The general idea is: single click opens menu, double click closes
the window. The problem is that the when the menu is opened after
the single click, the menu will eat the second click. So double
click will not work.
This commit brings back the workaround from Aurorae2. The clicked
event is not used at all, but we start a timer on the press event
with the doubleClickInterval. If no double click appears during the
interval we open the menu, if there is a double click we close the
window.
The downside of this approach is that there is a slight delay between
clicking the menu button and the menu appearing. For that the right
click behavior is unchanged. That is right clicking opens the menu
instantly and double click to close it, is broken.
Buttons are exported as a global "options" in the factory.
Additionally the theme's buttons are also exported. The thme decided
based on the custom button positions property which one to use.
In the kcm the button options are also exported.
Each decoration gets a graphicsview and scene instead and a declarative
item is created for each decoration.
There's probably still room for improvments. E.g. never render the
scene onto the widget but directly into the textures?
Switches to the explicit maximized decoration element and animates
the button groups and caption.
Legacy support for just the centered element is still missing. Unsure
if it should be added or if it makes sense to break compatibility here.
What's working:
* background for active and inactive decorations inclusive transitions
* all buttons get loaded
* transition between button states
* all borders, paddings etc is working
* mouse interaction with buttons and title area
What's not yet working:
* special maximize mode
* mouse wheel on title area
* window tabs
* changing themes
* crash resistence (currently a not compiling QML file crashes KWin badly)
* window/blur mask (tricky - we need the alpha mask of the background SVG)
What's going to be dropped:
* special opaque mode
* decoration position at left/right/bottom instead of top
Why? Because nobody uses these features
