Preferences can be used in non-UI contexts

Fixed bug running app_preferences.lua from tests repository.

src/app/context.cpp

@@ -17,6 +17,7 @@
 #include "app/commands/commands.h"
 #include "app/console.h"
 #include "app/doc.h"
+#include "app/pref/preferences.h"
 #include "app/site.h"
 #include "base/scoped_value.h"
 #include "doc/layer.h"
@@ -32,10 +33,12 @@ Context::Context()
   , m_lastSelectedDoc(nullptr)
 {
   m_docs.add_observer(this);
+  m_docs.add_observer(&Preferences::instance());
 }
 
 Context::~Context()
 {
+  m_docs.remove_observer(&Preferences::instance());
   m_docs.remove_observer(this);
 }
 

src/app/pref/preferences.h

@@ -76,6 +76,7 @@ namespace app {
     void removeDocument(Doc* doc);
 
   protected:
+    // DocsObserver impl
     void onRemoveDocument(Doc* doc) override;
 
   private:

src/app/ui_context.cpp

@@ -14,7 +14,6 @@
 #include "app/app.h"
 #include "app/doc.h"
 #include "app/modules/editors.h"
-#include "app/pref/preferences.h"
 #include "app/site.h"
 #include "app/ui/color_bar.h"
 #include "app/ui/doc_view.h"
@@ -39,8 +38,6 @@ UIContext* UIContext::m_instance = nullptr;
 UIContext::UIContext()
   : m_lastSelectedView(nullptr)
 {
-  documents().add_observer(&Preferences::instance());
-
   ASSERT(m_instance == NULL);
   m_instance = this;
 }
@@ -50,8 +47,6 @@ UIContext::~UIContext()
   ASSERT(m_instance == this);
   m_instance = NULL;
 
-  documents().remove_observer(&Preferences::instance());
-
   // The context must be empty at this point. (It's to check if the UI
   // is working correctly, i.e. closing all files when the user can
   // take any action about it.)