Appendix D
Overlay and Display-Mode Compatibility
Which overlays attach to which display modes. A ✓ works; a · is refused at configuration time rather than at the point it would have drawn. c64cast --compat prints this at the terminal.
The Matrix#
| Overlay | hires_edges |
hires |
mhires |
mcm |
petscii |
blank |
|---|---|---|---|---|---|---|
big_text |
· | · | · | ✓ | · | ✓ |
callsign |
✓ | ✓ | ✓ | · | ✓ | ✓ |
clock |
✓ | ✓ | ✓ | · | ✓ | ✓ |
countdown |
✓ | ✓ | ✓ | · | ✓ | ✓ |
logo |
✓ | ✓ | ✓ | · | ✓ | ✓ |
marquee |
✓ | ✓ | ✓ | · | ✓ | ✓ |
network |
✓ | ✓ | ✓ | · | ✓ | ✓ |
obs_status |
✓ | ✓ | ✓ | · | ✓ | ✓ |
rss |
✓ | ✓ | ✓ | · | ✓ | ✓ |
scrolling_text |
✓ | ✓ | ✓ | · | ✓ | ✓ |
spectrum_bitmap |
· | · | ✓ | · | · | · |
spectrum_petscii |
· | · | · | · | ✓ | ✓ |
weather |
✓ | ✓ | ✓ | · | ✓ | ✓ |
Why a Cell Is Refused#
A gap is one of three rules, not an accident of implementation. Text overlays need somewhere to put characters; a few overlays are written against one mode's memory layout; and an overlay that reads the audio stream needs the audio stream to exist.
| Rule | Overlays |
|---|---|
| Only on blank/mcm | big_text |
| Needs a text-capable mode (petscii/blank/hires/mhires) | callsign, clock, countdown, logo, marquee, network, obs_status, rss, scrolling_text, weather |
| Only on mhires | spectrum_bitmap |
| Needs PETSCII-compatible mode (petscii/blank) | spectrum_petscii |