include/Mw/LowLevel.h

@@ -83,11 +83,15 @@ typedef struct _MwLLDBusContext {
 	DBusMessageIter dbus_args, dbus_variant, dbus_inner_variant;
 } MwLLDBusContext;
 
+typedef void (*MwLLDBusPortalPollListener)(MwLL handle, MwU32 new_value);
+
 /* setup the dbus func table. Returns false and prints a warning if dbus couldn't be found.  */
 MWDECL MwBool MwLLDBusFuncSetup(MwLLDBusFuncTable* tbl);
 
 MWDECL MwBool MwLLDBusNewContext(MwLLDBusFuncTable* tbl, MwLLDBusContext* ctx);
 MWDECL MwBool MwLLDBusPortalGet(MwLLDBusFuncTable* tbl, MwLLDBusContext* ctx, const char* portal, const char* namespace, const char* key, void* out);
+MWDECL MwBool MwLLDBusPortalWatch(MwLLDBusFuncTable* tbl, MwLLDBusContext* ctx, const char* portal);
+MWDECL MwBool MwLLDBusPortalPoll(MwLLDBusFuncTable* tbl, MwLLDBusContext* ctx, MwLL handle, const char* portal, const char* namespace, const char* key, MwLLDBusPortalPollListener);
 MWDECL void   MwLLDBusFreeContext(MwLLDBusFuncTable* tbl, MwLLDBusContext* ctx);
 
 #endif

src/backend/wayland.c

@@ -17,6 +17,8 @@
 wayland_call_table_t wl_call_tbl;
 MwBool		     MwWaylandAlwaysRender = MwFALSE;
 
+MwU32 wl_dark_theme = -1;
+
 /* Standard procedure before most event callbacks in Wayland ("most" because the setup ones don't need this). Wait for the Mutex to be freed, if we're deadlocking for longer then a quarter of a second then do nothing with the event. */
 #define WAYLAND_EVENT_OP_START(self) \
 	do { \
@@ -1818,14 +1820,21 @@ static void widget_setup(MwLL r, MwLL parent, int x, int y, int width, int heigh
 }
 
 #ifdef USE_DBUS
+static void dark_theme_listener(MwLL handle, MwU32 new_value) {
+	wl_dark_theme = (new_value == 1) ? 1 : 0;
+
+	MwLLDispatch(handle, dark_theme, &wl_dark_theme);
+}
+
 static void detect_dark_theme(MwLL handle) {
 	MwU32 value	 = 0;
-	MwU32 dark_theme = 0;
+
 	MwLLDBusPortalGet(&wl_call_tbl.dbus, &handle->wayland.dbus, "org.freedesktop.portal.Settings", "org.freedesktop.appearance", "color-scheme", &value);
+	wl_dark_theme = (value == 1) ? 1 : 0;
 
-	dark_theme = (value == 1) ? 1 : 0;
+	MwLLDBusPortalWatch(&wl_call_tbl.dbus, &handle->wayland.dbus, "org.freedesktop.portal.Settings");
 
-	MwLLDispatch(handle, dark_theme, &dark_theme);
+	MwLLDispatch(handle, dark_theme, &wl_dark_theme);
 }
 #endif
 
@@ -2164,15 +2173,18 @@ static int MwLLPendingImpl(MwLL handle) {
 	};
 	int pending = 0;
 
-	if(handle->wayland.dark_theme_detection) {
-		handle->wayland.dark_theme_detection = MwFALSE;
 #ifdef USE_DBUS
-		if(wl_call_tbl.has_dbus) {
+	if(wl_call_tbl.has_dbus) {
+		if(handle->wayland.dark_theme_detection) {
+
+			handle->wayland.dark_theme_detection = MwFALSE;
 			detect_dark_theme(handle);
 			MwLLDispatch(handle, draw, NULL);
+		} else {
+			MwLLDBusPortalPoll(&wl_call_tbl.dbus, &handle->wayland.dbus, handle, "org.freedesktop.portal.Settings", "org.freedesktop.appearance", "color-scheme", &dark_theme_listener);
 		}
-#endif
 	}
+#endif
 
 	if(!handle->wayland.did_initial_resize) {
 		recursive_dispatch_resize(handle);

src/lowlevel.c

@@ -176,6 +176,69 @@ MWDECL MwBool MwLLDBusPortalGet(MwLLDBusFuncTable* tbl, MwLLDBusContext* ctx, co
 	return MwTRUE;
 }
 
+MWDECL MwBool MwLLDBusPortalWatch(MwLLDBusFuncTable* tbl, MwLLDBusContext* ctx, const char* portal) {
+	if(!ctx->dbus_conn) {
+		return MwFALSE;
+	}
+
+	char filter_string[2048];
+	MwStringPrintIntoBuffer(filter_string, sizeof(filter_string), "type='%s',interface=%s", "signal", portal);
+
+    dbus_bus_add_match(ctx->dbus_conn, filter_string, &ctx->dbus_err);
+    dbus_connection_flush(ctx->dbus_conn);
+
+	return MwTRUE;
+}
+
+// Technically this will swallow all other results, so this is not usable multiple times.
+// TODO: Use a hashmap instead
+MWDECL MwBool MwLLDBusPortalPoll(MwLLDBusFuncTable* tbl, MwLLDBusContext* ctx, MwLL handle, const char* portal, const char* namespace, const char* key, MwLLDBusPortalPollListener listener) {
+	DBusMessage* msg;
+	DBusMessageIter args, msg_value;
+	const char* msg_namespace;
+	const char* msg_key;
+	MwU32 msg_value_content;
+
+	if(!ctx->dbus_conn) {
+		return MwFALSE;
+	}
+
+ 	dbus_connection_read_write(ctx->dbus_conn, 0);
+	msg = dbus_connection_pop_message(ctx->dbus_conn);
+
+	if (NULL == msg) { 
+		return MwFALSE;
+	}
+
+	// check if the message is a signal from the correct interface and with the correct name
+	if (dbus_message_is_signal(msg, portal, "SettingChanged")) {
+		// read the parameters
+		if (!dbus_message_iter_init(msg, &args))
+			fprintf(stderr, "[WARNING] Message has no arguments\n"); 
+		else if (DBUS_TYPE_STRING != dbus_message_iter_get_arg_type(&args)) 
+			fprintf(stderr, "[WARNING] Argument is not string\n"); 
+		else {
+			dbus_message_iter_get_basic(&args, &msg_namespace);
+
+			dbus_message_iter_next(&args);
+			dbus_message_iter_get_basic(&args, &msg_key);
+
+			// Check that key and namespace match
+			if (strcmp(msg_namespace, namespace) == 0 && strcmp(msg_key, key) == 0) {
+				// Assuming the value is a basic type
+				dbus_message_iter_next(&args);
+				dbus_message_iter_recurse(&args, &msg_value);
+				dbus_message_iter_get_basic(&msg_value, &msg_value_content);
+
+				listener(handle, msg_value_content);
+			}
+		}
+	}
+
+	// free the message
+	dbus_message_unref(msg);
+}
+
 void MwLLDBusFreeContext(MwLLDBusFuncTable* tbl, MwLLDBusContext* ctx) {
 	if(!tbl->lib) {
 		return;