LGTM Reviewed-by: Jason Ekstrand <jason.ekstr...@intel.com>
On Thu, Aug 21, 2014 at 2:52 AM, Pekka Paalanen <ppaala...@gmail.com> wrote: > From: Pekka Paalanen <pekka.paala...@collabora.co.uk> > > Define what a role is, and what restrictions there are. > > A change to existing behaviour is that a role cannot be changed at all > once set. However, this is unlikely to cause problems, as there is no > reason to re-use wl_surfaces in clients. > > v2: give more concrete examples of roles, define losing a role, Jasper > rewrote the paragraph on how a role is set. > > v3: make role permanent, there is no such thing as "losing a role". > Re-issuing the same role again must be allowed for wl_pointer.set_cursor > et al. to work. > > v4: clarify the semantics of destroying a role object. > > Signed-off-by: Pekka Paalanen <pekka.paala...@collabora.co.uk> > --- > protocol/wayland.xml | 33 +++++++++++++++++++++++++++++++-- > 1 file changed, 31 insertions(+), 2 deletions(-) > > diff --git a/protocol/wayland.xml b/protocol/wayland.xml > index bb457bc..621c64d 100644 > --- a/protocol/wayland.xml > +++ b/protocol/wayland.xml > @@ -973,8 +973,37 @@ > local coordinates of the pixel content, in case a buffer_transform > or a buffer_scale is used. > > - Surfaces are also used for some special purposes, e.g. as > - cursor images for pointers, drag icons, etc. > + A surface without a "role" is fairly useless, a compositor does > + not know where, when or how to present it. The role is the > + purpose of a wl_surface. Examples of roles are a cursor for a > + pointer (as set by wl_pointer.set_cursor), a drag icon > + (wl_data_device.start_drag), a sub-surface > + (wl_subcompositor.get_subsurface), and a window as defined by a > + shell protocol (e.g. wl_shell.get_shell_surface). > + > + A surface can have only one role at a time. Initially a > + wl_surface does not have a role. Once a wl_surface is given a > + role, it is set permanently for the whole lifetime of the > + wl_surface object. Giving the current role again is allowed, > + unless explicitly forbidden by the relevant interface > + specification. > + > + Surface roles are given by requests in other interfaces such as > + wl_pointer.set_cursor. The request should explicitly mention > + that this request gives a role to a wl_surface. Often, this > + request also creates a new protocol object that represents the > + role and adds additional functionality to wl_surface. When a > + client wants to destroy a wl_surface, they must destroy this 'role > + object' before the wl_surface. > + > + Destroying the role object does not remove the role from the > + wl_surface, but it may stop the wl_surface from "playing the role". > + For instance, if a wl_subsurface object is destroyed, the wl_surface > + it was created for will be unmapped and forget its position and > + z-order. It is allowed to create a wl_subsurface for the same > + wl_surface again, but it is not allowed to use the wl_surface as > + a cursor (cursor is a different role than sub-surface, and role > + switching is not allowed). > </description> > > <enum name="error"> > -- > 1.8.5.5 > >
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