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Syplheed-Reborn/docs
Claude (auto-RE) ac10d3bd19 t8ad: a surface is a list of sub-rectangles, not a 256 grid -- disc decode 96% -> 100%
The "~15% deferred variants" were not variants. Auditing every T8aD on the disc
gave 19216 surfaces, 18442 decoding (96.0%) and 774 failing in two clusters:
GP_DIALOG strips declaring 524x63 with a "tile count" of 1 or 2 instead of 3, and
small textures in the six *2D language paks whose pixels ran past the end of the
file.

Both fall out of the per-tile header, which is not opaque flags: it is four BE
u32 -- dst X, dst Y, width, height. A 15x18 icon stores a 13x18 rectangle at
(1,0); pdmes010 stores (59,6,256,54) and (315,6,149,54), the second beginning
exactly 16 + 256*54*4 bytes after the first. So 0x1c is a RECTANGLE COUNT and the
256-grid reading was an accident of most surfaces being stored as full-width
bands.

Parser rewritten to that model, still refusing to guess: a rectangle must fit the
declared surface and its pixels must fit the file, else None. Disc decode is now
19216/19216 = 100.00%.

Two test fixtures were built to the old model and are corrected rather than
worked around. lsta's t8ad_frame wrote NO offset-table entry, so the decoder read
"pixels" from inside the header -- the test passed only because it checked
dimensions alone.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-11 22:37:21 +00:00
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