Tag Archives: plasma

Declarative Knowledge Base

As I described in the latest entry, with the KDE Plasma Workspace 4.6 there will be a new feature that will be a key one for the future evolution of the Plasma platform: the ability to write plasmoids with just QML and Javascript.

So, let’s try to see if it’s possible rewrite the average widget in with the declarative scriptengine…

We have a dataengine (using a neat library called Attica) that can query the various functionalities of websites that offer an API compatible with the Open Collaboration Services, such as OpenDesktop.org. One of the features offered by this API is the Knowledge Base: users subscribed to the site can ask any question (in topic with the website) and other users can answer to them. Plasma offers a desktop widget that can query and visualize those question/answers. It’s written in c++ and is about 400-500 lines of code.

How much QML code would take to write a very minimal Declarative Plasmoid that can access the knowledge base entries trough the Plasma dataengine? Here it is

import Qt 4.7
import org.kde.plasma.core 0.1 as PlasmaCore

ListView {
    clip: true
    width: 200
    height: 300

    PlasmaCore.DataSource {
        id: source
        engine: "ocs"
        source: "KnowledgeBaseList\provider:https://api.opendesktop.org/v1/\query:opendesktop\sortMode:new\page:0\pageSize:10"
        interval: 120000
    }

    model: PlasmaCore.DataModel {
        dataSource: source
        key: "KnowledgeBase-[\d]*"
    }

    delegate: Text {
        text: Name
    }
}

24 lines 😉

What is important to look here is the DataSource{} definition that defines to what engine we’re connecting and to what source. And the DataModel{} that hooks up what has been fetched by the DataSource to a suitable model for the use by the ListView.

Let’s expand from this to something that can be compared to the C++ version in terms of functionality. You can download an early example of the code from here. (all is available from the playground svn repo). It’s still early to include it in the 4.6 release for various reasons, but the path is definitely clear 🙂

Here you can see a brief screencast of the two plasmoids, the C++ and the declarative one working side by side.

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Here is a video tutorial that explains the steps taken to write this plasmoid.

It is also a little demo of the Plasmate IDE that while it’s still at early development stages, it’s pretty impressive already: all you have to do is write the code and test it in the preview side panel. zero worries about creating the package structure, desktop files or installing :p

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A Declaration of Plasma Love

Declarative RSS reader The image on the left is a new (example) plasmoid that marks an important change… this is going to be a quite massive blog post, with pretty technical details about what I think is going to be a feature of an higly important strategic relevance on the road towards Plasma as a mature and powerful platform.

The Plasma declarative bindings have landed into kdebase! This means it will be possible to use the new QML language part on Qt 4.7.

As Aaron noted some days ago, QML in conjunction with now in heavy development technologies like QtComponents (and in the future Qt cene-graph) will play a key role in the creation of user interfaces in the future, and gives us a very important puzzle piece we were still sorta missing.

So we deceided to be (as usual 😉 erly adopters of the technology and with the KDE Plasma workspace 4.6 the first pieces will be in place for the roadmap that will lead us basically to this path:

Separate the implementation of the logic from the user interface
Avoid C++ (and well, any imperative language) as much as possible for the UI
Be flexible, an application should be able to jump between different devices as easily as possible
do applications that can chose the proper ui amond different choiced depending on the device used, the screen size, the input methods and what not
With QtComponents, use what will be the native set of widgets/components for the given platform: on a MeeGo phone, use its own widgets, theme and UI paradigms, but a different interface somewhere else
Performance, perforance, performance, enter Qt scene graph

So, what will have the KDE Plasma platform 4.6 of all of this?

Use QML from C++ Plasma widgets

The first pass (needed to do the following one) is to have a way to easily load a QML file into a normal C++ plasmoid. Now, loading a QML file into a QGraphicsScene (and making it well behave inside the QGraphicsLayout based Plasma widgets) is a quite simple operation, however it is a bit long and repetitive amount of boilerplate code… enter Plasma::DeclarativeWidget.

This is a normal QGraphicsWidget just like the other Plasma widgets, all you have to do is to add it in the QGraphicsLayout of the applet, set the path of a QML file in it et voil

Some updates from the mobile land

Have been quiet on the Plasma mobile land lately but this doesn’t mean there weren’t developments on that, as this small video, on the usual two ugly pieces of hardware, shows two quite foundamental those days features that recently got in.

