Implement the special workspace ~ for assignments, which will set clients floating automatically

docs/userguide

@@ -237,6 +237,9 @@ i3 will get the title as soon as the application maps the window (mapping means
 actually displaying it on the screen), you’d need to have to match on Firefox
 in this case.
 
+You can use the special workspace +~+ to specify that matching clients should
+be put into floating mode.
+
 *Syntax*:
 ----------------------------------------------------
 assign ["]window class[/window title]["] [→] workspace
@@ -248,6 +251,7 @@ assign urxvt 2
 assign urxvt → 2
 assign "urxvt" → 2
 assign "urxvt/VIM" → 3
+assign "gecko" → ~
 ----------------------
 
 === Automatically starting applications on startup

include/data.h

@@ -223,6 +223,9 @@ struct Autostart {
  */
 struct Assignment {
         char *windowclass_title;
+        /* floating is true if this was an assignment to the special workspace "~".
+         * Matching clients will be put into floating mode automatically. */
+        bool floating;
         int workspace;
         TAILQ_ENTRY(Assignment) assignments;
 };

src/config.c

@@ -241,14 +241,16 @@ void load_configuration(xcb_connection_t *conn, const char *override_configpath)
                                 die("Malformed assignment, couldn't find target\n");
                         target++;
 
-                        if (atoi(target) < 1 || atoi(target) > 10)
+                        if (*target != '~' && (atoi(target) < 1 || atoi(target) > 10))
                                 die("Malformed assignment, invalid workspace number\n");
 
                         LOG("assignment parsed: \"%s\" to \"%s\"\n", class_title, target);
 
-                        struct Assignment *new = smalloc(sizeof(struct Assignment));
+                        struct Assignment *new = scalloc(sizeof(struct Assignment));
                         new->windowclass_title = class_title;
-                        new->workspace = atoi(target);
+                        if (*target == '~')
+                                new->floating = true;
+                        else new->workspace = atoi(target);
                         TAILQ_INSERT_TAIL(&assignments, new, assignments);
                         continue;
                 }

src/manage.c

@@ -315,6 +315,12 @@ void reparent_window(xcb_connection_t *conn, xcb_window_t child,
                         if (get_matching_client(conn, assign->windowclass_title, new) == NULL)
                                 continue;
 
+                        if (assign->floating) {
+                                new->floating = FLOATING_AUTO_ON;
+                                LOG("Assignment matches, putting client into floating mode\n");
+                                break;
+                        }
+
                         LOG("Assignment \"%s\" matches, so putting it on workspace %d\n",
                             assign->windowclass_title, assign->workspace);