The following are brief descriptions of the layers library functions and
related routines from the graphics library.  See the Amiga ROM Kernel
Reference Manual: Includes and Autodocs for details on each function call.


                  Table 30-5: Layers Library Functions
  ______________________________________________________________________
 |                                                                      |
 |              Function                   Description                  |
 |======================================================================|
 |              NewLayerInfo()  Allocating a Layer_Info structure.      |
 |          DisposeLayerInfo()  Deallocating a Layer_Info structure.    |
 |----------------------------------------------------------------------|
 |        CreateUpfrontLayer()  Make a new layer in front of others.    |
 |         CreateBehindLayer()  Make a new layer behind others.         |
 |               DeleteLayer()  Remove and delete an existing layer.    |
 |----------------------------------------------------------------------|
 |                 MoveLayer()  Change the position (not depth) of a    |
 |                              layer.                                  |
 |                 SizeLayer()  Change the size of a layer.             |
 |               ScrollLayer()  Change the internal coordinates of a    |
 |                              layer.                                  |
 |----------------------------------------------------------------------|
 |               BehindLayer()  Depth arrange a layer behind others.    |
 |              UpfrontLayer()  Depth arrange a layer in front of       |
 |                              others.                                 |
 |        MoveLayerInFrontOf()  Depth arrange a layer to a specific     |
 |                              position.                               |
 |----------------------------------------------------------------------|
 |                WhichLayer()  Find the frontmost layer at a position. |
 |----------------------------------------------------------------------|
 |  SwapBitsRastPortClipRect()  Fast, non-layered and non-damaging      |
 |                              display operation.                      |
 |----------------------------------------------------------------------|
 |               BeginUpdate()  Synchronize optimized refreshing for    |
 |                              layer.                                  |
 |                 EndUpdate()  End optimized layer refresh.            |
 |----------------------------------------------------------------------|
 |                 LockLayer()  Lock out rendering in a single layer.   |
 |               UnlockLayer()  Release LockLayer() lock.               |
 |                LockLayers()  Lock out rendering in all layers of a   |
 |                              display.                                |
 |              UnlockLayers()  Release LockLayers() lock.              |
 |             LockLayerInfo()  Gain exclusive access to the display's  |
 |                              layers.                                 |
 |           UnlockLayerInfo()  Release LockLayerInfo() lock.           |
 |----------------------------------------------------------------------|
 |         InstallClipRegion()  Add a clipping region to a layer.       |
 |______________________________________________________________________|


The following routines from graphics library are also required for certain
layers library functions:

  ______________________________________________________________________
 |                                                                      |
 |            Routine                        Description                |
 |======================================================================|
 |         LockLayerRom()  Same as LockLayer(), from layers library.    |
 |       UnlockLayerRom()  Release LockLayerRom() lock.                 |
 |  AttemptLockLayerRom()  Lock layer only if it is immediately         |
 |                         available.                                   |
 |----------------------------------------------------------------------|
 |            NewRegion()  Create a new, empty region.                  |
 |        DisposeRegion()  Dispose of an existing region and its        |
 |                         rectangles.                                  |
 |----------------------------------------------------------------------|
 |        AndRectRegion()  AND a rectangle into a region.               |
 |         OrRectRegion()  OR a rectangle into a region.                |
 |        XorRectRegion()  Exclusive-OR a rectangle into a region.      |
 |      ClearRectRegion()  Clear a region.                              |
 |      AndRegionRegion()  AND two regions together.                    |
 |       OrRegionRegion()  OR two regions together.                     |
 |      XorRegionRegion()  Exclusive-OR two regions together.           |
 |          ClearRegion()  Clear a region.                              |
 |______________________________________________________________________|