[gtk/speed-up-event-matching] keymap: Cache key info

[Matthias Clasen <matthiasc src gnome org>]

commit 99c3928cecb0bf4dd7c33c1f7fd078b256aa8a78
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Apr 30 00:33:06 2020 -0400

    keymap: Cache key info
    
    We currently calling gdk_display_map_keyval up to
    once per key event per shortcut trigger, and that function
    does an expensive loop over the entire keymap and
    allocates an array. Avoid this by caching the entries
    in a single array, and have a lookup table for finding
    the entries for a keyval.
    
    To do this, change the GdkKeymap.get_entries_for_keyval
    signature, and change the ::keys-changed signal to be
    RUN_FIRST, since we want to clear the cache in the class
    handler before running signal handlers. These changes are
    possible now, since keymaps are no longer public API.

 gdk/broadway/gdkkeys-broadway.c |  19 ++++---
 gdk/gdkevents.c                 |  11 ++--
 gdk/gdkkeys.c                   | 108 ++++++++++++++++++++++++++++++++++++----
 gdk/gdkkeysprivate.h            |  19 ++++++-
 gdk/wayland/gdkkeys-wayland.c   |  16 ++----
 gdk/win32/gdkkeys-win32.c       |  26 ++--------
 gdk/x11/gdkkeys-x11.c           |  29 +++--------
 7 files changed, 144 insertions(+), 84 deletions(-)
---
diff --git a/gdk/broadway/gdkkeys-broadway.c b/gdk/broadway/gdkkeys-broadway.c
index f58f332dc6..60d8715663 100644
--- a/gdk/broadway/gdkkeys-broadway.c
+++ b/gdk/broadway/gdkkeys-broadway.c
@@ -123,17 +123,16 @@ gdk_broadway_keymap_get_scroll_lock_state (GdkKeymap *keymap)
 
 static gboolean
 gdk_broadway_keymap_get_entries_for_keyval (GdkKeymap     *keymap,
-                                           guint          keyval,
-                                           GdkKeymapKey **keys,
-                                           gint          *n_keys)
+                                            guint          keyval,
+                                            GArray        *retval)
 {
-  if (n_keys)
-    *n_keys = 1;
-  if (keys)
-    {
-      *keys = g_new0 (GdkKeymapKey, 1);
-      (*keys)->keycode = keyval;
-    }
+  GdkKeymapKey key;
+
+  key.keycode = keyval;
+  key.group = 0;
+  key.level = 0;
+
+  g_array_append_val (retval, key);
 
   return TRUE;
 }
diff --git a/gdk/gdkevents.c b/gdk/gdkevents.c
index 41706885af..9d2a689381 100644
--- a/gdk/gdkevents.c
+++ b/gdk/gdkevents.c
@@ -1604,6 +1604,7 @@ gdk_key_event_matches (GdkEvent        *event,
                        GdkModifierType  modifiers)
 {
   GdkKeyEvent *self = (GdkKeyEvent *) event;
+  GdkKeymap *keymap;
   guint keycode;
   GdkModifierType state;
   guint ev_keyval;
@@ -1644,7 +1645,7 @@ gdk_key_event_matches (GdkEvent        *event,
     {
       /* modifier match */
       GdkKeymapKey *keys;
-      int n_keys;
+      guint n_keys;
       int i;
       guint key;
 
@@ -1667,7 +1668,8 @@ gdk_key_event_matches (GdkEvent        *event,
           return GDK_KEY_MATCH_EXACT;
         }
 
-      gdk_display_map_keyval (gdk_event_get_display (event), keyval, &keys, &n_keys);
+      keymap = gdk_display_get_keymap (gdk_event_get_display (event));
+      gdk_keymap_get_cached_entries_for_keyval (keymap, keyval, &keys, &n_keys);
 
       for (i = 0; i < n_keys; i++)
         {
@@ -1676,14 +1678,9 @@ gdk_key_event_matches (GdkEvent        *event,
               /* Only match for group if it's an accel mod */
               (!group_mod_is_accel_mod || keys[i].group == layout))
             {
-              /* partial match */
-              g_free (keys);
-
               return GDK_KEY_MATCH_PARTIAL;
             }
         }
-
-      g_free (keys);
     }
 
   return GDK_KEY_MATCH_NONE;
diff --git a/gdk/gdkkeys.c b/gdk/gdkkeys.c
index 469d204e0b..4d8978e552 100644
--- a/gdk/gdkkeys.c
+++ b/gdk/gdkkeys.c
@@ -195,14 +195,44 @@ gdk_keymap_set_property (GObject      *object,
     }
 }
 
