settings: Add a :theme-change signal

This signal allows applications to intercept and override
what theme gets loaded when the theme settings change.
One possibility is to only load themes from a fixed list
of supported themes. Another is to ignore the user preference
and only load dark themes.

demos/widget-factory/widget-factory.c

@@ -25,23 +25,46 @@
 #include <glib/gi18n.h>
 #include <gtk/gtk.h>
 
+static char *current_theme;
+
 static void
 change_dark_state (GSimpleAction *action,
                     GVariant      *state,
                     gpointer       user_data)
 {
   GtkSettings *settings = gtk_settings_get_default ();
+  gboolean prefer_dark = g_variant_get_boolean (state);
+  char *theme;
+  const char *new_theme = NULL;
 
-  g_object_set (G_OBJECT (settings),
-                "gtk-application-prefer-dark-theme",
-                g_variant_get_boolean (state),
+  g_object_get (G_OBJECT (settings),
+                "gtk-theme-name", &theme,
                 NULL);
 
-  g_simple_action_set_state (action, state);
-}
+  if (prefer_dark)
+    {
+      if (strcmp (theme, "Adwaita") == 0)
+        new_theme = "Adwaita-dark";
+      else if (strcmp (theme, "HighContrastInverse") == 0)
+        new_theme = "HighContrast";
+    }
+  else
+    {
+      if (strcmp (theme, "Adwaita-dark") == 0)
+        new_theme = "Adwaita";
+      else if (strcmp (theme, "HighContrast") == 0)
+        new_theme = "HighContrastInverse";
+    }
 
-static char *current_theme;
-static gboolean current_dark;
+  if (new_theme)
+    g_object_set (G_OBJECT (settings),
+                  "gtk-theme-name", new_theme,
+                  NULL);
+
+  g_simple_action_set_state (action, state);
+
+  g_free (theme);
+}
 
 static void
 change_theme_state (GSimpleAction *action,
@@ -51,41 +74,34 @@ change_theme_state (GSimpleAction *action,
   GtkSettings *settings = gtk_settings_get_default ();
   const char *s;
   const char *theme;
-  gboolean prefer_dark = FALSE;
 
   s = g_variant_get_string (state, NULL);
 
   if (strcmp (s, "adwaita") == 0)
     {
       theme = "Adwaita";
-      prefer_dark = FALSE;
     }
   else if (strcmp (s, "adwaita-dark") == 0)
     {
-      theme = "Adwaita";
-      prefer_dark = TRUE;
+      theme = "Adwaita-dark";
     }
   else if (strcmp (s, "highcontrast") == 0)
     {
       theme = "HighContrast";
-      prefer_dark = FALSE;
     }
   else if (strcmp (s, "highcontrast-inverse") == 0)
     {
       theme = "HighContrastInverse";
-      prefer_dark = FALSE;
     }
   else if (strcmp (s, "current") == 0)
     {
       theme = current_theme;
-      prefer_dark = current_dark;
     }
   else
     return;
 
   g_object_set (G_OBJECT (settings),
                 "gtk-theme-name", theme,
-                "gtk-application-prefer-dark-theme", prefer_dark,
                 NULL);
 
   g_simple_action_set_state (action, state);
@@ -1739,7 +1755,6 @@ activate (GApplication *app)
 
   g_object_get (gtk_settings_get_default (),
                 "gtk-theme-name", &current_theme,
-                "gtk-application-prefer-dark-theme", &current_dark,
                 NULL);
 
   g_type_ensure (my_text_view_get_type ());

docs/reference/gtk/gtk4-sections.txt

@@ -2304,6 +2304,12 @@ GtkSettingsValue
 gtk_settings_get_default
 gtk_settings_get_for_display
 gtk_settings_reset_property
+
+<SUBSECTION>
+gtk_theme_get_dark_variant
+gtk_theme_get_light_variant
+gtk_theme_get_available_themes
+
 <SUBSECTION Standard>
 GtkSettingsClass
 GTK_IS_SETTINGS

gtk/gen-gtk-gresources-xml.py

@@ -33,7 +33,7 @@ def get_files(subdir,extension):
 xml += '''
     <file>theme/Empty/gtk.css</file>
     <file>theme/Adwaita/gtk.css</file>
-    <file>theme/Adwaita/gtk-dark.css</file>
+    <file alias='theme/Adwaita-dark/gtk.css'>theme/Adwaita/gtk-dark.css</file>
     <file>theme/Adwaita/Adwaita.css</file>
     <file>theme/Adwaita/Adwaita-dark.css</file>
 '''

gtk/gtk.h

@@ -230,6 +230,7 @@
 #include <gtk/gtktexttag.h>
 #include <gtk/gtktexttagtable.h>
 #include <gtk/gtktextview.h>
+#include <gtk/gtktheme.h>
 #include <gtk/gtktogglebutton.h>
 #include <gtk/gtktooltip.h>
 #include <gtk/gtktestutils.h>

gtk/gtkcssprovider.c

@@ -1221,17 +1221,16 @@ _gtk_css_provider_get_theme_dir (GtkCssProvider *provider)
 
