On Mon, Nov 30, 2015 at 10:55:04AM -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.
The new text is IMHO an improvement, so Reviewed-by: Jonas Ådahl <jad...@gmail.com> Jonas > > This will eventually resolve: > https://bugs.freedesktop.org/show_bug.cgi?id=78190 > by making the problem irrelevant. > > Reviewed-by: Pekka Paalanen <pekka.paala...@collabora.co.uk> > Reviewed-by: Jason Ekstrand <ja...@jlekstrand.net> > Signed-off-by: Derek Foreman <der...@osg.samsung.com> > --- > > v5 changes from v4: > replaced the last paragraph with Jason's new text explaining the same thing > with a less "you must implement it this way" vibe to it. > > I've kept Pekka and Jason's RBs on this as that seemed appropriate from > the conversation (pekka approved the new test, Jason wrote it) - Jonas' > has been dropped because he hasn't yet signed off on the new text. > > protocol/wayland.xml | 50 ++++++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 48 insertions(+), 2 deletions(-) > > diff --git a/protocol/wayland.xml b/protocol/wayland.xml > index f9e6d76..7ca5049 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 +1329,48 @@ > </description> > <arg name="scale" type="int"/> > </request> > + > + <!-- Version 4 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. > + > + Note: Because buffer transformation changes and damage requests may > + be interleaved in the protocol stream, It is impossible to determine > + the actual mapping between surface and buffer damage until > + wl_surface.commit time. Therefore, compositors wishing to take both > + kinds of damage into account will have to accumulate damage from the > + two requests separately and only transform from one to the other > + after receiving the wl_surface.commit. > + </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
