AmigaOS knows three functions in graphics.library that output
chunky pixels to a RastPort: WritePixelLine8, WritePixelArray8
and WriteChunkyPixels.

The original versions of these routines in the KickstartROM
are rather slow and have a bug that trashes the chunky source
buffer.

This patch installs improved versions that are often faster by
a factor of 10 (on a fast CPU).

-- Requirements:

AmigaOS3.0 or AmigaOS3.1. The WriteChunkyPixels function exists
only in AmigaOS3.1.

An 68020 or higher CPU.

-- Operation:

The core of the patch are four routines that translate chunky data
into 1..4 bitplanes and that write only complete words into a bitmap.

For destinations with 5..8 bitplanes the planes are written in two
passes translating upper and lower nibbles of the source data.

If the destination rectangle is not aligned to words in the bitmap
the unaligned border words are first converted into a buffer on the
stack and then masked and copied to the destination bitmap.

The patch utilizes the DoHookClipRects() function of AmigaOS3.x to
write directly into the destination bitmap, even for layered RastPorts.
This avoids completely the temporary bitmap you pass to the WPL8 and
WPA8 functions, but of course programs must not rely on this.

-- Installation:

Add the newwpa8 command directly after SetPatch in your startup-sequence.
The patch detaches itself from the Shell, there is no need to RUN it.

It is most important that the patch is run before any other patch to
the graphics system like the CyberGraphics driver that intercepts
the calls itself.

-- History

1.0 initial version, used tmprp and blitter, WPA8 and WPL8
1.1 new c2p
1.2 direct destination writing for aligned rectangles
1.3 direct destination writing for non-aligned rectangles, added WCP
1.4 bugfix for modulo calculation in WPA8, WPL8

Michael van Elst

 PERMSSN    UID  GID    PACKED    SIZE  RATIO     CRC       STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[generic]                 1463    2504  58.4% -lh5- e450 May  1  1997 NewWPA8
[generic]                  983    1962  50.1% -lh5- 50c8 May  1  1997 NewWPA8.readme
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total         2 files    2446    4466  54.8%            May  2  1997