Mitter/mitterlib/ui/helpers/gdk_avatarcache.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Mitter, a micro-blogging client with multiple interfaces.
# Copyright (C) 2007-2010  Mitter Contributors
#
# 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 logging
import urllib2

import gtk

# ----------------------------------------------------------------------
# Constants
# ----------------------------------------------------------------------
_log = logging.getLogger('ui.helpers.avatarcache')

# ----------------------------------------------------------------------
# The cache class
# ----------------------------------------------------------------------

class AvatarCache(object):
    """An avatar cache, storing GDK pixbufs references."""

    def __init__(self, connection, default, timeout=None):
        """Initialization of the cache.

        connection:
           A :class:`ThreadManager`, which will be used as thread pool to
           request the avatars.

        default:
           A gdk_pixbuf to be used as placeholder while the real avatar is
           being downloaded.

        timeout:
           Request timeout when downloading the avatars."""

        self._connection = connection
        self._default = default
        self._cache = {}
        self._timeout = timeout

    def get(self, owner, avatar, url=None):
        """Return the avatar from the cache or, if the avatar isn't available
        yet, returns the default avatar and queue the download of it.

        owner:
           The object requesting the avatar. Must have a "queue_draw()"
           method, which will be called once the avatar is available. Can be
           None.

        avatar:
           The identification of the avatar. Can be any string.

        url:
           URL to download the avatar. If not passed, *avatar* **must** be a
           valid URL."""

        if avatar in self._cache:
            return self._cache[avatar]

        if not url:
            url = avatar

        self._connection.add_work(self._post_avatar_download,
                self._exception_avatar_download,
                self._download_pic,
                avatar,
                url,
                owner)

        # add the default avatar in the cache just to avoid a new request for
        # it. It will be overwritten anyway later.
        self._cache[avatar] = self._default
        return self._default

    # ------------------------------------------------------------
    # Network functions
    # ------------------------------------------------------------
    def _download_pic(self, avatar, url, owner):
        """Download a picture from the web. Can be used in a thread."""
        request = urllib2.Request(url=url)
        timeout = self._timeout
        _log.debug('Starting request of %s (timeout %ds)' % (
            url, timeout))
        try:
            response = urllib2.urlopen(request, timeout=timeout)
        except TypeError, e:
            # Python 2.5 doesn't have a timeout parameter
            response = urllib2.urlopen(request)
        data = response.read()
        _log.debug('Request completed')
        return (avatar, owner, data)

    def _post_avatar_download(self, widget, data):
        """Called after the data from the picture is available."""
        (avatar, owner, data) = data

        loader = gtk.gdk.PixbufLoader()
        loader.write(data)
        loader.close()

        user_pic = loader.get_pixbuf()
        user_pic = user_pic.scale_simple(48, 48, gtk.gdk.INTERP_BILINEAR)
        self._cache[avatar] = user_pic

        if owner:
            owner.queue_draw()
        return

    def _exception_avatar_download(self, widget, exception):
        """Called in case we have a problem downloading an user avatar."""
        _log.debug('Exception trying to get an avatar.')
        _log.debug(str(exception))
        return