GTK3: Support freedesktop color-scheme

On desktops which support the org.freedesktop.appearance
settings portal, the application will switch automatically
between light and dark themes.

BasiliskII/src/Unix/color_scheme.cpp

@@ -0,0 +1,290 @@
+/* color_scheme.cpp - Change application theme based on D-Bus
+ *
+ * Copyright (C) 2022-2024 Rob Hall
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "color_scheme.h"
+
+#if GTK_CHECK_VERSION(3, 22, 0)
+
+#define APP_DARK  APP_PREFERS_DARK /* 1 */
+#define APP_FORCE APP_FORCES_LIGHT /* 2 */
+#define DBUS_TIMEOUT 1000 /* Timeout for D-Bus to respond in ms */
+
+#if GLIB_CHECK_VERSION(2, 72, 0)
+#define SETTING_CHANGED_SIGNAL "g-signal::SettingChanged"
+#else
+#define SETTING_CHANGED_SIGNAL "g-signal"
+#endif
+
+static AppColorScheme app_scheme = APP_FORCES_LIGHT;
+static GDBusProxy *desktop_portal;
+static GtkSettings *settings;
+static gboolean init_done = FALSE;
+
+static void
+set_gtk_theme (gboolean dark)
+{
+    g_object_set(settings, "gtk-application-prefer-dark-theme", dark, NULL);
+}
+
+/*
+ * Returns the currently selected app colour scheme.
+ */
+AppColorScheme
+color_scheme_get_app_scheme (void)
+{
+    return app_scheme;
+}
+
+/*
+ * Returns TRUE if the app is currently using the dark theme.
+ */
+gboolean
+color_scheme_is_dark_theme (void)
+{
+    gboolean is_dark;
+
+    g_object_get (settings, "gtk-application-prefer-dark-theme", &is_dark, NULL);
+    return is_dark;
+}
+
+/*
+ * Switches the color state of the app, no matter which color
+ * is currently in use. Afterwards, the app color scheme is
+ * changed to APP_FORCES_LIGHT or APP_FORCES_DARK, so changes
+ * to the desktop color scheme no longer have any effect.
+ */
+gboolean
+color_scheme_toggle (void)
+{
+    gboolean set_dark = !color_scheme_is_dark_theme();
+    g_object_set(settings, "gtk-application-prefer-dark-theme",
+                 set_dark, NULL);
+
+    /* Change app_scheme to APP_FORCES_[DARK|LIGHT] */
+    app_scheme = (AppColorScheme) (set_dark | APP_FORCE);
+
+    return set_dark;
+}
+
+static void
+setting_changed (GDBusProxy *proxy, char *sender_name, char *signal_name,
+                  GVariant *parameters, gpointer user_data)
+{
+    const char *namespace_;
+    const char *key;
+    g_autoptr (GVariant) var = NULL;
+    guint32 portal_value;
+    gboolean set_dark;
+
+    if (g_strcmp0(signal_name, "SettingChanged"))
+        return;
+
+    g_variant_get(parameters, "(&s&sv)", &namespace_, &key, &var);
+
+    if (!g_strcmp0(namespace_, "org.freedesktop.appearance") &&
+          !g_strcmp0(key, "color-scheme"))
+    {
+        g_variant_get(var, "u", &portal_value);
+        set_dark = (portal_value == DESKTOP_PREFERS_DARK) ? TRUE : FALSE;
+        if (!(app_scheme & APP_FORCE))
+            set_gtk_theme(set_dark);
+    }
+}
+
+static GDBusProxy *
+portal_init (void)
+{
+    GDBusProxy *portal;
+    GError *error = NULL;
+
+    portal = g_dbus_proxy_new_for_bus_sync (G_BUS_TYPE_SESSION,
+                                            G_DBUS_PROXY_FLAGS_NONE, NULL,
+                                            "org.freedesktop.portal.Desktop",
+                                            "/org/freedesktop/portal/desktop",
+                                            "org.freedesktop.portal.Settings",
+                                            NULL, &error);
+    if (!portal)
+        g_debug ("Could not access portal: %s", error->message);
+
+    return portal;
+}
+
+static void
+set_theme (void)
+{
+    DesktopColorScheme desktop_scheme;
+    gboolean set_dark;
+
+    desktop_scheme = color_scheme_get_desktop_scheme();
+    if ((app_scheme & APP_FORCE) || desktop_scheme == DESKTOP_NO_PREFERENCE)
+        set_dark = (app_scheme & APP_DARK);
+    else
+        set_dark = (desktop_scheme == DESKTOP_PREFERS_DARK);
+
+    set_gtk_theme(set_dark);
+}
+
+static void
+init_color_scheme_cb (GObject *object, GAsyncResult *res, gpointer user_data)
+{
+    GDBusProxy *portal;
+    GError *error = NULL;
+
