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staging/color-management: target color volume defines the bounds

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In an attempt to specify clipping behavior[1] it was found that it would
lead to predictable behavior turning into undefined behavior when a
compositor gains support for extended_color_volume. That would be
awkward.

Instead of specifying clipping to the primary color volume bounds (which
may then disappear), let's leave it undefined, and emphasize the
undefined-ness of exceeding the target color volume instead.

[1]: https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/453

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>
This commit is contained in:
Pekka Paalanen 2025-10-20 17:02:30 +03:00
parent 0b8283f7f3
commit ce96b5f177
1 changed files with 20 additions and 9 deletions
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29
staging/color-management/color-management-v1.xml
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@ -674,18 +674,18 @@
All image descriptions which are ready (see wp_image_description_v1)
are allowed and must always be accepted by the compositor.
A rendering intent provides the client's preference on how content
colors should be mapped to each output. The render_intent value must
be one advertised by the compositor with
When an image description is set on a surface, it establishes an
explicit link between surface pixel values and surface colorimetry.
This link may be undefined for some pixel values, see the image
description creator interfaces for the conditions. Non-finite
floating-point values (NaN, Inf) always have an undefined colorimetry.
A rendering intent provides the client's preference on how surface
colorimetry should be mapped to each output. The render_intent value
must be one advertised by the compositor with
wp_color_manager_v1.render_intent event, otherwise the protocol error
render_intent is raised.
When an image description is set on a surface, the Transfer
Characteristics of the image description defines the valid range of
the nominal (real-valued) color channel values. The processing of
out-of-range color channel values is undefined, but compositors are
recommended to clamp the values to the valid range when possible.
By default, a surface does not have an associated image description
nor a rendering intent. The handling of color on such surfaces is
compositor implementation defined. Compositors should handle such
@ -834,6 +834,10 @@
Once all properties have been set, the create request must be used to
create the image description object, destroying the creator in the
process.
The link between a pixel value (a device value in ICC) and its respective
colorimetry is defined by the details of the particular ICC profile.
Those details also determine when colorimetry becomes undefined.
</description>
<enum name="error">
@ -964,6 +968,13 @@
description (the viewing environment included), is assumed to be fully
adapted to the primary color volume's white point.
Any of the following conditions will cause the colorimetry of a pixel
to become undefined:
- Values outside of the defined range of the transfer characteristic.
- Tristimulus that exceeds the target color volume.
- If extended_target_volume is not supported: tristimulus that exceeds
the primary color volume.
The closest correspondence to an image description created through this
interface is the Display class of profiles in ICC.
</description>