4.3. User Interface

Alot sets up a widget tree and a mainloop in the constructor of alot.ui.UI. The visible area is a urwid.Frame, where the footer is used as a status line and the body part displays the currently active alot.buffers.Buffer.

To be able to bind keystrokes and translate them to Commands, keypresses are not propagated down the widget tree as is customary in urwid. Instead, the root widget given to urwids mainloop is a custom wrapper (alot.ui.Inputwrap) that interprets key presses. A dedicated SendKeypressCommand can be used to trigger key presses to the wrapped root widget and thereby accessing standard urwid behaviour.

In order to keep the interface non-blocking and react to events like terminal size changes, alot makes use of twisted’s deferred - a framework that makes it easy to deal with callbacks. Many commands in alot make use of inline callbacks, which allow you to treat deferred-returning functions almost like syncronous functions. Consider the following example of a function that prompts for some input and acts on it:

from twisted.internet import defer

def greet(ui):  # ui is instance of alot.ui.UI
    name = yield ui.prompt('pls enter your name')
    ui.notify('your name is: ' + name)

4.3.1. UI - the main component

4.3.2. Buffers

A buffer defines a view to your data. It knows how to render itself, to interpret keypresses and is visible in the “body” part of the widget frame. Different modes are defined by subclasses of the following base class.

Available modes are:

Mode Buffer Subclass
search SearchBuffer
thread ThreadBuffer
bufferlist BufferlistBuffer
taglist TagListBuffer
envelope EnvelopeBuffer

4.3.3. Widgets

What follows is a list of the non-standard urwid widgets used in alot. Some of them respect user settings, themes in particular. utils

Utility Widgets not specific to alot

class alot.widgets.utils.AttrFlipWidget(w, maps, init_map='normal')

An AttrMap that can remember attributes to set globals bufferlist

Widgets specific to Bufferlist mode

class alot.widgets.bufferlist.BufferlineWidget(buffer)

selectable text widget that represents a Buffer in the BufferlistBuffer. thread

4.3.4. Completion

alot.ui.UI.prompt() allows tab completion using a Completer object handed as ‘completer’ parameter. alot.completion defines several subclasses for different occasions like completing email addresses from an AddressBook, notmuch tagstrings. Some of these actually build on top of each other; the QueryCompleter for example uses a TagsCompleter internally to allow tagstring completion after “is:” or “tag:” keywords when typing a notmuch querystring.

All these classes overide the method complete(), which for a given string and cursor position in that string returns a list of tuples (completed_string, new_cursor_position) that are taken to be the completed values. Note that completed_string does not need to have the original string as prefix. complete() may rise alot.errors.CompletionError exceptions.