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Dev Week -- Fun with Python Plasmoids -- agateau and Riddell -- Mon Aug 31st, 2009

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(04:02:23 PM) agateau: Shall we start now?
(04:02:25 PM) jawnsy: *round of applause for Riddell and agateau* :-)
(04:02:43 PM) agateau: thanks jawnsy :)
(04:03:12 PM) agateau: Riddell and myself are now going to introduce you to plasmoid developments in Python
(04:03:37 PM) Riddell: and we want you to follow along at home!
(04:03:37 PM) agateau: I'll do a short intro of Plasma and Python, then Riddell will take you through your first plasmoid
(04:04:04 PM) agateau: and I'll come back with more widgetry for your plasmoids
(04:04:14 PM) agateau: First things first,
(04:04:22 PM) agateau: What is Plasma?
(04:04:36 PM) agateau: It's the new implementation of the desktop
(04:04:39 PM) agateau: in KDE4
(04:05:20 PM) agateau: Riddell reminds me I should tell you what packages you need to install while I talk:
(04:05:36 PM) agateau: apt-get install kdebase-workspace-bin plasma-scriptengine-python
(04:05:41 PM) agateau: and you should be all set
(04:06:06 PM) agateau: so, Plasma is based on Qt Graphics View framework, which is, quoting Qt doc:
(04:06:13 PM) agateau: "Graphics View provides a surface for managing and interacting with a large
(04:06:13 PM) agateau: number of custom-made 2D graphical items, and a view widget for visualizing the
(04:06:13 PM) agateau: items, with support for zooming and rotation."
(04:06:29 PM) agateau: it can use hardward acceleration, and be themed with SVG files
(04:06:40 PM) agateau: what are plasmoid?
(04:07:00 PM) agateau: plasmoids are little gadgets you can put on your desktop
(04:07:08 PM) agateau: the whole KDE4 desktop is made of plasmoids
(04:07:17 PM) agateau: (taskbar, pager, K menu, clock, systray...)
(04:07:32 PM) agateau: some examples:
(04:07:38 PM) agateau: http://kde.org/announcements/4.2/screenshots/plasma-other-widgets.png
(04:07:45 PM) agateau: http://kde.org/announcements/4.3/screenshots/desktop.png
(04:08:04 PM) agateau: Plasmoids can be developed in C++, JavaScript, Ruby...
(04:08:06 PM) agateau: and Python
(04:08:12 PM) agateau: our beloved language
(04:08:44 PM) agateau: Python is an interpreted, dynamic programming language
(04:08:54 PM) agateau: it's simple yet powerful,
(04:08:59 PM) agateau: and very versatile
(04:09:13 PM) agateau: it can be used for throw away scripts, desktop applications, web servers...
(04:09:18 PM) agateau: and plasmoids
(04:09:28 PM) agateau: as Riddell is now going to show you...
(04:09:35 PM) Riddell: we had some questions first
(04:09:42 PM) Riddell: 21:05 < wizz_> is plasmoid available for ubuntu 9.04 and python2.6?
(04:09:55 PM) Riddell: yes, you need to install python-plasma in jaunty
(04:10:06 PM) Riddell: as well as kdebase-workspace-bin
(04:10:17 PM) Riddell: 21:06 < msp301> will plasma work under gnome??
(04:10:23 PM) Riddell: yes, you can use the plasmoidviewer app
(04:10:37 PM) Riddell: or you can try running plasma-desktop on top of gnome, goodness knows how that will end up
(04:11:05 PM) Riddell: so let's get coding!
