[PATCH wayland v2] protocol: Add wl_surface.damage_buffer

[Jonas Ådahl]

On Wed, Nov 18, 2015 at 04:17:58PM -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 <derekf at osg.samsung.com>
> ---
> 
> Differnces from v1:
>  - Don't make such a big deal about GL in the request documentation
>  - rename the request about 3 times, eventually settle on damage_buffer
>  - don't say anything about mixing damage and damage_buffer
> 
>  protocol/wayland.xml | 44 ++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 42 insertions(+), 2 deletions(-)
> 
> diff --git a/protocol/wayland.xml b/protocol/wayland.xml
> index 9c22d45..7665307 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.
> @@ -1111,6 +1111,10 @@
>  	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"/>
> @@ -1327,6 +1331,42 @@
>        </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 pending buffer
> +	must be set by wl_surface.attach before sending damage. The

I guess the order of attach and damage_buffer here should be dropped, as
we are dropping it from wl_surface.damage already.

> +	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.  While this generally is more intuitive than surface
> +	co-ordinates, it is especially desirable when using wl_viewport

s/wl_viewport/wp_viewport/.

With those two fixed: Reviewed-by: Jonas Ådahl <jadahl at gmail.com>


Jonas


> +	or when a drawing library (like EGL) is unaware of buffer scale
> +	and buffer transform.
> +      </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 at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/wayland-devel