ico_header.nx

ico_header.nx -- parse Windows ICO / CUR icon container headers. ICO is a container for multiple icon images of different sizes + color depths. Every browser needs ICO parsing for favicon.ico. Every Windows app ships one. Nishi sites need to emit and detect their own. Format: ICONDIR (6 bytes, fixed) 0 2 reserved (0) 2 2 image_type (1 = ICO, 2 = CUR cursor) 4 2 num_images then num_images × ICONDIRENTRY (16 bytes): 0 1 width (0 means 256) 1 1 height (0 means 256) 2 1 color_count (0 if >= 256 colors) 3 1 reserved (0) 4 2 planes (ICO) / hotspot_x (CUR) 6 2 bpp (ICO) / hotspot_y (CUR) 8 4 data_size 12 4 data_offset Image payloads are then either: - BMP without the BITMAPFILEHEADER (just DIB + pixel data), OR - complete PNG (detect via PNG signature) Invariants: I1 image_type must be 1 (ICO) or 2 (CUR). I2 num_images >= 1. I3 Zero-alloc: entries[] passes in by caller; we fill offsets.