[platform-text-dev] Preference reorganization

[Tom Eicher <eclipse@xxxxxxxxxxxxxxx>]

We have reorganized the preferences and the preference pages in text 
land quite a bit, which will be of interest to editor implementors, 
especially those that have been matching the text and java editor or 
even have been using their preferences.


Here we go:

A) Removed Preferences (in the text & java editors):
- Show overview ruler (overview ruler is always shown)


B) Shared Preferences
Some settings have been made shared, e.g. the settings are configured on 
the new 'All Text Editors' preference page and apply to all text based 
editors such as Java, Text, Properties files...:

- All previous text editor settings:
  - highlight current line (+color)
  - print margin (+ color + column)
  - show line numbers (+ color)
  - selection fore- and background colors
  - displayed tab width

- All accessibility settings (moved to their own page):
  - use custom caret (+ thick caret)
  - quick diff character mode

In a custom editor implementation you may or may not respect the shared 
preferences. If you do, you can remove all references on your preference 
pages and also from your code if:
-  you inherit from AbstractDecoratedTextEditor, and
-  you use a CombinedPreferenceStore to read preferences from your own 
preference store, but also from the preference store of the 
org.eclipse.ui.editors preference store. See 
JavaPlugin.getCombinedPreferenceStore for an example.

If you want to keep rolling your own editor-specific preferences, that's 
fine as well - but you may have to hide some property change events from 
your editor's super class (JavaEditor does that for the 'displayed tab 
width' value).


C) Moved & Shared Preferences

Some settings previously only available in the Java editor have been 
pushed down to text land and made shared preferences.

- hyperlink navigation (+ colors + modifier)
   This is a bigger issue as the hyperlink navigation framework has 
been pushed down to text.
   See the build notes.
- editor fore- and background colors - disable overwrite mode


D) Behavioral changes

- Show quickdiff and Enable Folding now are global settings, no longer 
"defaults for new editors". So changing the preference (which you can 
also do from the ruler context menu now) is immediately reflected in all 
open editors.  This change is still being debated over.

- AbstractDecoratedTextEditor now includes a 'Toggle Quick Diff' action 
in its set of pre-installed actions. There is no need any longer for you 
to contribute such an action to get in enabled per default.


E) API extensions

AbstractDecoratedTextEditor shows a 'Preferences...' action in both its 
context and ruler context menus. Once the preference page supports 
filtering, only a subset of 'interesting' pages will be displayed in the 
such opened preference dialog. You can change the set of pages by 
extending or replacing 
AbstractDecoratedTextEditor.collectContextMenuPreferencePages.