=== yofel_ is now known as yofel === Jr is now known as Jrsquee === soreau_ is now known as soreau === _LibertyZero is now known as LibertyZero === msnsachin12 is now known as msnsachin === jhernandez_afk is now known as jhernandez === davidcalle_ is now known as davidcalle [16:39] The next day of App Developer Week is starting in ~20 minutes! [16:39] Everyone ready? :-) [16:46] I'm ready. kind of ;) [16:46] ah, hi jryannel, welcome! :-) [16:46] thx [16:52] jryannel: could you also join #ubuntu-classroom-backstage ? :) [16:59] How's everyone? [16:59] Are you all ready for some more development goodness on Ubuntu App Developer Week? [17:00] Ok, let's start the day with one of the newest and coolest technologies in Free Software today: [17:01] Qt Quick, and in particular the QML language === ChanServ changed the topic of #ubuntu-classroom to: Welcome to the Ubuntu Classroom - https://wiki.ubuntu.com/Classroom || Support in #ubuntu || Upcoming Schedule: http://is.gd/8rtIi || Questions in #ubuntu-classroom-chat || Event: Ubuntu App Developer Week - Current Session: Qt Quick: QML the Language - Instructors: jryannel [17:01] jryannel, from the makers of Qt knows all about it and will be thrilled to tell you [17:01] Logs for this session will be available at http://irclogs.ubuntu.com/2011/04/13/%23ubuntu-classroom.html following the conclusion of the session. [17:02] Ok. Hi I'm jryannel from QtDF acting as Training Manager. This is my first irc training session so bear with me [17:02] I want to give short intro to Qt Quick's QML language and how to use it [17:02] First things first [17:03] You need Qt + Qt Creator, easiest [17:03] install - QtSDK (http://labs.qt.nokia.com/2011/04/06/qt-sdk-1-1-rc-released/) [17:03] or on ubuntu search for apt-cache search qt4; apt-cache search creator [17:04] To run QtQuick you need Qt 4.7.0 or better, latest is Qt 4.7.3 [17:04] or grab it from gitorious [17:04] So what is Qt Quick? [17:05] It's based on GraphicsView as 2.5d canvas API with graphics items [17:05] the graphicsview was developed in c++ and creating rich ui takes a long time [17:06] So our developers came up with a declarative way. [17:06] It looks like CSS or JSON [17:06] import QtQuick 1.0 [17:06] Rectangle { [17:06] width: 360 [17:06] height: 360 [17:06] } [17:07] First you import QtQuick module with major and minor version than you define a root element. [17:07] In this case a rectangle with a width of 360 and height of 360. [17:08] But live is easier if I don't type a book here; [17:08] Please visit: http://developer.qt.nokia.com/wiki/Qt_Quick_Tutorial_Basics [17:08] I will walk you through this and then another example [17:09] the qmlviewer is the declarative runner for developing purposes [17:09] it has many options, which you can ask with --help [17:09] It comes with Qt (in the bin folder) [17:10] qmlviewer main.qml will interpret the qml file and show the ui [17:10] The qmlviewer is made with the Qt Declarative module [17:10] a C++ module. You can write your own declarative viewer [17:11] see here how: http://doc.qt.nokia.com/4.7-snapshot/qdeclarativeview.html#details [17:11] It's 3 lines of code [17:11] QDeclarativeView *view = new QDeclarativeView; [17:11] view->setSource(QUrl::fromLocalFile("myqmlfile.qml")); [17:11] view->show(); [17:12] That's in essence it the qmlviewer, which interprets the qml file. [17:12] But back to the qml side of coding [17:13] width : 300 means a property binding [17:14] It's different from assignment. It's kind of a contract. [17:14] So you can write "width: 2 * height" [17:14] with this width is always 2 times the height. [17:15] When the height changes the right side will be re-evaluated and assigned to the left [17:15] Another aspect width: 2 * height" shows: [17:15] JavaScript. Every right side can contain any kind of javascript code [17:16] A good javascript tutorial is at [17:16] https://developer.mozilla.org/en/JavaScript [17:17] Qt Quick is finally a declartive UI (QML) with C++ backend and JavaScript enhanced [17:18] Let's jump to "Composition of Components" on the wiki page I posted earlier [17:18] You can nest qml elements [17:18] A element has a name and propertis and child elments, like HTMl has [17:19] (I hope someone is correcting my spelling mistakes later :) ) [17:19] 1 [17:19] 2 [17:19] 3 [17:19] 4 [17:19] 5 [17:19] 6 [17:19] 7 [17:19] 8 [17:19] 9 [17:19] 10 [17:19] 11 [17:19] 12 [17:19] 13 [17:19] 14 [17:19] 15 [17:19] 16 [17:19] 17 [17:19] 18 [17:19] / File: BasicSteps_2.qml [17:19] import Qt 4.7 [17:19] [17:19] Rectangle { [17:19] width: 300 [17:19] height: 300 [17:19] color: "#FFF8DC" // cornsilk [17:19] [17:19] Image { [17:19] x: 10; y: 45 [17:20] source: "voringsfossen1.jpg" [17:20] } [17:20] [17:20] Text { [17:20] x: 10; y: 265 [17:20] text: "Voringsfossen" [17:20] } [17:20] } [17:20] ohh, sorry [17:20] so we have a rectangle with an image and text child [17:20] The child elements have a corrdinate system relative to the parents [17:21] so a x:10, means 10 px relative to parent. [17:22] E.g. all elements are derived from the Item element: http://doc.qt.nokia.com/4.7-snapshot/qml-item.html [17:22] You find an overview about which items are available here: http://doc.qt.nokia.com/4.7-snapshot/qmlbasicelements.html [17:23] so when you write "x:10" you actually overwrite the default property value (in this case "x:0"). [17:24] For example if you don't specify a width or height to an element, it will be invisible! [17:25] Let's come back to "http://developer.qt.nokia.com/wiki/Qt_Quick_Tutorial_Basics" -> Custom Properties [17:26] besides the default properties you can add own properties. [17:26] E.g. "property int frameSize: 300" [17:27] which data types are supported? See here: http://doc.qt.nokia.com/4.7-snapshot/qdeclarativebasictypes.html [17:27] Can I add own data types. Sure. You can extend Qt Quick from the C++ side: http://doc.qt.nokia.com/4.7-snapshot/qml-extending.html [17:28] Even you can write own elements. E.g. a chart type or everything what can be painted. [17:29] Besides visual items you can also use non-visual items, e.g. timer (http://doc.qt.nokia.com/4.7-snapshot/qml-timer.html) [17:30] And you can also push QObjects from the c++ world into Qt Quick, e.g. for example for a D-Bus binding, or... [17:30] Now visit shortly http://doc.qt.nokia.com/4.7-snapshot/qml-tutorial1.html for another start into qt quick [17:31] It's just another hello world in qt quick [17:32] In Qt Creator our ide you can create a qt quick project with "New Project" -> "Qt Quick UI" [17:32] If you choose Qt Quick Application, it will generate a C++ qml viewer for you additional [17:33] So just copy the helloworld from (http://doc.qt.nokia.com/4.7-snapshot/qml-tutorial1.html) in your new project and run the project (no need for compilation) [17:34] Qt Creator (http://doc.qt.nokia.com/qtcreator-snapshot/index.html) is very much keyboard driven [17:34] It has also support got git, mercurial and I think svn and some other version control systems [17:35] Also for pastebin. Which I need to remember to use more [17:35] Here is a list of shortcuts: http://doc.qt.nokia.com/qtcreator-snapshot/creator-keyboard-shortcuts.html [17:36] One of our partners has created a reference card: http://www.kdab.com/index.php?option=com_content&view=article&id=126 [17:36] for Qt Creator. [17:36] But now back to qml... [17:37] http://doc.qt.nokia.com/4.7-snapshot/qml-tutorial2.html shows how to create a custom qml component [17:37] A component is a piece of qml code in a separate qml file [17:38] E.g. if you want create your own button you write a "Button.qml" file [17:38] Inside would be possible a Rectangle a Mousearea (which receives mouse clicks). [17:39] In the example tutorial they create a Cell in a "Cell.qml" file [17:39] The signal keyword allows to emit signal from a qml element. Just by calling the function name [17:40] The id property is a special property. It allows to identify an element inside a qml file ... [17:40] ... but also across other qml files. [17:40] As a convention I always give my root element the "id: root" [17:41] I give application wide used components a nice name so that I can reference them from other qml files. [17:42] When referencing an id from another qml file you make yourself depending. So think about if you really want to be dependent on the other qml (component). [17:42] Id's are only known to the qml runtime when the qml file is actually loaded [17:42] Have a look at the "The main QML file" section [17:43] There we use the "Cell.qml" component with a simple call to "Cell". [17:43] Any qml file (with upper-camelcase" ) in the same folder can be used directly. (Others need to imported) [17:44] "onClicked: helloText" - is a handler to the signal clicked() from Cell.qml [17:44] Great. We can make some rectangles and text and place them somewhere so what? [17:45] With a little bit of C++ and some motivated developers you can make something more ... [17:45] ... see here http://labs.qt.nokia.com/2011/03/10/qml-components-for-desktop/ [17:46] Jens presents the desktop components (a little bit more complicated Cell.qml with some C++ backend) [17:48] It's a research project (that's why it's on labs). But I think they will be happy about feewdback [17:48] But