On Fri, 27 Nov 2015 16:47:19 +0800 Jonas Ådahl <jad...@gmail.com> wrote:
> On Thu, Nov 26, 2015 at 03:44:12PM -0600, Derek Foreman wrote: > > wl_surface.damage uses surface local co-ordinates. > > > > Buffer scale and buffer transforms came along, and EGL surfaces > > have no understanding of them. > > > > Theoretically, clients pass damage rectangles - in Y-inverted surface > > co-ordinates) to EGLSwapBuffersWithDamage, and the EGL implementation > > passed them on to wayland. However, for this to work the EGL > > implementation must be able to flip those rectangles into the space > > the compositor is expecting, but it's unable to do so because it > > doesn't know the height of the transformed buffer. > > > > So, currently, EGLSwapBuffersWithDamage is unusable and EGLSwapBuffers > > has to pass (0,0) - (INT32_MAX, INT32_MAX) damage to function. > > > > wl_surface.damage_buffer allows damage to be registered on a surface > > in buffer co-ordinates, avoiding this problem. > > > > Credit where it's due, these ideas are not entirely my own: > > Over a year ago the idea of changing damage co-ordinates to buffer > > co-ordinates was suggested (by Jason Ekstrand), and it was at least > > partially rejected and abandoned. At the time it was also suggested > > (by Pekka Paalanen) that adding a new wl_surface.damage_buffer request > > was another option. > > > > This will eventually resolve: > > https://bugs.freedesktop.org/show_bug.cgi?id=78190 > > by making the problem irrelevant. > > > > Signed-off-by: Derek Foreman <der...@osg.samsung.com> > > Reviewed-by: Jonas Ådahl <jad...@gmail.com>, with a couple of comments > below. Reviewed-by: Pekka Paalanen <pekka.paala...@collabora.co.uk> ... > > --- > > > > Changes from v3: > > replaced the last paragraph with Pekka's version > > (with one tiny grammar change) > > > > protocol/wayland.xml | 49 +++++++++++++++++++++++++++++++++++++++++++++++-- > > 1 file changed, 47 insertions(+), 2 deletions(-) > > > > diff --git a/protocol/wayland.xml b/protocol/wayland.xml > > index f9e6d76..4e97bb9 100644 > > --- a/protocol/wayland.xml > > +++ b/protocol/wayland.xml > > @@ -176,7 +176,7 @@ > > </event> > > </interface> > > > > - <interface name="wl_compositor" version="3"> > > + <interface name="wl_compositor" version="4"> > > <description summary="the compositor singleton"> > > A compositor. This object is a singleton global. The > > compositor is in charge of combining the contents of multiple > > @@ -986,7 +986,7 @@ > > </event> > > </interface> > > > > - <interface name="wl_surface" version="3"> > > + <interface name="wl_surface" version="4"> > > <description summary="an onscreen surface"> > > A surface is a rectangular area that is displayed on the screen. > > It has a location, size and pixel contents. > > @@ -1109,6 +1109,10 @@ > > wl_surface.commit assigns pending damage as the current damage, > > and clears pending damage. The server will clear the current > > damage as it repaints the surface. > > + > > + Alternatively, damage can be posted with wl_surface.damage_buffer > > + which uses buffer co-ordinates instead of surface co-ordinates, > > + and is probably the preferred and intuitive way of doing this. > > </description> > > > > <arg name="x" type="int"/> > > @@ -1325,6 +1329,47 @@ > > </description> > > <arg name="scale" type="int"/> > > </request> > > + > > + <!-- Version 4 additions --> > > Bikeshed mode enabled: missing empty line between "Version N additions" > and actual additions. > > > + <request name="damage_buffer" since="4"> > > + <description summary="mark part of the surface damaged using buffer > > co-ordinates"> > > + This request is used to describe the regions where the pending > > + buffer is different from the current surface contents, and where > > + the surface therefore needs to be repainted. The compositor > > + ignores the parts of the damage that fall outside of the surface. > > + > > + Damage is double-buffered state, see wl_surface.commit. > > + > > + The damage rectangle is specified in buffer coordinates. > > + > > + The initial value for pending damage is empty: no damage. > > + wl_surface.damage_buffer adds pending damage: the new pending > > + damage is the union of old pending damage and the given rectangle. > > + > > + wl_surface.commit assigns pending damage as the current damage, > > + and clears pending damage. The server will clear the current > > + damage as it repaints the surface. > > + > > + This request differs from wl_surface.damage in only one way - it > > + takes damage in buffer co-ordinates instead of surface local > > + co-ordinates. While this generally is more intuitive than surface > > + co-ordinates, it is especially desirable when using wp_viewport > > + or when a drawing library (like EGL) is unaware of buffer scale > > + and buffer transform. > > + > > + Since it is impossible to convert between buffer and surface > > + co-ordinates until all the possible parameters affecting the > > + surface size and the buffer-surface mapping are known at > > + wl_surface.commit time, damage from wl_surface.damage and > > + wl_surface.damage_buffer must be accumulated separately in a > > + compositor and combined during wl_surface.commit at the earliest. > > As Jason already pointed out, this looks out of place. With some > imagination, it might also not entirely true. A compositor may put > damage "together" in a single list, with "transform this way" flags next > to regions in different coordinate spaces, and then later process and > combine at commit when all information is available. Sure, it makes > little sense to do things this way, but it wouldn't be wrong while > still, depending on how interpreted, not really doing what the above > paragraph said. Yeah. It's implementation guideline for compositor writers. Maybe it should have started by stating that, so that client writers don't get confused. I suppose we all agree that in lack of better wording for the moment, this is good to land. If someone comes up with a better wording, we can patch that later. I restored a couple of CCs, and since 26th was thanksgiving in the US, maybe this should land early next week if no-one objects. Thanks, pq > > + </description> > > + > > + <arg name="x" type="int"/> > > + <arg name="y" type="int"/> > > + <arg name="width" type="int"/> > > + <arg name="height" type="int"/> > > + </request> > > </interface> > > > > <interface name="wl_seat" version="5"> > > -- > > 2.6.2 > > > > _______________________________________________ > > wayland-devel mailing list > > wayland-devel@lists.freedesktop.org > > http://lists.freedesktop.org/mailman/listinfo/wayland-devel
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