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Screen rotation, with a nice animation: so now screen rotation is supported both on devices that will rotate the screen in a “traditional” way, by actually rotating the screen resolution, and devices that will rely on the application painting itself rotated (such as MeeGo) in this case such kind of animation becomes possible.
Our on screen keyboard now has also a “compact” mode for mobile devices, you can see it there reduced on the smaller device and full on the bigger one.
More importantly, the keyboad knows when showing itself: when the user taps any editable text area.

Here it is also a smaller video that shows most of the things I’ve talked about in those months. (the nice musical background is by Nuno Povoa, made for the KDE4 launch)

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Plasma: now comes in tablets

When designing Plasma Mobile, it was immediately clear that wouldn’t have been possible to do a “one design fits all” application: mobile devices vould have come in pretty diffrent forms:

Different resolution
Different phisical size
That implies, different DPI
Different use cases: an internet tablet and a phone put the emphasis on very different primary functions

What we have seen right now, is the development of completely different code, from the ground up for different platforms.

In Plasma we always tried to avoid this, by having everything as a plugin, so it will be necessary to replace maybe the shell itself and just the components that really have to be changed.

With Qt 4.7 a new framework ha been introduced: the declarative UI, that permits to do quite fancy stuff in the QML language in a very short time.

So with the development of Plasma mobile we started an experiment, and here it is (usual VESA drivers disclaimer about the speed that applies to all screencasts done on that weird tablet):

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Besides bindings to write plasmoids entirely in QML (or using QML bits into C++ plasmoids), the behaviour of the entire shell, how activities appear/disappear/are chosen is completely controlled by this language, so in theory should be enough to change the QML files set to achieve a completely different ui and behaviour.

In theory. But it gets interesting when this becomes actually practice: with just some adaptions to the C++ code of the shell to make it more flexible, last days I wrote a different QML set and a different default layout configuration aimed for bigger, but still touchscreen based tablets.

Those kind of devices always were for me one of the main targets of the netbook “Newspaper” containment, that’s why a quite big amount of attention has been put into the behaviour of “flicking” arouund things in it.

Here the pages concept is taken to the extreme: you can phisically change pace with a swipe of the finger, dragging the new one into the screen, as you would change real pages 😉

The search and launch interface is dragged in a similar way, but from the bottom, since it should always be quicly available with a single gesture, no matter on what page you are.

This is just a quick proof of concet, but that shows itself very promising for the future.

Plasma Mobile Widgets explorer

Work on Plasma Mobile continues.

Bit after bit all the pieces come together: what’s impressing is how much the Plasma framework we have built into years is paying now.

Plasma Mobile still lacked a widget explorer: the particular formfactor really required a custom one since the one used in the desktop has a pretty different usage pattern and is targeted at a really different form factor (here we are targetting -really- small screen sizes).

I was expecting that writing one could take a quite long amount of time, after all getting there the firt time taken a fair amount of work…

I couldn’t have been more wrong. In less than two days I have now a working widget explorer, that works pretty well on small touch screens, using a mix of QML, Plasma Widgets and C++ models

The main interface is a big flicking icon grid, with a side panel that shows detailed informations on the widget (that can be scrolled with the finger as well).

To add a new widget into the screen, just click at the “+” icon positioned where the widget will be. Interaction wise is way simpler than the Plasma Desktop mechanism, because of both precision of the input device (where with device I mean a fat finger :p) and of screen size (where with size i mean actual phisical size, not pixel resolution)

This little video shows it in action on the usual device. ah, and a curiosity, at some point you see the screen switches to an activity with a big numeric keypad.. that’s not a mockup, as Artur announced during Akademy, if it runs on a N900 phone, that can do actual phone calls.

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Documentation: it has to be done

Plasma has a wonderful theming engine, that enables the creation of a really stunning visual appearance, with a great amount of customizability, just look at what is available right now, to not mention that being vector based makes the widget set pretty flexible and able to be used on really different hardware form factors with different sizes and dpi.

But we’re developers and we like to write code, hack on stuff, we often forget to document things, and this is an area that really can get better.

