diff --git a/.circleci/config.yml b/.circleci/config.yml
index 69520b014..1cf4bc885 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -27,6 +27,17 @@ jobs:
       # Ignoring assembler complains, https://stackoverflow.com/a/39867021
       - run: make 2>&1 | grep -v -e '^/var/folders/*' -e '^[[:space:]]*\.section' -e '^[[:space:]]*\^[[:space:]]*~*'
 
+  macos-notest-ios:
+    macos:
+      xcode: "10.0.0"
+    steps:
+      - checkout
+      - run: brew update-reset
+      - run: brew install cmake
+      # not needed to be a framework but we like to test that also
+      - run: cmake -DBUILD_FRAMEWORK=ON -H. -Bbuild -GXcode -DHB_IOS=ON
+      - run: cd build && xcodebuild -sdk iphoneos12.0 -configuration Release build -arch arm64
+
   distcheck:
     docker:
       - image: ubuntu:17.10
@@ -274,6 +285,7 @@ workflows:
       # macOS
       - macos-llvm-gcc-4.2
       - macos-notest-apple-gcc-i686-4.2
+      - macos-notest-ios
 
       # both autotools and cmake
       - distcheck
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d97f7c269..760883fda 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -82,12 +82,21 @@ if (HB_CHECK)
   endif ()
 endif ()
 
+set (HB_DISABLE_SUBSET OFF)
+set (HB_DISABLE_TESTS OFF)
+option(HB_IOS "Apply iOS specific build flags" OFF)
+if (HB_IOS)
+  # We should fix their issue and enable them
+  set (HB_DISABLE_SUBSET ON)
+  set (HB_DISABLE_TESTS ON)
+  set (HB_HAVE_CORETEXT OFF)
+endif ()
+
 include_directories(AFTER
   ${PROJECT_SOURCE_DIR}/src
   ${PROJECT_BINARY_DIR}/src
 )
 
-add_definitions(-DHAVE_OT)
 add_definitions(-DHAVE_FALLBACK)
 
 # We need PYTHON_EXECUTABLE to be set for running the tests...
@@ -359,12 +368,32 @@ if (APPLE AND HB_HAVE_CORETEXT)
   list(APPEND project_sources ${PROJECT_SOURCE_DIR}/src/hb-coretext.cc)
   list(APPEND project_headers ${PROJECT_SOURCE_DIR}/src/hb-coretext.h)
 
-  find_library(APPLICATION_SERVICES_FRAMEWORK ApplicationServices)
-  if (APPLICATION_SERVICES_FRAMEWORK)
-    list(APPEND THIRD_PARTY_LIBS ${APPLICATION_SERVICES_FRAMEWORK})
-  endif (APPLICATION_SERVICES_FRAMEWORK)
+  if (HB_IOS)
+    find_library(COREFOUNDATION CoreFoundation)
+    if (COREFOUNDATION)
+      list(APPEND THIRD_PARTY_LIBS ${COREFOUNDATION})
+    endif ()
+    mark_as_advanced(COREFOUNDATION)
 
-  mark_as_advanced(APPLICATION_SERVICES_FRAMEWORK)
+    find_library(CORETEXT CoreText)
+    if (CORETEXT)
+      list(APPEND THIRD_PARTY_LIBS ${CORETEXT})
+    endif ()
+    mark_as_advanced(CORETEXT)
+
+    find_library(COREGRAPHICS CoreGraphics)
+    if (COREGRAPHICS)
+      list(APPEND THIRD_PARTY_LIBS ${COREGRAPHICS})
+    endif ()
+    mark_as_advanced(COREGRAPHICS)
+  else ()
+    find_library(APPLICATION_SERVICES_FRAMEWORK ApplicationServices)
+    if (APPLICATION_SERVICES_FRAMEWORK)
+      list(APPEND THIRD_PARTY_LIBS ${APPLICATION_SERVICES_FRAMEWORK})
+    endif ()
+
+    mark_as_advanced(APPLICATION_SERVICES_FRAMEWORK)
+  endif ()
 endif ()
 
 if (WIN32 AND HB_HAVE_UNISCRIBE)
@@ -527,12 +556,14 @@ add_library(harfbuzz ${project_sources} ${project_extra_sources} ${project_heade
 target_link_libraries(harfbuzz ${THIRD_PARTY_LIBS})
 
 ## Define harfbuzz-subset library
-add_library(harfbuzz-subset ${subset_project_sources} ${subset_project_headers})
-add_dependencies(harfbuzz-subset harfbuzz)
-target_link_libraries(harfbuzz-subset harfbuzz ${THIRD_PARTY_LIBS})
+if (NOT HB_DISABLE_SUBSET)
+  add_library(harfbuzz-subset ${subset_project_sources} ${subset_project_headers})
+  add_dependencies(harfbuzz-subset harfbuzz)
+  target_link_libraries(harfbuzz-subset harfbuzz ${THIRD_PARTY_LIBS})
 
-if (BUILD_SHARED_LIBS)
-  set_target_properties(harfbuzz harfbuzz-subset PROPERTIES VISIBILITY_INLINES_HIDDEN TRUE)
+  if (BUILD_SHARED_LIBS)
+    set_target_properties(harfbuzz harfbuzz-subset PROPERTIES VISIBILITY_INLINES_HIDDEN TRUE)
+  endif ()
 endif ()
 
 if (UNIX OR MINGW)
@@ -549,7 +580,9 @@ if (UNIX OR MINGW)
     set (CMAKE_CXX_IMPLICIT_LINK_LIBRARIES "m") # libm
     set (CMAKE_CXX_IMPLICIT_LINK_DIRECTORIES "")
     set_target_properties(harfbuzz PROPERTIES LINKER_LANGUAGE C)
-    set_target_properties(harfbuzz-subset PROPERTIES LINKER_LANGUAGE C)
+    if (NOT HB_DISABLE_SUBSET)
+      set_target_properties(harfbuzz-subset PROPERTIES LINKER_LANGUAGE C)
+    endif ()
 
     # No threadsafe statics as we do it ourselves
     set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-threadsafe-statics")
@@ -828,51 +861,53 @@ if (UNIX AND CMAKE_GENERATOR STREQUAL "Ninja")
 endif ()
 
 
-## src/ executables
-foreach (prog main test test-would-substitute test-size-params test-buffer-serialize hb-ot-tag test-unicode-ranges)
-  set (prog_name ${prog})
-  if (${prog_name} STREQUAL "test")
-    # test can not be used as a valid executable name on cmake, lets special case it
-    set (prog_name test-test)
-  endif ()
-  add_executable(${prog_name} ${PROJECT_SOURCE_DIR}/src/${prog}.cc)
-  target_link_libraries(${prog_name} harfbuzz ${THIRD_PARTY_LIBS})
-endforeach ()
-set_target_properties(hb-ot-tag PROPERTIES COMPILE_FLAGS "-DMAIN")
+if (NOT HB_DISABLE_TESTS)
+  ## src/ executables
+  foreach (prog main test test-would-substitute test-size-params test-buffer-serialize hb-ot-tag test-unicode-ranges)
+    set (prog_name ${prog})
+    if (${prog_name} STREQUAL "test")
+      # test can not be used as a valid executable name on cmake, lets special case it
+      set (prog_name test-test)
+    endif ()
+    add_executable(${prog_name} ${PROJECT_SOURCE_DIR}/src/${prog}.cc)
+    target_link_libraries(${prog_name} harfbuzz ${THIRD_PARTY_LIBS})
+  endforeach ()
+  set_target_properties(hb-ot-tag PROPERTIES COMPILE_FLAGS "-DMAIN")
 