+    portal = g_dbus_proxy_new_for_bus_finish(res, &error);
+
+    if (portal)
+    {
+        g_signal_connect(portal, SETTING_CHANGED_SIGNAL,
+                         G_CALLBACK(setting_changed), NULL);
+    }
+    else
+    {
+        g_debug("Could not access portal: %s", error->message);
+    }
+    init_done = TRUE;
+}
+
+static void
+init_color_scheme_async (void)
+{
+    static size_t init = 0;
+
+    if (g_once_init_enter(&init))
+    {
+        settings = gtk_settings_get_default();
+        g_dbus_proxy_new_for_bus (G_BUS_TYPE_SESSION,
+                                  G_DBUS_PROXY_FLAGS_NONE, NULL,
+                                  "org.freedesktop.portal.Desktop",
+                                  "/org/freedesktop/portal/desktop",
+                                  "org.freedesktop.portal.Settings",
+                                  NULL,
+                                  (GAsyncReadyCallback)init_color_scheme_cb,
+                                  NULL);
+        g_once_init_leave(&init, 1);
+    }
+    set_theme();
+}
+
+static gboolean
+init_color_scheme (void)
+{
+    static GMutex init_mutex;
+
+    g_mutex_lock(&init_mutex);
+    {
+        if (!init_done)
+        {
+            settings = gtk_settings_get_default();
+            desktop_portal = portal_init();
+            if (desktop_portal)
+            {
+                g_signal_connect(desktop_portal, SETTING_CHANGED_SIGNAL,
+                                 G_CALLBACK(setting_changed), NULL);
+            }
+        }
+    }
+    init_done = TRUE;
+    g_mutex_unlock(&init_mutex);
+    return TRUE;
+}
+
+/*
+ * Returns the current desktop color scheme, given by
+ * the org.freedesktop.portal.Settings portal. If the portal
+ * is not available, DESKTOP_NO_PREFERENCE is returned.
+ */
+DesktopColorScheme
+color_scheme_get_desktop_scheme (void)
+{
+    g_autoptr (GVariant) outer = NULL;
+    g_autoptr (GVariant) inner = NULL;
+    g_autoptr (GVariant) result = NULL;
+    g_autoptr (GError) error = NULL;
+    DesktopColorScheme scheme;
+
+    if (!init_done && !init_color_scheme())
+        return DESKTOP_NO_PREFERENCE;
+
+    if (!desktop_portal)
+        return DESKTOP_NO_PREFERENCE;
+
+    GVariant *call = g_variant_new("(ss)", "org.freedesktop.appearance",
+                                   "color-scheme");
+    result = g_dbus_proxy_call_sync(desktop_portal, "Read", call,
+                                    G_DBUS_CALL_FLAGS_NONE, DBUS_TIMEOUT,
+                                    NULL, &error);
+    if (!result)
+    {
+        g_debug("%s", error->message);
+        return DESKTOP_NO_PREFERENCE;
+    }
+
+    g_variant_get(result, "(v)", &outer);
+    g_variant_get(outer, "v", &inner);
+    scheme = (DesktopColorScheme) g_variant_get_uint32(inner);
+
+    if (scheme > DESKTOP_PREFERS_LIGHT)
+        scheme = DESKTOP_NO_PREFERENCE;
+    return scheme;
+}
+
+/*
+ * Sets the color scheme to one of the four options.
+ * Can be called once GTK has been initialised.
+ * Returns FALSE if the color scheme could not be set.
+ * If the return value is not needed, use color_scheme_set_async instead.
+ */
+gboolean
+color_scheme_set (AppColorScheme scheme)
+{
+    gboolean set_dark;
+    DesktopColorScheme desktop_scheme;
+
+    if (!init_done && !init_color_scheme())
+        return FALSE;
+
+    app_scheme = scheme;
+    desktop_scheme = color_scheme_get_desktop_scheme();
+
+    if ((app_scheme & APP_FORCE) || desktop_scheme == DESKTOP_NO_PREFERENCE)
+        set_dark = (app_scheme & APP_DARK);
+    else
+        set_dark = (desktop_scheme == DESKTOP_PREFERS_DARK);
+
+    set_gtk_theme(set_dark);
+    return TRUE;
+}
+
+/*
+ * Sets the color scheme to one of the four options.
+ * Can be called once GTK has been initialised.
+ * Runs asynchronously, so preferred over color_scheme_set.
+ */
+void
+color_scheme_set_async (AppColorScheme scheme)
+{
+    app_scheme = scheme;
+    if (init_done)
+        set_theme();
+    else
+        init_color_scheme_async();
+}
+
+#endif // GTK_CHECK_VERSION

