D854 - A one-byte alpha target is drawn in the frame's alpha and written back as it is held

Status: decided Date: 2026-10-14

A colour target whose CB_COLOR0_INFO names COLOR_8, NUMBER_UNORM and SWAP_ALT_REV holds one byte a texel, alpha. It lies by the one-byte layout, as a red COLOR_8 target does. A drawer stands an Rgba8 frame in for it, as for the red one: each byte is read into the frame's alpha, with the colour channels zero, and written back from the frame's alpha. A draw into it writes alpha alone, as its write mask already says.

A fill pattern is a uniform clear only when every texel in its word is alike: four bytes at one byte a texel, two halves at two (D852). A pattern whose texels differ is laid out where the layout puts them.

Why: SWAP_ALT_REV on one channel is ___X, alpha (ac_formats.c 586). Grand Theft Auto V draws into a 1920 x 1080 target of it, once its earlier draws run (D851-D853). The two-byte fill check fixes D852, which took a word whose halves differ as one value.

Rejected:

• Reading the byte into red as for SWAP_STD: blending reads destination alpha from the frame, and an alpha target's blend would read a constant.