Speed up by storing frame faces in hash tables instead of alists

* src/frame.h (struct frame): Add face_hash_table, remove face_alist.
(fset_face_hash_table): New function.
(fset_face_alist): Remove.
* src/frame.c (make_frame): Initialize f->face_hash_table.
(Fmake_terminal_frame): Update to work with hash tables instead of
alists.
* src/xfaces.c (lface_from_face_name_no_resolve):
(Finternal_make_lisp_face):
(update_face_from_frame_parameter): Update to work with hash tables
instead of alists.
(Fframe_face_hash_table): New function.
(Fframe_face_alist): Move to faces.el as frame-face-alist.
(syms_of_xfaces): Add frame_face_hash_table.

* lisp/progmodes/elisp-mode.el (elisp--eval-defun-1):
* lisp/frame.el (frame-set-background-mode): Update to work with hash
tables instead of alists.
* lisp/faces.el (face-new-frame-defaults): Mark obsolete.
(face-list): Update to use face--new-frame-defaults.
(frame-face-alist): Moved here from src/xfaces.c.
(x-create-frame-with-faces): Update to handle subtle semantic change
to how frame faces propagate, which otherwise breaks frame creation
with reverse video enabled (bug#41200).

Reworked from a patch by Clément Pit-Claudel <clement.pitclaudel@live.com>.

3 files changed, 60 insertions, 51 deletions

diff --git a/src/frame.c b/src/frame.c
index 623e4ba2cde..b105268d423 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -1018,6 +1018,10 @@ make_frame (bool mini_p)
   rw->total_lines = FRAME_LINES (f) - (mini_p ? 1 : 0);
   rw->pixel_height = rw->total_lines * FRAME_LINE_HEIGHT (f);
 
+  fset_face_hash_table
+    (f, make_hash_table (hashtest_eq, DEFAULT_HASH_SIZE, DEFAULT_REHASH_SIZE,
+                         DEFAULT_REHASH_THRESHOLD, Qnil, false));
+
   if (mini_p)
     {
       mw->top_line = rw->total_lines;
@@ -1326,7 +1330,7 @@ affects all frames on the same terminal device.  */)
 {
   struct frame *f;
   struct terminal *t = NULL;
-  Lisp_Object frame, tem;
+  Lisp_Object frame;
   struct frame *sf = SELECTED_FRAME ();
 
 #ifdef MSDOS
@@ -1408,14 +1412,16 @@ affects all frames on the same terminal device.  */)
   store_in_alist (&parms, Qminibuffer, Qt);
   Fmodify_frame_parameters (frame, parms);
 
-  /* Make the frame face alist be frame-specific, so that each
+  /* Make the frame face hash be frame-specific, so that each
      frame could change its face definitions independently.  */
-  fset_face_alist (f, Fcopy_alist (sf->face_alist));
-  /* Simple Fcopy_alist isn't enough, because we need the contents of
-     the vectors which are the CDRs of associations in face_alist to
+  fset_face_hash_table (f, Fcopy_hash_table (sf->face_hash_table));
+  /* Simple copy_hash_table isn't enough, because we need the contents of
+     the vectors which are the values in face_hash_table to
      be copied as well.  */
-  for (tem = f->face_alist; CONSP (tem); tem = XCDR (tem))
-    XSETCDR (XCAR (tem), Fcopy_sequence (XCDR (XCAR (tem))));
+  ptrdiff_t idx = 0;
+  struct Lisp_Hash_Table *table = XHASH_TABLE (f->face_hash_table);
+  for (idx = 0; idx < table->count; ++idx)
+    set_hash_value_slot (table, idx, Fcopy_sequence (HASH_VALUE (table, idx)));
 
   f->can_set_window_size = true;
   f->after_make_frame = true;
diff --git a/src/frame.h b/src/frame.h
index cad3df5ae10..a8ad011889d 100644
--- a/src/frame.h
+++ b/src/frame.h
@@ -158,8 +158,8 @@ struct frame
      There are four additional elements of nil at the end, to terminate.  */
   Lisp_Object menu_bar_items;
 
-  /* Alist of elements (FACE-NAME . FACE-VECTOR-DATA).  */
-  Lisp_Object face_alist;
+  /* Hash table of FACE-NAME keys and FACE-VECTOR-DATA values.  */
+  Lisp_Object face_hash_table;
 
   /* A vector that records the entire structure of this frame's menu bar.
      For the format of the data, see extensive comments in xmenu.c.
@@ -672,9 +672,9 @@ fset_condemned_scroll_bars (struct frame *f, Lisp_Object val)
   f->condemned_scroll_bars = val;
 }
 INLINE void
-fset_face_alist (struct frame *f, Lisp_Object val)
+fset_face_hash_table (struct frame *f, Lisp_Object val)
 {
-  f->face_alist = val;
+  f->face_hash_table = val;
 }
 #if defined (HAVE_WINDOW_SYSTEM)
 INLINE void
diff --git a/src/xfaces.c b/src/xfaces.c
index fed7b3336a2..207f0d6a36e 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -95,9 +95,10 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
    with the symbol `face' in slot 0, and a slot for each of the face
    attributes mentioned above.
 
