Demo: comments (#414)

imgui_demo.cpp

@@ -2180,6 +2180,8 @@ static void ShowExampleAppPropertyEditor(bool* opened)
         return;
     }
 
+    ShowHelpMarker("This example shows how you may implement a property editor using two columns.\nAll objects/fields data are dummies here.\nRemember that in many simple cases, you can use ImGui::SameLine(xxx) to position\nyour cursor horizontally instead of using the Columns() API.");
+
     ImGui::PushStyleVar(ImGuiStyleVar_FramePadding, ImVec2(2,2));
     ImGui::Columns(2);
     ImGui::Separator();