 /*
  * Look for
- * $dir/$subdir/gtk-4.16/gtk-$variant.css
- * $dir/$subdir/gtk-4.14/gtk-$variant.css
+ * $dir/$subdir/gtk-4.16/gtk.css
+ * $dir/$subdir/gtk-4.14/gtk.css
  *  ...
- * $dir/$subdir/gtk-4.0/gtk-$variant.css
+ * $dir/$subdir/gtk-4.0/gtk.css
  * and return the first found file.
  */
 static gchar *
 _gtk_css_find_theme_dir (const gchar *dir,
                          const gchar *subdir,
-                         const gchar *name,
-                         const gchar *variant)
+                         const gchar *name)
 {
   gchar *file;
   gchar *base;
@@ -1239,10 +1238,7 @@ _gtk_css_find_theme_dir (const gchar *dir,
   gint i;
   gchar *path;
 
-  if (variant)
-    file = g_strconcat ("gtk-", variant, ".css", NULL);
-  else
-    file = g_strdup ("gtk.css");
+  file = g_strdup ("gtk.css");
 
   if (subdir)
     base = g_build_filename (dir, subdir, name, NULL);
@@ -1270,9 +1266,8 @@ _gtk_css_find_theme_dir (const gchar *dir,
 
 #undef MINOR
 
-static gchar *
-_gtk_css_find_theme (const gchar *name,
-                     const gchar *variant)
+char *
+_gtk_css_find_theme (const char *name)
 {
   gchar *path;
   const char *const *dirs;
@@ -1280,12 +1275,12 @@ _gtk_css_find_theme (const gchar *name,
   char *dir;
 
   /* First look in the user's data directory */
-  path = _gtk_css_find_theme_dir (g_get_user_data_dir (), "themes", name, variant);
+  path = _gtk_css_find_theme_dir (g_get_user_data_dir (), "themes", name);
   if (path)
     return path;
 
   /* Next look in the user's home directory */
-  path = _gtk_css_find_theme_dir (g_get_home_dir (), ".themes", name, variant);
+  path = _gtk_css_find_theme_dir (g_get_home_dir (), ".themes", name);
   if (path)
     return path;
 
@@ -1293,14 +1288,14 @@ _gtk_css_find_theme (const gchar *name,
   dirs = g_get_system_data_dirs ();
   for (i = 0; dirs[i]; i++)
     {
-      path = _gtk_css_find_theme_dir (dirs[i], "themes", name, variant);
+      path = _gtk_css_find_theme_dir (dirs[i], "themes", name);
       if (path)
         return path;
     }
 
   /* Finally, try in the default theme directory */
   dir = _gtk_get_theme_dir ();
-  path = _gtk_css_find_theme_dir (dir, NULL, name, variant);
+  path = _gtk_css_find_theme_dir (dir, NULL, name);
   g_free (dir);
 
   return path;
@@ -1310,8 +1305,6 @@ _gtk_css_find_theme (const gchar *name,
  * gtk_css_provider_load_named:
  * @provider: a #GtkCssProvider
  * @name: A theme name
- * @variant: (allow-none): variant to load, for example, "dark", or
- *     %NULL for the default
  *
  * Loads a theme from the usual theme paths. The actual process of
  * finding the theme might change between releases, but it is
@@ -1320,8 +1313,7 @@ _gtk_css_find_theme (const gchar *name,
  **/
 void
 gtk_css_provider_load_named (GtkCssProvider *provider,
-                             const gchar    *name,
-                             const gchar    *variant)
+                             const gchar    *name)
 {
   gchar *path;
   gchar *resource_path;
@@ -1334,10 +1326,7 @@ gtk_css_provider_load_named (GtkCssProvider *provider,
   /* try loading the resource for the theme. This is mostly meant for built-in
    * themes.
    */
-  if (variant)
-    resource_path = g_strdup_printf ("/org/gtk/libgtk/theme/%s/gtk-%s.css", name, variant);
-  else
-    resource_path = g_strdup_printf ("/org/gtk/libgtk/theme/%s/gtk.css", name);
+  resource_path = g_strdup_printf ("/org/gtk/libgtk/theme/%s/gtk.css", name);
 
   if (g_resources_get_info (resource_path, 0, NULL, NULL, NULL))
     {
@@ -1348,7 +1337,7 @@ gtk_css_provider_load_named (GtkCssProvider *provider,
   g_free (resource_path);
 
   /* Next try looking for files in the various theme directories. */
-  path = _gtk_css_find_theme (name, variant);
+  path = _gtk_css_find_theme (name);
   if (path)
     {
       GtkCssProviderPrivate *priv = gtk_css_provider_get_instance_private (provider);
@@ -1375,17 +1364,8 @@ gtk_css_provider_load_named (GtkCssProvider *provider,
     {
       /* Things failed! Fall back! Fall back! */
 
-      if (variant)
-        {
-          /* If there was a variant, try without */
-          gtk_css_provider_load_named (provider, name, NULL);
-        }
-      else
-        {
-          /* Worst case, fall back to the default */
-          g_return_if_fail (!g_str_equal (name, DEFAULT_THEME_NAME)); /* infloop protection */
-          gtk_css_provider_load_named (provider, DEFAULT_THEME_NAME, NULL);
-        }
+      g_return_if_fail (!g_str_equal (name, DEFAULT_THEME_NAME)); /* infloop protection */
+      gtk_css_provider_load_named (provider, DEFAULT_THEME_NAME);
     }
 }
 

gtk/gtkcssprovider.h

@@ -63,8 +63,7 @@ void             gtk_css_provider_load_from_resource (GtkCssProvider *css_provid
 
