Add support for system dark mode (Linux)

- Use `org.freedesktop.appearance color-scheme` to support system dark mode.

1 files changed, 135 insertions, 0 deletions

diff --git a/platform/linuxbsd/freedesktop_portal_desktop.cpp b/platform/linuxbsd/freedesktop_portal_desktop.cpp
new file mode 100644
index 0000000000..ed54084694
--- /dev/null
+++ b/platform/linuxbsd/freedesktop_portal_desktop.cpp
@@ -0,0 +1,135 @@
+/*************************************************************************/
+/*  freedesktop_portal_desktop.cpp                                       */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#include "freedesktop_portal_desktop.h"
+
+#ifdef DBUS_ENABLED
+
+#include "core/error/error_macros.h"
+#include "core/os/os.h"
+#include "core/string/ustring.h"
+
+#include "dbus-so_wrap.h"
+
+#include "core/variant/variant.h"
+
+#define BUS_OBJECT_NAME "org.freedesktop.portal.Desktop"
+#define BUS_OBJECT_PATH "/org/freedesktop/portal/desktop"
+
+#define BUS_INTERFACE_SETTINGS "org.freedesktop.portal.Settings"
+
+static bool try_parse_variant(DBusMessage *p_reply_message, int p_type, void *r_value) {
+	DBusMessageIter iter[3];
+
+	dbus_message_iter_init(p_reply_message, &iter[0]);
+	if (dbus_message_iter_get_arg_type(&iter[0]) != DBUS_TYPE_VARIANT) {
+		return false;
+	}
+
+	dbus_message_iter_recurse(&iter[0], &iter[1]);
+	if (dbus_message_iter_get_arg_type(&iter[1]) != DBUS_TYPE_VARIANT) {
+		return false;
+	}
+
+	dbus_message_iter_recurse(&iter[1], &iter[2]);
+	if (dbus_message_iter_get_arg_type(&iter[2]) != p_type) {
+		return false;
+	}
+
+	dbus_message_iter_get_basic(&iter[2], r_value);
+	return true;
+}
+
+bool FreeDesktopPortalDesktop::read_setting(const char *p_namespace, const char *p_key, int p_type, void *r_value) {
+	if (unsupported) {
+		return false;
+	}
+
+	DBusError error;
+	dbus_error_init(&error);
+
+	DBusConnection *bus = dbus_bus_get(DBUS_BUS_SESSION, &error);
+	if (dbus_error_is_set(&error)) {
+		dbus_error_free(&error);
+		unsupported = true;
+		if (OS::get_singleton()->is_stdout_verbose()) {
+			ERR_PRINT(String() + "Error opening D-Bus connection: " + error.message);
+		}
+		return false;
+	}
+
+	DBusMessage *message = dbus_message_new_method_call(
+			BUS_OBJECT_NAME, BUS_OBJECT_PATH, BUS_INTERFACE_SETTINGS,
+			"Read");
+	dbus_message_append_args(
+			message,
+			DBUS_TYPE_STRING, &p_namespace,
+			DBUS_TYPE_STRING, &p_key,
+			DBUS_TYPE_INVALID);
+
+	DBusMessage *reply = dbus_connection_send_with_reply_and_block(bus, message, 50, &error);
+	dbus_message_unref(message);
+	if (dbus_error_is_set(&error)) {
+		dbus_error_free(&error);
+		dbus_connection_unref(bus);
+		if (OS::get_singleton()->is_stdout_verbose()) {
+			ERR_PRINT(String() + "Error on D-Bus communication: " + error.message);
+		}
+		return false;
+	}
+
+	bool success = try_parse_variant(reply, p_type, r_value);
+
+	dbus_message_unref(reply);
+	dbus_connection_unref(bus);
+
+	return success;
+}
+
+uint32_t FreeDesktopPortalDesktop::get_appearance_color_scheme() {
+	if (unsupported) {
+		return 0;
+	}
+
+	uint32_t value = 0;
+	read_setting("org.freedesktop.appearance", "color-scheme", DBUS_TYPE_UINT32, &value);
+	return value;
+}
+
+FreeDesktopPortalDesktop::FreeDesktopPortalDesktop() {
+#ifdef DEBUG_ENABLED
+	int dylibloader_verbose = 1;
+#else
+	int dylibloader_verbose = 0;
+#endif
+	unsupported = (initialize_dbus(dylibloader_verbose) != 0);
+}
+
+#endif // DBUS_ENABLED