[conf] move colorization to post_linebreak_filter

Addresses this behavior: http://tex.stackexchange.com/q/238539/14066

This is a breaking change but it hardly matters since font-based
colorization is deprecated and the old behavior can be restored by means
of a configuration setting.

2 files changed, 44 insertions, 11 deletions

diff --git a/doc/luaotfload.conf.rst b/doc/luaotfload.conf.rst
index b0d19d9..2a339ce 100644
--- a/doc/luaotfload.conf.rst
+++ b/doc/luaotfload.conf.rst
@@ -6,9 +6,9 @@
                      Luaotfload configuration file
 -----------------------------------------------------------------------
 
-:Date:                  2014-06-09
+:Date:                  2015-04-20
 :Copyright:             GPL v2.0
-:Version:               2.5
+:Version:               2.6
 :Manual section:        5
 :Manual group:          text processing
 
@@ -98,8 +98,9 @@ VARIABLES
 Variables in belong into a configuration section and their values must
 be of a certain type. Some of them have further constraints. For
 example, the “color callback” must be a string of one of the values
-``pre_linebreak_filter`` or ``pre_output_filter``, defined in the
-section *run*.
+``post_linebreak_filter``, ``pre_linebreak_filter``, or
+``pre_output_filter``, defined in the section *run* of the
+configuration file.
 
 Currently, the configuration is organized into four sections:
 
@@ -267,7 +268,7 @@ Section ``run``
 +------------------+--------+------------------------------+
 |  variable        |  type  |  default                     |
 +------------------+--------+------------------------------+
-|  color-callback  |   s    |  ``"pre_linebreak_filter"``  |
+|  color-callback  |   s    |  ``"post_linebreak_filter"`` |
 +------------------+--------+------------------------------+
 |  definer         |   s    |  ``"patch"``                 |
 +------------------+--------+------------------------------+
@@ -278,10 +279,14 @@ Section ``run``
 
 The ``color-callback`` option determines the stage at which fonts that
 defined with a ``color=xxyyzz`` feature will be colorized. By default
-this happens in a ``pre_linebreak_filter`` but alternatively the
-``pre_output_filter`` may be chosen, which is faster but might produce
-inconsistent output. The latter also was the default in the 1.x series
-of Luaotfload.
+this happens in a ``post_linebreak_filter`` but alternatively the
+``pre_linebreak_filter`` or ``pre_output_filter`` may be chosen, which
+is faster but might produce inconsistent output. The
+``pre_output_filter`` used to be the default in the 1.x series of
+Luaotfload, whilst later versions up to and including 2.5 hooked into
+the ``pre_linebreak_filter`` which naturally didn’t affect any glyphs
+inserting during hyphenation. Both are kept around as options to
+restore the previous behavior if necessary.
 
 The ``definer`` allows for switching the ``define_font`` callback.
 Apart from the default ``patch`` one may also choose the ``generic``
diff --git a/src/luaotfload-configuration.lua b/src/luaotfload-configuration.lua
index 657d671..7791503 100644
--- a/src/luaotfload-configuration.lua
+++ b/src/luaotfload-configuration.lua
@@ -144,6 +144,23 @@ local registered_loaders = {
   tl2013     = "tl2013",
 }
 
+--[[doc--
+
+  The ``post_linebreak_filter`` has been made the default callback for
+  hooking the colorizer into. This helps with the linebreaking whose
+  inserted hyphens would remain unaffected by the coloring otherwise.
+
+  http://tex.stackexchange.com/q/238539/14066
+
+--doc]]--
+
+local permissible_color_callbacks = {
+  default               = "post_linebreak_filter",
+  pre_linebreak_filter  = "pre_linebreak_filter",
+  post_linebreak_filter = "post_linebreak_filter",
+  pre_output_filter     = "pre_output_filter",
+}
+
 
 -------------------------------------------------------------------------------
 ---                                DEFAULTS
@@ -479,9 +496,20 @@ local option_spec = {
     color_callback = {
       in_t      = string_t,
       out_t     = string_t,
-      transform = function (cb)
+      transform = function (cb_spec)
         --- These are the two that make sense.
-        return cb == "pre_output_filter" and cb or "pre_linebreak_filter"
+        local cb = permissible_color_callbacks[cb_spec]
+        if cb then
+          logreport ("log", 3, "conf",
+                     "Using callback \"%s\" for font colorization.",
+                     cb)
+          return cb
+        end
+        logreport ("log", 0, "conf",
+                    "Requested callback identifier \"%s\" invalid, "
+                    .. "falling back to default.",
+                    cb_spec)
+        return permissible_color_callbacks.default
       end,
     },
   },