Implement the window_role criterion (checks WM_WINDOW_ROLE)

Closes: #446

This is handy for matching specific windows of a multi-window application, for
example only Pidgin’s buddy list window.

include/atoms.xmacro

@@ -21,5 +21,6 @@ xmacro(UTF8_STRING)
 xmacro(WM_STATE)
 xmacro(WM_CLIENT_LEADER)
 xmacro(WM_TAKE_FOCUS)
+xmacro(WM_WINDOW_ROLE)
 xmacro(I3_SOCKET_PATH)
 xmacro(I3_CONFIG_PATH)

include/data.h

@@ -264,6 +264,11 @@ struct Window {
      * application supports _NET_WM_NAME, in COMPOUND_TEXT otherwise). */
     char *name_x;
 
+    /** The WM_WINDOW_ROLE of this window (for example, the pidgin buddy window
+     * sets "buddy list"). Useful to match specific windows in assignments or
+     * for_window. */
+    char *role;
+
     /** Flag to force re-rendering the decoration upon changes */
     bool name_x_changed;
 
@@ -298,6 +303,7 @@ struct Match {
     struct regex *class;
     struct regex *instance;
     struct regex *mark;
+    struct regex *role;
     enum {
         M_DONTCHECK = -1,
         M_NODOCK = 0,

include/window.h

@@ -42,4 +42,10 @@ void window_update_transient_for(i3Window *win, xcb_get_property_reply_t *prop);
  */
 void window_update_strut_partial(i3Window *win, xcb_get_property_reply_t *prop);
 
+/**
+ * Updates the WM_WINDOW_ROLE
+ *
+ */
+void window_update_role(i3Window *win, xcb_get_property_reply_t *prop, bool before_mgmt);
+
 #endif