bug#41200: Displaying a tooltip with x-show-tip gets very slow as more faces are defined

["Clément Pit-Claudel" <cpitclaudel@gmail.com>]

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On 15/05/2020 13.28, Eli Zaretskii wrote:
>> Cc: 41200@debbugs.gnu.org, Anders Lindgren <andlind@gmail.com>
>> From: Clément Pit-Claudel <cpitclaudel@gmail.com>
>> Date: Fri, 15 May 2020 12:22:53 -0400
>>
>>>>> face_hash_table?
>>>>
>>>> Thanks, good idea.  I also liked Stefan's frame_face_map.
>>>
>>> "Map" is too general, IMO, it doesn't tell enough about the kind of
>>> object it is.
>>
>> Got it.  Is face_table better? (that was Stefan's other suggestion)
> 
> Is anything wrong with face_hash_table?

Nope; I've attached a new patch.

>> Btw, I have one more question: some callers of face-list seems to rely on the order of faces added to it, so it would be better to preserve that order.  Since hash-tables are not necessarily ordered, should I sort faces by face-id before returning them? 

Done in the attached patch as well.

>>> I think the problem is that tab-line is declared a basic face, but its
>>> defface form is not in faces.el.
>>
>> Ah, good catch.  Current there's a defface for tab-bar in lisp/tab-bar, and since that's preloaded it works, but the defface for tab-line is in lisp/tab-line.el and so isn't preloaded.
>> Should I move both to faces.el?
>>
> Yes, I think so.

Thanks.  I will ask Juri to confirm before moving them, because I realize now that they have a custom group.
Juri (CC'd; hi Juri!), was there a reason to make tab-bar and tab-line basic faces?  I see they are both in their own files and groups, instead of being in faces.el.

>>>>> I'm not sure I understand why do you need to look at the existing
>>>>> face's 'face' property?  The original code didn't.
>>>>
>>>> The original code iterated over face-frame-alist in the order in which entries were added to it.  If I understand correctly, iteration order isn't guaranteed on hash tables (is it?), so I had to find a different source of truth for these.
>>>
>>> Maybe we should store the ID with the face?  I think we wanted to get
>>> rid of the 'face' property of the faces at some point.
>>
>> Sounds reasonable; but where would we store it?  Right now faces are just symbols, right?
> 
> Don't hash-tables allow us to store more than one item in each slot?

They do, so I can certainly store (face-id . face-vector) in the hash table.  Done in the attached patch.  I only do this in Vface_new_frame_defaults, not in frame->face_hash_table.

>>> No, I was asking why not start with it as nil and actually make a
>>> hash-table when we first need it.
>>
>> Oh, I thought it would be simpler to always have a hash table instead of having to sanity check every time.
> 
> What is the default size of a hash-table?

65 entries, I think.


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From be915d6d2ea7a739026dc4a53fab64f78efab2bd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Pit-Claudel?= <clement.pitclaudel@live.com>
Date: Tue, 12 May 2020 21:48:32 -0400
Subject: [PATCH] Store 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/emacs-lisp/edebug.el (edebug-eval-defun):
* 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.
---
 lisp/custom.el               |  2 +-
 lisp/emacs-lisp/edebug.el    |  3 +-
 lisp/faces.el                | 23 ++++++++--
 lisp/frame.el                |  2 +-
 lisp/progmodes/elisp-mode.el |  3 +-
 src/frame.c                  | 20 ++++++---
 src/frame.h                  |  8 ++--
 src/xfaces.c                 | 82 ++++++++++++++++++------------------
 8 files changed, 83 insertions(+), 60 deletions(-)

diff --git a/lisp/custom.el b/lisp/custom.el
index 885c486c5e..3ac8bac40f 100644
--- a/lisp/custom.el
+++ b/lisp/custom.el
@@ -898,7 +898,7 @@ custom-push-theme
 	  ;; the value to a fake theme, `changed'.  If the theme is
 	  ;; later disabled, we use this to bring back the old value.
 	  ;;
-	  ;; For faces, we just use `face-new-frame-defaults' to
+	  ;; For faces, we just use `face--new-frame-defaults' to
 	  ;; recompute when the theme is disabled.
 	  (when (and (eq prop 'theme-value)
 		     (boundp symbol))
diff --git a/lisp/emacs-lisp/edebug.el b/lisp/emacs-lisp/edebug.el
index 78461185d3..76a75c04df 100644
--- a/lisp/emacs-lisp/edebug.el
+++ b/lisp/emacs-lisp/edebug.el
@@ -488,8 +488,7 @@ edebug-eval-defun
 	   (set-default (nth 1 form) (eval (nth 2 form) lexical-binding)))
           ((eq (car form) 'defface)
            ;; Reset the face.
-           (setq face-new-frame-defaults
-                 (assq-delete-all (nth 1 form) face-new-frame-defaults))
+           (remhash (nth 1 form) face--new-frame-defaults)
            (put (nth 1 form) 'face-defface-spec nil)
            (put (nth 1 form) 'face-documentation (nth 3 form))
 	   ;; See comments in `eval-defun-1' for purpose of code below
diff --git a/lisp/faces.el b/lisp/faces.el
index e707f6f4b6..bb51797a38 100644
--- a/lisp/faces.el
+++ b/lisp/faces.el
@@ -176,10 +176,27 @@ face-font-registry-alternatives
 ;;; Creation, copying.
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
+(make-obsolete-variable
+ 'face-new-frame-defaults
+ "use `face--new-frame-defaults' or `face-alist' instead."
+ "28.1")
+
+(defun frame-face-alist (&optional frame)
+  "Return an alist of frame-local faces defined on FRAME.
+This alist is a copy of the contents of `frame--face-hash-table'.
+For internal use only."
+  (declare (obsolete frame--face-hash-table "28.1"))
+  (let ((faces))
+    (maphash (lambda (face spec) (push `(,(car spec) ,face . ,(cdr spec)) faces))
+             (frame--face-hash-table frame))
+    (mapcar #'cdr (sort faces (lambda (f1 f2) (< (car f1) (car f2)))))))
 
