Convert unsigned enum class consts to static constexpr

Part of https://github.com/harfbuzz/harfbuzz/issues/1553

src/hb-aat-layout-common.hh

@@ -77,7 +77,7 @@ struct LookupFormat0
 template <typename T>
 struct LookupSegmentSingle
 {
-  enum { TerminationWordCount = 2u };
+  static constexpr unsigned TerminationWordCount = 2u;
 
   int cmp (hb_codepoint_t g) const
   { return g < first ? -1 : g <= last ? 0 : +1 ; }
@@ -136,7 +136,7 @@ struct LookupFormat2
 template <typename T>
 struct LookupSegmentArray
 {
-  enum { TerminationWordCount = 2u };
+  static constexpr unsigned TerminationWordCount = 2u;
 
   const T* get_value (hb_codepoint_t glyph_id, const void *base) const
   {
@@ -207,7 +207,7 @@ struct LookupFormat4
 template <typename T>
 struct LookupSingle
 {
-  enum { TerminationWordCount = 1u };
+  static constexpr unsigned TerminationWordCount = 1u;
 
   int cmp (hb_codepoint_t g) const { return glyph.cmp (g); }
 

src/hb-aat-layout-kerx-table.hh

@@ -980,7 +980,7 @@ struct kerx : KerxTable<kerx>
   friend struct KerxTable<kerx>;
 
   static constexpr hb_tag_t tableTag = HB_AAT_TAG_kerx;
-  enum { minVersion = 2u };
+  static constexpr unsigned minVersion = 2u;
 
   typedef KerxSubTableHeader SubTableHeader;
   typedef SubTableHeader::Types Types;

src/hb-buffer.hh

@@ -119,7 +119,7 @@ struct hb_buffer_t
   /* Text before / after the main buffer contents.
    * Always in Unicode, and ordered outward.
    * Index 0 is for "pre-context", 1 for "post-context". */
-  enum { CONTEXT_LENGTH = 5u };
+  static constexpr unsigned CONTEXT_LENGTH = 5u;
   hb_codepoint_t context[2][CONTEXT_LENGTH];
   unsigned int context_len[2];
 

src/hb-open-type.hh

@@ -159,7 +159,7 @@ typedef HBUINT16 GlyphID;
 
 /* Script/language-system/feature index */
 struct Index : HBUINT16 {
-  enum { NOT_FOUND_INDEX = 0xFFFFu };
+  static constexpr unsigned NOT_FOUND_INDEX = 0xFFFFu;
 };
 DECLARE_NULL_NAMESPACE_BYTES (OT, Index);
 

src/hb-ot-kern-table.hh

@@ -198,7 +198,7 @@ struct KernOT : AAT::KerxTable<KernOT>
   friend struct AAT::KerxTable<KernOT>;
 
   static constexpr hb_tag_t tableTag = HB_OT_TAG_kern;
-  enum { minVersion = 0u };
+  static constexpr unsigned minVersion = 0u;
 
   typedef KernOTSubTableHeader SubTableHeader;
   typedef SubTableHeader::Types Types;
@@ -253,7 +253,7 @@ struct KernAAT : AAT::KerxTable<KernAAT>
   friend struct AAT::KerxTable<KernAAT>;
 
   static constexpr hb_tag_t tableTag = HB_OT_TAG_kern;
-  enum { minVersion = 0x00010000u };
+  static constexpr unsigned minVersion = 0x00010000u;
 
   typedef KernAATSubTableHeader SubTableHeader;
   typedef SubTableHeader::Types Types;

src/hb-ot-layout-common.hh

@@ -1949,7 +1949,7 @@ struct FeatureVariationRecord
 
 struct FeatureVariations
 {
-  enum { NOT_FOUND_INDEX = 0xFFFFFFFFu };
+  static constexpr unsigned NOT_FOUND_INDEX = 0xFFFFFFFFu;
 
   bool find_index (const int *coords, unsigned int coord_len,
 			  unsigned int *index) const

src/hb-ot-layout.cc

@@ -1299,7 +1299,7 @@ hb_ot_layout_feature_get_characters (hb_face_t      *face,
 
 struct GSUBProxy
 {
-  enum { table_index = 0u };
+  static constexpr unsigned table_index = 0u;
   static constexpr bool inplace = false;
   typedef OT::SubstLookup Lookup;
 
@@ -1313,7 +1313,7 @@ struct GSUBProxy
 
 struct GPOSProxy
 {
-  enum { table_index = 1u };
+  static constexpr unsigned table_index = 1u;
   static constexpr bool inplace = true;
   typedef OT::PosLookup Lookup;