[rkward-devel] KDE 4 status update

[Thomas Friedrichsmeier]

Hi,

On Sunday 28 October 2007, Prasenjit Kapat wrote:
> I am not sure if you got to this issue, neither the File browser nor
> the workspace browser opens up properly the first time... I have to
> drag it out. Need debug/valgrind  info?

no, I didn't get to this issue, yet. It's not so much related to file browser 
or workspace browser, but (technically) a window management issue. I have a 
good idea what's causing this, so no debug info needed. Will take care of 
this sooner or later.

> I had a crazy idea here.. Is it possible to access a variable (as
> read-only) when it is part of a running code? (smell debugger?)

This is not easy to do. The problem is that R itself is not designed to allow 
multiple concurrent threads, and hence only one command can run at a time. 
Therefore we can't really do anything while a command is running.

Now R has some facilities for debugging (see ?debug, ?browser). These work by 
interrupting the code at defined places, and allowing the user to step to the 
next line, or to print some local variable. Unfortunately, right now there is 
no nice way for a GUI to hook into this, and offer a decent debugger. So this 
will take some lobbying efforts (and of course efforts to write a debugger 
GUI), and the R devels are highly conservative about changes in the core R 
code. All in all, therefore, it's a considerable effort, and will not work in 
the near term.

It would really be a nice feature though.

> In this regard, a non KDE4 issue:
> I was trying the following code: i=1; while (i>0) {}
> If it executed by-passing the console and I try print(i) in the
> console, then the R engine / threading system somehow stops, doesn't
> freeze, doesn't crash! If I try to cancel through the "Pending jobs"
> window, some "sync" situation arises. The same can be achieved when
> the code is executed through the console and I use the workspace
> browser to "View" i.

Not sure what you mean by non KDE4 issue? In the KDE3 version of rkward, the 
command sometimes gets shown at a wrong place in the Pending Jobs window, but 
can be cancelled alright. In the KDE4 version, the command showed up 
correctly in the Pending Jobs window, but most of the time it was not 
actually possible to cancel it (I think I've fixed this, now).

Of course the larger issue is how to deal with interrupting locked-up commands 
that were not entered in the R console. The problem is that the "Pending 
Jobs" window is not easily discoverable, but it's the only way to cancel 
those commands, ATM. One idea was to detect commands that run longer than a 
configurable threshold (say 30 seconds by default), and then ask whether 
those should be stopped. I guess we'll need something like this, sooner or 
later.

Regards
Thomas

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