in general Qt Quick is a very much design driven easy to code ui language. Where the heavy lifting is done in C++ [17:49] It's very flexible. With flexibility also comes a price [17:50] There are many solutions to the same problem. So you need a good practice to master the different elements and C++ extension possibilities to come to a good solution [17:50] Not every solution is simple and beautiful [17:51] There are 10 minutes remaining in the current session. [17:51] http://doc.qt.nokia.com/4.7-snapshot/qdeclarativeexamples.html here you find more examples [17:52] Tomorrow we will go into the dynamic side of Qt Quick. Animations - States - Transitions [17:53] You can find learning material (e.g. videos and whole courses) here: http://qt.nokia.com/developer/learning/elearning [17:53] I hope I haven't confused you all to much. Qml is simple [17:53] Elements, Properties, Child Elements, [17:54] Property Binding [17:54] and JavaScript + C++ for application logic. [17:54] Take care. [17:54] Python and Qt Quick. Yes [17:55] There is PyQt and PySide [17:55] checkout: http://developer.qt.nokia.com/wiki/Category:LanguageBindings::PySide [17:56] There are 5 minutes remaining in the current session. [17:56] Sorry question was: Can I use Qt Quick with a python backend instead of C++? === ChanServ changed the topic of #ubuntu-classroom to: Welcome to the Ubuntu Classroom - https://wiki.ubuntu.com/Classroom || Support in #ubuntu || Upcoming Schedule: http://is.gd/8rtIi || Questions in #ubuntu-classroom-chat || Event: Ubuntu App Developer Week - Current Session: Make your applications work in the cloud with Ubuntu One - Instructors: aquarius [18:01] Logs for this session will be available at http://irclogs.ubuntu.com/2011/04/13/%23ubuntu-classroom.html following the conclusion of the session. [18:02] Hi, all! [18:02] I'm Stuart Langridge, from the Ubuntu One team, and I'm here to talk about our upcoming app developer programme. [18:02] Do please ask questions throughout the talk: in the #ubuntu-classroom-chat channel, write QUESTION: here is my question [18:02] and so, on with the show. :) [18:02] Up until now, your ability as developers to do cool things with Ubuntu One has been limited. [18:02] But I'm going to change all that. [18:03] We want to make it possible, and easy, for you to add the cloud to your apps and to make new apps for the cloud [18:03] So we do all the heavy lifting, and your users (and you!) get the benefits. [18:03] Imagine, for example, you've made a recipe manager application. [18:03] So you can type in all the recipes you like to cook, and you've got a permanent record of them. [18:04] (For me, that would be: get a pizza base; put pepperoni on it. You'll be better at that than me.) [18:04] Don't really want to take your laptop into the kitchen, though, of course. [18:04] So, build a mobile app which you sign into with Ubuntu One, and have that show all your recipes too. [18:04] And a web app which you sign into with Ubuntu One, so that you can look up recipes while you're at a friend's house. [18:04] This is the sort of thing that we want to make easy; giving your users and you quick access to the Ubuntu One technology. [18:05] Mobile access to your data; web app access to your data; saving files direct into Ubuntu One; publishing files and photos from all your apps; adding playlists to the Ubuntu One music streaming app; streaming the user's own music into a game you've written. [18:06] Bringing all that stuff into apps on Ubuntu; Quickly apps or Qt Quick apps or Flash apps or C apps or JavaScript apps or Air apps or whatever you want to develop. [18:06] We give you the APIs to do it; you build cool stuff. Deal? Deal. [18:06] This stuff is all being heavily worked on right now as we speak. [18:06] So this talk won't be too detailed with specifics, because they might change. [18:06] I want to give you a flavour of what will soon be possible, and answer questions, and give some pointers, and get your thoughts. [18:07] Also, this is App Developer Week, so I can talk about what the components we're working on are and then admire all the cool ways you all come up with for snapping them together, rather than waiting for marketing to come up with a "product" for you to use :) [18:07] So, some components that can be snapped together. [18:07] You'll be able to sign in to a web application with Ubuntu One. [18:08] This means that you don't have to manage your own identity system, think about password renewal, all that. [18:08] And that's the hard annoying part of running web apps; working out what to do if a user forgets their password, etc, etc. "Enter