[Chandler-dev] Proposal/Call for volunteers/Brain dump: Showing reminders when Chandler isn't running

[Grant Baillie]

One commonly found Calendar feature that we'd like to implement is  
the ability to have reminder dialogs for events be displayed even  
when the Chandler GUI isn't visible (see https:// 
bugzilla.osafoundation.org/show_bug.cgi?id=5407).

Presumably, this would be something users could turn on and off, lest  
we be accused of propagating some kind of CPU-hogging virus :). It's  
unlikely we'll have time to do this in the α4 time frame, but I'd  
like to request comments and/or propose some ideas for how we could  
get this done.

Also, since I'm somewhat of a Mac guy, and solving the issue will  
probably require different behaviours on Windows & Linux, it would be  
good to enlist the help of people who know the other platforms well.  
For instance, there may be OS-specific services that I'm not aware of  
that could be helpful here. The main technical stumbling block that I  
see is one that probably has a platform-specific answer:

+++ How do we make sure that some kind of background process or app  
runs whenever the user is logged in?

[[For instance, on the Mac, you can add a "background" app to the  
user's list of login items; in 10.4 (Tiger) there may be a way to  
leverage launchd. I know there's a Service facility on Windows you  
can use to launch background processes, though I'm not sure if this  
would be the right thing to be using. What's the story with Linux?  
Probably there are mechanisms in KDE/Gnome... ]].


Assuming that issue has been resolved, I can see at least four  
different options:

1) Have two separate processes, the app and a background daemon/ 
service, that both access the user's repository. The way I understand  
things (Andi, correct me if I'm wrong), both processes would need to  
poll (via the repository view refresh() API) to detect when changes  
have occurred. It turns out Chandler does this already (in a wx idle  
event callback), while the reminder process could presumably just  
check every minute (if it's not displaying any UI).

2) Have two processes, but have the background daemon not use the  
repository at all. (Maybe we're worried that people will try to store  
their repositories on volumes that don't support file locking, or  
something). Instead, the two communicate via a config file and/or  
named pipes or something (insert sound of two hands waving profusely  
here).

3) Along the lines of 2, have two processes, but have them handshake  
at launch/quit so that only one is running (and responsible for  
displaying reminders) at any given time.

4) Have just one process, today's Chandler, but add the ability for  
it to switch between full UI & background (reminder-only) mode. So,  
if background mode is in effect, and the user launches Chandler, a  
little plastic garden gnome waves a sparkly wand and tells the  
background process to display the full UI. Similarly, when you "quit"  
the full UI app, it goes back into background (stealth) mode. (This  
is easier, so the gnome gets a break).

Further options, or opinions as to what you think will or won't work,  
would be appreciated.

--Grant