Course web page: Introduction to Computer Science for Majors I by James Tam

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Developing Graphical Assignments  On The Computer Science Network

Note: this posting only applies when you are trying to develop a graphical version of the assignments using QuickDraw on the computers in the Computer Science lab. It shouldn't apply when you are writing your graphical programs at home or if you are developing a text-only version of the assignments (either in the lab or at home).

What happened:

QuickDraw uses Java libraries for the drawing of graphics. It's a long story where there was a somewhat gradual degradation of the Java install on our network. Synopsis: During one of the updates the Java code libraries were corrupted. The result is that you will get some strange error message when your program employs some of Java's graphical libraries (required by QuickDraw):

#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00002ad4e352b259, pid=17080, tid=1094609216

etc. etc. etc.

Fortunately there are still a handful of machines in the lab that are still working okay so we do have a workaround that you can employ this semester:

  1. When logged into one of the computers in the lab open up a command line.
  2. At the command line type: ssh -X <a name of one of the machines that still work1>
  3. You will then be required to enter your UNIX login information (because you are logging into this machine remotely)
  4. You can now code that contains references to QuickDraw as normal but only using the command line where you typed in the previous command. If you want to run programs from multiple command lines then you would have to enter step #2 in each of those command lines.

1 The following machines should work: 'zone50wa', 'helper1', 'helper2', 'helper3', 'helper4'. So to open up the SSH X connection you could type "ssh -X helper2". If you find that a particular machine isn't working then try establishing a remote connection to one of the others. Note this is a graphical SSH connection, not the text-only connection that you may have been using earlier in the semester to work from home is different i.e., http://pages.cpsc.ucalgary.ca/~tamj/231/starting/ssh.html