Make sub-panels also URL addressable

src/pyj/book_list/router.pyj

@@ -76,4 +76,10 @@ def back():
     if history_count > 0:
         window.history.back()
     else:
-        push_state({}, replace=True)
+        cq = get_current_query()
+        handler = mode_handlers[cq.mode] or default_mode_handler
+        if handler.back_from_current:
+            q = handler.back_from_current(cq)
+        else:
+            q = {}
+        push_state(q, replace=True)

src/pyj/book_list/ui.pyj

@@ -7,7 +7,7 @@ from elementmaker import E
 
 from book_list.constants import book_list_container_id
 from book_list.globals import get_current_query
-from book_list.router import push_state, back as router_back
+from book_list.router import push_state
 from book_list.library_data import current_library_id
 
 
@@ -44,10 +44,6 @@ def currently_showing_panel():
     c = document.getElementById(book_list_container_id)
     return c.dataset.panel
 
-def number_of_subpanels():
-    c = document.getElementById(book_list_container_id)
-    return c.lastChild.childNodes.length
-
 
 def show_panel(panel, query_data, replace=False):
     query = {k:query_data[k] for k in query_data}
@@ -59,29 +55,19 @@ def show_panel(panel, query_data, replace=False):
     push_state(query, replace=replace)
 
 
-def close_subpanel():
-    c = document.getElementById(book_list_container_id).lastChild
-    panel_to_remove = c.lastChild
-    if panel_to_remove:
-        c.remove(panel_to_remove)
-        if c.lastChild:
-            c.lastChild.style.display = 'block'
-        else:
-            c.style.display = 'none'
-
-
-def back():
-    if number_of_subpanels() > 0:
-        return close_subpanel()
-    router_back()
-
-
 def apply_url_state(state):
     panel = state.panel or 'home'
     c = document.getElementById(book_list_container_id)
     clear(c)
     c.appendChild(E.div())
-    c.appendChild(E.div(style='display:none'))
     c.dataset.panel = panel
     handler = panel_handlers[panel] or default_panel_handler
     handler(ensure_id(c.firstChild, 'panel'))
+
+
+apply_url_state.back_from_current = def back_from_current(current_query):
+    q = current_query
+    if q.panel and '^' in q.panel:
+        q = {k:q[k] for k in q}
+        q.panel = q.panel.rpartition('^')[0]
+    return q

src/pyj/book_list/views.pyj

@@ -11,7 +11,8 @@ from session import get_interface_data
 from book_list.globals import get_session_data
 from book_list.cover_grid import cover_grid_css, create_item as create_cover_grid_item, init as init_cover_grid, append_item as cover_grid_append_item
 from book_list.top_bar import create_top_bar
-from book_list.ui import back, set_panel_handler
+from book_list.router import back
+from book_list.ui import set_panel_handler
 from book_list.library_data import current_library_id, load_status, ensure_current_library_data, library_data
 
 ALLOWED_MODES = {'cover_grid'}