Add a "placeholder" MeshPrimitive::Meshlets.

Just so I can create custom Trade::MeshData instances with meshlet
contents, nothing else.

doc/changelog.dox

@@ -265,6 +265,9 @@ See also:
 
 @subsection changelog-latest-changes Changes and improvements
 
+-   Added @ref MeshPrimitive::Meshlets as a placeholder for future meshlet
+    support in @ref Trade::MeshData
+
 @subsubsection changelog-latest-changes-debugtools DebugTools library
 
 -   @ref DebugTools::CompareImage now supports comparing half-float pixel

src/Magnum/GL/Mesh.cpp

@@ -62,7 +62,8 @@ constexpr MeshPrimitive PrimitiveMapping[]{
     MeshPrimitive::TriangleFan,
     MeshPrimitive(~UnsignedInt{}), /* Instances */
     MeshPrimitive(~UnsignedInt{}), /* Faces */
-    MeshPrimitive(~UnsignedInt{})  /* Edges */
+    MeshPrimitive(~UnsignedInt{}), /* Edges */
+    MeshPrimitive(~UnsignedInt{})  /* Meshlets */
 };
 
 constexpr MeshIndexType IndexTypeMapping[]{

src/Magnum/Implementation/meshPrimitiveMapping.hpp

@@ -35,4 +35,5 @@ _c(TriangleFan)
 _c(Instances)
 _c(Faces)
 _c(Edges)
+_c(Meshlets)
 #endif

src/Magnum/Mesh.h

@@ -183,7 +183,17 @@ enum class MeshPrimitive: UnsignedInt {
      * half-edge mesh representation.
      * @see @ref Trade::meshAttributeCustom()
      */
-    Edges
+    Edges,
+
+    /**
+     * Meshlet data.
+     * @m_since_latest
+     *
+     * Can be used to annotate @ref Trade::MeshData containing meshlet chunks,
+     * i.e. groups of vertex references together with per-meshlet culling
+     * information such as a bounding sphere or visibility cone.
+     */
+    Meshlets
 };
 
 /** @debugoperatorenum{MeshPrimitive} */

src/Magnum/Vk/MeshLayout.cpp

@@ -45,7 +45,8 @@ constexpr MeshPrimitive MeshPrimitiveMapping[]{
     MeshPrimitive::TriangleFan,
     MeshPrimitive(~Int{}), /* Instances */
     MeshPrimitive(~Int{}), /* Faces */
-    MeshPrimitive(~Int{})  /* Edges */
+    MeshPrimitive(~Int{}), /* Edges */
+    MeshPrimitive(~Int{})  /* Meshlets */
 };
 
 }