(04:11:23 PM) Riddell: a basic plasmoid is made up of a metadata file
(04:11:38 PM) Riddell: which tells plasma the name and other vital information about the plasmoid
(04:11:42 PM) Riddell: and some code
(04:11:54 PM) Riddell: that all gets zipped up
(04:12:10 PM) Riddell: and finally you install the zip file so you can run the plasmoid
(04:12:23 PM) Riddell: so start off in a new directory
(04:12:43 PM) Riddell: and make the directories needed for our "hello-python" plasmoid
(04:12:52 PM) Riddell: mkdir -p hello-python/contents/code
(04:13:15 PM) Riddell: cd hello-python
(04:13:25 PM) Riddell: here we'll put our metadata which is in .desktop format
(04:13:44 PM) Riddell: [Desktop Entry]
(04:13:44 PM) Riddell: Encoding=UTF-8
(04:13:44 PM) Riddell: Name=Hello Python
(04:13:44 PM) Riddell: Type=Service
(04:13:44 PM) Riddell: ServiceTypes=Plasma/Applet
(04:13:46 PM) Riddell: Icon=chronometer
(04:14:08 PM) Riddell: is the top, that gives it a name and tells plasma that it's an applet, also gives it an icon to use for the Add Applet dialogue
(04:14:38 PM) Riddell: next some vital plasma info lines
(04:14:39 PM) Riddell: X-Plasma-API=python
(04:14:40 PM) Riddell: X-Plasma-MainScript=code/main.py
(04:14:58 PM) Riddell: so plasma knows it's looking for Python and it knows what code it's looking for
(04:15:23 PM) Riddell: finally some plugin info lines
(04:15:25 PM) Riddell: X-KDE-PluginInfo-Author=Simon Edwards
(04:15:26 PM) Riddell: X-KDE-PluginInfo-Email=simon@simonzone.com
(04:15:26 PM) Riddell: X-KDE-PluginInfo-Name=hello-python
(04:15:26 PM) Riddell: X-KDE-PluginInfo-Version=1.0
(04:15:26 PM) Riddell: X-KDE-PluginInfo-Website=http://plasma.kde.org/
(04:15:28 PM) Riddell: X-KDE-PluginInfo-Category=Examples
(04:15:31 PM) Riddell: X-KDE-PluginInfo-Depends=
(04:15:33 PM) Riddell: X-KDE-PluginInfo-License=GPL
(04:15:36 PM) Riddell: X-KDE-PluginInfo-EnabledByDefault=true
(04:15:38 PM) Riddell: 21:15 < keffie_jayx> Riddell: what is the file name .Desktop?
(04:15:48 PM) Riddell: this all goes in a file called "metadata.desktop"
(04:15:57 PM) Riddell: and here's the full thing
(04:15:58 PM) Riddell: http://people.canonical.com/~jriddell/plasma-python/hello-python/metadata.desktop
(04:16:32 PM) Riddell: so if you were following closely, you'll have worked out that code/main.py will be where the real code is
(04:17:05 PM) Riddell: cd contents/code  and emacs code.py
(04:17:13 PM) Riddell: we all use emacs don't we? :)
(04:17:36 PM) Riddell: sorry   emacs main.py
(04:18:03 PM) Riddell: python always starts with importing the relevant libraries
(04:18:07 PM) Riddell: in this case it's PyQt and PyKDE
(04:18:10 PM) Riddell: from PyQt4.QtCore import *
(04:18:10 PM) Riddell: from PyQt4.QtGui import *
(04:18:10 PM) Riddell: from PyKDE4.plasma import Plasma
(04:18:10 PM) Riddell: from PyKDE4 import plasmascript
(04:18:56 PM) Riddell: we want to make a class inheriting from the plasma Applet base class
(04:19:28 PM) Riddell: if you know object orientated programming, python is very simple
(04:19:30 PM) Riddell: class HelloPython(plasmascript.Applet):
(04:19:30 PM) Riddell:     def __init__(self,parent,args=None):
(04:19:30 PM) Riddell:         plasmascript.Applet.__init__(self,parent)
(04:19:59 PM) Riddell: that's the class header and the constructor, which just calls the parent constructor
(04:20:32 PM) Riddell: we want an init() method to do some basic setup
(04:20:32 PM) Riddell:     def init(self):
(04:20:32 PM) Riddell:         self.setHasConfigurationInterface(False)
(04:20:32 PM) Riddell:         self.resize(125, 125)
(04:20:32 PM) Riddell:         self.setAspectRatioMode(Plasma.Square)
(04:21:03 PM) Riddell: Plasma prefers we don't do the basic setup in the constructor so it gives us this separate init() method instead
(04:21:26 PM) Riddell: the code should be pretty self readable because KDE APIs are like that, and Python is clean as programming languages come
(04:21:51 PM) Riddell: the main body we're interested in is the paint method which will paint our hello message
(04:21:55 PM) Riddell:     def paintInterface(self, painter, option, rect):
(04:21:55 PM) Riddell:         painter.save()
(04:21:55 PM) Riddell:         painter.setPen(Qt.white)
(04:21:55 PM) Riddell:         painter.drawText(rect, Qt.AlignVCenter | Qt.AlignHCenter, "Hello Kubuntu!")
(04:21:58 PM) Riddell:         painter.restore()
(04:22:40 PM) Riddell: which is also pretty self explanatory, it uses the painting object to put some text on the screen
(04:23:11 PM) Riddell: finally plasma needs us to create the applet object from our class
(04:23:12 PM) Riddell: def CreateApplet(parent): return HelloPython(parent)
...