1) Add a tweak to turn on/off multi-character first-letter partioning in the tag browser

2) Change preferences.tweaks to add a "tweak number" to the tweak name string. This helps tell people which tweak to look at. To keep these valid, we should always add tweaks to the end.

resources/default_tweaks.py

@@ -515,3 +515,13 @@
 #   default_tweak_format = 'remember'
 default_tweak_format = None
 
+#: Enable multi-character first-letters in the tag browser
+# Some languages have letters that can be represented by multiple characters.
+# For example, Czech has a 'character' "ch" that sorts between "h" and "i".
+# If this tweak is True, then the tag browser will take these characters into
+# consideration when partitioning by first letter.
+# Examples:
+#    enable_multicharacters_in_tag_browser = True
+#    enable_multicharacters_in_tag_browser = True
+enable_multicharacters_in_tag_browser = True
+

src/calibre/gui2/preferences/tweaks.py

@@ -39,7 +39,7 @@ def paint(self, p, opt, idx):
 
 class Tweak(object): # {{{
 
-    def __init__(self, name, doc, var_names, defaults, custom):
+    def __init__(self, name, doc, var_names, defaults, custom, tweak_num):
         translate = _
         self.name = translate(name)
         self.doc = doc.strip()
@@ -53,6 +53,7 @@ def __init__(self, name, doc, var_names, defaults, custom):
         for x in var_names:
             if x in custom:
                 self.custom_values[x] = custom[x]
+        self.tweak_num = tweak_num
 
     def __str__(self):
         ans = ['#: ' + self.name]
@@ -92,6 +93,10 @@ def restore_to_default(self):
     def update(self, varmap):
         self.custom_values.update(varmap)
 
+    @property
+    def name_with_position_number(self):
+        return "%d: %s"%(self.tweak_num, self.name)
+
 # }}}
 
 class Tweaks(QAbstractListModel, SearchQueryParser): # {{{
@@ -113,7 +118,7 @@ def data(self, index, role):
         except:
             return NONE
         if role == Qt.DisplayRole:
-            return textwrap.fill(tweak.name, 40)
+            return textwrap.fill(tweak.name_with_position_number, 40)
         if role == Qt.FontRole and tweak.is_customized:
             ans = QFont()
             ans.setBold(True)
@@ -182,7 +187,7 @@ def read_tweak(self, lines, pos, defaults, custom):
             pos += 1
         if not var_names:
             raise ValueError('Failed to find any variables for %r'%name)
-        self.tweaks.append(Tweak(name, doc, var_names, defaults, custom))
+        self.tweaks.append(Tweak(name, doc, var_names, defaults, custom, len(self.tweaks)+1))
         #print '\n\n', self.tweaks[-1]
         return pos
 

src/calibre/gui2/tag_browser/model.py

@@ -260,7 +260,7 @@ def set_database(self, db):
         db.prefs.set('tag_browser_hidden_categories', list(self.hidden_categories))
 
         conts = contractions()
-        if len(conts) == 0:
+        if len(conts) == 0 or not tweaks['enable_multicharacters_in_tag_browser']:
             self.do_contraction = False
         else:
             self.do_contraction = True