: What is wrong when I run a Swarm program and it crashes, saying bltGraph.tcl is missing?

A. This is caused by a change in the packaging of blt between versions 2.4u and 2.4y. The file formerly called bltGraph.tcl is now called graph.tcl. If you go into the place where BLT is installed, say /usr/lib/blt2.4, you can create a symbolic link to make the error go away:

ln -sf /usr/lib/blt2.4/graph.tcl /usr/lib/blt2.4/bltGraph.tcl

I believe we will change the Swarm code to look for the newer file name soon.

Paul Johnson <pauljohn@ku.edu> 2003-11-22