the name of your first pet", etc. [18:08] This is just like "sign in with Facebook" or "sign in with Twitter"; it's OpenID-based, and lets your users sign in to a web app and you'll know their Ubuntu identity. [18:09] Once you've signed in to an app with Ubuntu One, that app can ask for permission to work with your data. [18:09] This lets you, developers, build applications that work on the desktop, on the web, on mobile phones. [18:10] The recipe manager example I mentioned above is one sort of thing you could do, there [18:11] Your users use the nice recipe manager app on Ubuntu, which you've built with Quickly or whatever you prefer [18:11] (QML, now that you're all experts in it :)) [18:11] And then they can go to yourrecipemanager.com and sign in with Ubuntu One [18:11] yourrecipemanager.com then asks them for permission to access their "recipes" database [18:11] and can then show them all their recipes on the web! [18:12] Your app (yourrecipemanager.com) does this via OAuth; it goes through the standard OAuth dance to get an OAuth token which can be used to access the user's recipes CouchDB database [18:12] And your users can be happy that it's secure, because yourrecipemanager.com will only have access to their recipes database; it can't read their contacts, or their files, or their credit card info. [18:13] So, this gives you the chance to build a brilliant Ubuntu app and yet still extend that app out to other platforms, for people who end up sometimes being away from their Ubuntu machine [18:13] so they can use the website when they're at work, and the Ubuntu app when they're at home [18:14] But you can imagine sharing other sorts of data between applications. [18:14] Imagine, for example, an achievements system. [18:14] You write a few games; some on the web, some on mobile phones, some on the Ubuntu desktop, some on Windows. [18:15] And every time the user achieves something in a game, you save that achievement to that user's "achievements" database. [18:15] ("100 levels completed!", or perhaps "100 enemies killed" if it's that sort of game...) [18:16] On Ubuntu, you'd save it into desktopcouch, and Ubuntu One will take care of synchronising that into the cloud. [18:16] On Android, your game would include the DroidCouch library which gives you simple access to save data directly into the user's personal cloud databases. [18:17] On the web, your game's backend could use the u1couch Python library to do the same thing, save directly into the cloud, or you could just use the underlying REST API (which is just standard CouchDB with OAuth signing; u1couch is just a wrapper) [18:17] The u1couch library is at https://launchpad.net/ubuntuone-couch for people who want to play with it. [18:18] it's Python, but it provides a good example of how to take a request to Ubuntu One, discover the user's Ubuntu One tokens, and maek requests using them [18:18] Or you could write your own wrapper library for PHP or Rails or Flash or whatever you prefer (and then tell me about it so I can point to the documentation for it!) [18:18] (feel free to use u1couch as a basis, or develop your own if you prefer) [18:18] At that point, all your games save achievements to the same place, so all your games can show you the achievements you've won in any game [18:19] And, as before, you can set up yourachievements.com where a user can log in and see all their achievements. [18:19] There's loads of stuff you can do with shared data. [18:19] The idea here is that all your stuff is everywhere -- more importantly, all your users' stuff is everywhere. [18:19] So they get the benefit of all their machines sharing the same information. [18:20] win an achievement in a game on your Ubuntu laptop, and your Ubuntu netbook also knows you've won that achievement, and which level you got up to [18:20] and so does your port of the game to a tablet or a web app or whichever other platform you want. [18:21] and you, developer with limited time, can concentrate on the stuff you're interested in -- making your app, your game, your program -- be great, and just not have to worry about all this data storage stuff. [18:21] your apps look better because they handle all this, and you don't have to worry about how to do it. :) [18:22] But Ubuntu One's not just about data. [18:23] Take the music streaming service, for example. [18:23] You can currently stream music to Android and iPhone, and you'll be able to add that music to the cloud from Ubuntu and Windows. [18:24] any music your users have got, that they've purchased from U1 or from elsewhere or ripped from their own CDs or whatever, they