 GDK_AVAILABLE_IN_ALL
 void             gtk_css_provider_load_named     (GtkCssProvider  *provider,
-                                                  const char      *name,
-                                                  const char      *variant);
+                                                  const char      *name);
 
 G_END_DECLS
 

gtk/gtkcssproviderprivate.h

@@ -26,6 +26,8 @@ gchar *_gtk_get_theme_dir (void);
 
 const gchar *_gtk_css_provider_get_theme_dir (GtkCssProvider *provider);
 
+char *_gtk_css_find_theme (const char *theme);
+
 void   gtk_css_provider_set_keep_css_sections (void);
 
 G_END_DECLS

gtk/gtksettings.c

@@ -29,6 +29,7 @@
 #include "gtkstyleproviderprivate.h"
 #include "gtktypebuiltins.h"
 #include "gtkversion.h"
+#include "gtktheme.h"
 #include "gtkwidget.h"
 
 #include "gdk/gdk-private.h"
@@ -122,6 +123,8 @@ struct _GtkSettings
 struct _GtkSettingsClass
 {
   GObjectClass parent_class;
+
+  char * (* theme_change) (GtkSettings *settings);
 };
 
 struct _GtkSettingsValuePrivate
@@ -136,6 +139,13 @@ struct _GtkSettingsPropertyValue
   GtkSettingsSource source;
 };
 
+enum {
+  THEME_CHANGE,
+  LAST_SIGNAL
+};
+
+static guint signals[LAST_SIGNAL];
+
 enum {
   PROP_0,
   PROP_DOUBLE_CLICK_TIME,
@@ -146,6 +156,7 @@ enum {
   PROP_SPLIT_CURSOR,
   PROP_CURSOR_ASPECT_RATIO,
   PROP_THEME_NAME,
+  PROP_USER_THEME_PREFERENCE,
   PROP_ICON_THEME_NAME,
   PROP_DND_DRAG_THRESHOLD,
   PROP_FONT_NAME,
@@ -170,7 +181,6 @@ enum {
   PROP_ENABLE_INPUT_FEEDBACK_SOUNDS,
   PROP_ENABLE_EVENT_SOUNDS,
   PROP_PRIMARY_BUTTON_WARPS_SLIDER,
-  PROP_APPLICATION_PREFER_DARK_THEME,
   PROP_ENTRY_SELECT_ON_FOCUS,
   PROP_ENTRY_PASSWORD_HINT_TIMEOUT,
   PROP_LABEL_SELECT_ON_FOCUS,
@@ -223,6 +233,7 @@ static void gtk_settings_load_from_key_file      (GtkSettings           *setting
 static void settings_update_provider             (GdkDisplay            *display,
                                                   GtkCssProvider       **old,
                                                   GtkCssProvider        *new);
+static char *gtk_settings_theme_change (GtkSettings *settings);
 
 /* --- variables --- */
 static GQuark            quark_gtk_settings = 0;
@@ -321,6 +332,8 @@ gtk_settings_class_init (GtkSettingsClass *class)
   gobject_class->set_property = gtk_settings_set_property;
   gobject_class->notify = gtk_settings_notify;
 
+  class->theme_change = gtk_settings_theme_change;
+
   quark_gtk_settings = g_quark_from_static_string ("gtk-settings");
 
   result = settings_install_property_parser (class,
@@ -401,6 +414,14 @@ gtk_settings_class_init (GtkSettingsClass *class)
                                                                   GTK_PARAM_READWRITE));
   g_assert (result == PROP_THEME_NAME);
 
+  result = settings_install_property_parser (class,
+                                             g_param_spec_int ("gtk-user-theme-preference",
+                                                               P_("User theme preference"),
+                                                               P_("User theme preference, 0=light, 1=dark, -1=default"),
+                                                               -1, 1, -1,
+                                                               GTK_PARAM_READWRITE));
+  g_assert (result == PROP_USER_THEME_PREFERENCE);
+
   result = settings_install_property_parser (class,
                                              g_param_spec_string ("gtk-icon-theme-name",
                                                                   P_("Icon Theme Name"),
@@ -715,29 +736,6 @@ gtk_settings_class_init (GtkSettingsClass *class)
                                                                    GTK_PARAM_READWRITE));
   g_assert (result == PROP_PRIMARY_BUTTON_WARPS_SLIDER);
 
