[Bug]: Alien Breed II (AGA) - Horizontal scrolling issue

[hobbo91]

Area

Emulation accuracy (display, audio, timing, chipset behaviour)

Summary

Attached a video to better demonstrate. Vertical scrolling is perfect, but horizontal scrolling is not. Stock A1200 config other than 8MB Fast RAM and an attached HDD image.

Alien.Breed.2.AGA.-.compressed.mp4

Copperline version

0.12.0 g2c925b77

Host system

macOS (M4)

Machine/configuration

Stock Amiga 1200 config other than 8MB of Fast RAM

Reproduction steps

Play Alien Breed II: The Horror Continues on an Amiga 1200

Actual behaviour

Horizontal scroll jumping

Expected behaviour

Smooth scrolling like with vertical

Logs or debugger output

[LinuxJedi]

Ouch. I think that is a regression as I tested it before 0.12 😕
I’ll look into it tomorrow

[LinuxJedi]

I was wrong, it was 1 I was testing, not 2. Reproduced it now.

[LinuxJedi]

Root cause found and fixed in #250 - an AGA wide-FMODE scroll modelling gap (not a regression; it reproduces on 0.11 and 0.12 too). Headless before/after capture of the fix, walking left in the landing zone:

ab2-scroll-before-after.mp4