Added check to ensure we are in lighttable view prior to callling darktable.register_lib. If darktable was invoked in single image (darkroom) mode, then an event handler is registered to detect the change from darkroom mode to lighttable mode so that we can then call darktable.register_lib.

tools/executable_manager.lua

@@ -40,6 +40,10 @@ local gettext = dt.gettext
 
 gettext.bindtextdomain("executable_manager",dt.configuration.config_dir.."/lua/locale/")
 
+local exec_man = {} -- our own namespace
+exec_man.module_installed = false
+exec_man.event_registered = false
+
 -- - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 -- F U N C T I O N S
 -- - - - - - - - - - - - - - - - - - - - - - - - - - - - 
@@ -86,12 +90,30 @@ local function update_combobox_choices(combobox, choice_table, selected)
   combobox.value = selected
 end
 
+local function install_module()
+  if not exec_man.module_installed then
+    dt.register_lib(
+      "executable_manager",     -- Module name
+      "executable manager",     -- Visible name
+      true,                -- expandable
+      false,               -- resetable
+      {[dt.gui.views.lighttable] = {"DT_UI_CONTAINER_PANEL_LEFT_BOTTOM", 100}},   -- containers
+      dt.new_widget("box") -- widget
+      {
+        orientation = "vertical",
+        exec_man.selector,
+        exec_man.stack,
+      },
+      nil,-- view_enter
+      nil -- view_leave
+    )
+    exec_man.module_installed = true
+  end
+end
 -- - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 -- M A I N   P R O G R A M
 -- - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 
-local exec_man = {} -- our own namespace
-
 local DARKTABLERC = dt.configuration.config_dir .. PS .. "darktablerc"
 
 
@@ -187,19 +209,18 @@ update_combobox_choices(exec_man.selector, exec_table, 1)
 -- register the lib
 
 
-dt.register_lib(
-  "executable_manager",     -- Module name
-  "executable manager",     -- Visible name
-  true,                -- expandable
-  false,               -- resetable
-  {[dt.gui.views.lighttable] = {"DT_UI_CONTAINER_PANEL_LEFT_BOTTOM", 100}},   -- containers
-  dt.new_widget("box") -- widget
-  {
-    orientation = "vertical",
-    exec_man.selector,
-    exec_man.stack,
-  },
-  nil,-- view_enter
-  nil -- view_leave
-)
-
+if dt.gui.current_view().name == "lighttable" then
+  install_module()
+else
+  if not exec_man.event_registered then
+    dt.register_event(
+      "view-changed",
+      function(event, old_view, new_view)
+        if new_view.name == "lighttable" and old_view.name == "darkroom" then
+          install_module()
+         end
+      end
+    )
+    exec_man.event_registered = true
+  end
+end