 (defun face-list ()
   "Return a list of all defined faces."
-  (mapcar #'car face-new-frame-defaults))
+  (let ((faces))
+    (maphash (lambda (face spec) (push `(,(car spec) . ,face) faces))
+             face--new-frame-defaults)
+    (mapcar #'cdr (sort faces (lambda (f1 f2) (< (car f1) (car f2)))))))
 
 (defun make-face (face)
   "Define a new face with name FACE, a symbol.
@@ -2097,7 +2114,7 @@ x-create-frame-with-faces
 (defun face-set-after-frame-default (frame &optional parameters)
   "Initialize the frame-local faces of FRAME.
 Calculate the face definitions using the face specs, custom theme
-settings, X resources, and `face-new-frame-defaults'.
+settings, X resources, and `face--new-frame-defaults'.
 Finally, apply any relevant face attributes found amongst the
 frame parameters in PARAMETERS."
   ;; The `reverse' is so that `default' goes first.
@@ -2106,7 +2123,7 @@ face-set-after-frame-default
 	(progn
 	  ;; Initialize faces from face spec and custom theme.
 	  (face-spec-recalc face frame)
-	  ;; Apply attributes specified by face-new-frame-defaults
+	  ;; Apply attributes specified by face--new-frame-defaults
 	  (internal-merge-in-global-face face frame))
       ;; Don't let invalid specs prevent frame creation.
       (error nil)))
diff --git a/lisp/frame.el b/lisp/frame.el
index 6c2f774709..66b5c6aa8d 100644
--- a/lisp/frame.el
+++ b/lisp/frame.el
@@ -1227,7 +1227,7 @@ frame-set-background-mode
                          ;; during startup with -rv on the command
                          ;; line for the initial frame, because frames
                          ;; are not recorded in the pdump file.
-                         (assq face (frame-face-alist))
+                         (gethash face (frame--face-hash-table))
                          (face-spec-match-p face
                                             (face-user-default-spec face)
                                             ;; FIXME: why selected-frame and
diff --git a/lisp/progmodes/elisp-mode.el b/lisp/progmodes/elisp-mode.el
index b737134f90..75054b8818 100644
--- a/lisp/progmodes/elisp-mode.el
+++ b/lisp/progmodes/elisp-mode.el
@@ -1304,8 +1304,7 @@ elisp--eval-defun-1
 	((eq (car form) 'custom-declare-face)
 	 ;; Reset the face.
 	 (let ((face-symbol (eval (nth 1 form) lexical-binding)))
-	   (setq face-new-frame-defaults
-		 (assq-delete-all face-symbol face-new-frame-defaults))
+	   (remhash face--new-frame-defaults face-symbol)
 	   (put face-symbol 'face-defface-spec nil)
 	   (put face-symbol 'face-override-spec nil))
 	 form)
diff --git a/src/frame.c b/src/frame.c
index c871e4fd99..0843d53559 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -946,6 +946,10 @@ make_frame (bool mini_p)
   rw->total_lines = mini_p ? 9 : 10;
   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;
@@ -1254,7 +1258,7 @@ DEFUN ("make-terminal-frame", Fmake_terminal_frame, Smake_terminal_frame,
 {
   struct frame *f;
   struct terminal *t = NULL;
-  Lisp_Object frame, tem;
+  Lisp_Object frame;
   struct frame *sf = SELECTED_FRAME ();
 
 #ifdef MSDOS
@@ -1336,14 +1340,16 @@ DEFUN ("make-terminal-frame", Fmake_terminal_frame, Smake_terminal_frame,
   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 476bac67fa..9761253085 100644
--- a/src/frame.h
+++ b/src/frame.h
@@ -158,8 +158,8 @@ #define EMACS_FRAME_H
      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.
@@ -661,9 +661,9 @@ 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 7d7aff95c1..eae991d1c2 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -95,9 +95,10 @@ Copyright (C) 1993-1994, 1998-2020 Free Software Foundation, Inc.
    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
@@ -1843,13 +1844,11 @@ 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);
@@ -2734,11 +2733,6 @@ DEFUN ("internal-make-lisp-face", Finternal_make_lisp_face,
   /* 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
@@ -2748,9 +2742,14 @@ DEFUN ("internal-make-lisp-face", Finternal_make_lisp_face,
 	  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)
@@ -2763,7 +2762,7 @@ DEFUN ("internal-make-lisp-face", Finternal_make_lisp_face,
 	{
 	  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)
@@ -2924,7 +2923,7 @@ DEFUN ("internal-set-lisp-face-attribute", Finternal_set_lisp_face_attribute,
       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.
@@ -3508,7 +3507,7 @@ 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))
@@ -4174,14 +4173,13 @@ DEFUN ("internal-lisp-face-empty-p", Finternal_lisp_face_empty_p,
   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;
 }
 
 
@@ -6678,30 +6676,32 @@ 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;
@@ -6855,7 +6855,7 @@ 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);
@@ -6879,9 +6879,11 @@ syms_of_xfaces (void)
 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 =
+    make_hash_table (hashtest_eq, DEFAULT_HASH_SIZE, DEFAULT_REHASH_SIZE,
+                     DEFAULT_REHASH_THRESHOLD, Qnil, false);
 
   DEFVAR_LISP ("face-default-stipple", Vface_default_stipple,
     doc: /* Default stipple pattern used on monochrome displays.
-- 
2.17.1