Yesterday I’ve forced myself to look at the quite incomplete and outdate documentation for the Plasma theme system and I’ve looked file by file, element by element and completed and ordered the whole theme.

Now if you have any doubt on the Plasma theme structure, just go to the relevant techbase page, and you’ll find the complete list of every file and every element in every file, updated to the upcoming 4.5 release. this should ease a lot the construction of themes.

It has been a long and painful work, of which developers may really want to avoid it, but it incredibly pays the effort, because it’s a really important part of the elegance we are trying to reach. A complete, pretty and documented framework is what is elegant to a quite relevant part of our audience: developers that are approaching the platform for the first time.

Now we are restructuring the techbase page for Plasma, moving here the pages that makes more sense here, having the two wikis more in focus and comprehensible.

If you are interested, if you are trying to approach the development in Plasma and have difficulties to grok some of the concepts, if you already work on some plasma aspects such as plasmoids, just stop on #plasma on freenode and you can give an hand in the documenting effort, being tutorials, wiki pages or API docs, you’ll learn quite a lot of the internals in the process and will make easier for others to learn.

Developments on Plasma Mobile

Sometimes we have to clone ourselves 5 or 6 times to manage to do everything. It’s a kind of magic we rarely succeed, but sometimes we do 🙂

Between Akademy and bugfixes for the SC 4.5 release, I managed to get some work done on the Plasma Mobile front, and a quick video of it can be seen there:

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Now there is a new kind of activity for managing widgets there, a new addition to the Desktop (that you normally use on normal computers) and the newspaper (designed for netbooks and big tablets)

This one, that is called mobile desktop, is explicitly tought for very small screens (in phisical size, pixel resolution has nothing to do with size!). It’s based on a big flicking scroll widget, just as the newspaper, because the main method of interaction if a touchscreen, but shows only 2 widgets per screen, (at their minimal size to still make sense)

If you scroll everything around no interaction with the widgets will happen, but if you tap one, it will get maximized, getting a size big enough to be really interacted.

The behaviour of the shell changed a bit as well, since it was quite difficult to hit empty areas to make the whole thing flip, now dragging the panel of the activities, pulls the whole screen, making everything rotate in a 3d way (it has also considerably been optimized for speed)

In the video you can also see the progress of the mobile status indicator summer of code, by Yuen.

More on netbooks, devices and everything

Memory is starting to be fuzzy already, so, since i promised a blog about the same topics on my talk about the netbook, here it is, mostly because the netbook project (but more important its implications in helping Plasma being ported and be optimized for a long spectrum of devices) has really soft spot in my hearth.

We started from the most familiar non-desktop platform: The netbooks, but…

Aren’t netbooks just underpowered little laptops? Indeed today are sold like that, with just still XP or Windows 7 preinstalled, but that’s the reason the interest in them is decreased recently. they are just not good general purpose machines.

But, they are pretty good as devices that can be used on the move to look at online content such as news, emails or social networks, and ultimately as a communication tool, rather that a content production workstation.

KDE SC and Plasma:why?

We still hear again and again that KDE is to heavy and too bloated to run on any modest hardware. Of course technically the situation can be improved and it will, for instance the platform profiles that are being cooked right now will be able to provide a law fat (as in Kevin words 🙂 you will find information about that in the upcoming future on the planet.

n the other hand, complaints are often not completely true, we need better communication about what the advantages of a KDE based solution are, and where the problems are: we pushes the edges of what all the layers of our platform can do, Being Qt, X, or graphics drivers, due to our hard beating the quality of the whole stack is really increasing (and this funningly enough is benefiting non KDE users as well).

About Plasma, it’s the primary UI on desktop, can be on completely different devices too?

Yes, because the Plasma library was designed with no assumptions on a particular form factor in mind. We started from netbooks to taste the waters, because was the less alien one and because we can provide a rich and complete user experience from day one.

What do you want?

Why Plasma can be good on a netbook, on a mediacenter, on a mobile phone?
because it can give people what they want, both to users that actually get to use it and developers, that want to create the most wonderful application in the world with it.

Users

So what users want? they want something useful. Now “useful” can mean different things in different form factors. On a netbook, and even more so on tablets and smartphones, is to be efficient instruments of communication and content fetching, perfect web clients, better than even just a browser.

