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protocol: crop & scale RFC v3

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Add cropping and scaling to wl_surface.

Add a global factory interface wl_scaler, which creates
wl_scaler_surface objects tied to a given wl_surface. The
wl_scaler_surface object can be used to set a cropping and scaling
transformation to change how a wl_buffer maps to wl_surface contents.

Changes in v2:

Take into account buffer_transform and buffer_scale, and try to explain
more clearly how the coordinate transformations work and what their
order is. Add, that crop and scale state is double-buffered. Explain
missing dst_x, dst_y.  Clarify that undefined content still is some
content, but NULL buffer implies no content nor size.

Changes in v3:

Disallow zero values for dst_width and dst_height.

Open issues:

Should this be a separate interface like here, or just a wl_surface
request?

If we keep this as a separate interface, rename wl_surface_scaler to
wl_viewport.
dev
Pekka Paalanen 11 years ago committed by Kristian Høgsberg
parent 5c11a3340b
commit f565d80ff5
2 changed files with 158 additions and 1 deletions
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  1. 3
      protocol/Makefile.am
  2. 156
      protocol/scaler.xml

3
protocol/Makefile.am
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@ -7,7 +7,8 @@ protocol_sources = \
workspaces.xml \
text-cursor-position.xml \
wayland-test.xml \
xdg-shell.xml
xdg-shell.xml \
scaler.xml
if HAVE_XMLLINT
.PHONY: validate

156
protocol/scaler.xml
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@ -0,0 +1,156 @@
<?xml version="1.0" encoding="UTF-8"?>
<protocol name="scaler">
<copyright>
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
warranty.
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.
</copyright>
<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 direct relationship between the buffer and the
surface size.
</description>
<request name="destroy" type="destructor">
<description summary="unbind from the cropping and scaling interface">
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.
</description>
</request>
<enum name="error">
<entry name="scaler_exists" value="0"
summary="the surface already has a scaler object associated"/>
</enum>
<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.
</description>
<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"/>
</request>
</interface>
<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, which allows the
client to specify the 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 as defined in wl_surface.attach.
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. If the wl_buffer is
NULL, the surface has no content and therefore no size.
The coordinate transformations from buffer pixel coordinates up to
the surface-local coordinates happen in the following order:
1. buffer_transform (wl_surface.set_buffer_transform)
2. buffer_scale (wl_surface.set_buffer_scale)
3. crop and scale (wl_surface_scaler.set)
This means, that the source rectangle coordinates of crop and scale
are given in the coordinates after the buffer transform and scale,
i.e. in the coordinates that would be the surface-local coordinates
if the crop and scale was not applied.
If the source rectangle is partially or completely outside of the
wl_buffer, then the surface contents are undefined (not void), 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.
</description>
<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.
</description>
</request>
<enum name="error">
<entry name="bad_value" value="0"
summary="negative values in width or height"/>
</enum>
<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.
The bad_value protocol error is raised if src_width or
src_height is negative, or if dst_width or dst_height is not
positive.
The crop and scale state is double-buffered state, and will be
applied on the next wl_surface.commit.
Arguments dst_x and dst_y do not exist here, use the x and y
arguments to wl_surface.attach. The x, y, dst_width, and dst_height
define the surface-local coordinate system irrespective of the
attached wl_buffer size.
</description>
<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 height"/>
<arg name="dst_width" type="int" summary="surface width"/>
<arg name="dst_height" type="int" summary="surface height"/>
</request>
</interface>
</protocol>
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