FNT — Bitmap Font (.FNT)

FA_1.LIB contains 15 .FNT files. These define the bitmapped fonts used for HUD text, menus, and briefing screens. Each is a Win32 PE DLL loaded at runtime. File sizes vary — 4X12.FNT decompresses to 12800 bytes (0x3200); the large size relative to other 4608-byte overlays reflects the glyph function code covering the full printable ASCII range.

Tools

fx

fx fnt info   <file.FNT>              # font height and glyph metrics
fx fnt unpack <file.FNT> [-o dir]     # render glyphs to glyph_sheet.png + metrics.csv
fx fnt pack   <orig.FNT> <dir> [-o out.FNT]   # recompile glyphs back into the DLL

Glyph extraction works by interpreting each glyph's x86 write pattern against a pixel buffer; pack inverts it, recompiling edited glyph bitmaps to x86 with the original compiler's canonical encoding (below) and rebuilding the function table — an unedited unpack→pack loop is byte-identical for every install font. Edited glyph code must fit the original code region (the container is otherwise carried verbatim).

File Layout

All multi-byte integers are little-endian.

FNT files use Phar Lap PE format (signature PL\0\0). No imports. The CODE section contains a FONT struct — a pointer table of compiled x86 glyph functions followed by a width table, then the glyph function bodies.

FONT struct

Starts at CODE section offset 0 (VA 0x1000). Confirmed from tracing @G_Print@16 in the game executable (0x004986B0), which accesses the loaded FNT DLL via the global ?cFont@@3PAUFONT@@A:

u32  font_height          height of all glyphs in this font, in pixels
u32  glyph_fn[256]        VAs of compiled glyph functions, one per ASCII 0–255
u32  glyph_width[256]     advance width of each glyph in pixels

• cFont[0] — font height (used in @G_Print@16 clip bounds check)
• cFont[char + 1] — called as a function pointer: (*(code *)cFont[char + 1])(dst_ptr)
• cFont[char + 0x101] — advance width; passed to _G_Blit@36 as the glyph width

Total struct: 1 + 256 + 256 = 513 u32 values = 2052 bytes minimum before glyph bodies.

Glyph functions

Each glyph is a compiled x86 function, not encoded bitmap data. @G_Print@16 calls each glyph function directly, passing the destination framebuffer position in registers.

Confirmed calling convention (traced from @G_Print@16 at 0x004986B0 + glyph body at raw file offset 0xA25):

Register	Role
EDI	Current row pointer in destination framebuffer
ECX	Scanline stride (bytes per row)
AL	Pixel color value

Instruction pattern:

Sequence	Meaning
03 F9 = ADD EDI, ECX	Advance to next row
88 07 / 88 47 NN = MOV [EDI(+NN)], AL	1-pixel write at column 0 / NN
66 89 07 / 66 89 47 NN = MOV [EDI(+NN)], AX	2-pixel run write
89 07 / 89 47 NN = MOV [EDI(+NN)], EAX	4-pixel run write
ADD EDI, ECX alone	Skip a blank row (no pixel written)
C3 = RET	End of glyph

G_Print primes AL/AX/EAX with the colour replicated per byte, so the word/dword forms paint uniform horizontal runs. This vocabulary is complete: every glyph function of all 15 install fonts decodes with it (#97 census, 3,840 bodies).

Canonical encoding (confirmed — all 3,840 install bodies re-emit byte-identically): per pixel row, ascending runs split greedily into 4/2/1-pixel writes (dword, then word, then byte; the short [EDI] forms whenever the column is 0), followed by one row advance; a glyph therefore carries exactly font_height advances — writes for row r appear before the (r+1)-th advance, so a lit top row writes before the first ADD. An all-blank glyph is a lone RET with no advances. Bodies are laid out back-to-back in character order (0–255, one body per character, no sharing and no gaps), starting immediately after the FONT struct.

0xC3 = RET — the blank/space glyph is a single-byte function that returns immediately, writing nothing. Control characters (ASCII 0–31) and space (ASCII 32) all point to 0xC3 bytes (VA 0x1804–0x1824).

Printable character functions begin at VA 0x1825 (raw file offset 0xA25). Confirmed disassembly of ASCII 33 (!):

ADD  EDI, ECX      ; row 0 blank — advance
MOV  [EDI], AL     ; row 1 — lit (bar)
ADD  EDI, ECX
MOV  [EDI], AL     ; row 2 — lit
ADD  EDI, ECX
MOV  [EDI], AL     ; row 3 — lit
ADD  EDI, ECX
ADD  EDI, ECX      ; row 4 blank — advance only
MOV  [EDI], AL     ; row 5 — lit (dot)
ADD  EDI, ECX
ADD  EDI, ECX      ; row 6 blank (inter-line spacing)
RET

(An earlier revision put each write before its label's advance; the #97 census fixed the row accounting: writes belong to the row preceding the next advance, and row-0 writes come before any ADD.)

7 row advances for a font named 4X6 confirms cFont[0] (font height) = 7 — the cell is 6 glyph rows + 1 inter-line spacing row. The raw bytes {03 F9 88 07} are two x86 instructions, not an encoded bitmap format.

Ghidra navigation note: when importing a FNT file as a raw binary with base 0x1000, the CODE section (file offset 0x200) appears at Ghidra address 0x1200. Loaded VAs (e.g. 0x1825) correspond to Ghidra address 0x1000 + file_offset = 0x1000 + (VA - 0x1000 + 0x200) = VA + 0x200.

$$DOSX metadata

The $$DOSX section (512 bytes) contains a small header. Both 4X6.FNT and 4X12.FNT show identical $$DOSX values (u16[4]=16, u16[5]=6). These are system constants shared by all FNT files, not per-file cell dimensions.

File Inventory

font_height confirmed by reading the dword at CODE section offset 0 (file offset 0x200) for all 15 files.

File	font_height	Decompressed size	Context
4X6.FNT	7	8704	Tiny fixed-pitch text (4 wide × 6 glyph rows + 1 spacing = 7)
4X12.FNT	12	12800	Fixed-pitch 4×12 text
HUD00.FNT	5	8704	HUD text — 320×200 mode
HUD01.FNT	10	12800	HUD text — hi-res mode A
HUD11.FNT	10	12800	HUD text — hi-res mode B
HUDSYM00.FNT	15	12800	HUD symbols — 320×200 mode
HUDSYM01.FNT	29	16896	HUD symbols — hi-res mode A
HUDSYM11.FNT	31	20992	HUD symbols — hi-res mode B
HUI11.FNT	10	12800	HUD interface text
HUISYM11.FNT	31	16896	HUD interface symbols
MAPFONT.FNT	10	12800	Theater map labels
WII11.FNT	10	12800	Window interface text
WIN00.FNT	6	12800	Window/dialog text — 320×200 mode
WIN01.FNT	12	16896	Window/dialog text — hi-res mode A
WIN11.FNT	10	12800	Window/dialog text — hi-res mode B

All 15 live in FA_1.LIB.

Suffix semantics confirmed: 00 = 320×200 (small font, short font_height), 01/11 = higher-resolution display modes (larger font_height). The 01 vs 11 distinction is inferred to target different colour depths or renderer paths — both are hi-res but 01 fonts are taller than their 11 counterparts for the WIN/HUDSYM families.

Related

Formats: PIC — 8-bit indexed bitmaps, also in FA_1.LIB; HUD — HUD layouts that consume font data (hudsym, winfont references).