BasiliskII/src/Unix/configure.ac

@@ -503,7 +503,7 @@ fi
 if [[ "x$WANT_GTK" != "xno" -a "x$WANT_STANDALONE_GUI" = "xno" ]]; then
   AC_DEFINE(ENABLE_GTK, 1, [Define if using GTK.])
   if [[ "$WANT_GTK" = "GTK3" ]]; then
-    UISRCS="prefs_editor_gtk3.cpp g_resource.cpp"
+    UISRCS="prefs_editor_gtk3.cpp g_resource.cpp color_scheme.cpp"
   else
     UISRCS="prefs_editor_gtk.cpp"
   fi

BasiliskII/src/Unix/main_unix.cpp

@@ -73,6 +73,10 @@ struct sigstate {
 # if GTK_CHECK_VERSION(3, 14, 0)
 #  define ENABLE_GTK3
 # endif
+# if GTK_CHECK_VERSION(3, 22, 0)
+#  define ENABLE_GTK_3_22
+#  include "color_scheme.h"
+# endif
 #endif
 
 #ifdef ENABLE_XF86_DGA
@@ -423,6 +427,9 @@ GtkWindow *win;
 
 static void gui_startup (void)
 {
+#ifdef ENABLE_GTK_3_22
+	color_scheme_set(APP_PREFERS_LIGHT);
+#endif
 	if (!PrefsEditor())
 		QuitEmulator();
 }

BasiliskII/src/include/color_scheme.h

@@ -0,0 +1,58 @@
+/* color_scheme.h - Change application theme based on D-Bus
+ *
+ * Copyright (C) 2022-2024 Rob Hall
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#pragma once
+
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+/*
+ * An enum representing the color state requested by
+ * the application. Before the color-scheme library is
+ * set up, the application is effectively in the
+ * APP_FORCES_LIGHT state.
+ */
+typedef enum {
+    APP_PREFERS_LIGHT,
+    APP_PREFERS_DARK,
+    APP_FORCES_LIGHT,
+    APP_FORCES_DARK
+} AppColorScheme;
+
+/*
+ * An enum representing the color state given by the
+ * desktop portal. If the portal is not available, it
+ * defaults to DESKTOP_NO_PREFERENCE.
+ */
+typedef enum {
+    DESKTOP_NO_PREFERENCE,
+    DESKTOP_PREFERS_DARK,
+    DESKTOP_PREFERS_LIGHT
+} DesktopColorScheme;
+
+gboolean color_scheme_set (AppColorScheme scheme);
+void color_scheme_set_async (AppColorScheme scheme);
+gboolean color_scheme_is_dark_theme (void);
+gboolean color_scheme_toggle (void);
+AppColorScheme color_scheme_get_app_scheme (void);
+DesktopColorScheme color_scheme_get_desktop_scheme (void);
+
+G_END_DECLS

