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fadden / CiderPress2

Tool for working with Apple II and vintage Mac disk images and file archives.
https://ciderpress2.com/
Apache License 2.0
44 stars 7 forks source link

Shape table conversion isn't quite right #21

Closed fadden closed 2 months ago

fadden commented 2 months ago

The game Rescue at Rigel starts with an animated title screen that uses shape tables. However, the conversion of the file RIGEL.BEGIN DATA doesn't look quite right:

image

The problem is spelled out in all caps in the Applesoft manual:

At any section in the byte, IF ALL THE REMAINING SECTIONS OF THE BYTE CONTAIN ONLY ZEROS, THEN THOSE SECTIONS ARE IGNORED.

The current code is correctly treating zero in the two MSBs as a no-op, but if the high 5 bits are all zero then the middle bits should also be ignored, not treated as an upward move.

fadden commented 2 months ago

Fixed version:

image

fadden commented 2 months ago

Fixed in v1.0.3-dev1: https://github.com/fadden/CiderPress2/releases/tag/v1.0.3-dev1