+static void
+gdk_keymap_finalize (GObject *object)
+{
+  GdkKeymap *keymap = GDK_KEYMAP (object);
+
+  g_array_free (keymap->cached_keys, TRUE);
+  g_hash_table_unref (keymap->cache);
+
+  G_OBJECT_CLASS (gdk_keymap_parent_class)->finalize (object);
+}
+
+static void
+gdk_keymap_keys_changed (GdkKeymap *keymap)
+{
+  GdkKeymapKey key;
+
+  g_array_set_size (keymap->cached_keys, 0);
+
+  key.keycode = 0;
+  key.group = 0;
+  key.level = 0;
+
+  g_array_append_val (keymap->cached_keys, key);
+
+  g_hash_table_remove_all (keymap->cache);
+}
+
 static void
 gdk_keymap_class_init (GdkKeymapClass *klass)
 {
   GObjectClass *object_class = G_OBJECT_CLASS (klass);
 
+  object_class->finalize = gdk_keymap_finalize;
   object_class->get_property = gdk_keymap_get_property;
   object_class->set_property = gdk_keymap_set_property;
 
+  klass->keys_changed = gdk_keymap_keys_changed;
+
   props[PROP_DISPLAY] =
     g_param_spec_object ("display",
                          "Display",
@@ -237,13 +267,13 @@ gdk_keymap_class_init (GdkKeymapClass *klass)
    */
   signals[KEYS_CHANGED] =
     g_signal_new (g_intern_static_string ("keys-changed"),
-                 G_OBJECT_CLASS_TYPE (object_class),
-                 G_SIGNAL_RUN_LAST,
-                 G_STRUCT_OFFSET (GdkKeymapClass, keys_changed),
-                 NULL, NULL,
-                 NULL,
-                 G_TYPE_NONE,
-                 0);
+                  G_OBJECT_CLASS_TYPE (object_class),
+                  G_SIGNAL_RUN_FIRST,
+                  G_STRUCT_OFFSET (GdkKeymapClass, keys_changed),
+                  NULL, NULL,
+                  NULL,
+                  G_TYPE_NONE,
+                  0);
 
   /**
    * GdkKeymap::state-changed:
@@ -267,6 +297,17 @@ gdk_keymap_class_init (GdkKeymapClass *klass)
 static void
 gdk_keymap_init (GdkKeymap *keymap)
 {
+  GdkKeymapKey key;
+
+  keymap->cached_keys = g_array_new (FALSE, FALSE, sizeof (GdkKeymapKey));
+
+  key.keycode = 0;
+  key.group = 0;
+  key.level = 0;
+
+  g_array_append_val (keymap->cached_keys, key);
+
+  keymap->cache = g_hash_table_new (g_direct_hash, g_direct_equal);
 }
 
 /**
@@ -502,13 +543,62 @@ gdk_keymap_get_entries_for_keyval (GdkKeymap     *keymap,
                                    GdkKeymapKey **keys,
                                    gint          *n_keys)
 {
+  GArray *array;
+
   g_return_val_if_fail (GDK_IS_KEYMAP (keymap), FALSE);
   g_return_val_if_fail (keys != NULL, FALSE);
   g_return_val_if_fail (n_keys != NULL, FALSE);
   g_return_val_if_fail (keyval != 0, FALSE);
 
-  return GDK_KEYMAP_GET_CLASS (keymap)->get_entries_for_keyval (keymap, keyval,
-                                                                keys, n_keys);
+  array = g_array_new (FALSE, FALSE, sizeof (GdkKeymapKey));
+
+  GDK_KEYMAP_GET_CLASS (keymap)->get_entries_for_keyval (keymap, keyval, array);
+
+  *n_keys = array->len;
+  *keys = (GdkKeymapKey *)g_array_free (array, FALSE);
+
+  return TRUE;
+}
+
+void
+gdk_keymap_get_cached_entries_for_keyval (GdkKeymap     *keymap,
+                                          guint          keyval,
+                                          GdkKeymapKey **keys,
+                                          guint         *n_keys)
+{
+  guint cached;
+  guint offset;
+  guint len;
+
+  /* avoid using the first entry in cached_keys, so we can
+   * use 0 to mean 'not cached'
+   */
+  cached = GPOINTER_TO_UINT (g_hash_table_lookup (keymap->cache, GUINT_TO_POINTER (keyval)));
+  if (cached == 0)
+    {
+      GdkKeymapKey key;
+
+      offset = keymap->cached_keys->len;
+
+      GDK_KEYMAP_GET_CLASS (keymap)->get_entries_for_keyval (keymap, keyval, keymap->cached_keys);
+
+      g_array_append_val (keymap->cached_keys, key);
+
+      len = keymap->cached_keys->len - offset;
+      g_assert (len <= 255);
+
+      cached = (offset << 8) | len;
+
+      g_hash_table_insert (keymap->cache, GUINT_TO_POINTER (keyval), GUINT_TO_POINTER (cached));
+    }
+  else
+    {
+      len = cached & 255;
+      offset = cached >> 8;
+    }
+
+  *n_keys = len;
+  *keys = (GdkKeymapKey *)&g_array_index (keymap->cached_keys, GdkKeymapKey, offset);
 }
 