sync with U1, and then they can stream it to their mobiles. [18:24] Maybe you want to be able to stream music back to your Ubuntu machine without syncing it, or your Mac, or your Palm Pre, or your LG mobile phone, or your toaster. [18:24] So, just use the music streaming API, which is a simple REST HTTP API, based on the Subsonic API, or help people to get at their music by showing them our HTML5 web player for streaming music. [18:25] But there's more interesting ideas around music streaming than just "listen to the music". [18:26] Playlists, for example. The Ubuntu One Streaming apps on Android and iPhone know how to create playlists. [18:26] But how they do that is not a secret. Your playlists are just stored in your cloud databases. [18:27] So, why not sync your playlists from Banshee or Rhythmbox or Amarok or Exaile or Quod Libet or iTunes or Windows Media Player? [18:27] (or whichever music player you use yourself. :)) [18:27] Copy the playlists from your media player into desktopcouch on Ubuntu or into the cloud directly with u1couch on Windows or the Mac or anywhere else, in the correct format, and those playlists will instantly show up on your phone! [18:28] A simple example of this is https://code.launchpad.net/~sil/%2Bjunk/m3u2u1ms/ which is a quick script I wrote to take an m3u playlist and store it in desktopcouch on Ubuntu. [18:29] the whole script is about 200 lines, so as you can see this isn't hard [18:29] it just walks through an m3u file, finds a reference to all the songs in it, and creates that as a U1 playlist [18:29] So you can make your Banshee playlists available to the Ubuntu One app on your Android phone by exporting them as m3u and then importing them with the script. [18:31] Tighter integration is great, here; what we want to do is to make it easy for you all to build the stuff that you want on top of Ubuntu One. [18:31] So if you want to have your Amarok playlists available for streaming, it should be possible to do. [18:31] I rather like the idea of playing a Flash game on the web and having the background music be the most appropriate music chosen from *my* music collection. That'd be cool. [18:32] Ubuntu One also, as you know, does file sync. === tubadaz is now known as tubadaz_away [18:32] But just syncing files is already taken care of by Ubuntu One itself, on Ubuntu and Windows. [18:33] What's more interesting is working with those files. [18:33] So, for example, imagine being able to instantly, one-click-ly, publish a file from your application to a public URL and then tweet that URL. [18:34] Instant get-this-out-there-ness from your apps. [18:34] The screenshot tool Shutter, for example, can do this already; PrtSc to take a screenshot, then "Export > Ubuntu One". [18:34] They did a bunch of hard work to do that, and I massively applaud them; nice one Shutter team! [18:34] Based on what they did, that's the sort of thing that should be easier to do. [18:35] The shutter team built U1 publishing into their app, and it was harder than it should have been because the APIs were very much in flux, and they weren't very well documented [18:35] and we recognised that that needs fixing :) [18:36] So there will be easy-to-use APIs so your apps can do the same. Imagine quickly sharing your newly created image or document or recipe with the world. [18:36] Your app could have a button to "store all my files in the cloud", or "publish all my files when I save them", or "automatically share files that are part of Project X with my boss". [18:37] More to the point, you'll be able to work with files directly *in* the cloud. [18:37] So a backup program, for example, could back up your files straight into Ubuntu One and not sync them to your local machines. [18:38] that makes it easy for your app's files to be saved away from the local machine if that's what you want [18:39] which is ideal if you're a backup program, as mentioned [18:39] so your users can just say "yeah, save this straight into my online storage, I don't need it locally" [18:40] And of course being able to save things in and out of the cloud means that you can get an Ubuntu One sync solution on other platforms. [18:40] So you could work with your files from your non-Android mobile phone (we've already got the great mkarnicki working on that for Android!) [18:40] Build a fuse or gvfs backend for Ubuntu or Fedora or SuSE or Arch Linux. Build a WebDAV server which works with Ubuntu One and mount your Ubuntu One storage as a remote folder on your Mac. [18:41] so if you prefer to think of your online storage as a drive, rather than something which files are synced