#!/usr/bin/env python3
"""Rasterise Niveus's interface face into a header the boot manager can draw.

The loader cannot carry a TrueType rasteriser, and the answer to that has been
the same since include/gfx/font.h: do the work at build time and commit the
result. This takes Instrument Sans (SIL OFL, see docs/Website/niveus/fonts/)
at three sizes and writes 8-bit coverage bitmaps, one per printable ASCII
character, with the metrics needed to lay them out proportionally.

    python3 tools/python/mknvfont.py docs/Website/niveus/fonts/static include/gfx/nvfont.h

Needs Pillow; nothing else, and nothing at all at build time of the OS.
"""
import sys, os
from PIL import ImageFont

# Each size twice: x1 for ordinary screens and x2 for the ones where a 15 px
# face would be a speck. Rendering at the real size beats doubling pixels.
SIZES = []
for _scale in (1, 2):
    SIZES += [
        ("body%d"  % _scale, "InstrumentSans-Medium.ttf",   15 * _scale),
        ("small%d" % _scale, "InstrumentSans-Regular.ttf",  12 * _scale),
        ("title%d" % _scale, "InstrumentSans-SemiBold.ttf", 24 * _scale),
    ]
FIRST, LAST = 32, 126


def render(path, px):
    f = ImageFont.truetype(path, px)
    asc, desc = f.getmetrics()
    glyphs, blob = [], bytearray()
    for code in range(FIRST, LAST + 1):
        ch = chr(code)
        adv = int(round(f.getlength(ch) * 64))   # 26.6 fixed point: whole-pixel advances make text look cramped
        mask, (ox, oy) = f.getmask2(ch, mode="L", anchor="ls")
        w, h = mask.size
        data = bytes(mask) if (w and h) else b""
        glyphs.append((len(blob), w, h, ox, oy, adv))
        blob += data
    return asc, desc, glyphs, blob


def main():
    src, out = sys.argv[1], sys.argv[2]
    lines = [
        "#pragma once",
        "",
        "// GENERATED by tools/python/mknvfont.py -- do not edit. Run `make nvfont`.",
        "//   source: docs/Website/niveus/fonts/static (Instrument Sans, SIL OFL 1.1)",
        "//",
        "// 8-bit coverage bitmaps for printable ASCII, proportionally spaced, used by",
        "// the boot manager (boot/common/ui.c). Not included by the kernel.",
        "",
        "struct nvglyph { unsigned short off; unsigned char w, h; signed char ox, oy; unsigned short adv; /* 1/64 px */ };",
        "struct nvfont  { unsigned char ascent, descent; const struct nvglyph *g; const unsigned char *bits; };",
        "#define NVFONT_FIRST %d" % FIRST,
        "#define NVFONT_LAST  %d" % LAST,
        "",
    ]
    for name, fn, px in SIZES:
        asc, desc, glyphs, blob = render(os.path.join(src, fn), px)
        lines.append("static const struct nvglyph nvg_%s[] = {" % name)
        for (o, w, h, ox, oy, adv) in glyphs:
            lines.append("    {%d,%d,%d,%d,%d,%d}," % (o, w, h, ox, oy, adv))
        lines.append("};")
        lines.append("static const unsigned char nvb_%s[] = {" % name)
        for i in range(0, len(blob), 24):
            lines.append("    " + ",".join(str(b) for b in blob[i:i + 24]) + ",")
        if not blob:
            lines.append("    0")
        lines.append("};")
        lines.append("static const struct nvfont nvfont_%s = { %d, %d, nvg_%s, nvb_%s };" %
                     (name, asc, desc, name, name))
        lines.append("")
    open(out, "w").write("\n".join(lines) + "\n")
    print("wrote", out)


main()