-## Tests
-if (UNIX OR MINGW)
-  if (BUILD_SHARED_LIBS)
-    # generate harfbuzz.def after build completion
-    add_custom_command(TARGET harfbuzz POST_BUILD
-      COMMAND "${PYTHON_EXECUTABLE}" ${PROJECT_SOURCE_DIR}/src/gen-def.py ${PROJECT_BINARY_DIR}/harfbuzz.def ${project_headers}
-      WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}/src)
+  ## Tests
+  if (UNIX OR MINGW)
+    if (BUILD_SHARED_LIBS)
+      # generate harfbuzz.def after build completion
+      add_custom_command(TARGET harfbuzz POST_BUILD
+        COMMAND "${PYTHON_EXECUTABLE}" ${PROJECT_SOURCE_DIR}/src/gen-def.py ${PROJECT_BINARY_DIR}/harfbuzz.def ${project_headers}
+        WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}/src)
 
-    add_test(NAME check-static-inits.sh
-      COMMAND ${PROJECT_SOURCE_DIR}/src/check-static-inits.sh
-      WORKING_DIRECTORY ${PROJECT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/harfbuzz.dir/src # ugly hack
-    )
-    add_test(NAME check-libstdc++.sh COMMAND ${PROJECT_SOURCE_DIR}/src/check-libstdc++.sh)
-    add_test(NAME check-symbols.sh COMMAND ${PROJECT_SOURCE_DIR}/src/check-symbols.sh)
+      add_test(NAME check-static-inits.sh
+        COMMAND ${PROJECT_SOURCE_DIR}/src/check-static-inits.sh
+        WORKING_DIRECTORY ${PROJECT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/harfbuzz.dir/src # ugly hack
+      )
+      add_test(NAME check-libstdc++.sh COMMAND ${PROJECT_SOURCE_DIR}/src/check-libstdc++.sh)
+      add_test(NAME check-symbols.sh COMMAND ${PROJECT_SOURCE_DIR}/src/check-symbols.sh)
 
+      set_tests_properties(
+        check-static-inits.sh check-libstdc++.sh check-symbols.sh
+        PROPERTIES
+          ENVIRONMENT "libs=.;srcdir=${PROJECT_SOURCE_DIR}/src"
+          SKIP_RETURN_CODE 77)
+    endif ()
+
+    add_test(NAME check-c-linkage-decls.sh COMMAND ./check-c-linkage-decls.sh)
+    add_test(NAME check-header-guards.sh COMMAND ./check-header-guards.sh)
+    add_test(NAME check-externs.sh COMMAND ./check-externs.sh)
+    add_test(NAME check-includes.sh COMMAND ./check-includes.sh)
     set_tests_properties(
-      check-static-inits.sh check-libstdc++.sh check-symbols.sh
+      check-c-linkage-decls.sh check-header-guards.sh check-externs.sh check-includes.sh
       PROPERTIES
-        ENVIRONMENT "libs=.;srcdir=${PROJECT_SOURCE_DIR}/src"
+        WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}/src
         SKIP_RETURN_CODE 77)
   endif ()
 
-  add_test(NAME check-c-linkage-decls.sh COMMAND ./check-c-linkage-decls.sh)
-  add_test(NAME check-header-guards.sh COMMAND ./check-header-guards.sh)
-  add_test(NAME check-externs.sh COMMAND ./check-externs.sh)
-  add_test(NAME check-includes.sh COMMAND ./check-includes.sh)
-  set_tests_properties(
-    check-c-linkage-decls.sh check-header-guards.sh check-externs.sh check-includes.sh
-    PROPERTIES
-      WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}/src
-      SKIP_RETURN_CODE 77)
+  # Needs to come last so that variables defined above are passed to
+  # subdirectories.
+  add_subdirectory(test)
 endif ()
-
-# Needs to come last so that variables defined above are passed to
-# subdirectories.
-add_subdirectory(test)
diff --git a/configure.ac b/configure.ac
index 3aa41ff21..1b9ddfe7c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -148,12 +148,6 @@ AM_CONDITIONAL(HAVE_PTHREAD, $have_pthread)
 
 dnl ==========================================================================
 
-have_ot=true
-if $have_ot; then
-	AC_DEFINE(HAVE_OT, 1, [Have native OpenType Layout backend])
-fi
-AM_CONDITIONAL(HAVE_OT, $have_ot)
-
 have_fallback=true
 if $have_fallback; then
 	AC_DEFINE(HAVE_FALLBACK, 1, [Have simple TrueType Layout backend])
diff --git a/src/Makefile.am b/src/Makefile.am
index 2eca356b4..c4ae2bcb2 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -29,11 +29,9 @@ HBSOURCES =  $(HB_BASE_sources)
 HBSOURCES += $(HB_BASE_RAGEL_GENERATED_sources)
 HBHEADERS = $(HB_BASE_headers)
 
-if HAVE_OT
 HBSOURCES += $(HB_OT_sources)
 HBSOURCES += $(HB_OT_RAGEL_GENERATED_sources)
 HBHEADERS += $(HB_OT_headers)
-endif
 
 if HAVE_FALLBACK
 HBSOURCES += $(HB_FALLBACK_sources)
diff --git a/src/hb-aat-layout-common.hh b/src/hb-aat-layout-common.hh
index 5845ab516..37ab53539 100644
--- a/src/hb-aat-layout-common.hh
+++ b/src/hb-aat-layout-common.hh
@@ -260,6 +260,12 @@ struct Lookup
     }
   }
 
+  inline const T& get_value_or_null (hb_codepoint_t glyph_id, unsigned int num_glyphs) const
+  {
+    const T *v = get_value (glyph_id, num_glyphs);
+    return v ? *v : Null(T);
+  }
+
   inline bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
diff --git a/src/hb-aat-layout-kerx-table.hh b/src/hb-aat-layout-kerx-table.hh
index e5934c39f..3cff334a9 100644
--- a/src/hb-aat-layout-kerx-table.hh
+++ b/src/hb-aat-layout-kerx-table.hh
@@ -44,21 +44,38 @@ namespace AAT {
 using namespace OT;
 
 
+struct KerxSubTableHeader
+{
+  inline bool sanitize (hb_sanitize_context_t *c) const
+  {
+    TRACE_SANITIZE (this);
+    return_trace (likely (c->check_struct (this)));
+  }
+
+  public:
+  HBUINT32	length;
+  HBUINT32	coverage;
+  HBUINT32	tupleCount;
+  public:
+  DEFINE_SIZE_STATIC (12);
+};
+
 struct KerxSubTableFormat0
 {
   inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right) const
   {
     hb_glyph_pair_t pair = {left, right};
     int i = pairs.bsearch (pair);
-    if (i == -1)
-      return 0;
-    return pairs[i].get_kerning ();
+    return i == -1 ? 0 : pairs[i].get_kerning ();
   }
 
   inline bool apply (hb_aat_apply_context_t *c) const
   {
     TRACE_APPLY (this);
 
