First a summary of informations :
With the PIXELFORMATDESCRIPTOR, I use always iLayerType as PFD_MAIN_PLANE.
If I look at the documentation of PIXELFORMATDESCRIPTOR, I see it’s possible to set other value to this member
PFD_MAIN_PLANE The layer is the main plane.
PFD_OVERLAY_PLANE The layer is the overlay plane.
PFD_UNDERLAY_PLANE The layer is the underlay plane.
The documentation with Visual C++ add the comment : “iLayerType Ignored. Earlier implementations of OpenGL used this member, but it is no longer used.”
The documentation with C++ Builder add the comment :“the current version supports only the main plane (there is no support for overlay or underlay planes)”
In the red book, I see some functions with specific use for layers
ex: wglDescribeLayerPlane(), wglCreateLayerContext, wglSwapLayerBuffers(), …
So the Questions :
Where is the truth ?
Is it possible to define a PIXELFORMATDESCRIPTOR with iLayerType different of PFD_MAIN_PLANE?
What are the advantages and disadvantages of working with layers?
Is there some codes examples of use opengl with layers?