Author: pete

Here I am, at about 2 in the morning thinking about timely information. Take for example accessing a file’s Version Information (Windows applications). The API is piss easy, it’s jut a bit noxious. I wrote myself up a small class to extract this for my applications. The problem is that this code is to all intents obsolete – there is a class in .NET that covers it.
This is the two forked problem with the internet. When you have a problem, by the time you’ve either (a) solved it or (b) found the solution, the world has gone and passed you by. Almost depressing, I might add.

It’s not unusual to encounter undocumented methods in a programming language, it’s just the nature of the beast. Take for example Delphi 2005. It has a new Queue method, for allowing a programmer to queue a call to the main user thread, rather than serially invoke it (it’s not quite serial, there’s a WaitForSingleObject in there).
This interestingly brings up another item. There are two models generally associated with timed events. The first model is the Invoke, leaving at least an interval gap between the invocations, the second model is the invoke, and even if it’s not finished invoke it again when the interval elapses. The first model can be emulated using the standard Synchronize call, the second can be emulated using the Queue call. Because they both are operating from the one task queue, either method would be safe to use on mt-unsafe code. The advantage of the Queue method is that you can interlock the thread and the GUI in a looser manner, as the thread does not wait for the GUI to do it’s stuff before continuing. This means that, for example you could be informing a gui component to repaint itself when the underlying dataset changes.

As I’ve been through most of these at one point or another, and finding them is a pain in the ass:

• Apple Mac OS X Human Interface Guidelines
• Microsoft XP ‘Design Guidelines’ (or Buy the book argh)
• Palm OS Application Design Guidelines Pre PalmOS 6; and Post PalmOS 6 (aka Protein)
• Java Look and Feel Guidelines (Version 2)
• Gnome Human Interface Guidelines (Gnome-HIG)
• KDE UI Standards

I’m of course still stuck with a PalmOS 4 handheld, so the pre PalmOS6 docs are what I refer to the most. I have no real motivation to buy another handheld when they’re looking like the entire market is going to be eaten by micro PCs like the OQO.
[links edited, text slightly changed 2005-10-14]

The brother has a problem today, his dispensing system kept keeling over when he dispensed to some people, but not to others.
Firing up the utility which is what all normal pharmacy people would have had access to would only show that the system failed to validate a table, and that the connection to the database was broken. The only clue I had was the table name that I last saw in the utility. I’ll just say from the get-go that this is Not good diagnostic programming practice.
Firing up the SQLPlus worksheet, I ran the ANALYZE TABLE <foo> VALIDATE command over the table, and saw no error. I ran it with the CASCADE, option and the same thing happened as the utility – the database fell over.
It turns out that one of the indexes was corrupt on the table. Iterating over all the indexes using ALTER INDEX <foo> rebuild, which narrowed down the indexes. Then I extracted the DDL for the index, dropped and recreated them, re-validated the table and everything was hunky dory.
Full documentation on the ANALYZE command is in the oracle documentation. For the purposes of this exercise we used ANALYZE TABLE BLOB VALIDATE CASCADE to see the error.
Solving the problem took about an hour, most of which was spent chewing on a sandwich and booking tickets to see Star Wars, and of course cardboard programming by another friend. A backup of the database would not have helped in this case as the corruption occurred silently some time ago, and was only uncovered when certain customer’s records were accessed, so the loss of all the data input from the point of corruption to then would have been unacceptable.