+    if (!c->plan->requested_kerning)
+      return false;
+
     hb_kern_machine_t<KerxSubTableFormat0> machine (*this);
 
     machine.kern (c->font, c->buffer, c->plan->kern_mask);
@@ -73,10 +90,11 @@ struct KerxSubTableFormat0
   }
 
   protected:
+  KerxSubTableHeader	header;
   BinSearchArrayOf<KernPair, HBUINT32>
-		pairs;	/* Sorted kern records. */
+			pairs;	/* Sorted kern records. */
   public:
-  DEFINE_SIZE_ARRAY (16, pairs);
+  DEFINE_SIZE_ARRAY (28, pairs);
 };
 
 struct KerxSubTableFormat1
@@ -85,6 +103,9 @@ struct KerxSubTableFormat1
   {
     TRACE_APPLY (this);
 
+    if (!c->plan->requested_kerning)
+      return false;
+
     /* TODO */
 
     return_trace (true);
@@ -98,23 +119,24 @@ struct KerxSubTableFormat1
   }
 
   protected:
+  KerxSubTableHeader		header;
   StateTable<HBUINT16>		stateHeader;
   LOffsetTo<ArrayOf<HBUINT16> >	valueTable;
   public:
-  DEFINE_SIZE_STATIC (20);
+  DEFINE_SIZE_STATIC (32);
 };
 
 struct KerxSubTableFormat2
 {
   inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right,
-			  const char *end, unsigned int num_glyphs) const
+			  unsigned int num_glyphs) const
   {
-    unsigned int l = *(this+leftClassTable).get_value (left, num_glyphs);
-    unsigned int r = *(this+rightClassTable).get_value (right, num_glyphs);
+    unsigned int l = (this+leftClassTable).get_value_or_null (left, num_glyphs);
+    unsigned int r = (this+rightClassTable).get_value_or_null (right, num_glyphs);
     unsigned int offset = l + r;
     const FWORD *v = &StructAtOffset<FWORD> (&(this+array), offset);
     if (unlikely ((const char *) v < (const char *) &array ||
-		  (const char *) v > (const char *) end - 2))
+		  (const char *) v + v->static_size - (const char *) this <= header.length))
       return 0;
     return *v;
   }
@@ -123,8 +145,10 @@ struct KerxSubTableFormat2
   {
     TRACE_APPLY (this);
 
+    if (!c->plan->requested_kerning)
+      return false;
+
     accelerator_t accel (*this,
-			 c->sanitizer.end,
 			 c->face->get_num_glyphs ());
     hb_kern_machine_t<accelerator_t> machine (accel);
     machine.kern (c->font, c->buffer, c->plan->kern_mask);
@@ -145,32 +169,31 @@ struct KerxSubTableFormat2
   struct accelerator_t
   {
     const KerxSubTableFormat2 &table;
-    const char *end;
     unsigned int num_glyphs;
 
     inline accelerator_t (const KerxSubTableFormat2 &table_,
-			  const char *end_, unsigned int num_glyphs_)
-			  : table (table_), end (end_), num_glyphs (num_glyphs_) {}
+			  unsigned int num_glyphs_)
+			  : table (table_), num_glyphs (num_glyphs_) {}
 
     inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right) const
     {
-      return table.get_kerning (left, right, end, num_glyphs);
+      return table.get_kerning (left, right, num_glyphs);
     }
   };
 
   protected:
-  HBUINT32	rowWidth;	/* The width, in bytes, of a row in the table. */
+  KerxSubTableHeader	header;
+  HBUINT32		rowWidth;	/* The width, in bytes, of a row in the table. */
   LOffsetTo<Lookup<HBUINT16> >
-		leftClassTable;	/* Offset from beginning of this subtable to
-				 * left-hand class table. */
+			leftClassTable;	/* Offset from beginning of this subtable to
+					 * left-hand class table. */
   LOffsetTo<Lookup<HBUINT16> >
-		rightClassTable;/* Offset from beginning of this subtable to
-				 * right-hand class table. */
-  LOffsetTo<FWORD>
-		array;		/* Offset from beginning of this subtable to
-				 * the start of the kerning array. */
+			rightClassTable;/* Offset from beginning of this subtable to
+					 * right-hand class table. */
+  LOffsetTo<FWORD>	array;		/* Offset from beginning of this subtable to
+					 * the start of the kerning array. */
   public:
-  DEFINE_SIZE_STATIC (16);
+  DEFINE_SIZE_STATIC (28);
 };
 
 struct KerxSubTableFormat4
@@ -193,17 +216,60 @@ struct KerxSubTableFormat4
   }
 
   protected:
+  KerxSubTableHeader	header;
   public:
-  DEFINE_SIZE_STATIC (1);
+  DEFINE_SIZE_STATIC (12);
 };
 
 struct KerxSubTableFormat6
 {
+  enum Flags
+  {
+    ValuesAreLong	= 0x00000001,
+  };
+
+  inline bool is_long (void) const { return flags & ValuesAreLong; }
+
+  inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right,
+			  unsigned int num_glyphs) const
+  {
+    if (is_long ())
+    {
+      const U::Long &t = u.l;
+      unsigned int l = (this+t.rowIndexTable).get_value_or_null (left, num_glyphs);
+      unsigned int r = (this+t.columnIndexTable).get_value_or_null (right, num_glyphs);
+      unsigned int offset = l + r;
+      const FWORD32 *v = &StructAtOffset<FWORD32> (&(this+t.array), offset * sizeof (FWORD32));
+      if (unlikely ((const char *) v < (const char *) &t.array ||
+		    (const char *) v + v->static_size - (const char *) this <= header.length))
+	return 0;
+      return *v;
+    }
+    else
+    {
+      const U::Short &t = u.s;
+      unsigned int l = (this+t.rowIndexTable).get_value_or_null (left, num_glyphs);
+      unsigned int r = (this+t.columnIndexTable).get_value_or_null (right, num_glyphs);
+      unsigned int offset = l + r;
+      const FWORD *v = &StructAtOffset<FWORD> (&(this+t.array), offset * sizeof (FWORD));
+      if (unlikely ((const char *) v < (const char *) &t.array ||
+		    (const char *) v + v->static_size - (const char *) this <= header.length))
+	return 0;
+      return *v;
+    }
+  }
+
   inline bool apply (hb_aat_apply_context_t *c) const
   {
     TRACE_APPLY (this);
 
-    /* TODO */
+    if (!c->plan->requested_kerning)
+      return false;
+
+    accelerator_t accel (*this,
+			 c->face->get_num_glyphs ());
+    hb_kern_machine_t<accelerator_t> machine (accel);
+    machine.kern (c->font, c->buffer, c->plan->kern_mask);
 
     return_trace (true);
   }
@@ -212,30 +278,63 @@ struct KerxSubTableFormat6
   {
     TRACE_SANITIZE (this);
     return_trace (likely (c->check_struct (this) &&
-			  rowIndexTable.sanitize (c, this) &&
-			  columnIndexTable.sanitize (c, this) &&
-			  kerningArray.sanitize (c, this) &&
-			  kerningVector.sanitize (c, this)));
+			  is_long () ?
+			  (
+			    u.l.rowIndexTable.sanitize (c, this) &&
+			    u.l.columnIndexTable.sanitize (c, this) &&
+			    u.l.array.sanitize (c, this)
+			  ) : (
+			    u.s.rowIndexTable.sanitize (c, this) &&
+			    u.s.columnIndexTable.sanitize (c, this) &&
+			    u.s.array.sanitize (c, this)
+			  )));
   }
 