to, you can make that happen for yourself and for your users if you want to [18:42] And web apps can work with your cloud too, for files as well as data. [18:45] Imagine, say, a torrent client, running on the web, which can download something like a movie or music from legittorrents.info and save it directly into your cloud storage. [18:45] So you see an album you want on that torrent site (say, Ghosts I by Nine Inch Nails) and go tell this web torrent client about it (and you've signed in to that web torrent client with Ubuntu One) [18:46] And the website then downloads that NIN album directly into your personal cloud -- which of course makes it available for streaming direct to your phone. [18:47] You could do that with videos as well: choose a torrentable video (say, Beyond the Game, the documentary about World of Warcraft) and download that directly into your cloud, if someone built the web torrent client. [18:47] (Of course, that would be cooler if Ubuntu One offered a video streaming service as well as music streaming, wouldn't it. Hm... ;-) [18:47] But it's not just about your content for yourself; think about sharing. === tubadaz_away is now known as tubadaz [18:48] Ubuntu One lets you share a folder with people. This would be great for distribution. [18:48] Imagine that you publish an online magazine. [18:48] So, you create a folder on your desktop, and put issues of the magazine in it. [18:48] Then, you put a button on your website saying "Sign in with Ubuntu One to get our magazine". [18:49] When someone signs in, your website connects to the Ubuntu One files API, with your private OAuth token, and adds that signed-in user to the list of people that your magazine folder is shared with. [18:49] Then, whenever your magazine has a new issue, you just drop it into that folder on your desktop. [18:49] (Or even upload it to Ubuntu One directly through the website.) [18:49] All the subscribed people will get the new issue instantly, on all the machines they want it on, and in the cloud. [18:50] No-one has to do anything. No polling of RSS feeds, no bandwidth use by your website [18:51] You could build a cool Ubuntu app for your readers which would see that a new issue of the magazine has arrived on the machine and lets them read it [18:51] You could distribute anything like this. Imagine a podcast, or chapters of a novel. [18:51] It would also work for paid-for content; when someone pays, have your code share a folder with them, and put their paid-for stuff in that folder. That's all doable through the files API. [18:51] There are 10 minutes remaining in the current session. [18:51] We're building the files API itself (an HTTP-based REST API) and also some wrappers for it to make it easier to use in your apps from Python and the like. [18:52] OK, I've talked about a blizzard of ideas that'll be made possible, and shown you almost no code. [18:52] Which is because, as mentioned at the beginning, a lot of this code is currently being written and tested as part of the 11.04 release :) [18:52] However, code is nothing without documentation, and that's really important. [18:52] My main task for this cycle is to build documentation for all of this stuff; how to use Ubuntu One and all the APIs we provide in the cloud, on Android, on Windows, on iOS, on Ubuntu. [18:52] So there'll be documentation for all this stuff so all of you clever people can build things that I haven't even dreamed of. [18:52] We did some user research (thanks ivanka and the user research team!) on which sites have great API documentation and which don't, so we have an idea of good directions to go in. [18:53] And I'm working away feverishly on getting an alpha version out! [18:53] So, what I'd like to know is: what are your cool ideas? What help do you need from me in making them happen? What do you want to use Ubuntu One for in your apps and your scripts and your work? [18:53] and I've got about five minutes left, I think, so I'm happy to answer questions if anyone has any [18:54] otherwise, thanks for listening and I can hand over to alecu who is going to talk about DBus :) [18:56] hello all [18:56] There are 5 minutes remaining in the current session. [18:56] let's wait a couple more minutes and then we'll start [18:58] chadadavis asked: What's the best way to stay up to date on the API documentation status? [18:58] chadadavis, watch the U1 blog where we'll announce that the developer site is available [19:01] hello all === ChanServ changed the topic of #ubuntu-classroom to: Welcome to the Ubuntu Classroom - https://wiki.ubuntu.com/Classroom || Support in #ubuntu || Upcoming Schedule: