New cpp folder structure

Signed-off-by: Alexander Borsuk <me@alex.bio>

libs/drape/visual_scale.hpp

@@ -0,0 +1,17 @@
+#pragma once
+#include "platform/platform.hpp"
+
+namespace dp
+{
+/// This fuction is called in iOS/Android native code.
+inline double VisualScale(double exactDensityDPI)
+{
+  // In case of tablets and iPads increased DPI is used to make visual scale bigger.
+  if (GetPlatform().IsTablet())
+    exactDensityDPI *= 1.2;
+
+  // For some old devices (for example iPad 2) the density could be less than 160 DPI (mdpi).
+  // Returns one in that case to keep readable text on the map.
+  return std::max(1.35, exactDensityDPI / 160.0);
+}
+} //  namespace dp