+  struct accelerator_t
+  {
+    const KerxSubTableFormat6 &table;
+    unsigned int num_glyphs;
+
+    inline accelerator_t (const KerxSubTableFormat6 &table_,
+			  unsigned int num_glyphs_)
+			  : table (table_), num_glyphs (num_glyphs_) {}
+
+    inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right) const
+    {
+      return table.get_kerning (left, right, num_glyphs);
+    }
+  };
+
   protected:
-  HBUINT32	flags;
-  HBUINT16	rowCount;
-  HBUINT16	columnCount;
-  LOffsetTo<Lookup<HBUINT16> >	rowIndexTable;
-  LOffsetTo<Lookup<HBUINT16> >	columnIndexTable;
-  LOffsetTo<Lookup<HBUINT16> >	kerningArray;
-  LOffsetTo<Lookup<HBUINT16> >	kerningVector;
+  KerxSubTableHeader		header;
+  HBUINT32			flags;
+  HBUINT16			rowCount;
+  HBUINT16			columnCount;
+  union U
+  {
+    struct Long
+    {
+      LOffsetTo<Lookup<HBUINT32> >	rowIndexTable;
+      LOffsetTo<Lookup<HBUINT32> >	columnIndexTable;
+      LOffsetTo<FWORD32>		array;
+    } l;
+    struct Short
+    {
+      LOffsetTo<Lookup<HBUINT16> >	rowIndexTable;
+      LOffsetTo<Lookup<HBUINT16> >	columnIndexTable;
+      LOffsetTo<FWORD>			array;
+    } s;
+  } u;
   public:
-  DEFINE_SIZE_STATIC (24);
+  DEFINE_SIZE_STATIC (32);
 };
 
 struct KerxTable
 {
   friend struct kerx;
 
-  inline unsigned int get_size (void) const { return length; }
-  inline unsigned int get_type (void) const { return coverage & SubtableType; }
+  inline unsigned int get_size (void) const { return u.header.length; }
+  inline unsigned int get_type (void) const { return u.header.coverage & SubtableType; }
 
   enum Coverage
   {
@@ -269,19 +368,16 @@ struct KerxTable
   inline bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
-    if (!length.sanitize (c) ||
-	length < min_size ||
-	!c->check_range (this, length))
+    if (!u.header.sanitize (c) ||
+	!c->check_range (this, u.header.length))
       return_trace (false);
 
     return_trace (dispatch (c));
   }
 
 protected:
-  HBUINT32	length;
-  HBUINT32	coverage;
-  HBUINT32	tupleCount;
   union {
+  KerxSubTableHeader	header;
   KerxSubTableFormat0	format0;
   KerxSubTableFormat1	format1;
   KerxSubTableFormat2	format2;
@@ -312,21 +408,22 @@ struct kerx
     {
       bool reverse;
 
+      if (table->u.header.coverage & (KerxTable::CrossStream | KerxTable::Variation) ||
+	  table->u.header.tupleCount)
+	goto skip; /* We do NOT handle cross-stream or variation kerning. */
+
       if (HB_DIRECTION_IS_VERTICAL (c->buffer->props.direction) !=
-	  bool (table->coverage & KerxTable::Vertical))
-        goto skip;
+	  bool (table->u.header.coverage & KerxTable::Vertical))
+	goto skip;
 
-      if (table->coverage & KerxTable::CrossStream)
-        goto skip; /* We do NOT handle cross-stream kerning.  None of Apple fonts use it. */
-
-      reverse = bool (table->coverage & KerxTable::Backwards) !=
+      reverse = bool (table->u.header.coverage & KerxTable::Backwards) !=
 		HB_DIRECTION_IS_BACKWARD (c->buffer->props.direction);
 
       if (!c->buffer->message (c->font, "start kerx subtable %d", c->lookup_index))
-        goto skip;
+	goto skip;
 
       if (reverse)
-        c->buffer->reverse ();
+	c->buffer->reverse ();
 
       c->sanitizer.set_object (*table);
 
@@ -337,7 +434,7 @@ struct kerx
       table->dispatch (c);
 
       if (reverse)
-        c->buffer->reverse ();
+	c->buffer->reverse ();
 
       (void) c->buffer->message (c->font, "end kerx subtable %d", c->lookup_index);
 
diff --git a/src/hb-aat-layout.cc b/src/hb-aat-layout.cc
index 71932e798..3fd4f9f89 100644
--- a/src/hb-aat-layout.cc
+++ b/src/hb-aat-layout.cc
@@ -54,6 +54,21 @@ _get_morx (hb_face_t *face, hb_blob_t **blob = nullptr)
     *blob = hb_ot_face_data (face)->morx.get_blob ();
   return morx;
 }
+static inline const AAT::kerx&
+_get_kerx (hb_face_t *face, hb_blob_t **blob = nullptr)
+{
+  if (unlikely (!hb_ot_shaper_face_data_ensure (face)))
+  {
+    if (blob)
+      *blob = hb_blob_get_empty ();
+    return Null(AAT::kerx);
+  }
+  const AAT::kerx& kerx = *(hb_ot_face_data (face)->kerx.get ());
+  if (blob)
+    *blob = hb_ot_face_data (face)->kerx.get_blob ();
+  return kerx;
+}
+
 
 hb_bool_t
 hb_aat_layout_has_substitution (hb_face_t *face)
@@ -73,19 +88,21 @@ hb_aat_layout_substitute (hb_ot_shape_plan_t *plan,
   morx.apply (&c);
 }
 
+
+hb_bool_t
+hb_aat_layout_has_positioning (hb_face_t *face)
+{
+  return _get_kerx (face).has_data ();
+}
+
 void
 hb_aat_layout_position (hb_ot_shape_plan_t *plan,
 			hb_font_t *font,
 			hb_buffer_t *buffer)
 {
-#if 0
   hb_blob_t *blob;
-  const AAT::ankr& ankr = _get_ankr (font->face, &blob);
   const AAT::kerx& kerx = _get_kerx (font->face, &blob);
-  const AAT::trak& trak = _get_trak (font->face, &blob);
 
-  AAT::hb_aat_apply_context_t c (font, buffer, blob);
-  kerx.apply (&c, &ankr);
-  trak.apply (&c);
-#endif
+  AAT::hb_aat_apply_context_t c (plan, font, buffer, blob);
+  kerx.apply (&c);
 }
diff --git a/src/hb-aat-layout.hh b/src/hb-aat-layout.hh
index 8b12833d9..aafc3278f 100644
--- a/src/hb-aat-layout.hh
+++ b/src/hb-aat-layout.hh
@@ -39,6 +39,9 @@ hb_aat_layout_substitute (hb_ot_shape_plan_t *plan,
 			  hb_font_t *font,
 			  hb_buffer_t *buffer);
 
+HB_INTERNAL hb_bool_t
+hb_aat_layout_has_positioning (hb_face_t *face);
+
 HB_INTERNAL void
 hb_aat_layout_position (hb_ot_shape_plan_t *plan,
 			hb_font_t *font,
diff --git a/src/hb-common.cc b/src/hb-common.cc
index 41b1601de..eda41dd87 100644
--- a/src/hb-common.cc
+++ b/src/hb-common.cc
@@ -47,8 +47,27 @@ _hb_options_init (void)
   u.i = 0;
   u.opts.initialized = 1;
 