-  /**
-   * GtkSettings:gtk-application-prefer-dark-theme:
-   *
-   * Whether the application prefers to use a dark theme. If a GTK theme
-   * includes a dark variant, it will be used instead of the configured
-   * theme.
-   *
-   * Some applications benefit from minimizing the amount of light pollution that
-   * interferes with the content. Good candidates for dark themes are photo and
-   * video editors that make the actual content get all the attention and minimize
-   * the distraction of the chrome.
-   *
-   * Dark themes should not be used for documents, where large spaces are white/light
-   * and the dark chrome creates too much contrast (web browser, text editor...).
-   */
-  result = settings_install_property_parser (class,
-                                             g_param_spec_boolean ("gtk-application-prefer-dark-theme",
-                                                                 P_("Application prefers a dark theme"),
-                                                                 P_("Whether the application prefers to have a dark theme."),
-                                                                 FALSE,
-                                                                 GTK_PARAM_READWRITE));
-  g_assert (result == PROP_APPLICATION_PREFER_DARK_THEME);
-
   result = settings_install_property_parser (class,
                                              g_param_spec_boolean ("gtk-entry-select-on-focus",
                                                                    P_("Select on focus"),
@@ -964,6 +962,33 @@ gtk_settings_class_init (GtkSettingsClass *class)
                                                                    TRUE,
                                                                    GTK_PARAM_READWRITE));
   g_assert (result == PROP_OVERLAY_SCROLLING);
+
+  /**
+   * GtkSettings::theme-change:
+   * @settings: the #GtkSettings object
+   *
+   * The ::theme-change signal is emitted whenever the
+   * #GtkSettings:gtk-theme-name or #GtkSettings:gtk-user-theme-preference
+   * settings change. A handler for this signal can inspect the
+   * values of these properties, and return the name of the theme
+   * to load.
+   *
+   * The default handler will try to find a light or dark variant
+   * of the theme named by :gtk-theme-name, depending on the value
+   * of :gtk-user-theme-preference.
+   *
+   * Returns: (transfer full): a newly allocated string naming the
+   *     theme to load
+   */
+  signals[THEME_CHANGE] =
+    g_signal_new (I_("theme-change"),
+                  G_TYPE_FROM_CLASS (gobject_class),
+                  G_SIGNAL_RUN_LAST,
+                  G_STRUCT_OFFSET (GtkSettingsClass, theme_change),
+                  g_signal_accumulator_first_wins, NULL,
+                  NULL,
+                  G_TYPE_STRING, 0);
+
 }
 
 static GtkSettings *
@@ -980,6 +1005,7 @@ gtk_settings_provider_iface_init (GtkStyleProviderInterface *iface)
 
 static void
 gtk_settings_finalize (GObject *object)
+
 {
   GtkSettings *settings = GTK_SETTINGS (object);
   guint i;
@@ -1248,7 +1274,7 @@ gtk_settings_notify (GObject    *object,
       gtk_style_context_reset_widgets (settings->display);
       break;
     case PROP_THEME_NAME:
-    case PROP_APPLICATION_PREFER_DARK_THEME:
+    case PROP_USER_THEME_PREFERENCE:
       settings_update_theme (settings);
       break;
     case PROP_XFT_DPI:
@@ -1638,62 +1664,64 @@ settings_update_provider (GdkDisplay      *display,
     }
 }
 
-static void
-get_theme_name (GtkSettings  *settings,
-                gchar       **theme_name,
-                gchar       **theme_variant)
-{
-  gboolean prefer_dark;
+/* Implement the user theme preference, as well as we can
+ * without proper theme apis. We treat the builting themes
+ * as light/dark pairs:
+ * 
+ * Adwaita/Adwaita-dark
+ * HighContrast/HighContrastInverse
+ *
+ * and we also look for theme pairs of the form
+ *
+ * NAME/NAME-dark
+ */
 
-  *theme_name = NULL;
-  *theme_variant = NULL;
+static char *
+gtk_settings_theme_change (GtkSettings  *settings)
+{
+  char *theme_name = NULL;
+  char *theme;
+  int user_pref;
 
   if (g_getenv ("GTK_THEME"))
-    *theme_name = g_strdup (g_getenv ("GTK_THEME"));
+    theme_name = g_strdup (g_getenv ("GTK_THEME"));
 
-  if (*theme_name && **theme_name)
-    {
-      char *p;
-      p = strrchr (*theme_name, ':');
-      if (p) {
-        *p = '\0';
-        p++;
-        *theme_variant = g_strdup (p);
-      }
-
-      return;
-    }
-
-  g_free (*theme_name);
+  if (theme_name)
+    return theme_name;
 
   g_object_get (settings,
-                "gtk-theme-name", theme_name,
-                "gtk-application-prefer-dark-theme", &prefer_dark,
+                "gtk-theme-name", &theme_name,
+                "gtk-user-theme-preference", &user_pref,
                 NULL);
 
-  if (prefer_dark)
-    *theme_variant = g_strdup ("dark");
+  switch (user_pref)
+    {
+    case 0:
+      theme = gtk_theme_get_light_variant (theme_name);
+      g_free (theme_name);
+      break;
+    case 1:
+      theme = gtk_theme_get_dark_variant (theme_name);
+      g_free (theme_name);
+      break;
+    default:
+      theme = theme_name;
+      break;
+    }
 
-  if (*theme_name && **theme_name)
-    return;
-
-  g_free (*theme_name);
-  *theme_name = g_strdup (DEFAULT_THEME_NAME);
+  return theme;
 }
 
 static void
 settings_update_theme (GtkSettings *settings)
 {
-  gchar *theme_name;
-  gchar *theme_variant;
-  const gchar *theme_dir;
-  gchar *path;
+  char *theme_name;
+  const char *theme_dir;
+  char *path;
 
-  get_theme_name (settings, &theme_name, &theme_variant);
+  g_signal_emit (settings, signals[THEME_CHANGE], 0, &theme_name);
 
