Merge pull request #70 from hartlottery/fix_timer

An old problem is that the plugin cannot work normally if the i3wm starts before xfce4-panel as in #62, here we're using a timer to handle the ipc resources' acquisition.

May still have some segfault there.

Tested in archlinux with latest xfce4-panel (v4.18.4).

Investigating an error that causing the .xsession-errors during restart i3wm twice or more, crashed in g_io_channel_read_chars: and channel->is_readable.

Backtrace seems indicates an error of i3ipc-glib.

The problem is caused by an unhandled error status code from glib, submitted a PR to altdesktop/i3ipc-glib#41, but may not get merged due to unmaintained.

panel-plugin/i3w-plugin.c

@@ -92,7 +92,7 @@ static void
 on_ipc_shutdown(gpointer i3_w);
 
 static void
-recover_from_disconnect(i3WorkspacesPlugin *i3_workspaces);
+reconnect_i3wm_timer(i3WorkspacesPlugin *i3_workspaces);
 
 static void
 handle_change_output(i3WorkspacesPlugin* i3_workspaces);
@@ -187,6 +187,8 @@ construct_workspaces(XfcePanelPlugin *plugin)
 
     i3WorkspacesPlugin *i3_workspaces;
     GtkOrientation orientation;
+    fprintf(stderr, "xfce4_i3_workspaces: construct_workspace, plugin=%p\n",
+            plugin);
 
     /* allocate memory for the plugin structure */
     i3_workspaces = g_slice_new0(i3WorkspacesPlugin);
@@ -226,24 +228,16 @@ construct_workspaces(XfcePanelPlugin *plugin)
 
     i3_workspaces->workspace_buttons = g_hash_table_new(g_direct_hash, g_direct_equal);
 
-	/* Add a label for the binding mode */
-	i3_workspaces->mode_label = gtk_label_new(NULL);
+    /* Add a label for the binding mode */
+    i3_workspaces->mode_label = gtk_label_new(NULL);
     GtkStyleContext *mode_label_context = gtk_widget_get_style_context(
         GTK_WIDGET(i3_workspaces->mode_label));
     gtk_style_context_add_class(mode_label_context, "binding-mode");
-	gtk_box_pack_end(GTK_BOX(i3_workspaces->hvbox), i3_workspaces->mode_label, FALSE, FALSE, 0);
-	gtk_widget_show(i3_workspaces->mode_label);
+    gtk_box_pack_end(GTK_BOX(i3_workspaces->hvbox), i3_workspaces->mode_label, FALSE, FALSE, 0);
+    gtk_widget_show(i3_workspaces->mode_label);
 
-    GError *err = NULL;
-    i3_workspaces->i3wm = i3wm_construct(&err);
-    if (NULL != err)
-    {
-        recover_from_disconnect(i3_workspaces);
-    }
-
-    connect_callbacks(i3_workspaces);
-
-    add_workspaces(i3_workspaces);
+    /* Setup a timer to connect to the i3wm until success. */
+    reconnect_i3wm_timer(i3_workspaces);
 
     return i3_workspaces;
 }
@@ -302,8 +296,17 @@ destruct(XfcePanelPlugin *plugin, i3WorkspacesPlugin *i3_workspaces)
     /* destroy the panel widgets */
     gtk_widget_destroy(i3_workspaces->hvbox);
 
+    /* cancel the timer */
+    if (i3_workspaces->timeout) {
+        g_source_remove(i3_workspaces->timeout);
+        i3_workspaces->timeout = 0;
+    }
+
     /* destroy the i3wm delegate */
-    i3wm_destruct(i3_workspaces->i3wm);
+    if (i3_workspaces->i3wm) {
+        i3wm_destruct(i3_workspaces->i3wm);
+        i3_workspaces->i3wm = NULL;
+    }
 
     /* free the plugin structure */
     g_slice_free(i3WorkspacesPlugin, i3_workspaces);
@@ -395,6 +398,7 @@ config_changed(gpointer cb_data)
 static void
 add_workspaces(i3WorkspacesPlugin *i3_workspaces)
 {
+    g_assert(i3_workspaces->i3wm);
     GSList *wlist = i3wm_get_workspaces(i3_workspaces->i3wm);
 
