[plt-scheme] 204.8

The exp-tagged code in CVS for MzScheme and MrEd is now version 204.8.

The changes fall into several categories.

Collections and installation:

 * Added 'addon-dir for `find-system-path':

     Unix: "~/.plt-scheme"
     Windows: "PLT Scheme" in the user's Application Data folder.
     Mac OS X: "~/Library/PLT Scheme"
     Mac OS Classic: "PLT Scheme" in the preferences folder.

 * Changed Setup PLT to install PLT-relative ".plt" archives (which
   typically contain a collection) into

     (build-path (find-system-path 'addons-dir) (version))

   In other words, installing a ".plt" file now tends to writes to a
   user-specific directory.

 * Changed the default library collections path list to include

     (build-path (find-system-path 'addons-dir) (version) "collects")

   so that collections installed by ".plt" archives are in the
   collection path.

Syntax:

 * Changed eval handler so that when it is given a syntax object, it
   does not extend the object's lexical context with top-level
   bindings from the current namespace

 * Added `eval-syntax', `compile-syntax', `expand-syntax',
   `expand-syntax-once', and `expand-syntax-to-top-form', which are
   like the `-syntax'less procedures, but do not augment the argument's
   context with top-level bindings.

 * Added `namespace-syntax-introduce', which is what `eval', `expand',
   etc. use to augment a syntax object's context with top-level
   bindings.

 * Fixed bugs recently reported on this list.

Editors:

 * While an editor is being refreshed, calls to `begin-edit-sequence'
   block. This allows an editor be be modified from a thread other than
   its display's handler thread (assuming that all other accesses of the
   editor are also disabled).

 * Added `on-display-size-when-ready' to editor<%>. A display calls
   this instead of calling `on-display-size' directly, because the new
   method delays the message if an edit sequence is in progress.

 * Added `get-text!' to snip%. The default implementation uses
  `get-text'.

 * Added `locations-computed?' to editor<%>.

Miscellaneous:

 * Mac OS X: finally fixed menu-bar flashing bug, thanks Paul Schlie's
   detective work.

   I blame Mac OS X for having a refresh bug, but I wasn't able to find
   the sequence of MrEd actions that triggered the bug. Paul found it.

 * X with Xft: changed default 'modern mapping to " Courier 10 Pitch",
   because " Monospace" may have a different width for bold and
   non-bold text.


Matthew