-   There is also a global face alist `Vface_new_frame_defaults'.  Face
-   definitions from this list are used to initialize faces of newly
-   created frames.
+   There is also a global face map `Vface_new_frame_defaults',
+   containing conses of (FACE_ID . FACE_DEFINITION).  Face definitions
+   from this table are used to initialize faces of newly created
+   frames.
 
    A face doesn't have to specify all attributes.  Those not specified
    have a value of `unspecified'.  Faces specifying all attributes but
@@ -1965,13 +1966,11 @@ lface_from_face_name_no_resolve (struct frame *f, Lisp_Object face_name,
   Lisp_Object lface;
 
   if (f)
-    lface = assq_no_quit (face_name, f->face_alist);
+    lface = Fgethash (face_name, f->face_hash_table, Qnil);
   else
-    lface = assq_no_quit (face_name, Vface_new_frame_defaults);
+    lface = CDR (Fgethash (face_name, Vface_new_frame_defaults, Qnil));
 
-  if (CONSP (lface))
-    lface = XCDR (lface);
-  else if (signal_p)
+  if (signal_p && NILP (lface))
     signal_error ("Invalid face", face_name);
 
   check_lface (lface);
@@ -2870,11 +2869,6 @@ Value is a vector of face attributes.  */)
   /* Add a global definition if there is none.  */
   if (NILP (global_lface))
     {
-      global_lface = make_vector (LFACE_VECTOR_SIZE, Qunspecified);
-      ASET (global_lface, 0, Qface);
-      Vface_new_frame_defaults = Fcons (Fcons (face, global_lface),
-					Vface_new_frame_defaults);
-
       /* Assign the new Lisp face a unique ID.  The mapping from Lisp
 	 face id to Lisp face is given by the vector lface_id_to_name.
 	 The mapping from Lisp face to Lisp face id is given by the
@@ -2884,9 +2878,14 @@ Value is a vector of face attributes.  */)
 	  xpalloc (lface_id_to_name, &lface_id_to_name_size, 1, MAX_FACE_ID,
 		   sizeof *lface_id_to_name);
 
+      Lisp_Object face_id = make_fixnum (next_lface_id);
       lface_id_to_name[next_lface_id] = face;
-      Fput (face, Qface, make_fixnum (next_lface_id));
+      Fput (face, Qface, face_id);
       ++next_lface_id;
+
+      global_lface = make_vector (LFACE_VECTOR_SIZE, Qunspecified);
+      ASET (global_lface, 0, Qface);
+      Fputhash (face, Fcons (face_id, global_lface), Vface_new_frame_defaults);
     }
   else if (f == NULL)
     for (i = 1; i < LFACE_VECTOR_SIZE; ++i)
@@ -2899,7 +2898,7 @@ Value is a vector of face attributes.  */)
 	{
 	  lface = make_vector (LFACE_VECTOR_SIZE, Qunspecified);
 	  ASET (lface, 0, Qface);
-	  fset_face_alist (f, Fcons (Fcons (face, lface), f->face_alist));
+          Fputhash (face, lface, f->face_hash_table);
 	}
       else
 	for (i = 1; i < LFACE_VECTOR_SIZE; ++i)
@@ -3060,7 +3059,7 @@ FRAME 0 means change the face on all frames, and change the default
       f = NULL;
       lface = lface_from_face_name (NULL, face, true);
 
-      /* When updating face-new-frame-defaults, we put :ignore-defface
+      /* When updating face--new-frame-defaults, we put :ignore-defface
 	 where the caller wants `unspecified'.  This forces the frame
 	 defaults to ignore the defface value.  Otherwise, the defface
 	 will take effect, which is generally not what is intended.
@@ -3645,7 +3644,7 @@ update_face_from_frame_parameter (struct frame *f, Lisp_Object param,
   /* If there are no faces yet, give up.  This is the case when called
      from Fx_create_frame, and we do the necessary things later in
      face-set-after-frame-defaults.  */
-  if (NILP (f->face_alist))
+  if (XFIXNAT (Fhash_table_count (f->face_hash_table)) == 0)
     return;
 
   if (EQ (param, Qforeground_color))
@@ -4311,14 +4310,13 @@ If FRAME is omitted or nil, use the selected frame.  */)
   return i == LFACE_VECTOR_SIZE ? Qt : Qnil;
 }
 