 /**
diff --git a/gdk/gdkkeysprivate.h b/gdk/gdkkeysprivate.h
index c7cf7424b6..79ad146b14 100644
--- a/gdk/gdkkeysprivate.h
+++ b/gdk/gdkkeysprivate.h
@@ -43,8 +43,7 @@ struct _GdkKeymapClass
   gboolean (* get_scroll_lock_state)    (GdkKeymap *keymap);
   gboolean (* get_entries_for_keyval)   (GdkKeymap     *keymap,
                                          guint          keyval,
-                                         GdkKeymapKey **keys,
-                                         gint          *n_keys);
+                                         GArray        *array);
   gboolean (* get_entries_for_keycode)  (GdkKeymap     *keymap,
                                          guint          hardware_keycode,
                                          GdkKeymapKey **keys,
@@ -73,6 +72,17 @@ struct _GdkKeymap
 {
   GObject     parent_instance;
   GdkDisplay *display;
+
+  /* We cache an array of GdkKeymapKey entries for keyval -> keycode
+   * lookup. Position 0 is unused.
+   *
+   * The hash table maps keyvals to values that have the number of keys
+   * in the low 8 bits, and the position in the array in the rest.
+   *
+   * The cache is cleared before ::keys-changed is emitted.
+   */
+  GArray *cached_keys;
+  GHashTable *cache;
 };
 
 GType gdk_keymap_get_type (void) G_GNUC_CONST;
@@ -106,6 +116,11 @@ gboolean       gdk_keymap_get_num_lock_state       (GdkKeymap           *keymap)
 gboolean       gdk_keymap_get_scroll_lock_state    (GdkKeymap           *keymap);
 guint          gdk_keymap_get_modifier_state       (GdkKeymap           *keymap);
 
+void           gdk_keymap_get_cached_entries_for_keyval (GdkKeymap     *keymap,
+                                                         guint          keyval,
+                                                         GdkKeymapKey **keys,
+                                                         guint         *n_keys);
+
 G_END_DECLS
 
 #endif
diff --git a/gdk/wayland/gdkkeys-wayland.c b/gdk/wayland/gdkkeys-wayland.c
index 1b98c73e85..802463298e 100644
--- a/gdk/wayland/gdkkeys-wayland.c
+++ b/gdk/wayland/gdkkeys-wayland.c
@@ -126,17 +126,14 @@ gdk_wayland_keymap_get_scroll_lock_state (GdkKeymap *keymap)
 }
 
 static gboolean
-gdk_wayland_keymap_get_entries_for_keyval (GdkKeymap     *keymap,
-                                          guint          keyval,
-                                          GdkKeymapKey **keys,
-                                          gint          *n_keys)
+gdk_wayland_keymap_get_entries_for_keyval (GdkKeymap *keymap,
+                                           guint      keyval,
+                                           GArray    *retval)
 {
   struct xkb_keymap *xkb_keymap = GDK_WAYLAND_KEYMAP (keymap)->xkb_keymap;
-  GArray *retval;
   guint keycode;
   xkb_keycode_t min_keycode, max_keycode;
-
-  retval = g_array_new (FALSE, FALSE, sizeof (GdkKeymapKey));
+  guint len = retval->len;
 
   min_keycode = xkb_keymap_min_keycode (xkb_keymap);
   max_keycode = xkb_keymap_max_keycode (xkb_keymap);
@@ -170,10 +167,7 @@ gdk_wayland_keymap_get_entries_for_keyval (GdkKeymap     *keymap,
         }
     }
 