-  gtk_css_provider_load_named (settings->theme_provider,
-                               theme_name,
-                               theme_variant);
+  gtk_css_provider_load_named (settings->theme_provider, theme_name);
 
   /* reload per-theme settings */
   theme_dir = _gtk_css_provider_get_theme_dir (settings->theme_provider);
@@ -1706,7 +1734,6 @@ settings_update_theme (GtkSettings *settings)
     }
 
   g_free (theme_name);
-  g_free (theme_variant);
 }
 
 const cairo_font_options_t *

gtk/gtktheme.c

@@ -0,0 +1,181 @@
+/* GTK - The GIMP Toolkit
+ * Copyright (C) 2020 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include "gtktheme.h"
+#include "gtkcssproviderprivate.h"
+
+static gboolean
+theme_exists (const char *theme)
+{
+  char *path;
+
+  path = _gtk_css_find_theme (theme);
+  if (path)
+    {
+      g_free (path);
+      return TRUE;
+    }
+
+  return FALSE;
+}
+
+/**
+ * gtk_theme_get_dark_variant:
+ * @theme: a theme name
+ *
+ * Returns the name of the dark variant of the
+ * given theme, if such a variant is available.
+ * Otherwise, @theme is returned.
+ *
+ * Returns: (transfer full): name of the dark variant
+ *     of @theme. Free with g_free()
+ */
+char *
+gtk_theme_get_dark_variant (const char *theme)
+{
+  if (g_str_equal (theme, "HighContrast"))
+    return g_strdup ("HighContrastInverse");
+
+  if (g_str_equal (theme, "Adwaita"))
+    return g_strdup ("Adwaita-dark");
+
+  if (!g_str_has_suffix (theme, "-dark"))
+    {
+      char *dark = g_strconcat (theme, "-dark", NULL);
+      if (theme_exists (dark))
+        return dark;
+
+      g_free (dark);
+    }
+
+  return g_strdup (theme);
+}
+
+/**
+ * gtk_theme_get_light_variant:
+ * @theme: a theme name
+ *
+ * Returns the name of the light variant of the
+ * given theme, if such a variant is available.
+ * Otherwise, @theme is returned.
+ *
+ * Returns: (transfer full): name of the light variant
+ *     of @theme. Free with g_free()
+ */
+char *
+gtk_theme_get_light_variant (const char *theme)
+{
+  if (g_str_equal (theme, "HighContrastInverse"))
+    return g_strdup ("HighContrast");
+
+  if (g_str_equal (theme, "Adwaita-dark"))
+    return g_strdup ("Adwaita");
+
+  if (g_str_has_suffix (theme, "-dark"))
+    {
+      char *light = g_strndup (theme, strlen (theme) - strlen ("-dark"));
+      if (theme_exists (light))
+        return light;
+
+      g_free (light);
+    }
+
+  return g_strdup (theme);
+}
+
+static void
+fill_gtk (const gchar *path,
+          GHashTable  *t)
+{
+  const gchar *dir_entry;
+  GDir *dir = g_dir_open (path, 0, NULL);
+
+  if (!dir)
+    return;
+
+  while ((dir_entry = g_dir_read_name (dir)))
+    {
+      gchar *filename = g_build_filename (path, dir_entry, "gtk-4.0", "gtk.css", NULL);
+
+      if (g_file_test (filename, G_FILE_TEST_IS_REGULAR) &&
+          !g_hash_table_contains (t, dir_entry))
+        g_hash_table_add (t, g_strdup (dir_entry));
+
+      g_free (filename);
+    }
+
+  g_dir_close (dir);
+}
+
+/**
+ * gtk_theme_get_available_themes:
+ *
+ * Returns the list of available themes.
+ *
+ * Returns: (transfer full): an array of theme names
+ */
+char **
+gtk_theme_get_available_themes (void)
+{
+  GHashTable *t;
+  gchar *path;
+  gchar **builtin_themes;
+  guint i;
+  const gchar * const *dirs;
+  char **keys;
+  char **result;
+
+  t = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, NULL);
+
+  /* Builtin themes */
+  builtin_themes = g_resources_enumerate_children ("/org/gtk/libgtk/theme", 0, NULL);
+  for (i = 0; builtin_themes[i] != NULL; i++)
+    {
+      if (g_str_has_suffix (builtin_themes[i], "/"))
+        g_hash_table_add (t, g_strndup (builtin_themes[i], strlen (builtin_themes[i]) - 1));
+    }
+  g_strfreev (builtin_themes);
+
+  path = _gtk_get_theme_dir ();
+  fill_gtk (path, t);
+  g_free (path);
+
+  path = g_build_filename (g_get_user_data_dir (), "themes", NULL);
+  fill_gtk (path, t);
+  g_free (path);
+
+  path = g_build_filename (g_get_home_dir (), ".themes", NULL);
+  fill_gtk (path, t);
+  g_free (path);
+
+  dirs = g_get_system_data_dirs ();
+  for (i = 0; dirs[i]; i++)
+    {
+      path = g_build_filename (dirs[i], "themes", NULL);
+      fill_gtk (path, t);
+      g_free (path);
+    }
+
+  keys = (char **)g_hash_table_get_keys_as_array (t, NULL);
+  result = g_strdupv (keys);
+  g_free (keys);
+  g_hash_table_destroy (t);
+
+  return result;
+}