http://is.gd/8rtIi || Questions in #ubuntu-classroom-chat || Event: Ubuntu App Developer Week - Current Session: Take control of your desktop easily with DBus - Instructors: alecu [19:01] My name is alecu, some people also call me "Alejandro J. Cura" [19:01] Logs for this session will be available at http://irclogs.ubuntu.com/2011/04/13/%23ubuntu-classroom.html following the conclusion of the session. [19:02] I'm a developer on the Ubuntu One team, currently working on the desktop side of Ubuntu One. [19:03] For the past year or so I've been using DBus a lot to do bits and pieces of my work, so I'd like to share a bit of that during this session. [19:03] As you all probably know, DBus is a way for applications to request services from other applications. [19:04] For instance, Ubuntu One asks the gnome-keyring daemon for passwords. [19:04] Or the sound menu asks the music players to start playing or to change tracks. [19:04] so, let's dive into an example... [19:04] for this we need to have d-feet installed [19:05] sudo apt-get install d-feet [19:05] so, everybody has d-feet installed by now? [19:06] open it, and let's browse the Dbus bus a bit [19:06] go to File -> Connect to Session [19:06] and we will be able to explore the Session Bus [19:07] on the left we have a list of Bus Names. It's common for each application that's providing a service to use one, but some apps export more than one Bus Name. [19:07] clicking on one of the Bus Names, we'll see a list of Object Paths on the right [19:08] it's very common for one application to export more than one Object Path [19:09] if you click on one Bus Name and no object paths appear, that means that the application is not providing introspection data, and that means that we'll need to ask the app developers for more info on how to use those services thru dbus. [19:09] but the common case is to have both introspection data and some dbus documentation... [19:10] let's look at one example [19:10] let's open banshee, or some rhythmbox [19:11] when we run banshee, we'll see on d-feet that a new "Bus Name" was published to provide services to other apps [19:11] try clicking on d-feet on it: org.bansheeproject.Banshee [19:12] on the right hand we'll see a few Object Paths [19:12] let's open /org/mpris/MediaPlayer2 [19:12] and open the "org.mpris.MediaPlayer2.Player" interface === kevin4896 is now known as kdemarest [19:13] Inside that interface we'll see a list of Methods, Properties and Signals === tubadaz is now known as tubadaz_away [19:13] let's try one Method: play [19:13] sorry, Play() [19:14] double click on it, and a new small window opens "Execute D-Bus Method" [19:14] just click on Execute [19:14] banshee should start playing [19:15] (if it does not, try making it play some song by hand, then pausing it thru d-feet) [19:17] and then try playing with the other methods [19:17] for instance, Seek takes a parameter, try 30000000 [19:18] or -30000000 [19:18] chadadavis asked: there are a few 'play' methods under other object paths. Why are there so many? What's the difference, in the case of banshee here? [19:18] chadadavis, you mean Play and PlayPause? [19:19] I think Play always plays, but PlayPause is like a toggle. [19:19] chadadavis, the thing is that I don't know exactly how that works, and since it won't be documented in a DBus browser like d-feet we need to find some spec [19:20] and I was just pointing all of you to this example, because there's a lovely documentation for this interface, and it's common to many-many media players. [19:21] it's http://xmms2.org/wiki/MPRIS [19:22] and for the work I've been doing for the gnome-keyring and kwallet, I've been using the "Secrets Service API" http://people.collabora.co.uk/~stefw/secret-service/ === tubadaz_away is now known as tubadaz [19:23] so you'll probably need some similar docs for the service you are trying to use [19:23] or just use an explorer like d-feet to experiment with the interface you want. [19:24] So, after finding some service that you want to use, and some docs on it, you'll want to use DBus from your own application. [19:24] I've mostly used python for this, but I understand that other bindings are similar. [19:25] Here's a few examples I've made, so we can go over: [19:25] bzr branch lp:~alecu/+junk/dbus-lessons [19:26] crazedpsyc asked: if credentials are transported through DBus, can't I, or anyone else see them by using something like dbus-monitor? [19:27] crazedpsyc, there is one instance of DBus running for the system, and an instance per user that's logged in. [19:28] crazedpsyc, DBus connections are always local, and are