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.

examples/moduleExample.lua

@@ -46,6 +46,44 @@ local function _(msgid)
     return gettext.dgettext("moduleExample", msgid)
 end
 
+-- declare a local namespace and a couple of variables we'll need to install the module
+local mE = {}
+mE.widgets = {}
+mE.event_registered = false  -- keep track of whether we've added an event callback or not
+mE.module_installed = false  -- keep track of whether the module is module_installed
+
+--[[ We have to create the module in one of two ways depending on which view darktable starts
+     in.  In orker to not repeat code, we wrap the darktable.register_lib in a local function.
+  ]]
+
+local function install_module()
+  if not mE.module_installed then
+    -- https://www.darktable.org/lua-api/index.html#darktable_register_lib
+    dt.register_lib(
+      "exampleModule",     -- Module name
+      "exampleModule",     -- name
+      true,                -- expandable
+      false,               -- resetable
+      {[dt.gui.views.lighttable] = {"DT_UI_CONTAINER_PANEL_RIGHT_CENTER", 100}},   -- containers
+      -- https://www.darktable.org/lua-api/types_lua_box.html
+      dt.new_widget("box") -- widget
+      {
+        orientation = "vertical",
+        dt.new_widget("button")
+        {
+          label = _("MyButton"),
+          clicked_callback = function (_)
+            dt.print(_("Button clicked"))
+          end
+        },
+        table.unpack(mE.widgets),
+      },
+      nil,-- view_enter
+      nil -- view_leave
+    )
+    mE.module_installed = true
+  end
+end
 
 -- https://www.darktable.org/lua-api/types_lua_check_button.html
 local check_button = dt.new_widget("check_button"){label = _("MyCheck_button"), value = true}
@@ -90,35 +128,35 @@ local slider = dt.new_widget("slider")
   value = 52          -- The current value of the slider
 }
 
--- https://www.darktable.org/lua-api/index.html#darktable_register_lib
-dt.register_lib(
-  "exampleModule",     -- Module name
-  "exampleModule",     -- name
-  true,                -- expandable
-  false,               -- resetable
-  {[dt.gui.views.lighttable] = {"DT_UI_CONTAINER_PANEL_RIGHT_CENTER", 100}},   -- containers
-  -- https://www.darktable.org/lua-api/types_lua_box.html
-  dt.new_widget("box") -- widget
-  {
-    orientation = "vertical",
-    dt.new_widget("button")
-    {
-      label = _("MyButton"),
-      clicked_callback = function (_)
-        dt.print(_("Button clicked"))
+-- pack the widgets in a table for loading in the module
+
+table.insert(mE.widgets, check_button)
+table.insert(mE.widgets, combobox)
+table.insert(mE.widgets, entry)
+table.insert(mE.widgets, file_chooser_button)
+table.insert(mE.widgets, label)
+table.insert(mE.widgets, separator)
+table.insert(mE.widgets, slider)
+
+-- ... and tell dt about it all
+
+
+if dt.gui.current_view().name == "lighttable" then -- make sure we are in lighttable view
+  install_module()  -- register the lib
+else
+  if not mE.event_registered then -- if we are not in lighttable view then register an event to signal when we might be
+    -- https://www.darktable.org/lua-api/index.html#darktable_register_event
+    dt.register_event(
+      "view-changed",  -- we want to be informed when the view changes
+      function(event, old_view, new_view)
+        if new_view.name == "lighttable" and old_view.name == "darkroom" then  -- if the view changes from darkroom to lighttable
+          install_module()  -- register the lib
+         end
       end
-    },
-    check_button,
-    combobox,   
-    entry,
-    file_chooser_button,
-    label,
-    separator,
-    slider
-  },
-  nil,-- view_enter
-  nil -- view_leave
-)
+    )
+    mE.event_registered = true  --  keep track of whether we have an event handler installed
+  end
+end
 
 -- vim: shiftwidth=2 expandtab tabstop=2 cindent syntax=lua
 -- kate: hl Lua;