gtk/gtktheme.h

@@ -0,0 +1,38 @@
+/* GTK - The GIMP Toolkit
+ * Copyright (C) 2020 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GTK_THEME_H__
+#define __GTK_THEME_H__
+
+#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gtk/gtk.h> can be included directly."
+#endif
+
+#include <gtk/gtktypes.h>
+
+G_BEGIN_DECLS
+
+GDK_AVAILABLE_IN_ALL
+char * gtk_theme_get_dark_variant     (const char *theme);
+GDK_AVAILABLE_IN_ALL
+char * gtk_theme_get_light_variant    (const char *theme);
+GDK_AVAILABLE_IN_ALL
+char **gtk_theme_get_available_themes (void);
+
+G_END_DECLS
+
+#endif /* __GTK_THEME_H__ */

gtk/gtkwindow.c

@@ -462,12 +462,6 @@ static void     get_shadow_width                      (GtkWindow    *window,
 static gboolean    gtk_window_activate_menubar        (GtkWidget    *widget,
                                                        GVariant     *args,
                                                        gpointer      unused);
-#ifdef GDK_WINDOWING_X11
-static void        gtk_window_on_theme_variant_changed (GtkSettings *settings,
-                                                        GParamSpec  *pspec,
-                                                        GtkWindow   *window);
-#endif
-static void        gtk_window_set_theme_variant         (GtkWindow  *window);
 
 static void gtk_window_activate_default_activate (GtkWidget *widget,
                                                   const char *action_name,
@@ -1707,12 +1701,6 @@ gtk_window_init (GtkWindow *window)
   g_object_ref_sink (window);
   priv->has_user_ref_count = TRUE;
 
-#ifdef GDK_WINDOWING_X11
-  g_signal_connect (gtk_settings_get_for_display (priv->display),
-                    "notify::gtk-application-prefer-dark-theme",
-                    G_CALLBACK (gtk_window_on_theme_variant_changed), window);
-#endif
-
   widget_node = gtk_widget_get_css_node (GTK_WIDGET (window));
   priv->decoration_node = gtk_css_node_new ();
   gtk_css_node_set_name (priv->decoration_node, g_quark_from_static_string ("decoration"));
@@ -4055,12 +4043,6 @@ gtk_window_finalize (GObject *object)
                                         device_removed_cb,
                                         window);
 
-#ifdef GDK_WINDOWING_X11
-  g_signal_handlers_disconnect_by_func (gtk_settings_get_for_display (priv->display),
-                                        gtk_window_on_theme_variant_changed,
-                                        window);
-#endif
-
   g_free (priv->startup_id);
 
   if (priv->mnemonics_display_timeout_id)
@@ -4331,8 +4313,6 @@ gtk_window_map (GtkWidget *widget)
   if (priv->minimize_initially)
     gdk_toplevel_minimize (GDK_TOPLEVEL (priv->surface));
 
-  gtk_window_set_theme_variant (window);
-
   /* No longer use the default settings */
   priv->need_default_size = FALSE;
 
@@ -7081,14 +7061,6 @@ gtk_window_set_display (GtkWindow  *window,
   if (priv->transient_parent && gtk_widget_get_display (GTK_WIDGET (priv->transient_parent)) != display)
     gtk_window_set_transient_for (window, NULL);
 
-#ifdef GDK_WINDOWING_X11
-  g_signal_handlers_disconnect_by_func (gtk_settings_get_for_display (priv->display),
-                                        gtk_window_on_theme_variant_changed, window);
-  g_signal_connect (gtk_settings_get_for_display (display),
-                    "notify::gtk-application-prefer-dark-theme",
-                    G_CALLBACK (gtk_window_on_theme_variant_changed), window);
-#endif
-
   gtk_widget_unroot (widget);
   priv->display = display;
 
@@ -7102,33 +7074,6 @@ gtk_window_set_display (GtkWindow  *window,
   check_scale_changed (window);
 }
 
-static void
-gtk_window_set_theme_variant (GtkWindow *window)
-{
-#ifdef GDK_WINDOWING_X11
-  GtkWindowPrivate *priv = gtk_window_get_instance_private (window);
-  gboolean   dark_theme_requested;
-
-  g_object_get (gtk_settings_get_for_display (priv->display),
-                "gtk-application-prefer-dark-theme", &dark_theme_requested,
-                NULL);
-
-  if (GDK_IS_X11_SURFACE (priv->surface))
-    gdk_x11_surface_set_theme_variant (priv->surface,
-                                       dark_theme_requested ? "dark" : NULL);
-#endif
-}
-
-#ifdef GDK_WINDOWING_X11
-static void
-gtk_window_on_theme_variant_changed (GtkSettings *settings,
-                                     GParamSpec  *pspec,
-                                     GtkWindow   *window)
-{
-  gtk_window_set_theme_variant (window);
-}
-#endif
-
 /**
  * gtk_window_is_active:
  * @window: a #GtkWindow

gtk/inspector/visual.c

@@ -42,6 +42,7 @@
 #include "gskrendererprivate.h"
 #include "gtknative.h"
 #include "gtkbinlayout.h"
+#include "gtktheme.h"
 