-  char *c = getenv ("HB_OPTIONS");
-  u.opts.uniscribe_bug_compatible = c && strstr (c, "uniscribe-bug-compatible");
+  const char *c = getenv ("HB_OPTIONS");
+  if (c)
+  {
+    while (*c)
+    {
+      const char *p = strchr (c, ':');
+      if (!p)
+        p = c + strlen (c);
+
+#define OPTION(name, symbol) \
+	if (0 == strncmp (c, name, p - c) && strlen (name) == p - c) u.opts.symbol = true;
+
+      OPTION ("uniscribe-bug-compatible", uniscribe_bug_compatible);
+      OPTION ("aat", aat);
+
+#undef OPTION
+
+      c = *p ? p + 1 : p;
+    }
+
+  }
 
   /* This is idempotent and threadsafe. */
   _hb_options.set_relaxed (u.i);
diff --git a/src/hb-debug.hh b/src/hb-debug.hh
index 12b6c49ae..58c190d27 100644
--- a/src/hb-debug.hh
+++ b/src/hb-debug.hh
@@ -43,9 +43,10 @@
 
 struct hb_options_t
 {
-  unsigned int unused : 1; /* In-case sign bit is here. */
-  unsigned int initialized : 1;
-  unsigned int uniscribe_bug_compatible : 1;
+  bool unused : 1; /* In-case sign bit is here. */
+  bool initialized : 1;
+  bool uniscribe_bug_compatible : 1;
+  bool aat : 1;
 };
 
 union hb_options_union_t {
diff --git a/src/hb-machinery.hh b/src/hb-machinery.hh
index 8feb3773c..56914beae 100644
--- a/src/hb-machinery.hh
+++ b/src/hb-machinery.hh
@@ -257,6 +257,13 @@ struct hb_sanitize_context_t :
 
   inline void set_max_ops (int max_ops_) { max_ops = max_ops_; }
 
+  /* TODO
+   * This set_object() thing is to use sanitize at runtime lookup
+   * application time.  This is very distinct from the regular
+   * sanitizer operation, so, eventually, separate into another
+   * type and make hb_aat_apply_context_t use that one instead
+   * of abusing this one.
+   */
   template <typename T>
   inline void set_object (const T& obj)
   {
diff --git a/src/hb-open-type.hh b/src/hb-open-type.hh
index 9a0873369..2eae09d5c 100644
--- a/src/hb-open-type.hh
+++ b/src/hb-open-type.hh
@@ -92,6 +92,9 @@ typedef IntType<uint32_t, 3> HBUINT24;	/* 24-bit unsigned integer. */
 /* 16-bit signed integer (HBINT16) that describes a quantity in FUnits. */
 typedef HBINT16 FWORD;
 
+/* 32-bit signed integer (HBINT32) that describes a quantity in FUnits. */
+typedef HBINT32 FWORD32;
+
 /* 16-bit unsigned integer (HBUINT16) that describes a quantity in FUnits. */
 typedef HBUINT16 UFWORD;
 
diff --git a/src/hb-ot-kern-table.hh b/src/hb-ot-kern-table.hh
index ccb666e8c..dab7a805f 100644
--- a/src/hb-ot-kern-table.hh
+++ b/src/hb-ot-kern-table.hh
@@ -191,6 +191,12 @@ struct KernSubTableFormat2
 {
   inline int get_kerning (hb_codepoint_t left, hb_codepoint_t right, const char *end) const
   {
+    /* This subtable is disabled.  It's not cleaer to me *exactly* where the offests are
+     * based from.  I *think* they should be based from beginning of kern subtable wrapper,
+     * *NOT* "this".  Since we know of no fonts that use this subtable, we are disabling
+     * it.  Someday fix it and re-enable.  Better yet, find fonts that use it... Meh,
+     * Windows doesn't implement it.  Maybe just remove... */
+    return 0;
     unsigned int l = (this+leftClassTable).get_class (left);
     unsigned int r = (this+rightClassTable).get_class (right);
     unsigned int offset = l + r;
@@ -204,6 +210,7 @@ struct KernSubTableFormat2
   inline bool sanitize (hb_sanitize_context_t *c) const
   {
     TRACE_SANITIZE (this);
+    return_trace (true); /* Disabled.  See above. */
     return_trace (rowWidth.sanitize (c) &&
 		  leftClassTable.sanitize (c, this) &&
 		  rightClassTable.sanitize (c, this) &&
diff --git a/src/hb-ot-layout-gsubgpos.hh b/src/hb-ot-layout-gsubgpos.hh
index bdaf35a95..3a09803ee 100644
--- a/src/hb-ot-layout-gsubgpos.hh
+++ b/src/hb-ot-layout-gsubgpos.hh
@@ -621,6 +621,64 @@ struct hb_ot_apply_context_t :
 };
 
 
+struct hb_get_subtables_context_t :
+       hb_dispatch_context_t<hb_get_subtables_context_t, hb_void_t, HB_DEBUG_APPLY>
+{
+  template <typename Type>
+  static inline bool apply_to (const void *obj, OT::hb_ot_apply_context_t *c)
+  {
+    const Type *typed_obj = (const Type *) obj;
+    return typed_obj->apply (c);
+  }
+
+  typedef bool (*hb_apply_func_t) (const void *obj, OT::hb_ot_apply_context_t *c);
+
+  struct hb_applicable_t
+  {
+    template <typename T>
+    inline void init (const T &obj_, hb_apply_func_t apply_func_)
+    {
+      obj = &obj_;
+      apply_func = apply_func_;
+      digest.init ();
+      obj_.get_coverage ().add_coverage (&digest);
+    }
+
+    inline bool apply (OT::hb_ot_apply_context_t *c) const
+    {
+      return digest.may_have (c->buffer->cur().codepoint) && apply_func (obj, c);
+    }
+
+    private:
+    const void *obj;
+    hb_apply_func_t apply_func;
+    hb_set_digest_t digest;
+  };
+
+  typedef hb_vector_t<hb_applicable_t, 2> array_t;
+
+  /* Dispatch interface. */
+  inline const char *get_name (void) { return "GET_SUBTABLES"; }
+  template <typename T>
+  inline return_t dispatch (const T &obj)
+  {
+    hb_applicable_t *entry = array.push();
+    entry->init (obj, apply_to<T>);
+    return HB_VOID;
+  }
+  static return_t default_return_value (void) { return HB_VOID; }
+  bool stop_sublookup_iteration (return_t r HB_UNUSED) const { return false; }
+
+  hb_get_subtables_context_t (array_t &array_) :
+			      array (array_),
+			      debug_depth (0) {}
+
+  array_t &array;
+  unsigned int debug_depth;
+};
+
+
+
 
 typedef bool (*intersects_func_t) (const hb_set_t *glyphs, const HBUINT16 &value, const void *data);
 typedef void (*collect_glyphs_func_t) (hb_set_t *glyphs, const HBUINT16 &value, const void *data);
@@ -2562,6 +2620,39 @@ struct Extension
  * GSUB/GPOS Common
  */
 