They want to feel in control: the day for instance the facebook interface will change without them being able to choose they will get pissed, with rich clients there is always a slightly bigger degree of choice.

They want also something beautiful: between two systems that “just work” they will choose the one they find more aesthetically pleasing, even if it’s not technically the best, it’s irrational but it’s the human nature.

Developers

They want a powerful framework to build powerful applications as quickly as possible, Plasma offers a series of common components that makes the life of developers as easy as possible.

Plasma is heavily based on a strong separation between data and the visualization.

Everything in plasma is a plugin the data plugins are Data

Everything you see in Plasma is based on Svg, it’s theme engine makes easy to customize a potentially resolution independent widget set while maintaining pixel perfection.

Its widget set is based on QGraphicsView, like the other Qt widget sets conceived for the mobile, and is possible to integrate and use it together with them.

We have also a flick able scroll widget as well a flick able QtWebkit based one, that is very important, since the future on more and more devices is the touchscreen.

Plasmoids (or plasma widget, more generally), everything you see in a Plasma environment is one of those plugins. they can be specific for a certain formfactor, like kickoff or the taskbar, or they can be quite flexible, like the microblogging plasmoid.

They are done to work well in the desktop, panel, the netbook newspaper, as standalone little windows invoked from krunner (new from 4.5).

So, what about the netbook again?

First thing:window management: the desktop metaphor doesn’t work very well there…

KWin behaves slightly differently there, windows are maximized by default, maximize windows don’t have borders, and the panel is auto hide by default, so quite a lot of pixels are saved for the app

The boundary between primary UI and applications becomes blurred when some of the content can be fetched directly from the desktop, so it becomes a normal window like an application.

Search and Launch

After some usability tests done at Indt last year, what emerged is that Search is more intuitive than browsing trough many items in categories and subcategories. Search and launch uses all the search plugins of KRunner, even if is a completely different UI.

There is still a menu, but it’s flat, doesn’t have tree structure, that doesn’t work well on the human brain.

Of course uses flicking widgets and has an extensive support of drag and drop, that makes quite convenient to use it a mouse or even a stylus.

Netbook: Newspaper

Also the main widget view for the netbook is based on flicking widgets, this gives an infinite vertical space for our widgets, because the free layout of a desktop isn’t space-efficient enough for a small screen, so a layout that can be “browsed” like exactly an actual newspaper, feels more natural there.

Future

What the future reserves us? We need more widgets, especially PIM related, to make the “newspaper” really useful, a GSoc project is helping in this.

Also, the dataengines needs to cache their data for when the network connection is not available, there is a GSoc project working on this too.

Last two points, we need to expand on other devices, because I think netbooks won’t stay the way they are today, they will probably not converge with tablets, but for sure be strongly influenced by them, or become something even different.

Last but not least, the newspaper concept spawned some unintended at first but really interesting developments: two GSoc projects around Kontact and Skrooge, as well some work on KDevelop to provide a “dashboard” of useful widgets in standard desktop applications.

Akademy talk: Slides on the Plasma Netbook project

I gave my presentation today at 17:45, it gone pretty well, despite of the Germany argentina match at the same time (Martin’s KWin result plugin helped too eheh 🙂

Those are the slides, i hope to find time to write some more on that

Akademy talk: The KDE Plasma device spectrum: netbooks and mediacenters

I’ll give a talk at Akademy together with Alessandro Diaferia, so the topc can be easily guessable 🙂

We’ll talk about the adaption of Plasma to completely different use cases to its usual dress, that is to be the main user interface of a desktop system.

In particular i’ll talk more about the Netbook Shell and Alessandro will talk about the media center project.

I’ll leave Alessandro going in more details on the mediacenter, I’ll try instead to answer to some question, some generic, about porting plasma on different devices some specific to the Netbook use case:

Why netbooks need something different?
Why KDE SC is a good platform on non desktop devices?
What Plasma has to offer there?
What has to offer to users?
What about toys for developers?
What are the components of the Netbook shell and why they are designed the way they are?

It will be on Saturday 3 July, 17:45, at the mobile track, stay tuned 😀