Development Team/Almanac/Code Snippets

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HowTo [ID# 18149]  +/-

The Sugar Almanac also has lots of code snippets.

Smooth animation

PyGTK/Smooth_Animation_with_PyGTK

WebView

Use the WebView in a widget.

import os
import hulahop
from sugar import env
hulahop.startup(os.path.join(env.get_profile_path(), 'gecko'))

from hulahop.webview import WebView

import gtk

win = gtk.Window(gtk.WINDOW_TOPLEVEL)
win.set_size_request(800,600)
win.connect('destroy', gtk.main_quit)
wv = WebView()
wv.load_uri('http://wiki.laptop.org/go/Guido_van_Robot')
wv.show()

win.add(wv)

win.show()
gtk.main()

Notes

• I'm not sure what the purpose is of the call to hulahop.startup as the documentation is rather sparse. I only knows it's needed to get it to work Stas Zytkiewicz 2 Dec 2007

Toolbar

FIELD_MESSAGE_boboget

Files

This snippet shows how to get a path to files in the running Activity:

from sugar.activity import activity
bundle_path = activity.get_bundle_path()

This snippet shows how to get a path to an activity's writable directories (i.e. the SUGAR_ACTIVITY_ROOT environment variable; see also the activity DBus API):

class WebActivity(activity.Activity):
    def __init__(self, handle):
        activity.Activity.__init__(self, handle)
        temp_path = os.path.join(self.get_activity_root(), 'instance')

Images

• Loading an SVG file onto a surface with a transparent background:

target = ctx.get_target()
buf = target.create_similar(cairo.CONTENT_COLOR_ALPHA, w, h)
ctx.set_source_surface(buf, x, y)
ctx.paint()

• Measuring an SVG file's original dimensions

width, height = handle.get_dimension_data()

• Loading a JPEG file onto a surface:

pixbuf = gtk.gdk.pixbuf_new_from_file("foo.jpg")
ctx = # a cairo context
ctx.set_source_pixbuf(pixbuf, 0, 0)
ctx.paint()

libjpeg is said to be an alternative to using pixbuf. Which is better? Perhaps Sugar/HippoCanvas provides an easier way to do this?

Cairo image expansion is good quality, but expensive. Shrinking is fine and notably faster. So for images rendered large (ie, screen-size), you might want to start with a big image, rather than expanding a small one. A speed/space tradeoff. And use SVG instead if appropriate, of course. MitchellNCharity 10:37, 10 May 2007 (EDT)

Audio

• Playing a sound via csound:

import sys
sys.path.append('/usr/share/activities/Pippy.activity/sound')
from sound import *
playWave(sound='triangle')
audioOut()

Processes

• Starting an external process

Use Python's subprocess module.

• Starting a binary activity instead of a Python activity

Set the "exec" property of the activity.info file to your binary.

Not yet sorted

• Getting a unique ID for the XO user:

from sugar import profile

key = profile.get_pubkey()

# If you want a shorter key, you can hash that like:

from sugar import util

key_hash = util._sha_data(key)
hashed_key = util.printable_hash(key_hash)

• Avoid memory exhaustion from large dead pygtk objects by using

import gc

    gc.collect()

Not all trash pygtk objects are garbage collected promptly. If you are throwing away large pixmaps, for instance, this can be deadly. gc.collect() forces a garbage collection pass.

Performance Tips

This section belongs on a different, as yet non-existent page. But a good organization for software development tips is currently unclear to me, so I'll stash this here for now. MitchellNCharity 14:05, 10 May 2007 (EDT)

• ctx.stroke() several lines at once. stroke() currently has significant overhead. So it is faster to stroke several, than to stroke them individually. They need not be contiguous. MitchellNCharity 14:05, 10 May 2007 (EDT)

Old snippets which need to be overhauled

Toolbar

This snippet shows how an activity would have a toolbar with a button and a gtk.TextView widget embedded in a hippo Canvas:

import logging
import hippo
import gtk

from gettext import gettext as _

from sugar.activity import activity
from sugar.graphics.toolbar import Toolbar
from sugar.graphics.iconbutton import IconButton
from sugar.graphics.entry import Entry
from sugar.graphics.optionmenu import OptionMenu
from sugar.graphics.menu import MenuItem

class FooActivity(activity.Activity):

    _ACTION_ANYTHING = 1
    _ACTION_APPLES = 2
    _ACTION_ORANGES = 3

   def __init__(self, handle):
        activity.Activity.__init__(self, handle)

        vbox = hippo.CanvasBox()
        self.set_root(vbox)

        toolbar = Toolbar()
        vbox.append(toolbar)

        button = IconButton(icon_name='theme:stock-close')
        button.connect("activated", self._button_activated_cb)
        toolbar.append(button)

        entry = Entry()
        button.connect("activated", self._entry_activated_cb)
        toolbar.append(entry)

        option_menu = OptionMenu()
        option_menu.add_item(MenuItem(self._ACTION_ANYTHING, _('Anything')))
        option_menu.add_item(MenuItem(self._ACTION_APPLES, _('Apples'),
                                      'theme:stock-close'))
        option_menu.add_item(MenuItem(self._ACTION_ORANGES, _('Oranges')))
        option_menu.add_separator()
        toolbar.append(option_menu)

        text_view_widget = hippo.CanvasWidget()
        vbox.append(text_view_widget, hippo.PACK_EXPAND)

        text_view = gtk.TextView()
        text_view.get_buffer().set_text('Write here!', -1)
        text_view_widget.props.widget = text_view

    def _button_activated_cb(self, button):
        logging.debug('FooActivity._button_activated_cb')

    def _entry_activated_cb(self, entry):
        logging.debug('FooActivity._entry_activated_cb')

In build 443 (June '07), from sugar.graphics.entry import Entry yields ImportError: No module named entry. MitchellNCharity 19:52, 15 June 2007 (EDT)

And obsolete, now deleted code like sugar.graphics.toolbar is being used. Snippet needs to be overhauled. MitchellNCharity 18:04, 21 June 2007 (EDT)