refactor: turn StreamerMode into a singleton(-like thing) (#5216)

src/widgets/Notebook.cpp

@@ -7,10 +7,10 @@
 #include "controllers/hotkeys/HotkeyController.hpp"
 #include "singletons/Resources.hpp"
 #include "singletons/Settings.hpp"
+#include "singletons/StreamerMode.hpp"
 #include "singletons/Theme.hpp"
 #include "singletons/WindowManager.hpp"
 #include "util/InitUpdateButton.hpp"
-#include "util/StreamerMode.hpp"
 #include "widgets/dialogs/SettingsDialog.hpp"
 #include "widgets/helper/ChannelView.hpp"
 #include "widgets/helper/NotebookButton.hpp"
@@ -1437,9 +1437,8 @@ void SplitNotebook::addCustomButtons()
                          getIApp()->getWindows()->showSettingsDialog(
                              this, SettingsDialogPreference::StreamerMode);
                      });
-    this->signalHolder_.managedConnect(getApp()->streamerModeChanged, [this]() {
-        this->updateStreamerModeIcon();
-    });
+    QObject::connect(getIApp()->getStreamerMode(), &IStreamerMode::changed,
+                     this, &SplitNotebook::updateStreamerModeIcon);
     this->updateStreamerModeIcon();
 }
 
@@ -1462,7 +1461,8 @@ void SplitNotebook::updateStreamerModeIcon()
         this->streamerModeIcon_->setPixmap(
             getResources().buttons.streamerModeEnabledDark);
     }
-    this->streamerModeIcon_->setVisible(isInStreamerMode());
+    this->streamerModeIcon_->setVisible(
+        getIApp()->getStreamerMode()->isEnabled());
 }
 
 void SplitNotebook::themeChangedEvent()