+struct hb_ot_layout_lookup_accelerator_t
+{
+  template <typename TLookup>
+  inline void init (const TLookup &lookup)
+  {
+    digest.init ();
+    lookup.add_coverage (&digest);
+
+    subtables.init ();
+    OT::hb_get_subtables_context_t c_get_subtables (subtables);
+    lookup.dispatch (&c_get_subtables);
+  }
+  inline void fini (void)
+  {
+    subtables.fini ();
+  }
+
+  inline bool may_have (hb_codepoint_t g) const
+  { return digest.may_have (g); }
+
+  inline bool apply (hb_ot_apply_context_t *c) const
+  {
+     for (unsigned int i = 0; i < subtables.len; i++)
+       if (subtables[i].apply (c))
+         return true;
+     return false;
+  }
+
+  private:
+  hb_set_digest_t digest;
+  hb_get_subtables_context_t::array_t subtables;
+};
+
 struct GSUBGPOS
 {
   inline bool has_data (void) const { return version.to_int () != 0; }
diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index 975b7f8d4..4908076e8 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -1094,7 +1094,7 @@ struct GSUBProxy
     accels (hb_ot_face_data (face)->GSUB->accels) {}
 
   const OT::GSUB &table;
-  const hb_ot_layout_lookup_accelerator_t *accels;
+  const OT::hb_ot_layout_lookup_accelerator_t *accels;
 };
 
 struct GPOSProxy
@@ -1108,63 +1108,13 @@ struct GPOSProxy
     accels (hb_ot_face_data (face)->GPOS->accels) {}
 
   const OT::GPOS &table;
-  const hb_ot_layout_lookup_accelerator_t *accels;
+  const OT::hb_ot_layout_lookup_accelerator_t *accels;
 };
 
 
-struct hb_get_subtables_context_t :
-       hb_dispatch_context_t<hb_get_subtables_context_t, hb_void_t, HB_DEBUG_APPLY>
-{
-  template <typename Type>
-  static inline bool apply_to (const void *obj, OT::hb_ot_apply_context_t *c)
-  {
-    const Type *typed_obj = (const Type *) obj;
-    return typed_obj->apply (c);
-  }
-
-  typedef bool (*hb_apply_func_t) (const void *obj, OT::hb_ot_apply_context_t *c);
-
-  struct hb_applicable_t
-  {
-    inline void init (const void *obj_, hb_apply_func_t apply_func_)
-    {
-      obj = obj_;
-      apply_func = apply_func_;
-    }
-
-    inline bool apply (OT::hb_ot_apply_context_t *c) const { return apply_func (obj, c); }
-
-    private:
-    const void *obj;
-    hb_apply_func_t apply_func;
-  };
-
-  typedef hb_auto_t<hb_vector_t<hb_applicable_t> > array_t;
-
-  /* Dispatch interface. */
-  inline const char *get_name (void) { return "GET_SUBTABLES"; }
-  template <typename T>
-  inline return_t dispatch (const T &obj)
-  {
-    hb_applicable_t *entry = array.push();
-    entry->init (&obj, apply_to<T>);
-    return HB_VOID;
-  }
-  static return_t default_return_value (void) { return HB_VOID; }
-  bool stop_sublookup_iteration (return_t r HB_UNUSED) const { return false; }
-
-  hb_get_subtables_context_t (array_t &array_) :
-			      array (array_),
-			      debug_depth (0) {}
-
-  array_t &array;
-  unsigned int debug_depth;
-};
-
 static inline bool
 apply_forward (OT::hb_ot_apply_context_t *c,
-	       const hb_ot_layout_lookup_accelerator_t &accel,
-	       const hb_get_subtables_context_t::array_t &subtables)
+	       const OT::hb_ot_layout_lookup_accelerator_t &accel)
 {
   bool ret = false;
   hb_buffer_t *buffer = c->buffer;
@@ -1175,12 +1125,7 @@ apply_forward (OT::hb_ot_apply_context_t *c,
 	(buffer->cur().mask & c->lookup_mask) &&
 	c->check_glyph_property (&buffer->cur(), c->lookup_props))
      {
-       for (unsigned int i = 0; i < subtables.len; i++)
-         if (subtables[i].apply (c))
-	 {
-	   applied = true;
-	   break;
-	 }
+       applied = accel.apply (c);
      }
 
     if (applied)
@@ -1193,8 +1138,7 @@ apply_forward (OT::hb_ot_apply_context_t *c,
 
 static inline bool
 apply_backward (OT::hb_ot_apply_context_t *c,
-	       const hb_ot_layout_lookup_accelerator_t &accel,
-	       const hb_get_subtables_context_t::array_t &subtables)
+	       const OT::hb_ot_layout_lookup_accelerator_t &accel)
 {
   bool ret = false;
   hb_buffer_t *buffer = c->buffer;
@@ -1204,12 +1148,8 @@ apply_backward (OT::hb_ot_apply_context_t *c,
 	(buffer->cur().mask & c->lookup_mask) &&
 	c->check_glyph_property (&buffer->cur(), c->lookup_props))
     {
-     for (unsigned int i = 0; i < subtables.len; i++)
-       if (subtables[i].apply (c))
-       {
-	 ret = true;
-	 break;
-       }
+     if (accel.apply (c))
+       ret = true;
     }
     /* The reverse lookup doesn't "advance" cursor (for good reason). */
     buffer->idx--;
@@ -1223,7 +1163,7 @@ template <typename Proxy>
 static inline void
 apply_string (OT::hb_ot_apply_context_t *c,
 	      const typename Proxy::Lookup &lookup,
-	      const hb_ot_layout_lookup_accelerator_t &accel)
+	      const OT::hb_ot_layout_lookup_accelerator_t &accel)
 {
   hb_buffer_t *buffer = c->buffer;
 
@@ -1232,10 +1172,6 @@ apply_string (OT::hb_ot_apply_context_t *c,
 
   c->set_lookup_props (lookup.get_props ());
 
-  hb_get_subtables_context_t::array_t subtables;
-  hb_get_subtables_context_t c_get_subtables (subtables);
-  lookup.dispatch (&c_get_subtables);
-
   if (likely (!lookup.is_reverse ()))
   {
     /* in/out forward substitution/positioning */
@@ -1244,7 +1180,7 @@ apply_string (OT::hb_ot_apply_context_t *c,
     buffer->idx = 0;
 
     bool ret;
-    ret = apply_forward (c, accel, subtables);
+    ret = apply_forward (c, accel);
     if (ret)
     {
       if (!Proxy::inplace)
@@ -1260,7 +1196,7 @@ apply_string (OT::hb_ot_apply_context_t *c,
       buffer->remove_output ();
     buffer->idx = buffer->len - 1;
 
-    apply_backward (c, accel, subtables);
+    apply_backward (c, accel);
   }
 }
 
@@ -1319,7 +1255,7 @@ void hb_ot_map_t::position (const hb_ot_shape_plan_t *plan, hb_font_t *font, hb_
 void
 hb_ot_layout_substitute_lookup (OT::hb_ot_apply_context_t *c,
 				const OT::SubstLookup &lookup,
-				const hb_ot_layout_lookup_accelerator_t &accel)
+				const OT::hb_ot_layout_lookup_accelerator_t &accel)
 {
   apply_string<GSUBProxy> (c, lookup, accel);
 }
diff --git a/src/hb-ot-layout.hh b/src/hb-ot-layout.hh
index f5ffe3112..64b3d7480 100644
--- a/src/hb-ot-layout.hh
+++ b/src/hb-ot-layout.hh
@@ -112,32 +112,16 @@ hb_ot_layout_substitute_start (hb_font_t    *font,
 			       hb_buffer_t  *buffer);
 
