ImGuiFullscreen: Add LayoutUnscale()

src/util/imgui_fullscreen.cpp

@@ -64,6 +64,7 @@ ImFont* g_large_font = nullptr;
 ImFont* g_icon_font = nullptr;
 
 float g_layout_scale = 1.0f;
+float g_rcp_layout_scale = 1.0f;
 float g_layout_padding_left = 0.0f;
 float g_layout_padding_top = 0.0f;
 
@@ -430,6 +431,8 @@ bool ImGuiFullscreen::UpdateLayoutScale()
     g_layout_padding_left = 0.0f;
   }
 
+  g_rcp_layout_scale = 1.0f / g_layout_scale;
+
   return g_layout_scale != old_scale;
 }