 #include "fallback-c89.c"
 
@@ -62,7 +63,6 @@ struct _GtkInspectorVisualPrivate
   GtkWidget *box;
   GtkWidget *visual_box;
   GtkWidget *theme_combo;
-  GtkWidget *dark_switch;
   GtkWidget *icon_combo;
   GtkWidget *cursor_combo;
   GtkWidget *cursor_size_spin;
@@ -474,30 +474,6 @@ focus_activate (GtkSwitch          *sw,
   redraw_everything ();
 }
 
-static void
-fill_gtk (const gchar *path,
-          GHashTable  *t)
-{
-  const gchar *dir_entry;
-  GDir *dir = g_dir_open (path, 0, NULL);
-
-  if (!dir)
-    return;
-
-  while ((dir_entry = g_dir_read_name (dir)))
-    {
-      gchar *filename = g_build_filename (path, dir_entry, "gtk-4.0", "gtk.css", NULL);
-
-      if (g_file_test (filename, G_FILE_TEST_IS_REGULAR) &&
-          !g_hash_table_contains (t, dir_entry))
-        g_hash_table_add (t, g_strdup (dir_entry));
-
-      g_free (filename);
-    }
-
-  g_dir_close (dir);
-}
-
 static gchar*
 get_data_path (const gchar *subdir)
 {
@@ -515,57 +491,14 @@ get_data_path (const gchar *subdir)
 static void
 init_theme (GtkInspectorVisual *vis)
 {
-  GHashTable *t;
-  GHashTableIter iter;
-  gchar *theme, *path;
-  gchar **builtin_themes;
-  GList *list, *l;
-  guint i;
-  const gchar * const *dirs;
+  char **themes;
+  int i;
 
-  t = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, NULL);
-  /* Builtin themes */
-  builtin_themes = g_resources_enumerate_children ("/org/gtk/libgtk/theme", 0, NULL);
-  for (i = 0; builtin_themes[i] != NULL; i++)
-    {
-      if (g_str_has_suffix (builtin_themes[i], "/"))
-        g_hash_table_add (t, g_strndup (builtin_themes[i], strlen (builtin_themes[i]) - 1));
-    }
-  g_strfreev (builtin_themes);
+  themes = gtk_theme_get_available_themes ();
+  for (i = 0; themes[i]; i++)
+    gtk_combo_box_text_append (GTK_COMBO_BOX_TEXT (vis->priv->theme_combo), themes[i], themes[i]);
 
-  path = _gtk_get_theme_dir ();
-  fill_gtk (path, t);
-  g_free (path);
-
-  path = g_build_filename (g_get_user_data_dir (), "themes", NULL);
-  fill_gtk (path, t);
-  g_free (path);
-
-  path = g_build_filename (g_get_home_dir (), ".themes", NULL);
-  fill_gtk (path, t);
-  g_free (path);
-
-  dirs = g_get_system_data_dirs ();
-  for (i = 0; dirs[i]; i++)
-    {
-      path = g_build_filename (dirs[i], "themes", NULL);
-      fill_gtk (path, t);
-      g_free (path);
-    }
-
-  list = NULL;
-  g_hash_table_iter_init (&iter, t);
-  while (g_hash_table_iter_next (&iter, (gpointer *)&theme, NULL))
-    list = g_list_insert_sorted (list, theme, (GCompareFunc)strcmp);
-
-  for (l = list; l; l = l->next)
-    {
-      theme = l->data;
-      gtk_combo_box_text_append (GTK_COMBO_BOX_TEXT (vis->priv->theme_combo), theme, theme);
-    }
-
-  g_list_free (list);
-  g_hash_table_destroy (t);
+  g_strfreev (themes);
 
   g_object_bind_property (gtk_settings_get_for_display (vis->priv->display),
                           "gtk-theme-name",
@@ -583,25 +516,6 @@ init_theme (GtkInspectorVisual *vis)
     }
 }
 