 
-struct hb_ot_layout_lookup_accelerator_t
-{
-  template <typename TLookup>
-  inline void init (const TLookup &lookup)
-  {
-    digest.init ();
-    lookup.add_coverage (&digest);
-  }
-  inline void fini (void) {}
-
-  inline bool may_have (hb_codepoint_t g) const
-  { return digest.may_have (g); }
-
-  private:
-  hb_set_digest_t digest;
-};
-
 namespace OT {
   struct hb_ot_apply_context_t;
   struct SubstLookup;
+  struct hb_ot_layout_lookup_accelerator_t;
 }
 
 HB_INTERNAL void
 hb_ot_layout_substitute_lookup (OT::hb_ot_apply_context_t *c,
 				const OT::SubstLookup &lookup,
-				const hb_ot_layout_lookup_accelerator_t &accel);
+				const OT::hb_ot_layout_lookup_accelerator_t &accel);
 
 
 /* Should be called before all the position_lookup's are done. */
diff --git a/src/hb-ot-shape-complex-arabic-fallback.hh b/src/hb-ot-shape-complex-arabic-fallback.hh
index 0ef60f643..2aa036728 100644
--- a/src/hb-ot-shape-complex-arabic-fallback.hh
+++ b/src/hb-ot-shape-complex-arabic-fallback.hh
@@ -201,7 +201,7 @@ struct arabic_fallback_plan_t
 
   hb_mask_t mask_array[ARABIC_FALLBACK_MAX_LOOKUPS];
   OT::SubstLookup *lookup_array[ARABIC_FALLBACK_MAX_LOOKUPS];
-  hb_ot_layout_lookup_accelerator_t accel_array[ARABIC_FALLBACK_MAX_LOOKUPS];
+  OT::hb_ot_layout_lookup_accelerator_t accel_array[ARABIC_FALLBACK_MAX_LOOKUPS];
 };
 
 #if (defined(_WIN32) || defined(__CYGWIN__)) && !defined(HB_NO_WIN1256)
diff --git a/src/hb-ot-shape-fallback.cc b/src/hb-ot-shape-fallback.cc
index 556c34089..655f45ca4 100644
--- a/src/hb-ot-shape-fallback.cc
+++ b/src/hb-ot-shape-fallback.cc
@@ -460,6 +460,10 @@ _hb_ot_shape_fallback_kern (const hb_ot_shape_plan_t *plan,
 			    hb_font_t *font,
 			    hb_buffer_t *buffer)
 {
+  if (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction) ?
+      !font->has_glyph_h_kerning_func () :
+      !font->has_glyph_v_kerning_func ())
+    return;
   hb_ot_shape_fallback_kern_driver_t driver (font, buffer);
   hb_kern_machine_t<hb_ot_shape_fallback_kern_driver_t> machine (driver);
   machine.kern (font, buffer, plan->kern_mask);
diff --git a/src/hb-ot-shape.cc b/src/hb-ot-shape.cc
index 6753ceb29..3b1c93db4 100644
--- a/src/hb-ot-shape.cc
+++ b/src/hb-ot-shape.cc
@@ -42,6 +42,17 @@
 #include "hb-aat-layout.hh"
 
 
+static bool
+_hb_apply_morx (hb_face_t *face)
+{
+  if (hb_options ().aat &&
+      hb_aat_layout_has_substitution (face))
+    return true;
+
+  return !hb_ot_layout_has_substitution (face) &&
+	 hb_aat_layout_has_substitution (face);
+}
+
 void
 hb_ot_shape_planner_t::compile (hb_ot_shape_plan_t &plan,
 				const int          *coords,
@@ -55,24 +66,56 @@ hb_ot_shape_planner_t::compile (hb_ot_shape_plan_t &plan,
   plan.frac_mask = plan.map.get_1_mask (HB_TAG ('f','r','a','c'));
   plan.numr_mask = plan.map.get_1_mask (HB_TAG ('n','u','m','r'));
   plan.dnom_mask = plan.map.get_1_mask (HB_TAG ('d','n','o','m'));
-
-  plan.kern_mask = plan.map.get_mask (HB_DIRECTION_IS_HORIZONTAL (plan.props.direction) ?
-				      HB_TAG ('k','e','r','n') : HB_TAG ('v','k','r','n'));
-
   plan.has_frac = plan.frac_mask || (plan.numr_mask && plan.dnom_mask);
-  plan.kerning_requested = !!plan.kern_mask;
-  plan.has_gpos_mark = !!plan.map.get_1_mask (HB_TAG ('m','a','r','k'));
-
-  plan.apply_morx = !hb_ot_layout_has_substitution (face) &&
-		     hb_aat_layout_has_substitution (face);
+  hb_tag_t kern_tag = HB_DIRECTION_IS_HORIZONTAL (plan.props.direction) ?
+		      HB_TAG ('k','e','r','n') : HB_TAG ('v','k','r','n');
+  plan.kern_mask = plan.map.get_mask (kern_tag);
 
+  plan.requested_kerning = !!plan.kern_mask;
+  bool has_gpos_kern = plan.map.get_feature_index (1, kern_tag) != HB_OT_LAYOUT_NO_FEATURE_INDEX;
   bool disable_gpos = plan.shaper->gpos_tag &&
 		      plan.shaper->gpos_tag != plan.map.chosen_script[1];
-  plan.apply_gpos = !disable_gpos && hb_ot_layout_has_positioning (face);
-  plan.apply_kern = !plan.apply_gpos && hb_ot_layout_has_kerning (face);
-  plan.fallback_kerning = !plan.apply_gpos && !plan.apply_kern;
-  plan.fallback_mark_positioning = !plan.apply_gpos;
-  plan.fallback_glyph_classes = !hb_ot_layout_has_glyph_classes (face);
+
+  /*
+   * Decide who provides glyph classes. GDEF or Unicode.
+   */
+
+  if (!hb_ot_layout_has_glyph_classes (face))
+    plan.fallback_glyph_classes = true;
+
+  /*
+   * Decide who does substitutions. GSUB, morx, or fallback.
+   */
+
+  plan.apply_morx = _hb_apply_morx (face);
+
+  /*
+   * Decide who does positioning. GPOS, kerx, kern, or fallback.
+   */
+
+  if (hb_options ().aat && hb_aat_layout_has_positioning (face))
+    plan.apply_kerx = true;
+  else if (!disable_gpos && hb_ot_layout_has_positioning (face))
+    plan.apply_gpos = true;
+  else if (hb_aat_layout_has_positioning (face))
+    plan.apply_kerx = true;
+
+  if (plan.requested_kerning)
+  {
+    if (plan.apply_kerx)
+      ;/* kerx supercedes kern. */
+    else if (!has_gpos_kern)
+    {
+      if (hb_ot_layout_has_kerning (face))
+        plan.apply_kern = true;
+      else
+	plan.fallback_kerning = true;
+    }
+  }
+
+  plan.has_gpos_mark = !!plan.map.get_1_mask (HB_TAG ('m','a','r','k'));
+  if (!plan.apply_gpos)
+    plan.fallback_mark_positioning = true;
 }
 
 
@@ -229,8 +272,7 @@ _hb_ot_shaper_shape_plan_data_create (hb_shape_plan_t    *shape_plan,
 
