UI: Allow prop. view to be created via identifier

Allows a properties view control to be created only with an identifier
string instead of only being created with a pointer to an object.  This
way, we don't necessarily have to have an object for some arbitrary
settings we want the user to be able to modify.

obs/properties-view.cpp

@@ -42,7 +42,13 @@ static inline long long color_to_int(QColor color)
 
 void OBSPropertiesView::ReloadProperties()
 {
-	properties.reset(reloadCallback(obj));
+	if (obj) {
+		properties.reset(reloadCallback(obj));
+	} else {
+		properties.reset(reloadCallback((void*)type.c_str()));
+		obs_properties_apply_settings(properties.get(), settings);
+	}
+
 	RefreshProperties();
 }
 
@@ -97,6 +103,19 @@ OBSPropertiesView::OBSPropertiesView(OBSData settings_, void *obj_,
 	ReloadProperties();
 }
 
+OBSPropertiesView::OBSPropertiesView(OBSData settings_, const char *type_,
+		PropertiesReloadCallback reloadCallback_, int minSize_)
+	: VScrollArea    (nullptr),
+	  properties     (nullptr, obs_properties_destroy),
+	  settings       (settings_),
+	  type           (type_),
+	  reloadCallback (reloadCallback_),
+	  minSize        (minSize_)
+{
+	setFrameShape(QFrame::NoFrame);
+	ReloadProperties();
+}
+
 void OBSPropertiesView::resizeEvent(QResizeEvent *event)
 {
 	emit PropertiesResized();
@@ -694,7 +713,9 @@ void WidgetInfo::ControlChanged()
 			return;
 	}
 
-	view->callback(view->obj, view->settings);
+	if (view->callback)
+		view->callback(view->obj, view->settings);
+
 	if (obs_property_modified(property, view->settings)) {
 		view->lastFocused = setting;
 		QMetaObject::invokeMethod(view, "RefreshProperties",

obs/properties-view.hpp

@@ -59,6 +59,7 @@ private:
 	properties_t                             properties;
 	OBSData                                  settings;
 	void                                     *obj = nullptr;
+	std::string                              type;
 	PropertiesReloadCallback                 reloadCallback;
 	PropertiesUpdateCallback                 callback = nullptr;
 	int                                      minSize;
@@ -95,4 +96,7 @@ public:
 			PropertiesReloadCallback reloadCallback,
 			PropertiesUpdateCallback callback,
 			int minSize = 0);
+	OBSPropertiesView(OBSData settings, const char *type,
+			PropertiesReloadCallback reloadCallback,
+			int minSize = 0);
 };