Add a :help command.

doc/commands.asciidoc

@@ -10,6 +10,7 @@
 |<<download-page,download-page>>|Download the current page.
 |<<forward,forward>>|Go forward in the history of the current tab.
 |<<get,get>>|Get the value from a section/option.
+|<<help,help>>|Show help about a command or setting.
 |<<hint,hint>>|Start hinting.
 |<<home,home>>|Open main startpage in current tab.
 |<<inspector,inspector>>|Toggle the web inspector.
@@ -71,6 +72,19 @@ Get the value from a section/option.
 * +'sectname'+: The section where the option is in.
 * +'optname'+: The name of the option.
 
+[[help]]
+=== help
+Syntax: +:help 'topic'+
+
+Show help about a command or setting.
+
+==== positional arguments
+* +'topic'+: The topic to show help for. 
+
+ - :__command__ for commands.
+ - __section__\->__option__ for settings.
+
+
 [[hint]]
 === hint
 Syntax: +:hint ['group'] ['target'] ['args']+

qutebrowser/browser/commands.py

@@ -667,6 +667,41 @@ class CommandDispatcher:
         page = self._current_widget().page()
         self._tabs.download_get.emit(self._tabs.current_url(), page)
 
+    @cmdutils.register(instance='mainwindow.tabs.cmd', name='help',
+                       completion=[usertypes.Completion.helptopic])
+    def show_help(self, topic):
+        """Show help about a command or setting.
+
+        Args:
+            topic: The topic to show help for.
+
+                   - :__command__ for commands.
+                   - __section__\->__option__ for settings.
+        """
+        if topic.startswith(':'):
+            command = topic[1:]
+            if command not in cmdutils.cmd_dict:
+                raise cmdexc.CommandError("Invalid command {}!".format(
+                    command))
+            path = 'commands.html#{}'.format(command)
+        elif '->' in topic:
+            parts = topic.split('->')
+            if len(parts) != 2:
+                raise cmdexc.CommandError("Invalid help topic {}!".format(
+                    topic))
+            try:
+                config.get(*parts)
+            except config.NoSectionError:
+                raise cmdexc.CommandError("Invalid section {}!".format(
+                    parts[0]))
+            except config.NoOptionError:
+                raise cmdexc.CommandError("Invalid option {}!".format(
+                    parts[1]))
+            path = 'settings.html#{}'.format(topic.replace('->', '-'))
+        else:
+            raise cmdexc.CommandError("Invalid help topic {}!".format(topic))
+        self.openurl('qute://help/{}'.format(path))
+
     @cmdutils.register(instance='mainwindow.tabs.cmd',
                        modes=[usertypes.KeyMode.insert],
                        hide=True)

qutebrowser/models/completion.py

@@ -58,7 +58,7 @@ class SettingOptionCompletionModel(basecompletion.BaseCompletionModel):
         sectdata = configdata.DATA[section]
         self._misc_items = {}
         self._section = section
-        for name, _ in sectdata.items():
+        for name in sectdata.keys():
             try:
                 desc = sectdata.descriptions[name]
             except (KeyError, AttributeError):
@@ -165,3 +165,44 @@ class CommandCompletionModel(basecompletion.BaseCompletionModel):
         cat = self.new_category("Commands")
         for (name, desc) in sorted(cmdlist):
             self.new_item(cat, name, desc)
+
+
+
+class HelpCompletionModel(basecompletion.BaseCompletionModel):
+
+    """A CompletionModel filled with help topics."""
+
+    # pylint: disable=abstract-method
+
+    def __init__(self, parent=None):
+        super().__init__(parent)
+        self._init_commands()
+        self._init_settings()
+
+    def _init_commands(self):
+        assert cmdutils.cmd_dict
+        cmdlist = []
+        for obj in set(cmdutils.cmd_dict.values()):
+            if obj.hide or (obj.debug and not
+                            QCoreApplication.instance().args.debug):
+                pass
+            else:
+                cmdlist.append((':' + obj.name, obj.desc))
+        cat = self.new_category("Commands")
+        for (name, desc) in sorted(cmdlist):
+            self.new_item(cat, name, desc)
+
+    def _init_settings(self):
+        cat = self.new_category("Settings")
+        for sectname, sectdata in configdata.DATA.items():
+            for optname in sectdata.keys():
+                try:
+                    desc = sectdata.descriptions[optname]
+                except (KeyError, AttributeError):
+                    # Some stuff (especially ValueList items) don't have a
+                    # description.
+                    desc = ""
+                else:
+                    desc = desc.splitlines()[0]
+                name = '{}->{}'.format(sectname, optname)
+                self.new_item(cat, name, desc)

qutebrowser/network/qutescheme.py

@@ -127,4 +127,5 @@ class QuteHandlers:
     def help(cls, request):
         """Handler for qute:help. Return HTML content as bytes."""
         path = 'html/doc/{}'.format(request.url().path())
-        return utils.read_file(path).encode('ASCII')
+        return utils.read_file(path).encode('UTF-8',
+                                            errors='xmlcharrefreplace')

qutebrowser/utils/completer.py

@@ -57,13 +57,15 @@ class Completer(QObject):
             usertypes.Completion.option: {},
             usertypes.Completion.value: {},
         }
-        self._init_command_completion()
+        self._init_static_completions()
         self._init_setting_completions()
 
-    def _init_command_completion(self):
-        """Initialize the command completion model."""
+    def _init_static_completions(self):
+        """Initialize the static completion models."""
         self._models[usertypes.Completion.command] = CFM(
             models.CommandCompletionModel(self), self)
+        self._models[usertypes.Completion.helptopic] = CFM(
+            models.HelpCompletionModel(self), self)
 
     def _init_setting_completions(self):
         """Initialize setting completion models."""

qutebrowser/utils/usertypes.py

@@ -248,7 +248,8 @@ KeyMode = enum('KeyMode', 'normal', 'hint', 'command', 'yesno', 'prompt',
 
 
 # Available command completions
-Completion = enum('Completion', 'command', 'section', 'option', 'value')
+Completion = enum('Completion', 'command', 'section', 'option', 'value',
+                  'helptopic')
 
 
 class Question(QObject):