From b8e3ec43023af8d38d68d13b971a09580be310f2 Mon Sep 17 00:00:00 2001
From: Bill Ferguson <wpferguson@gmail.com>
Date: Sun, 9 Aug 2020 01:43:31 -0400
Subject: [PATCH] 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.

---
 contrib/HDRMerge.lua | 47 +++++++++++++++++++++++++++++++++-----------
 1 file changed, 36 insertions(+), 11 deletions(-)

diff --git a/contrib/HDRMerge.lua b/contrib/HDRMerge.lua
index ad7dd3a..aa13a1c 100644
--- a/contrib/HDRMerge.lua
+++ b/contrib/HDRMerge.lua
@@ -94,6 +94,10 @@ local GUI = { --GUI Elements Table
     }
 }
 
+HDRM.module_installed = false
+HDRM.event_registered = false
+
+
 --Detect User Styles--
 local styles = dt.styles
 local styles_count = 1 -- 'none' = 1
@@ -264,6 +268,23 @@ local function main()
 
 end
 
+local function install_module()
+  if not HDRM.module_installed then
+    dt.register_lib( -- register HDRMerge module
+        'HDRMerge_Lib', -- Module name
+        _('HDRMerge'), -- name
+        true,   -- expandable
+        true,   -- resetable
+        {[dt.gui.views.lighttable] = {'DT_UI_CONTAINER_PANEL_RIGHT_CENTER', 99}},   -- containers
+        dt.new_widget('box'){
+            orientation = 'vertical',
+            GUI.stack
+        }
+    )
+    HDRM.module_installed = true
+  end
+end
+
 -- GUI Elements --
 local lbl_hdr = dt.new_widget('section_label'){
     label = _('HDRMerge options')
@@ -411,14 +432,18 @@ else
     GUI.stack.active = 2
 end
 
-dt.register_lib( -- register HDRMerge module
-    'HDRMerge_Lib', -- Module name
-    _('HDRMerge'), -- name
-    true,   -- expandable
-    true,   -- resetable
-    {[dt.gui.views.lighttable] = {'DT_UI_CONTAINER_PANEL_RIGHT_CENTER', 99}},   -- containers
-    dt.new_widget('box'){
-        orientation = 'vertical',
-        GUI.stack
-        }
-)
+if dt.gui.current_view().name == "lighttable" then
+  install_module()
+else
+  if not HDRM.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
+    )
+    HDRM.event_registered = true
+  end
+end