     GSList *witem;
@@ -599,10 +603,14 @@ static void
 on_workspace_clicked(GtkWidget *button, gpointer data)
 {
     i3WorkspacesPlugin *i3_workspaces = (i3WorkspacesPlugin *)data;
-    GSList *wlist = i3wm_get_workspaces(i3_workspaces->i3wm);
+    GSList *wlist, *witem;
     i3workspace *workspace = NULL;
 
-    GSList *witem;
+    if (!i3_workspaces->i3wm) {
+        return;
+    }
+
+    wlist = i3wm_get_workspaces(i3_workspaces->i3wm);
     for (witem = wlist; witem != NULL; witem = witem->next)
     {
         workspace = (i3workspace *) witem->data;
@@ -635,6 +643,12 @@ on_workspace_scrolled(GtkWidget *ebox, GdkEventScroll *ev, gpointer data)
 {
     i3WorkspacesPlugin *i3_workspaces = (i3WorkspacesPlugin *)data;
 
+    if (!i3_workspaces->i3wm) {
+        /* Hasn't connected, so stop the event. Once connected the workspace
+         * is ensured to be updated. */
+        return TRUE;
+    }
+
     GList *wlist = g_hash_table_get_keys(i3_workspaces->workspace_buttons);
     wlist = g_list_sort(wlist, (GCompareFunc) i3wm_workspace_cmp);
 
@@ -676,29 +690,55 @@ static void
 on_ipc_shutdown(gpointer i3_w)
 {
     i3WorkspacesPlugin *i3_workspaces = (i3WorkspacesPlugin *) i3_w;
+    fprintf(stderr, "xfce4_i3_workspaces: on_ipc_shutdown, i3_w=%p\n", i3_w);
 
+    /* Remove previous resources */
     remove_workspaces(i3_workspaces);
-    i3wm_destruct(i3_workspaces->i3wm);
-    i3_workspaces->i3wm = NULL;
-
-    recover_from_disconnect(i3_workspaces);
-
-    connect_callbacks(i3_workspaces);
+    if (i3_workspaces->i3wm) {
+        i3wm_destruct(i3_workspaces->i3wm);
+        i3_workspaces->i3wm = NULL;
+    }
 
-    add_workspaces(i3_workspaces);
+    /* When shutdown, wake up the timer try to reconnect */
+    reconnect_i3wm_timer(i3_workspaces);
 }
 
-static void
-recover_from_disconnect(i3WorkspacesPlugin *i3_workspaces)
+static gboolean
+reconnect_i3wm_callback(gpointer data)
 {
+    i3WorkspacesPlugin *i3_workspaces = (i3WorkspacesPlugin *) data;
     GError *err = NULL;
 
+    if (i3_workspaces->i3wm) {
+        // maybe already initialized by other timers?
+        fprintf(stderr, "warn: other timer already reconnected?\n");
+        return G_SOURCE_REMOVE;
+    }
+
+    fprintf(stderr, "Connecting to i3 workspace manager...\n");
     i3_workspaces->i3wm = i3wm_construct(&err);
-    while (NULL != err)
-    {
-        fprintf(stderr, "Cannot connect to the i3 window manager: %s\n", err->message);
+    if (err != NULL) {
+        fprintf(stderr, "Still waiting for i3 window manager: %s\n",
+                err->message);
         g_error_free(err);
-        err = NULL;
-        i3_workspaces->i3wm = i3wm_construct(&err);
+        return G_SOURCE_CONTINUE;
+    }
+
+    // connected, doing the init things; todo: is memory barrier needed?
+    //   don't know whether the timer is sync or not
+    connect_callbacks(i3_workspaces);
+    add_workspaces(i3_workspaces);
+
+    i3_workspaces->timeout = 0;
+    return G_SOURCE_REMOVE;
+}
+
+static void
+reconnect_i3wm_timer(i3WorkspacesPlugin *i3_workspaces)
+{
+    guint id = g_timeout_add_seconds(1, reconnect_i3wm_callback, i3_workspaces);
+    if (id == 0) {
+        fprintf(stderr, "Timer broken! Plugin will no longer works.\n");
     }
+    i3_workspaces->timeout = id;
 }

panel-plugin/i3w-plugin.h

@@ -45,6 +45,7 @@ typedef struct
     i3WorkspacesConfig *config;
 
     i3windowManager *i3wm;
+    guint timeout;
 }
 i3WorkspacesPlugin;