   /* Ugly that we have to do this here...
    * If we are going to apply morx, choose default shaper. */
-  if (!hb_ot_layout_has_substitution (planner.face) &&
-       hb_aat_layout_has_substitution (planner.face))
+  if (_hb_apply_morx (planner.face))
     planner.shaper = &_hb_ot_complex_shaper_default;
   else
     planner.shaper = hb_ot_shape_complex_categorize (&planner);
@@ -792,6 +834,8 @@ hb_ot_position_complex (const hb_ot_shape_context_t *c)
 
   if (c->plan->apply_gpos)
     c->plan->position (c->font, c->buffer);
+  else if (c->plan->apply_kerx)
+    hb_aat_layout_position (c->plan, c->font, c->buffer);
 
   switch (c->plan->shaper->zero_width_marks)
   {
@@ -835,16 +879,12 @@ hb_ot_position (const hb_ot_shape_context_t *c)
 
   /* Visual fallback goes here. */
 
-  if (!c->plan->kerning_requested)
-    ;
-  else if (c->plan->apply_kern)
+  if (c->plan->apply_kern)
     hb_ot_layout_kern (c->font, c->buffer, c->plan->kern_mask);
   else if (c->plan->fallback_kerning)
     _hb_ot_shape_fallback_kern (c->plan, c->font, c->buffer);
 
   _hb_buffer_deallocate_gsubgpos_vars (c->buffer);
-
-  //hb_aat_layout_position (c->font, c->buffer);
 }
 
 static inline void
diff --git a/src/hb-ot-shape.hh b/src/hb-ot-shape.hh
index 43852d8ff..4943c5155 100644
--- a/src/hb-ot-shape.hh
+++ b/src/hb-ot-shape.hh
@@ -43,14 +43,15 @@ struct hb_ot_shape_plan_t
   hb_mask_t rtlm_mask, frac_mask, numr_mask, dnom_mask;
   hb_mask_t kern_mask;
 
+  bool requested_kerning : 1;
   bool has_frac : 1;
-  bool kerning_requested : 1;
   bool has_gpos_mark : 1;
   bool fallback_glyph_classes : 1;
   bool fallback_kerning : 1;
   bool fallback_mark_positioning : 1;
 
   bool apply_morx : 1;
+  bool apply_kerx : 1;
   bool apply_kern : 1;
   bool apply_gpos : 1;
 
diff --git a/src/hb-shaper-list.hh b/src/hb-shaper-list.hh
index b0835d31a..1fdb64810 100644
--- a/src/hb-shaper-list.hh
+++ b/src/hb-shaper-list.hh
@@ -39,9 +39,7 @@ HB_SHAPER_IMPLEMENT (graphite2)
 HB_SHAPER_IMPLEMENT (coretext_aat)
 #endif
 
-#ifdef HAVE_OT
 HB_SHAPER_IMPLEMENT (ot) /* <--- This is our main OpenType shaper. */
-#endif
 
 #ifdef HAVE_UNISCRIBE
 HB_SHAPER_IMPLEMENT (uniscribe)
diff --git a/src/hb.hh b/src/hb.hh
index 152285221..f37be7ad0 100644
--- a/src/hb.hh
+++ b/src/hb.hh
@@ -45,10 +45,8 @@
 
 #include "hb.h"
 #define HB_H_IN
-#ifdef HAVE_OT
 #include "hb-ot.h"
 #define HB_OT_H_IN
-#endif
 
 #include <math.h>
 #include <stdlib.h>
diff --git a/test/api/Makefile.am b/test/api/Makefile.am
index 871bd3e44..03cf815ca 100644
--- a/test/api/Makefile.am
+++ b/test/api/Makefile.am
@@ -73,14 +73,13 @@ test_unicode_LDADD += $(top_builddir)/src/libharfbuzz-icu.la $(ICU_LIBS)
 endif
 
 
-if HAVE_OT
-
 TEST_PROGS += \
 	test-ot-color \
 	test-ot-tag \
 	test-ot-extents-cff \
 	$(NULL)
 
+
 if HAVE_PTHREAD
 if HAVE_FREETYPE
 TEST_PROGS += test-multithread
@@ -100,7 +99,6 @@ test_ot_math_LDADD = $(LDADD) $(FREETYPE_LIBS)
 test_ot_math_CPPFLAGS = $(AM_CPPFLAGS) $(FREETYPE_CFLAGS)
 endif # HAVE_FREETYPE
 
-endif # HAVE_OT
 
 # Tests for header compilation
 TEST_PROGS += \
diff --git a/test/api/test-c.c b/test/api/test-c.c
index 78d6e974d..061f35cdc 100644
--- a/test/api/test-c.c
+++ b/test/api/test-c.c
@@ -32,6 +32,7 @@
 #endif
 
 #include <hb.h>
+#include <hb-ot.h>
 
 #ifdef HAVE_GLIB
 #include <hb-glib.h>
@@ -45,10 +46,6 @@
 #include <hb-ft.h>
 #endif
 
-#ifdef HAVE_OT
-#include <hb-ot.h>
-#endif
-
 #ifdef HAVE_UNISCRIBE
 #include <hb-uniscribe.h>
 #endif
diff --git a/util/Makefile.am b/util/Makefile.am
index b8bf88418..85f9edaa0 100644
--- a/util/Makefile.am
+++ b/util/Makefile.am
@@ -52,14 +52,11 @@ hb_subset_LDADD = \
 	$(top_builddir)/src/libharfbuzz-subset.la
 bin_PROGRAMS += hb-subset
 
-if HAVE_OT
 hb_ot_shape_closure_SOURCES = $(HB_OT_SHAPE_CLOSURE_sources)
 bin_PROGRAMS += hb-ot-shape-closure
-endif # HAVE_OT
 
 endif # HAVE_GLIB
 
-#if HAVE_OT
 #if HAVE_FONTCONFIG
 #hb_fc_list_SOURCES = \
 #	hb-fc.cc \
@@ -72,6 +69,5 @@ endif # HAVE_GLIB
 #	$(NULL)
 #bin_PROGRAMS += hb-fc-list
 #endif # HAVE_FONTCONFIG
-#endif # HAVE_OT
 
 -include $(top_srcdir)/git.mk
diff --git a/util/options.cc b/util/options.cc
index 090a9c254..26b0bd0a8 100644
--- a/util/options.cc
+++ b/util/options.cc
@@ -29,9 +29,7 @@
 #ifdef HAVE_FREETYPE
 #include <hb-ft.h>
 #endif
-#ifdef HAVE_OT
 #include <hb-ot.h>
-#endif
 
 static struct supported_font_funcs_t {
 	char name[4];
@@ -41,9 +39,7 @@ static struct supported_font_funcs_t {
 #ifdef HAVE_FREETYPE
   {"ft",	hb_ft_font_set_funcs},
 #endif
-#ifdef HAVE_OT
   {"ot",	hb_ot_font_set_funcs},
-#endif
 };
 
 
diff --git a/util/options.hh b/util/options.hh
index 5088adaba..3749b99be 100644
--- a/util/options.hh
+++ b/util/options.hh
@@ -46,9 +46,7 @@
 #endif
 
 #include <hb.h>
-#ifdef HAVE_OT
 #include <hb-ot.h>
-#endif
 #include <glib.h>
 #include <glib/gprintf.h>