-static void
-init_dark (GtkInspectorVisual *vis)
-{
-  g_object_bind_property (gtk_settings_get_for_display (vis->priv->display),
-                          "gtk-application-prefer-dark-theme",
-                          vis->priv->dark_switch, "active",
-                          G_BINDING_BIDIRECTIONAL | G_BINDING_SYNC_CREATE);
-
-  if (g_getenv ("GTK_THEME") != NULL)
-    {
-      GtkWidget *row;
-
-      /* theme is hardcoded, nothing we can do */
-      gtk_widget_set_sensitive (vis->priv->dark_switch, FALSE);
-      row = gtk_widget_get_ancestor (vis->priv->theme_combo, GTK_TYPE_LIST_BOX_ROW);
-      gtk_widget_set_tooltip_text (row, _("Theme is hardcoded by GTK_THEME"));
-    }
-}
-
 static void
 fill_icons (const gchar *path,
             GHashTable  *t)
@@ -959,12 +873,7 @@ row_activated (GtkListBox         *box,
                GtkListBoxRow      *row,
                GtkInspectorVisual *vis)
 {
-  if (gtk_widget_is_ancestor (vis->priv->dark_switch, GTK_WIDGET (row)))
-    {
-      GtkSwitch *sw = GTK_SWITCH (vis->priv->dark_switch);
-      gtk_switch_set_active (sw, !gtk_switch_get_active (sw));
-    }
-  else if (gtk_widget_is_ancestor (vis->priv->animation_switch, GTK_WIDGET (row)))
+  if (gtk_widget_is_ancestor (vis->priv->animation_switch, GTK_WIDGET (row)))
     {
       GtkSwitch *sw = GTK_SWITCH (vis->priv->animation_switch);
       gtk_switch_set_active (sw, !gtk_switch_get_active (sw));
@@ -1125,7 +1034,6 @@ gtk_inspector_visual_class_init (GtkInspectorVisualClass *klass)
   gtk_widget_class_bind_template_child_private (widget_class, GtkInspectorVisual, box);
   gtk_widget_class_bind_template_child_private (widget_class, GtkInspectorVisual, direction_combo);
   gtk_widget_class_bind_template_child_private (widget_class, GtkInspectorVisual, theme_combo);
-  gtk_widget_class_bind_template_child_private (widget_class, GtkInspectorVisual, dark_switch);
   gtk_widget_class_bind_template_child_private (widget_class, GtkInspectorVisual, cursor_combo);
   gtk_widget_class_bind_template_child_private (widget_class, GtkInspectorVisual, cursor_size_spin);
   gtk_widget_class_bind_template_child_private (widget_class, GtkInspectorVisual, cursor_size_adjustment);
@@ -1172,7 +1080,6 @@ gtk_inspector_visual_set_display  (GtkInspectorVisual *vis,
 
   init_direction (vis);
   init_theme (vis);
-  init_dark (vis);
   init_icons (vis);
   init_cursors (vis);
   init_cursor_size (vis);

gtk/inspector/visual.ui

@@ -74,34 +74,6 @@
                         </child>
                       </object>
                     </child>
-                    <child>
-                      <object class="GtkListBoxRow">
-                        <child>
-                          <object class="GtkBox">
-                            <property name="margin-start">10</property>
-                            <property name="margin-end">10</property>
-                            <property name="margin-top">10</property>
-                            <property name="margin-bottom">10</property>
-                            <property name="spacing">40</property>
-                            <child>
-                              <object class="GtkLabel" id="dark_label">
-                                <property name="label" translatable="yes">Dark Variant</property>
-                                <property name="halign">start</property>
-                                <property name="valign">baseline</property>
-                                <property name="xalign">0.0</property>
-                              </object>
-                            </child>
-                            <child>
-                              <object class="GtkSwitch" id="dark_switch">
-                                <property name="halign">end</property>
-                                <property name="valign">baseline</property>
-                                <property name="hexpand">1</property>
-                              </object>
-                            </child>
-                          </object>
-                        </child>
-                      </object>
-                    </child>
                     <child>
                       <object class="GtkListBoxRow">
                         <property name="activatable">0</property>
@@ -691,7 +663,6 @@
   <object class="GtkSizeGroup">
     <widgets>
       <widget name="theme_label"/>
-      <widget name="dark_label"/>
       <widget name="icon_label"/>
       <widget name="cursor_label"/>
       <widget name="cursor_size_label"/>

gtk/meson.build

@@ -370,6 +370,7 @@ gtk_public_sources = files([
   'gtktexttypes.c',
   'gtktextutil.c',
   'gtktextview.c',
+  'gtktheme.c',
   'gtktogglebutton.c',
   'gtktooltip.c',
   'gtktooltipwindow.c',
@@ -602,6 +603,7 @@ gtk_public_headers = files([
   'gtktexttag.h',
   'gtktexttagtable.h',
   'gtktextview.h',
+  'gtktheme.h',
   'gtktogglebutton.h',
   'gtktooltip.h',
   'gtktreednd.h',

testsuite/gtk/theme-validate.c

@@ -5,7 +5,6 @@ typedef struct _Theme Theme;
 struct _Theme
 {
   const char *name;
-  const char *variant;
 };
 
 static void
@@ -34,7 +33,7 @@ test_theme (gconstpointer data)
   provider = gtk_css_provider_new ();
   g_signal_connect (provider, "parsing-error",
                     G_CALLBACK (theme_parsing_error), NULL);
-  gtk_css_provider_load_named (provider, theme->name, theme->variant);
+  gtk_css_provider_load_named (provider, theme->name);
   g_object_unref (provider);
 }
 
@@ -42,10 +41,10 @@ int
 main (int argc, char *argv[])
 {
   const Theme themes[] = {
-    { "Adwaita", NULL },
-    { "Adwaita", "dark" },
-    { "HighContrast", NULL },
-    { "HighContrast", "dark" }
+    { "Adwaita" },
+    { "Adwaita-dark" },
+    { "HighContrast" },
+    { "HighContrastInverse" }
   };
   guint i;
 
@@ -56,10 +55,7 @@ main (int argc, char *argv[])
     {
       char *testname;
 
-      if (themes[i].variant == NULL)
-        testname = g_strdup_printf ("/theme-validate/%s", themes[i].name);
-      else
-        testname = g_strdup_printf ("/theme-validate/%s-%s", themes[i].name, themes[i].variant);
+      testname = g_strdup_printf ("/theme-validate/%s", themes[i].name);
 
       g_test_add_data_func (testname, &themes[i], test_theme);