Preferences: support dynamically computed defaults

[David Aspinall]

The preference mechanism should support dynamically computed defaults. This can be achieved by using reflection together with a method name given in the preference file:

 <pref name="ActiveHighlight" type="string" setDefault="setExample"/>

The method should be located in the already given class associated with the preference file, e.g. ExamplePrefs.java:

  public Boolean setExample() {
     return Eclipse.isRunningOnMac() ? "Orange" : "Blue";
  }

This is bogus and slightly silly example, but one reason we want this is to set platform-specific defaults for some values.

[David Aspinall]

I've now added a simpler mechanism for allowing OS-specific preference overrides in the preference table, as:

<pref name="Highlight colour" os="macosx" value="Orange"/>

The os attribute should be contained in Platform.getOS() for this to work (so mac would be another way).

This is a crude way of having OS-specific prefs: the first preference that appears will win, and non-specific preferences win defaults for all OS settings. The main crudeness is having to repeat the preference, description etc.

But this does for choosing the Default Symbol Table in ProofGeneralPrefs.xml.

[David Aspinall]

Milestone PG-Eclipse-1.0.7 deleted