The description for wl_surface.damage should be shortened to a minimal indication that this is for back-compatibility only and that refer to the buffer_damage request. Something like "identical to buffer_damage if the buffer and surface coordinates are equal, otherwise the behaviour is undefined".
On Fri, Nov 6, 2015 at 11:08 AM, Jasper St. Pierre <jstpie...@mecheye.net> wrote: > To help clear things up, I think we should deprecate the > wl_surface.damage request and document that the coordinates are > effectively undefined -- for legacy reasons, if you see > wl_surface.damage, it should be considered a damage for the entire > surface. > > On Fri, Nov 6, 2015 at 10:55 AM, Derek Foreman <der...@osg.samsung.com> > 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.buffer_damage 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.buffer_damage request > > was another option. > > > > Signed-off-by: Derek Foreman <der...@osg.samsung.com> > > --- > > > > Necro-posting on: > > > http://lists.freedesktop.org/archives/wayland-devel/2014-February/013440.html > > and > > > http://lists.freedesktop.org/archives/wayland-devel/2014-February/013442.html > > > > This came up on IRC again the other day, and it's still an unsolved > problem... > > I'm posting this as RFC to see if anyone's interested in it - I'll do an > > implementation if we can get an agreement on the protocol text. > > > > protocol/wayland.xml | 44 ++++++++++++++++++++++++++++++++++++++++++-- > > 1 file changed, 42 insertions(+), 2 deletions(-) > > > > diff --git a/protocol/wayland.xml b/protocol/wayland.xml > > index 9c22d45..1cb2f66 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. > > @@ -1327,6 +1327,46 @@ > > </description> > > <arg name="scale" type="int"/> > > </request> > > + > > + <!-- Version 4 additions --> > > + <request name="buffer_damage" 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 pending buffer > > + must be set by wl_surface.attach before sending damage. 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 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. This is desirable because EGL implementations > > + are unaware of buffer scale and buffer transform and can only > > + provide damage in buffer co-ordinates. Damage in buffer > > + co-ordinates is required for EGLSwapBuffersWithDamage to work > > + efficiently. > > + > > + Mixing wl_surface.buffer_damage and wl_surface.damage requests > > + on the same surface will result in undefined behaviour. > > + </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"> > > -- > > 2.6.1 > > > > _______________________________________________ > > wayland-devel mailing list > > wayland-devel@lists.freedesktop.org > > http://lists.freedesktop.org/mailman/listinfo/wayland-devel > > > > -- > Jasper > _______________________________________________ > wayland-devel mailing list > wayland-devel@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/wayland-devel >
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