Add a hints -> scatter option.

This is enabled by default to keep the same default behaviour which is like
Vimium - mixing e.g. single-char letters and double-char letters, and
scattering/shuffling the labels to have an uniform hint key distribution.

If disabled, the behaviour is more similiar to dwb, which has a fixed hint
string length and simply fills the string starting with the first possible hint
char.

doc/help/settings.asciidoc

@@ -150,6 +150,7 @@
 |<<hints-mode,mode>>|Mode to use for hints.
 |<<hints-chars,chars>>|Chars used for hint strings.
 |<<hints-min-chars,min-chars>>|Mininum number of chars used for hint strings.
+|<<hints-scatter,scatter>>|Whether to scatter hint key chains (like Vimium) or not (like dwb).
 |<<hints-uppercase,uppercase>>|Make chars in hint strings uppercase.
 |<<hints-auto-follow,auto-follow>>|Whether to auto-follow a hint if there's only one left.
 |<<hints-next-regexes,next-regexes>>|A comma-separated list of regexes to use for 'next' links.
@@ -1237,6 +1238,17 @@ Mininum number of chars used for hint strings.
 
 Default: +pass:[1]+
 
+[[hints-scatter]]
+=== scatter
+Whether to scatter hint key chains (like Vimium) or not (like dwb).
+
+Valid values:
+
+ * +true+
+ * +false+
+
+Default: +pass:[true]+
+
 [[hints-uppercase]]
 === uppercase
 Make chars in hint strings uppercase.

qutebrowser/browser/hints.py

@@ -202,8 +202,20 @@ class HintManager(QObject):
             chars = '0123456789'
         else:
             chars = config.get('hints', 'chars')
-
         min_chars = config.get('hints', 'min-chars')
+        if config.get('hints', 'scatter'):
+            return self._hint_scattered(min_chars, chars, elems)
+        else:
+            return self._hint_linear(min_chars, chars, elems)
+
+    def _hint_scattered(self, min_chars, chars, elems):
+        """Produce scattered hint labels with variable length (like Vimium).
+
+        Args:
+            min_chars: The minimum length of labels.
+            chars: The alphabet to use for labels.
+            elems: The elements to generate labels for.
+        """
         # Determine how many digits the link hints will require in the worst
         # case. Usually we do not need all of these digits for every link
         # single hint, so we can show shorter hints for a few of the links.
@@ -230,6 +242,20 @@ class HintManager(QObject):
 
         return self._shuffle_hints(strings, len(chars))
 
+    def _hint_linear(self, min_chars, chars, elems):
+        """Produce linear hint labels with constant length (like dwb).
+
+        Args:
+            min_chars: The minimum length of labels.
+            chars: The alphabet to use for labels.
+            elems: The elements to generate labels for.
+        """
+        strings = []
+        needed = max(min_chars, math.ceil(math.log(len(elems), len(chars))))
+        for i in range(len(elems)):
+            strings.append(self._number_to_hint_str(i, chars, needed))
+        return strings
+
     def _shuffle_hints(self, hints, length):
         """Shuffle the given set of hints so that they're scattered.
 

qutebrowser/config/configdata.py

@@ -627,6 +627,11 @@ DATA = collections.OrderedDict([
          SettingValue(typ.Int(minval=1), '1'),
          "Mininum number of chars used for hint strings."),
 
+        ('scatter',
+         SettingValue(typ.Bool(), 'true'),
+         "Whether to scatter hint key chains (like Vimium) or not (like "
+         "dwb)."),
+
         ('uppercase',
          SettingValue(typ.Bool(), 'false'),
          "Make chars in hint strings uppercase."),