Implemented by any layer module that hides text.
Assembly: Microsoft.VisualStudio.TextManager.Interop (in Microsoft.VisualStudio.TextManager.Interop.dll)
This interface is implemented by any layer module that hides text. In other words, if a given layer can ever return VIEW_E_LOCATION_HIDDEN, it must implement this interface to allow the text to be made visible if some user action (for example, the "Go To Line" command) makes it necessary.
When MakeBaseSpanVisible is called, the layer should make the text visible if it knows how. If it fails, the layout module will be destroyed! Layers that don't hide text must not implement this interface. However, when MakeBaseSpanVisible is called, layers can assume (and are welcome to ASSERT) that the base span has already been made visible by the layer below.