The port to KDecoration2 means quite some changes in the way how Aurorae
works. First of all: the theme to load is passed to the Deocoration ctor
and not searched for by Aurorae itself.
The rendering mechanismn didn't change significantly yet. It's still
rendering to an FBO and passing the image on. This needs some further
work as KDecoration2 does not support the padding any more. So all
themes using shadow are currently broken.
Another big change is the way how the rendering scene is constructed
and used. KDecoration2 doesn't want the the Decoration to be a native
window. But for being able to render a QtQuick scene at all we need a
QQuickWindow. Thus it creates a window parented to the decoration id,
but not accepting any input event. Input is nowadays controlled from
the outside: events are passed into the Decoration, so we don't want
the QtQuick window intercepting events.
In case of non-composited the normal FBO mechanism doesn't work and
Aurorae just renders to the QQuickWindow directly. This could use
some optimization in the decoration renderer in KWin core to not even
try to perform the normal rendering. On the other hand it's probably
too much a hassle for the use case.
The rendering architecture might hopefully be improved with Qt 5.4
and the new QQuickRenderControl class.
The QQuickWindow also exposes a problem for preview in the
kdecoration-viewer and the future KCM: we don't want a different
window, but best would be to get to the QML scene directly. A small
hack is added to have the previewers set a "visualParent" which Aurorae
uses to parent the QML scene to without the need to create a
QQuickWindow.
Defines the DecorationButton type in DecorationOptions (needs to be
re-defined due to QML limitations) and exports the buttons as a
QList<int> property (again QML limitations).
All QML files are switched from string to the new enum type.
The Plastik decoration buttons are provided by a declarative
extension plugin as the canvas drawing API would be needed to
draw these buttons. This should be changed with Qt 5.
But it's also a nice example to show how a QML based decoration
can have an extension in C++.
