documentation/accelerators

Some notes concerning accelerators.

There are _three_ differently sized accelerator structures exposed to the
user. The general layout is:

	BYTE   fVirt;
	WORD   key;
	WORD   cmd;

We now have three different appearances:

- Accelerators in NE resources. These have a size of 5 byte and do not have
  any padding. This is also the internal layout of the global handle HACCEL
  (16 and 32) in Windows 95 and WINE. Exposed to the user as Win16 global
  handles HACCEL16 and HACCEL32 by the Win16/Win32 API.

- Accelerators in PE resources. These have a size of 8 byte. Layout is:
	BYTE   fVirt;
	BYTE   pad0;
	WORD   key;
	WORD   cmd;
	WORD   pad1;
  They are exposed to the user only by direct accessing PE resources.

- Accelerators in the Win32 API. These have a size of 6 byte. Layout is:
	BYTE   fVirt;
	BYTE   pad0;
	WORD   key;
	WORD   cmd;
  These are exposed to the user by the CopyAcceleratorTable and
  CreateAcceleratorTable in the Win32 API.

Why two types of accelerators in the Win32 API? We can only guess, but
my best bet is that the Win32 resource compiler can/does not handle struct
packing. Win32 ACCEL is defined using #pragma(2) for the compiler but without
any packing for RC, so it will assume #pragma(4).

Findings researched by Uwe Bonnes, Ulrich Weigand and Marcus Meissner.