Merge branch 'mr/nosrgbtf' into 'main'

staging/color-management: replace two-piece TF

See merge request wayland/wayland-protocols!442

staging/color-management/appendix.md

@@ -53,6 +53,22 @@ The above are specified by [ITU-R BT.1886].
 Note, that $`E < 0`$ and $`E > 1`$ are possible with limited range
 quantization, as required by e.g. the calibration method in [ITU-R BT.814].
 
+### `compound_power_2_4`
+
+```math
+O = \begin{cases}
+\frac{E}{12.92}, & 0 \leq E < 0.04045\\
+\left( \frac{E + 0.055}{1.055} \right)^{2.4}, & 0.04045 \leq E \leq 1
+\end{cases}
+```
+
+The above is the IEC 61966-2-1 piece-wise transfer function,
+as recorded in [Khronos Data Format Specification][KDFS] 1.4.0
+Section 13.3, and restricted to the unit range.
+
+```math
+L = (L_W - L_B)O + L_B
+```
 
 ### `gamma22`
 
@@ -125,3 +141,4 @@ L = 10'000\ \mathrm{cd/m²} \cdot O + L_B
 [ITU-R BT.814]: https://gitlab.freedesktop.org/pq/color-and-hdr/-/blob/main/doc/specs.md#itu-r-bt814
 [ITU-R BT.1886]: https://gitlab.freedesktop.org/pq/color-and-hdr/-/blob/main/doc/specs.md#itu-r-bt1886
 [ITU-R BT.2100]: https://gitlab.freedesktop.org/pq/color-and-hdr/-/blob/main/doc/specs.md#itu-r-bt2100
+[KDFS]: https://registry.khronos.org/DataFormat/

staging/color-management/color-management-v1.xml

@@ -288,8 +288,7 @@
           - United States Federal Communications Commission (2003) Title 47 Code
             of Federal Regulations 73.682 (a) (20)
           - Rec. ITU-R BT.1700-0 625 PAL and 625 SECAM
-
-          Note: an sRGB display (IEC 61966-2-1) uses this transfer function.
+          - IEC 61966-2-1 (reference display)
         </description>
       </entry>
       <entry name="gamma28" value="3">
@@ -326,18 +325,18 @@
           - IEC 61966-2-4
         </description>
       </entry>
-      <entry name="srgb" value="9">
-        <description summary="sRGB piece-wise transfer function">
+      <entry name="srgb" value="9" deprecated-since="2">
+        <description summary="Deprecated (ambiguous sRGB transfer function)">
           Transfer characteristics as defined by
           - IEC 61966-2-1 sRGB
 
-          Note: This is not appropriate for describing sRGB material.
-          sRGB material is intended to be viewed on an sRGB display, and
-          that is described by gamma22.
+          As a rule of thumb, use gamma22 for video, motion picture and
+          computer graphics, or compound_power_2_4 for ICC calibrated print
+          workflows.
         </description>
       </entry>
-      <entry name="ext_srgb" value="10">
-        <description summary="Extended sRGB piece-wise transfer function">
+      <entry name="ext_srgb" value="10" deprecated-since="2">
+        <description summary="Deprecated (Extended sRGB piece-wise transfer function)">
           Transfer characteristics as defined by
           - IEC 61966-2-1 sYCC
         </description>
@@ -387,6 +386,12 @@
           ARIB STD-B67 or BT.2100.
         </description>
       </entry>
+      <entry name="compound_power_2_4" value="14" since="2">
+        <description summary="IEC 61966-2-1 encoding function">
+          Encoding characteristics as defined by IEC 61966-2-1, for displays
+          that invert the encoding function.
+        </description>
+      </entry>
     </enum>
 
     <request name="get_output">
@@ -520,6 +525,9 @@
       <description summary="supported rendering intent">
         When this object is created, it shall immediately send this event once
         for each rendering intent the compositor supports.
+
+        A compositor must not advertise intents that are deprecated in the
+        bound version of the interface.
       </description>
 
       <arg name="render_intent" type="uint" enum="render_intent"
@@ -530,6 +538,9 @@
       <description summary="supported features">
         When this object is created, it shall immediately send this event once
         for each compositor supported feature listed in the enumeration.
+
+        A compositor must not advertise features that are deprecated in the
+        bound version of the interface.
       </description>
 
       <arg name="feature" type="uint" enum="feature"
@@ -541,6 +552,9 @@
         When this object is created, it shall immediately send this event once
         for each named transfer function the compositor supports with the
         parametric image description creator.
+
+        A compositor must not advertise transfer functions that are deprecated
+        in the bound version of the interface.
       </description>
 
       <arg name="tf" type="uint" enum="transfer_function"
@@ -552,6 +566,9 @@
         When this object is created, it shall immediately send this event once
         for each named set of primaries the compositor supports with the
         parametric image description creator.
+
+        A compositor must not advertise names that are deprecated in the
+        bound version of the interface.
       </description>
 
       <arg name="primaries" type="uint" enum="primaries"