Re: [Alephmodular-devel] Brainstorming on bitmaps

[Br'fin <br...@ma...>]

Additional information on buffers and bitmaps, here's my initial 
definitions of each.

-Jeremy Parsons

Buffers

A buffer is a complete description of a surface that one can draw upon. 
It is an abstract base class with platform specific implementations. 
For instance, under Macintosh, a buffer would wrap around a 
GWorldPtr/CGraftPtr/GrafPtr.

Typical usage would be:
	Request current buffer from display system
		(it is limited as in dimensions, display system knows this)
	Lock down the buffer
	Get a bitmap from the buffer
	Render operations on the bitmap
	Release the bitmap
	Perform drawing operations on the buffer (access to platform native 
elements available?)
	Unlock the buffer
	Ask display system to swap buffers
	
A buffer helps support higher level options such as copying portions 
and displaying text using OS specific calls.

world_pixels would be a buffer.


Bitmaps

A bitmap, in contrast to a buffer, is a low level object that 
explicitly describes the pixels associated with a buffer. It knows very 
little, but is a stream of bytes in memory with precalculated 
row-addresses for jumping quickly to a scan line.

RLE encoded shapes are also implemented as a bitmap that is owned by a 
collection.

world_pixels_structure would be a bitmap.