strans/font.c

#define STB_TRUETYPE_IMPLEMENTATION
#include "stb_truetype.h"
#include "dat.h"
#include "fn.h"

typedef struct Glyph Glyph;
typedef struct Font Font;
struct Glyph
{
	uchar *bmp;
	int w, h, ox, oy, base;
};

struct Font
{
	stbtt_fontinfo info;
	uchar *data;
	float scale;
	int base;
};

enum { Maxfonts = 4 };

static Font fonts[Maxfonts];
static int nfonts;
static Glyph cache[Nglyphs];
static u32int blendtab[2][256];

static u32int
blend(u32int bg, u32int fg, int a)
{
	int r, g, b, inv;

	inv = 255 - a;
	r = ((bg >> 16 & 0xff) * inv + (fg >> 16 & 0xff) * a) / 255;
	g = ((bg >> 8 & 0xff) * inv + (fg >> 8 & 0xff) * a) / 255;
	b = ((bg & 0xff) * inv + (fg & 0xff) * a) / 255;
	return (r << 16) | (g << 8) | b;
}

static int
loadfont(char *path)
{
	Font *f;
	int ascent, descent, gap, fd;
	long sz, n;

	fd = open(path, OREAD);
	if(fd < 0){
		fprint(2, "strans: popup: can't open font: %s\n", path);
		return 0;
	}
	sz = seek(fd, 0, 2);
	seek(fd, 0, 0);
	if(sz <= 0){
		fprint(2, "strans: popup: empty font: %s\n", path);
		close(fd);
		return 0;
	}
	f = &fonts[nfonts];
	f->data = emalloc(sz);
	n = readn(fd, f->data, sz);
	close(fd);
	if(n != sz){
		fprint(2, "strans: popup: can't read font: %s\n", path);
		free(f->data);
		f->data = nil;
		return 0;
	}
	if(!stbtt_InitFont(&f->info, f->data,
	   stbtt_GetFontOffsetForIndex(f->data, 0))){
		fprint(2, "strans: popup: can't init font: %s\n", path);
		free(f->data);
		f->data = nil;
		return 0;
	}
	f->scale = stbtt_ScaleForPixelHeight(&f->info, Fontsz);
	stbtt_GetFontVMetrics(&f->info, &ascent, &descent, &gap);
	(void)descent;
	(void)gap;
	f->base = (int)(ascent * f->scale);
	nfonts++;
	return 1;
}

void
fontinit(char *dir)
{
	static char *names[] = {
		"NotoSans-Regular.ttf",
		"NotoSansMonoCJKjp-Regular.otf",
		"NotoEmoji-Regular.ttf",
	};
	int i, a;
	char path[256];

	nfonts = 0;
	memset(cache, 0, sizeof cache);
	for(i = 0; i < nelem(names); i++){
		if(strlen(dir) + 1 + strlen(names[i]) + 1 > sizeof path){
			fprint(2, "strans: popup: font path is too long\n");
			continue;
		}
		snprint(path, sizeof path, "%s/%s", dir, names[i]);
		loadfont(path);
	}
	for(a = 0; a < 256; a++){
		blendtab[0][a] = blend(Colbg, Colfg, a);
		blendtab[1][a] = blend(Colsel, Colfg, a);
	}
}

int
fontready(void)
{
	return nfonts != 0;
}

void
putfont(u32int *buf, int w, int h, int px, int py, Rune r)
{
	Glyph *g;
	int i, j, a, sel, f;
	int y0, j0, j1, x0, i0, i1;
	u32int *p;

	if(r >= Nglyphs)
		return;
	g = &cache[r];
	if(g->bmp == nil){
		for(f = 0; f < nfonts; f++){
			if(stbtt_FindGlyphIndex(&fonts[f].info, r) == 0)
				continue;
			g->bmp = stbtt_GetCodepointBitmap(&fonts[f].info,
				fonts[f].scale, fonts[f].scale, r,
				&g->w, &g->h, &g->ox, &g->oy);
			if(g->bmp != nil){
				g->base = fonts[f].base;
				break;
			}
		}
		if(g->bmp == nil)
			return;
	}

	y0 = py + g->base + g->oy;
	j0 = y0 < 0 ? -y0 : 0;
	j1 = y0 + g->h > h ? h - y0 : g->h;
	x0 = px + g->ox;
	i0 = x0 < 0 ? -x0 : 0;
	i1 = x0 + g->w > w ? w - x0 : g->w;
	for(j = j0; j < j1; j++){
		for(i = i0; i < i1; i++){
			a = g->bmp[j * g->w + i];
			if(a > 0){
				p = &buf[(y0 + j) * w + x0 + i];
				sel = (*p == Colsel) ? 1 : 0;
				*p = blendtab[sel][a];
			}
		}
	}
}