Proposal: EXT_conservative_depth (#3549)

extensions/proposals/EXT_conservative_depth/extension.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<proposal href="proposals/EXT_conservative_depth/">
+  <name>EXT_conservative_depth</name>
+
+  <contact> <a href="https://www.khronos.org/webgl/public-mailing-list/">WebGL
+  working group</a> (public_webgl 'at' khronos.org) </contact>
+
+  <contributors>
+    <contributor>Members of the WebGL working group</contributor>
+  </contributors>
+
+  <number>NN</number>
+
+  <depends>
+    <api version="2.0"/>
+  </depends>
+
+  <overview>
+    <mirrors href="https://www.khronos.org/registry/OpenGL/extensions/EXT/EXT_conservative_depth.txt"
+             name="EXT_conservative_depth">
+      <addendum>
+        The <code>depth_unchanged</code> layout qualifier is not supported.
+      </addendum>
+      <addendum>
+        If the final value of <code>gl_FragDepth</code> is inconsistent with its layout qualifier,
+        implementations may enforce consistency by clamping it to the value of <code>gl_FragCoord.z</code>.
+      </addendum>
+    </mirrors>
+    <features>
+      <glsl extname="GL_EXT_conservative_depth">
+        <stage type="fragment"/>
+        <feature>
+          The <code>gl_FragDepth</code> built-in output variable may be redeclared with a depth layout qualifier.
+        </feature>
+      </glsl>
+    </features>
+  </overview>
+
+  <idl xml:space="preserve">
+[Exposed=(Window,Worker), LegacyNoInterfaceObject]
+interface EXT_conservative_depth {
+};
+  </idl>
+
+  <samplecode xml:space="preserve">
+    <pre>
+    #ifdef GL_EXT_conservative_depth
+      #extension GL_EXT_conservative_depth : enable
+      layout (depth_greater) out float gl_FragDepth;
+    #endif
+
+    void main() {
+        // Assign to gl_FragDepth as usual
+    }
+    </pre>
+  </samplecode>
+
+  <history>
+    <revision date="2023/06/01">
+      <change>Initial Draft.</change>
+    </revision>
+  </history>
+</proposal>