This allows you to configure the width of each side of the border
individually. border.width can still be used, and will set all four
borders to the same width.
Closes#77
This is an integer that specifies the amount of scrolling that needs
to be accumulated before a wheel-up/down event is emitted.
A higher value means you need to drag your fingers a longer distance
before the event is emitted.
The default is 30.
This allows the backend to support multi-seat "properly", by checking
against the correct seat. Before this, when we used a single, global
xcursor value, a seat whose pointer needed to be updated would not be
updated.
This is trivial in the Wayland backend; just instantiate a pixman
pointing to the same mmapped memory as the wayland buffer.
In the XCB backend, we change the implementation slightly; instead of
rendering via a cairo XCB surface backend (to a server side pixmap),
which is then blitted to the window in commit(), we now render to a
client-side pixman pixmap, and blit it using xcb_put_image() in
commit().
All decoration, particle and module interfaces now takes a
pixman_image_t parameter, and all drawing is done using pixman APIs.
The wayland/xcb backends implement a new interface functions,
get_pixman_image(), that should return a pixman image instance that is
suitable for rendering.
In the wayland backend, the image uses the same backing data as the
cairo surface.
In the XCB backend, we create a new image each time, and then blit it
to the cairo surface at commit time.
