Start of a new user interface.

Started on the UI that I envisioned since the very beginning of this
project, 364 days ago.

The UI is inspired by TweetDeck, the column-like Twitter interface.
Every column is associated with a View object (which has a filter and a
sort order on the active todo.txt file). So each column can show a
particular part of the todo.txt files. E.g, a column for today's items,
a column for overdue items or a column for a particular project
(filter: GrepFilter("+SomeProject")).

The way topydo is designed was always with this UI in mind. Commands
('add', 'do', etc.) should be independent of the UI that invoked them,
therefore they never print to stdout but output to a function such that
the current UI will show it properly. Also the View class, which hasn't
been incredibly useful sofar, can finally fulfil its role better.

This is still a very immature version of the UI. It shows a single
column with all the todos. It can execute commands, but it will do so
silently, no output or errors are shown yet.

The navigation will be Vim-like. Press : to toggle the command-line at
the bottom of the screen, where you can enter any command that you're
used to. Press Escape entering a command to set the focus back on the
columns.

The next few items to address:
* show output, errors and handle input
* ability to dynamically add/edit/delete columns
* add navigation keys to 'walk' through the items in the columns and act
  on them with shortcuts. E.g. highlight a todo, press 'x' to complete
  it.

I chose urwid as the widget library for the console, since using curses
directly gave me a headache.

setup.py

@@ -14,6 +14,7 @@ setup(
     extras_require = {
         'ical': ['icalendar'],
         'prompt-toolkit': ['prompt-toolkit >= 0.39'],
+        'urwid': ['urwid >= 1.3.0'],
         'edit-cmd-tests': ['mock'],
     },
     entry_points= {

topydo/ui/CommandLineWidget.py

+# Topydo - A todo.txt client written in Python.
+# Copyright (C) 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import urwid
+
+class CommandLineWidget(urwid.Edit):
+    signals = [
+        'blur',
+        'execute_command',
+    ]
+
+    def clear(self):
+        self.set_edit_text(u"")
+
+    def _blur(self):
+        self.clear()
+        self._emit('blur')
+
+    def _emit_command(self):
+        self._emit('execute_command', self.edit_text)
+        self.clear()
+
+    def keypress(self, p_size, p_key):
+        dispatch = {
+            'enter': self._emit_command,
+            'esc': self._blur,
+        }
+
+        try:
+            dispatch[p_key]()
+        except KeyError:
+            super(CommandLineWidget, self).keypress(p_size, p_key)

topydo/ui/Main.py

+# Topydo - A todo.txt client written in Python.
+# Copyright (C) 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import urwid
+
+from topydo.cli.CLIApplicationBase import CLIApplicationBase
+from topydo.Commands import get_subcommand
+from topydo.ui.CommandLineWidget import CommandLineWidget
+from topydo.ui.TodoListWidget import TodoListWidget
+from topydo.lib.Config import config
+from topydo.lib.Sorter import Sorter
+from topydo.lib import TodoFile
+from topydo.lib import TodoList
+
+COLUMN_WIDTH = 40
+
+class UIApplication(CLIApplicationBase):
+    def __init__(self):
+        super(UIApplication, self).__init__()
+
+        self.columns = urwid.Columns([], dividechars=0, min_width=COLUMN_WIDTH)
+        self.commandline = CommandLineWidget('topydo> ')
+        urwid.connect_signal(self.commandline, 'blur',
+                             lambda _: self._blur_commandline())
+        urwid.connect_signal(self.commandline, 'execute_command',
+                             self._execute_input)
+
+        self.mainwindow = urwid.Pile([
+            ('weight', 1, self.columns),
+            (1, urwid.Filler(self.commandline)),
+        ])
+
+        # the columns should have keyboard focus
+        self._blur_commandline()
+
+        self.mainloop = urwid.MainLoop(
+            self.mainwindow,
+            unhandled_input=self._handle_input,
+            pop_ups=True
+        )
+
+    def _execute_input(self, _, p_command):
+        """
+        Callback for executing a command that was entered on the command line box.
+        """
+        (subcommand, args) = get_subcommand(p_command.split())
+
+        try:
+            command = subcommand(
+                args,
+                self.todolist,
+                lambda _: None, # TODO output
+                lambda _: None, # TODO error
+                lambda _: None, # TODO input
+            )
+
+            if command.execute() != False:
+                self._post_execute()
+
+        except TypeError:
+            # TODO: show error message
+            pass
+
+    def _focus_commandline(self):
+        self.mainwindow.focus_item = 1
+
+    def _blur_commandline(self):
+        self.mainwindow.focus_item = 0
+
+    def _handle_input(self, p_input):
+        dispatch = {
+            ':': self._focus_commandline,
+        }
+
+        try:
+            dispatch[p_input]()
+        except KeyError:
+            # the key is unknown, ignore
+            pass
+
+    def _add_column(self, p_view, p_title):
+        todolist = TodoListWidget(p_view, p_title)
+
+        options = self.columns.options(
+            width_type='given',
+            width_amount=COLUMN_WIDTH,
+            box_widget=True
+        )
+
+        item = (todolist, options)
+        self.columns.contents.append(item)
+
+    def run(self):
+        self.todofile = TodoFile.TodoFile(config().todotxt())
+        self.todolist = TodoList.TodoList(self.todofile.read())
+
+        view1 = self.todolist.view(Sorter(), [])
+        self._add_column(view1, "View 1")
+
+        self.mainloop.run()
+
+if __name__ == '__main__':
+    UIApplication().run()

topydo/ui/TodoListWidget.py

+# Topydo - A todo.txt client written in Python.
+# Copyright (C) 2015 Bram Schoenmakers <me@bramschoenmakers.nl>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import urwid
+
+class TodoListWidget(urwid.WidgetWrap):
+    def __init__(self, p_view, p_title):
+        self.view = p_view
+
+        title_widget = urwid.Filler(urwid.Text(p_title, align='center'))
+
+        todos = []
+
+        for todo in self.view.todos:
+            todos.append(('pack', urwid.Text(todo.source())))
+            todos.append(urwid.Divider(u'-'))
+
+        todo_pile = urwid.Pile(todos)
+
+        pile = urwid.Pile([
+            (1, title_widget),
+            (1, urwid.Filler(urwid.Divider(u'\u2500'))),
+            ('weight', 1, urwid.Filler(todo_pile, valign='top')),
+        ])
+
+        widget = urwid.LineBox(pile)
+
+        super(TodoListWidget, self).__init__(widget)