either in the context of your computer or your session. [19:28] crazedpsyc, there are security rules on the system DBus, so apps are limited on what they can listen to. [19:29] crazedpsyc, for the session DBus I haven't seen any security restrictions, so afaict any app can listen for all the Dbus traffic for every other app. [19:30] crazedpsyc, that includes listening for the same logged in user credentials, but any X window app can capture all keystrokes anyway, so there's no point in securing that. [19:30] crazedpsyc, makes sense? [19:31] crazedpsyc, we can discuss this on much detail later, since app sandboxing is an issue I find very interesting to work on. [19:32] anyway, let's go back to the samples [19:32] let's look at the first one: 01-call_method.py [19:34] DBus usually has to work together with the main loop of your application [19:34] usually it's the gtk or kde main loop, and DBus supports it. [19:34] But you can also use the twisted reactor as a main loop, and we'll be able to integrate that as well. [19:35] in this example I'm using the gobject main loop, as used by gtk. [19:35] this line joins dbus with the loop: "DBusGMainLoop(set_as_default=True)" [19:36] and on the following lines we get at the "Session Bus", get an object from it using a "Bus Name" and an "Object Path" [19:36] and we get an "Interface" from that object. [19:36] as you can see, it all matches what we are able to see on d-feet. [19:37] once we get an Interface, we can call on the Methods on it, and access its Properties [19:38] in this example I'm just changing the brightness of my laptop display, and depending on your hardware it might not work. [19:38] So I'll ask you all for homework to modify it so it changes the volume of the music player. [19:39] psusi asked: What is the use of naming the Interface of an object separtely from the name of the object itself? Can this be used to publish versioned interfaces to, for instance, add a new argument to a signal without breaking applications that depend on the interface without the argument? [19:41] psusi, exactly. We can add more than one interface for an object, to group interfaces per intent, so for instance the MPRIS spec separates the methods in the Player from the Playlist interfaces, and also as you very correctly point out to create a new interface and not break compatibility with older interfaces. [19:42] Ok, let's look a bit further into arguments for the Methods === crazedpsyc is now known as crazedpsyc_away [19:43] since DBus is language agnostic, it defines a way to specify the types of the arguments and return values of DBus Methods [19:44] each language binding will try to match it to native types. For instance the python binding will usually transform DBus byte arrays into python strings [19:44] (python 2 strings, that is :-) ) [19:45] so Dbus has a way of specifying a small string that will act as the signature for the types in a DBus method call === crazedpsyc_away is now known as crazedpsyc [19:47] for instance let's browse with d-feet the org.mpris.MediaPlayer2.Playlists interface [19:47] the GetPlaylists method has a very complicated signature [19:47] Uint32 index, Uint32 maxcount, String order, Boolean reverse_order [19:48] in dbus you'll usually see this as "uusb" [19:49] and the return value for that method is array of [struct of (object path, string, string)] [19:49] you'll see it defined as "a(oss)" [19:50] for a complete reference of this, and much more, try this tutorial: http://dbus.freedesktop.org/doc/dbus-python/doc/tutorial.html#data-types [19:50] we'll need to define strings similar to this when we export our own objects on DBus as services [19:51] so let's look at example 03-export_object.py [19:51] There are 10 minutes remaining in the current session. [19:52] in this example I'm exporting a DBus object on a given "Bus Name" and with a given "Object Path" [19:52] and when I run the example, I can use d-feet to call the example_method. Go ahead, try it. [19:53] In addition to the Method, I'm also exporting a "Signal" [19:53] Signals work backwards [19:54] Usually a dbus client calls a method. [19:54] But the clients subscribe to signals, and the dbus service calls them. [19:54] We can see how to subscribe to a signal in example 2 [19:55] in 02-listen_signal.py we connect to the bus, and using a "Bus Name", an "Object Path" and an "Interface", we connect a function of our code to a DBus signal. [19:56] There are 5 minutes remaining in the current session. [19:56] in this example I also use the BackLight, but as homework as well you may change listen to media player signals as well. [19:57]