Merge branch 'master' into jgrpp

# Conflicts:
#	src/lang/russian.txt
#	src/linkgraph/linkgraph_gui.cpp
#	src/news_gui.cpp
#	src/town_cmd.cpp
#	src/town_gui.cpp

src/zoom_func.h

@@ -79,6 +79,26 @@ static inline int UnScaleGUI(int value)
 	return UnScaleByZoom(value, ZOOM_LVL_GUI);
 }
 
+/**
+ * Scale zoom level relative to GUI zoom.
+ * @param value zoom level to scale
+ * @return scaled zoom level
+ */
+static inline ZoomLevel ScaleZoomGUI(ZoomLevel value)
+{
+	return std::clamp(ZoomLevel(value + (ZOOM_LVL_GUI - ZOOM_LVL_OUT_4X)), ZOOM_LVL_MIN, ZOOM_LVL_MAX);
+}
+
+/**
+ * UnScale zoom level relative to GUI zoom.
+ * @param value zoom level to scale
+ * @return un-scaled zoom level
+ */
+static inline ZoomLevel UnScaleZoomGUI(ZoomLevel value)
+{
+	return std::clamp(ZoomLevel(value - (ZOOM_LVL_GUI - ZOOM_LVL_OUT_4X)), ZOOM_LVL_MIN, ZOOM_LVL_MAX);
+}
+
 /**
  * Scale traditional pixel dimensions to GUI zoom level.
  * @param value Pixel amount at #ZOOM_LVL_BASE (traditional "normal" interface size).