[PATCH weston 4/8] protocol: crop & scale RFC v3
jonny.lamb at collabora.co.uk
Tue Nov 26 09:19:44 PST 2013
From: Pekka Paalanen <ppaalanen at gmail.com>
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.
Should this be a separate interface like here, or just a wl_surface
If we keep this as a separate interface, rename wl_surface_scaler to
protocol/Makefile.am | 1 +
protocol/scaler.xml | 156 +++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 157 insertions(+)
create mode 100644 protocol/scaler.xml
diff --git a/protocol/Makefile.am b/protocol/Makefile.am
index 14a4b5a..814e8fd 100644
@@ -7,6 +7,7 @@ protocol_sources = \
+ scaler.xml \
diff --git a/protocol/scaler.xml b/protocol/scaler.xml
new file mode 100644
@@ -0,0 +1,156 @@
+<?xml version="1.0" encoding="UTF-8"?>
+ 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 direct relationship between the buffer and the
+ surface size.
+ <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.
+ <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, which allows the
+ client to specify the cropping and scaling of the surface
+ 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.
+ <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.
+ The bad_value protocol error is raised if src_width or
+ src_height is negative, or if dst_width or dst_height is not
+ 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.
+ <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"/>
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