SheepShaver/Makefile

@@ -58,7 +58,7 @@ links:
 	       include/extfs.h include/extfs_defs.h include/pict.h \
 	       include/prefs.h include/scsi.h include/serial.h include/prefs_editor.h \
 	       include/serial_defs.h include/sony.h include/sys.h \
-	       include/timer.h include/xpram.h \
+	       include/timer.h include/xpram.h include/color_scheme.h \
 	       BeOS/audio_beos.cpp BeOS/extfs_beos.cpp BeOS/scsi_beos.cpp \
 	       BeOS/serial_beos.cpp BeOS/sys_beos.cpp BeOS/timer_beos.cpp \
 	       BeOS/xpram_beos.cpp BeOS/SheepDriver BeOS/SheepNet \
@@ -66,7 +66,7 @@ links:
                CrossPlatform/video_vosf.h CrossPlatform/video_blit.h CrossPlatform/video_blit.cpp \
 	       Unix/audio_oss_esd.cpp \
 	       Unix/vhd_unix.cpp \
-	       Unix/extfs_unix.cpp Unix/serial_unix.cpp \
+	       Unix/extfs_unix.cpp Unix/serial_unix.cpp Unix/color_scheme.cpp \
 	       Unix/sshpty.h Unix/sshpty.c Unix/strlcpy.h Unix/strlcpy.c \
 	       Unix/sys_unix.cpp Unix/timer_unix.cpp Unix/xpram_unix.cpp Unix/prefs_unix.cpp \
 	       Unix/semaphore.h Unix/posix_sem.cpp Unix/config.sub Unix/config.guess Unix/m4 \

SheepShaver/src/Unix/color_scheme.cpp

@@ -0,0 +1 @@
+../../../BasiliskII/src/Unix/color_scheme.cpp

SheepShaver/src/Unix/configure.ac

@@ -380,7 +380,7 @@ fi
 if [[ "x$WANT_GTK" != "xno" -a "x$WANT_STANDALONE_GUI" = "xno" ]]; then
   AC_DEFINE(ENABLE_GTK, 1, [Define if using GTK.])
   if [[ "$WANT_GTK" = "GTK3" ]]; then
-    UISRCS="prefs_editor_gtk3.cpp g_resource.cpp"
+    UISRCS="prefs_editor_gtk3.cpp g_resource.cpp color_scheme.cpp"
   else
     UISRCS="prefs_editor_gtk.cpp"
   fi

SheepShaver/src/Unix/main_unix.cpp

@@ -147,6 +147,10 @@
 #if GTK_CHECK_VERSION(3, 14, 0)
 #define ENABLE_GTK3
 #endif
+#if GTK_CHECK_VERSION(3, 22, 0)
+#define ENABLE_GTK_3_22
+#include "color_scheme.h"
+#endif
 #endif
 
 #ifdef ENABLE_XF86_DGA
@@ -762,6 +766,9 @@ GtkWindow *win;
 
 static void gui_startup (void)
 {
+#ifdef ENABLE_GTK_3_22
+    color_scheme_set(APP_PREFERS_LIGHT);
+#endif
 	if (use_gui && !PrefsEditor())
 		QuitEmulator();
 }

SheepShaver/src/include/color_scheme.h

@@ -0,0 +1 @@
+../../../BasiliskII/src/include/color_scheme.h