-
-DEFUN ("frame-face-alist", Fframe_face_alist, Sframe_face_alist,
+DEFUN ("frame--face-hash-table", Fframe_face_hash_table, Sframe_face_hash_table,
        0, 1, 0,
-       doc: /* Return an alist of frame-local faces defined on FRAME.
+       doc: /* Return a hash table of frame-local faces defined on FRAME.
 For internal use only.  */)
   (Lisp_Object frame)
 {
-  return decode_live_frame (frame)->face_alist;
+  return decode_live_frame (frame)->face_hash_table;
 }
 
 
@@ -6835,30 +6833,32 @@ DEFUN ("show-face-resources", Fshow_face_resources, Sshow_face_resources,
 
 #ifdef HAVE_PDUMPER
 /* All the faces defined during loadup are recorded in
-   face-new-frame-defaults, with the last face first in the list.  We
-   need to set next_lface_id to the next face ID number, so that any
-   new faces defined in this session will have face IDs different from
-   those defined during loadup.  We also need to set up the
-   lface_id_to_name[] array for the faces that were defined during
-   loadup.  */
+   face-new-frame-defaults.  We need to set next_lface_id to the next
+   face ID number, so that any new faces defined in this session will
+   have face IDs different from those defined during loadup.  We also
+   need to set up the lface_id_to_name[] array for the faces that were
+   defined during loadup.  */
 void
 init_xfaces (void)
 {
-  if (CONSP (Vface_new_frame_defaults))
+  int nfaces = XFIXNAT (Fhash_table_count (Vface_new_frame_defaults));
+  if (nfaces > 0)
     {
       /* Allocate the lface_id_to_name[] array.  */
-      lface_id_to_name_size = next_lface_id =
-	XFIXNAT (Flength (Vface_new_frame_defaults));
+      lface_id_to_name_size = next_lface_id = nfaces;
       lface_id_to_name = xnmalloc (next_lface_id, sizeof *lface_id_to_name);
 
       /* Store the faces.  */
-      Lisp_Object tail;
-      int i = next_lface_id - 1;
-      for (tail = Vface_new_frame_defaults; CONSP (tail); tail = XCDR (tail))
+      struct Lisp_Hash_Table* table = XHASH_TABLE (Vface_new_frame_defaults);
+      for (ptrdiff_t idx = 0; idx < nfaces; ++idx)
 	{
-	  Lisp_Object lface = XCAR (tail);
-	  eassert (i >= 0);
-	  lface_id_to_name[i--] = XCAR (lface);
+	  Lisp_Object lface = HASH_KEY (table, idx);
+	  Lisp_Object face_id = CAR (HASH_VALUE (table, idx));
+          if (FIXNATP (face_id)) {
+              int id = XFIXNAT (face_id);
+              eassert (id >= 0);
+              lface_id_to_name[id] = lface;
+            }
 	}
     }
   face_attr_sym[0] = Qface;
@@ -7014,7 +7014,7 @@ syms_of_xfaces (void)
   defsubr (&Sinternal_copy_lisp_face);
   defsubr (&Sinternal_merge_in_global_face);
   defsubr (&Sface_font);
-  defsubr (&Sframe_face_alist);
+  defsubr (&Sframe_face_hash_table);
   defsubr (&Sdisplay_supports_face_attributes_p);
   defsubr (&Scolor_distance);
   defsubr (&Sinternal_set_font_selection_order);
@@ -7038,9 +7038,12 @@ This variable is intended for use only by code that evaluates
 the "specifity" of a face specification and should be let-bound
 only for this purpose.  */);
 
-  DEFVAR_LISP ("face-new-frame-defaults", Vface_new_frame_defaults,
-    doc: /* List of global face definitions (for internal use only.)  */);
-  Vface_new_frame_defaults = Qnil;
+  DEFVAR_LISP ("face--new-frame-defaults", Vface_new_frame_defaults,
+    doc: /* Hash table of global face definitions (for internal use only.)  */);
+  Vface_new_frame_defaults =
+    /* 33 entries is enough to fit all basic faces */
+    make_hash_table (hashtest_eq, 33, DEFAULT_REHASH_SIZE,
+                     DEFAULT_REHASH_THRESHOLD, Qnil, false);
 
   DEFVAR_LISP ("face-default-stipple", Vface_default_stipple,
     doc: /* Default stipple pattern used on monochrome displays.