Plasma new animation classes

December 10, 2009 at 7:59 pm 2 comments

One of KDE 4 objectives was to create an organic and even more pleasant environment (and it is being achieved with both plasma-desktop and plasma-netbook). One of the features that contributes significantly to achieve a natural look and feel (together with really *great artwork*) are animations.

KDE 4 introduced plasma Animator class with the purpose of applying effects and animations to plasma widgets. With the new Qt 4.6 animation framework (a.k.a. kinetic), plasma effects started to be ported to it, introducing some new animations (e.g. Pulse, Rotation, Stacked rotation, kinetic scrolling) which are already being used in the upcoming KDE SC 4.4.

Kinetic scrolling made its debut in Plasma::ScrollWidget, used internally in uBlog (the twitter/identica plasmoid client) and plasma-netbook (i.e. to scroll through icons in application containment). It has a long story and was rewritten at least 4 times:
– Using a single timer and coordinates for scrolling (with bouncing effect);
– Using percentages for scrolling and properties for position;
– Using coordinates with properties again and implementing the concept of scrolling manager;
– Using QPropertyAnimation to do the animation instead of a timer (and having the bouncing by just changing the easing curve)

The new plasma animation classes has also an interesting story, being submitted through at least 4 big refactorings:
– Initial import based on gSoC project done by Mehmet Ali Akmanalp;
– Animation objects caching;
– Using QAbstractAnimation as base class;
– Reimplementing QAbstractAnimation::updateCurrentTime and non longer using an internal QPropertyAnimation/Group object to actually do the animation;

The good news are that the code is being made more flexible and paradoxically simpler at each review session. What about an example? Say that you want to have that nice pulse effect when a widget name button (i.e.that has QGraphicsWidget as base) is selected you just need to write something like this:

Animation *pulseAnim = Animator::create(Animator::PulseAnimation);
connect(button, SIGNAL(clicked()), pulseAnim, SLOT(start()));

And the same concept is used for the following animations: rotation (2D), fade, grow, zoom, slide, stacked rotation (‘3D’), geometry. Obviously, that depending on the animation type, you got to setup more parameters, like movement direction/reference/distance/axis. Selecting easing curves is also possible, but we are working to have good pre-selected curves that makes sense for each animation class.

Those plasma animations can easily be integrated together with your own animations and directly used in animation groups (i.e. QAnimationGroup) being parallel or linear. Finally, all those classes are being bind with javascript making it dirty easy to have future js plasmoids with nice animations.

So, where to start now? My suggestion is to have a look in kdeexamples where there is a test C++ plasmoid that exercises pretty much all the current available animations.

Next post: video showing the animations. 🙂


Entry filed under: KDE, linux, Qt.

Nokia Booklet 3G: KDE and plasma Plasma new animation classes: video

2 Comments Add your own

  • 1. Diederik van der Boor  |  December 10, 2009 at 8:31 pm


    out of curiosity, what was the reason to implement an animation framework on top of Qt Kinetic? Concistency, or is the kinetic API too hard to use? Guess you have a good reason for it, and I’m curious nevertheless.

    • 2. savago  |  December 10, 2009 at 8:45 pm

      Hello Diederik

      It is not a ‘framework’, they are a set of classes with ready to use animations (based on QAbstractAnimation class). This helps to improve consistency around plasma desktop and also makes libplasma users (i.e. programmers) life easier.

      Best regards



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