Inherited Folder Properties – revisited

In a previous posting, I introduced the concept of inherited folder properties in the Mozilla mailnews products (Thunderbird and SeaMonkey). In the months since, I have incorporated these into my extensions quite significantly, so here I would like to show the UI I am currently using for this, and also discuss some of the issues that I face.

(All references to extensions in this posting refer to the 1.0.0 versions, which as of this writing have not been posted to AMO yet. But they should be available in a few weeks.)

Implemented UI

Briefly, inherited properties are a property that can be defined globally, at the server, or at the folder, and its characteristics will be propagated to child objects. This make it easy to specify precisely how the property is applied.

As an example, I have recently implemented a feature “Index in Global Database” in GlodaQuilla which can be used to selectively suppress certain accounts or folders from being accessed by the global database indexer. In the account manager, where indexing can be disabled for an entire account, the UI looks like this:

Index in Global Database account settings

Each inherited property has default values which are typically set by the base code. In the case of the gloda database indexer, everything but newgroups are indexed by default. Initially each inherited property is set to just use the standard default processing, but if I clear the “default” checkbox, then I can turn off gloda indexing for this account.

If I do that, then go to a first-level folder in the account, I see the following under folder properties:

Index in Global Database by folder

At the folder level, because I disabled global indexing on the account, it is now shown as disabled on the folder. I could clear the inherit box and selectively enable it on just this folder and its children if I wanted.

This particular UI merges naturally with the existing methods of setting properties in mailnews, but I’m not sure it is optimum for an inherited property. The inherited nature could be more clearly shown, and a particular feature more quickly configured, if I showed a tree of accounts and folders, with checkboxes next to each account to enable or inherit the feature. Maybe in a future version.

Implemented properties

Here are some of the implementations of inherited properties that exist in my extensions:

  1. (GlodaQuilla) Index in Global Database – suppresses the running of the global database indexer
  2. (FiltaQuilla) Apply Filters to Folder – for Imap folders, allow incoming filters to run on that folder
  3. (JunQuilla) Analyze Junk – allow junk processing to be turned on or off. This also allows junk processing to run on RSS or news folders.
  4. (TaQuilla) Analyze particular automatic tags.

Issue: Existing mechanisms

Ideally, the inherited property would be the one and only way to manage a program feature. But for existing features, the existing mechanisms remain, which can lead to possible confusion. For example, with JunQuilla’s “Analyze Junk” property, there is existing UI to enable junk processing at the account level. Here the inherited property will always override the default mechanism (but that is mostly because I implemented it in core that way, and I have a little influence on how junk processing is handled in core.) For GlodaQuilla’s “Index in Global Database” the behaviour is different. Existing UI will only allow this to be enabled or disabled globally, and the inherited property does not override this. The inherited property code uses the default server preference as a global enable/disable for a property, so if gloda used that same mechanism instead of an independent preference, this issue would go away. I guess I could say the same thing about junk processing as well.

For FiltaQuilla’s “Apply Filters to Folder”, there is a subtle issue in the inherited nature. I did not implement in core the ability of the inherited property to override the existing default as applied to the Inbox, so incoming filters always run on the inbox. That creates 2 ui issues. First, although I show at the account level the “Apply Filters” option, it does not actually suppress application to the inbox as one would expect. Second, I currently do not show a folder property for “Apply Filters to Folder” for the IMAP inbox since it would not make sense there, so that also means there is no way to enable processing of filters for the children of the inbox. Maybe I should call this feature instead “Apply Filters to non-Inbox Folders” to solve this, or change the core code so that the feature also applied to the Inbox.

Issue: My RDF-inspired property for junk management

Looking ahead to a world where a number of extensions might try to define bayes filter traits, in code I recommended that properties used to manage junk processing use an RDF-inspired globally unique identifier. Then I followed my own advice and defined the identifier that controls junk processing on a folder as: “dobayes.mailnews@mozilla.org#junk” Unfortunately, the existing account manager code does not allow periods in property names, which means I could not use the account manager to manage this. I’ve filed bug 525024 on this issue, and perhaps that can be incorporated after TB 3.0 / SM 2.0.

Issue: Missing inheritance levels

I’ve heard others comment that often they want to set a property on a particular class of folders, say on all Trash folders, or all Sent folders. I’ve considered implementing another level in the inherited properties feature, that would be a folder type. So you would then set a property that would be inherited by any folder of a particular type, and its children – and of course also overridden by the local folder property.

Issue: UI for global property

All of the inherited properties could also be enabled globally using the “mail.server.default.<property>” preference, but I did not give any UI for that in my extensions. I thought that would be too confusing for the user to show those preferences, which would be very similar to existing mechanisms. This is not an issue for properties that use the preference system for server-level issues, but none of the existing server-level preferences are also inherited properties. Perhaps we could move that direction in the future.