[RFC] wl_surface scale and crop protocol extension
John Kåre Alsaker
john.kare.alsaker at gmail.com
Tue Apr 30 07:06:02 PDT 2013
I'd say we should split the cropping and scaling request into two.
Specifying a scaling with a NULL buffer should still set the surface size,
so we can have surfaces with only an input region.
I don't see a way to disable scaling and cropping, could passing 0 as width
and height do that?
On Tue, Apr 30, 2013 at 2:33 PM, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> Hi all,
> below is my first draft for a wl_surface scaling and cropping
> extension. I called it wl_scaler in the lack of a better name. It is
> designed similarly to the other wl_surface extensions wl_shell_surface
> and wl_subsurface.
> There probably isn't any interesting details to debate, right? ;-)
> I'd like to have a better name for it, and you might want the set
> request split into two or three, or not, but otherwise I'm quite
> satisfied with it. I tried to take into account all existing protocol
> that interacts with this.
> Comments? Is the language clear?
> <?xml version="1.0" encoding="UTF-8"?>
> <protocol name="scaler">
> Copyright © 2013 Collabora, Ltd.
> Permission to use, copy, modify, distribute, and sell this
> software and its documentation for any purpose is hereby granted
> without fee, provided that the above copyright notice appear in
> all copies and that both that copyright notice and this permission
> notice appear in supporting documentation, and that the name of
> the copyright holders not be used in advertising or publicity
> pertaining to distribution of the software without specific,
> written prior permission. The copyright holders make no
> representations about the suitability of this software for any
> purpose. It is provided "as is" without express or implied
> THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
> SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
> FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY
> SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
> WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
> AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
> ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
> THIS SOFTWARE.
> <interface name="wl_scaler" version="1">
> <description summary="surface cropping and scaling">
> The global interface exposing surface cropping and scaling
> capabilities is used to instantiate an interface extension for a
> wl_surface object. This extended interface will then allow
> cropping and scaling the surface contents, effectively
> disconnecting the 1:1 relationship between the buffer and the
> surface size.
> <request name="destroy" type="destructor">
> <description summary="unbind from the cropping and scaling
> Informs the server that the client will not be using this
> protocol object anymore. This does not affect any other objects,
> wl_surface_scaler objects included.
> <enum name="error">
> <entry name="scaler_exists" value="0"
> summary="the surface already has a scaler object associated"/>
> <request name="get_surface_scaler">
> <description summary="extend surface interface for crop and scale">
> Instantiate an interface extension for the given wl_surface to
> crop and scale its content. If the given wl_surface already has
> a wl_surface_scaler object associated, the scaler_exists
> protocol error is raised.
> <arg name="id" type="new_id" interface="wl_surface_scaler"
> summary="the new scaler interface id"/>
> <arg name="surface" type="object" interface="wl_surface"
> summary="the surface"/>
> <interface name="wl_surface_scaler" version="1">
> <description summary="crop and scale interface to a wl_surface">
> An additional interface to a wl_surface object, allowing cropping
> and scaling of the surface contents.
> This interface allows to define the source rectangle (src_x,
> src_y, src_width, src_height) from where to take the wl_buffer
> contents, and scale that to destination size (dst_width,
> dst_height). This state is double-buffered, and is applied on the
> next wl_surface.commit.
> Before the first set request, the wl_surface still behaves as if
> there was no crop and scale state. That is, no scaling is applied,
> and the surface size is the buffer size.
> On compositing, source rectangle coordinates are evaluated after
> wl_surface.set_buffer_transform is evaluated. This means that
> changing the buffer transform and correspondingly the client
> rendering does not require sending new source rectangle
> coordinates to keep the exact same image source rectangle. In
> other words, the source rectangle is given in the
> not-scaled-and-cropped surface coordinates, not buffer data
> The crop and scale state causes the surface size to become
> dst_width, dst_height. This overrides whatever the attached
> wl_buffer size is, unless the wl_buffer is NULL.
> The surface-local coordinate system is tied to the space of
> dst_width and dst_height. That is, surface-local coordinates are
> relative to the scaled and cropped surface, not the wl_buffer
> providing the content.
> If the source rectangle is partially or completely outside of the
> wl_buffer, then the surface contents are undefined, and the
> surface size is still dst_width, dst_height.
> The x, y arguments of wl_surface.attach are applied as normal to
> the surface. They indicate how many pixels to remove from the
> surface size from the left and the top. In other words, they are
> still in the surface-local coordinate system, just like dst_width
> and dst_height are.
> If the wl_surface associated with the wl_surface_scaler is
> destroyed, the wl_surface_scaler object becomes inert.
> If the wl_surface_scaler object is destroyed, the crop and scale
> state is removed from the wl_surface. The change will be applied
> on the next wl_surface.commit.
> <request name="destroy" type="destructor">
> <description summary="remove scaling and cropping from the surface">
> The associated wl_surface's crop and scale state is removed.
> The change is applied on the next wl_surface.commit.
> <enum name="error">
> <entry name="bad_value" value="0"
> summary="negative values in width or height"/>
> <request name="set">
> <description summary="set the crop and scale state">
> Set the crop and scale state of the associated wl_surface. See
> wl_surface_scaler for the description, and relation to the
> wl_buffer size.
> If any of src_width, src_height, dst_width, and dst_height is
> negative, the bad_value protocol error is raised.
> <arg name="src_x" type="fixed" summary="source rectangle x"/>
> <arg name="src_y" type="fixed" summary="source rectangle y"/>
> <arg name="src_width" type="fixed" summary="source rectangle width"/>
> <arg name="src_height" type="fixed" summary="source rectangle
> <arg name="dst_width" type="int" summary="surface width"/>
> <arg name="dst_height" type="int" summary="surface height"/>
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