-  *n_keys = retval->len;
-  *keys = (GdkKeymapKey*) g_array_free (retval, FALSE);
-
-  return TRUE;
+  return retval->len > len;
 }
 
 static gboolean
diff --git a/gdk/win32/gdkkeys-win32.c b/gdk/win32/gdkkeys-win32.c
index bae9a8e24d..972008492d 100644
--- a/gdk/win32/gdkkeys-win32.c
+++ b/gdk/win32/gdkkeys-win32.c
@@ -1283,19 +1283,14 @@ gdk_win32_keymap_get_scroll_lock_state (GdkKeymap *keymap)
 static gboolean
 gdk_win32_keymap_get_entries_for_keyval (GdkKeymap     *gdk_keymap,
                                          guint          keyval,
-                                         GdkKeymapKey **keys,
-                                         gint          *n_keys)
+                                         GArray        *retval)
 {
-  GArray *retval;
   GdkKeymap *default_keymap = gdk_display_get_keymap (gdk_display_get_default ());
+  guint len = retval->len;
 
   g_return_val_if_fail (gdk_keymap == NULL || GDK_IS_KEYMAP (gdk_keymap), FALSE);
-  g_return_val_if_fail (keys != NULL, FALSE);
-  g_return_val_if_fail (n_keys != NULL, FALSE);
   g_return_val_if_fail (keyval != 0, FALSE);
 
-  retval = g_array_new (FALSE, FALSE, sizeof (GdkKeymapKey));
-
   /* Accept only the default keymap */
   if (gdk_keymap == NULL || gdk_keymap == default_keymap)
     {
@@ -1344,7 +1339,7 @@ gdk_win32_keymap_get_entries_for_keyval (GdkKeymap     *gdk_keymap,
 
       g_print ("gdk_keymap_get_entries_for_keyval: %#.04x (%s):",
                keyval, gdk_keyval_name (keyval));
-      for (i = 0; i < retval->len; i++)
+      for (i = len; i < retval->len; i++)
         {
           GdkKeymapKey *entry = (GdkKeymapKey *) retval->data + i;
           g_print ("  %#.02x %d %d", entry->keycode, entry->group, entry->level);
@@ -1353,20 +1348,7 @@ gdk_win32_keymap_get_entries_for_keyval (GdkKeymap     *gdk_keymap,
     }
 #endif
 
-  if (retval->len > 0)
-    {
-      *keys = (GdkKeymapKey*) retval->data;
-      *n_keys = retval->len;
-    }
-  else
-    {
-      *keys = NULL;
-      *n_keys = 0;
-    }
-
-  g_array_free (retval, retval->len > 0 ? FALSE : TRUE);
-
-  return *n_keys > 0;
+  return len < retval->len;
 }
 
 static gboolean
diff --git a/gdk/x11/gdkkeys-x11.c b/gdk/x11/gdkkeys-x11.c
index f3c777390d..a322ff27c0 100644
--- a/gdk/x11/gdkkeys-x11.c
+++ b/gdk/x11/gdkkeys-x11.c
@@ -819,15 +819,12 @@ gdk_x11_keymap_get_modifier_state (GdkKeymap *keymap)
 }
 
 static gboolean
-gdk_x11_keymap_get_entries_for_keyval (GdkKeymap     *keymap,
-                                       guint          keyval,
-                                       GdkKeymapKey **keys,
-                                       gint          *n_keys)
+gdk_x11_keymap_get_entries_for_keyval (GdkKeymap *keymap,
+                                       guint      keyval,
+                                       GArray    *retval)
 {
   GdkX11Keymap *keymap_x11 = GDK_X11_KEYMAP (keymap);
-  GArray *retval;
-
-  retval = g_array_new (FALSE, FALSE, sizeof (GdkKeymapKey));
+  guint len = retval->len;
 
 #ifdef HAVE_XKB
   if (KEYMAP_USE_XKB (keymap))
@@ -870,8 +867,7 @@ gdk_x11_keymap_get_entries_for_keyval (GdkKeymap     *keymap,
 
                   g_array_append_val (retval, key);
 
-                  g_assert (XkbKeySymEntry (xkb, keycode, level, group) ==
-                            keyval);
+                  g_assert (XkbKeySymEntry (xkb, keycode, level, group) == keyval);
                 }
 
               ++level;
@@ -923,20 +919,7 @@ gdk_x11_keymap_get_entries_for_keyval (GdkKeymap     *keymap,
         }
     }
 
-  if (retval->len > 0)
-    {
-      *keys = (GdkKeymapKey*) retval->data;
-      *n_keys = retval->len;
-    }
-  else
-    {
-      *keys = NULL;
-      *n_keys = 0;
-    }
-
-  g_array_free (retval, retval->len > 0 ? FALSE : TRUE);
-
-  return *n_keys > 0;
+  return retval->len > len;
 }
 
 static gboolean