Subj : src/doors/syncduke/syncduke_io.c
To   : Git commit to main/sbbs/master
From : Rob Swindell (on Debian Linux)
Date : Sun Jun 28 2026 00:21:31

https://gitlab.synchro.net/main/sbbs/-/commit/9702f5ad2884a73ef51a3a35
Modified Files:
	src/doors/syncduke/syncduke_io.c
Log Message:
syncduke: aspect-preserve the sixel tier (fit, don't stretch to fill)

The sixel tier sized the encoded frame to out_w x out_h -- the terminal's pixel
canvas capped at 640x480 -- and nearest-scaled Duke's native 320x200 into it,
which is 4:3 on a tall terminal: the game came out vertically stretched (e.g.
encoded 320x240 at >=80x50 instead of ~320x200).

Run the sixel through the same termgfx_geom_fit/center as the JXL tier: fit
320x200 into the real graphics canvas (XTSMGRAPHICS via syncduke_canvas_w/h, not
the rows*16 text-area estimate) preserving 8:5, capped at 640 wide, then encode
at 1/scale of that.  The displayed sixel is now a constant 640x400 letter-boxed
and centered, exactly like SyncDOOM.

Side effects, all good:
  - no vertical stretch (keeps 8:5 on tall terminals);
  - the prior 80x50/60 over-hang is gone -- a fit is <= canvas by construction,
    so the frame can no longer scale past the real ~640x400 SyncTERM canvas;
  - ~18% less sixel bandwidth on tall terminals (320x198 vs 320x240).

Both image tiers now share termgfx_geom_fit, lining SyncDuke up with SyncDOOM
ahead of wiring Doom to the same helper.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

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