Once upon a time there was a window decoration which was KDE’s default decoration. But years ago it fell into a deep sleep. The world changed while the decoration slept. Compositing was added, decorations received shadows, Qt introduced the graphics system raster and many many more changes.
Now after years the decoration temporarily woke up, but it is no longer a beauty, but ugly and old. The changing world made the decoration break. The decoration’s bits started to rot and this is visible. The truth is that the decoration will stay in the broken state as there is nobody who would want to fix it or anybody knowing the code.
What I just highlighted here is true for basically all old decorations. Of the decorations we ship only Oxygen and my theme engine Aurorae are maintained. This is a situation which can no longer continue. We have to face the truth and remove all old decorations.
But of course we don’t want to remove decorations without adequate replacement and this leads us to the story of Aurorae.
Aurorae was written to experiment with new features introduced in KWin 4.3. It was based on our common decoration API and by that is rather limited. So for 4.5 I decided to port it to the generic decoration API and reimplement with GraphicsScene instead of QWidgets. Aurorae allowed to download decorations through Get Hot New Stuff.
But given that it is a theme engine the possibilities are still very limited. Only what the theme engine supports can be rendered. Porting our old decorations to the theme engine might not be possible and not to be recommended.
But still we would like to have those decorations on a modern basis without the maintenance costs. So I started to port Aurorae to QML. This does not only give us a more powerful theme engine but also introduces QML bindings for window decorations, allowing everybody to write decorations with QtQuick.
So we can write themes without the limitations of a theme engine This does not only remove 3000 lines of C++ code and replaces it by around 1000 lines of QML code, but also gives us an interactive decoration control module.
For Aurorae based themes all the buttons are interactive giving our users the possibility to really try the decoration before using it. But that’s not where it will end. I want to have new themes not based on Aurorae but using QML directly. For that I want to use the Plasma Package structure and would love to see integration in Plasmate. Another idea is to support deKorator themes inside QML.
But as always this does not come without disadvantages. Not all features which were possible with Aurorae will be available in Aurorae 3. Some features will also be dropped because hardly any theme makes use of the features, for example special backgrounds for non-composited setups. Aurorae 3 will hardly work without compositing, so it might be that we will make it a hard requirement somehow.
I hope to see many innovative QML based window decorations in 4.9.