Apply the font2 patch

See https://st.suckless.org/patches/font2/.

This patch allows to add spare font besides default. Some glyphs can be not
present in default font. For this glyphs st uses font-config and try to find
them in font cache first. This patch append fonts defined in font2 variable
to the beginning of font cache. So they will be used first for glyphs that
absent in default font.

This is required to improve the rendering of special unicode characters
we currently use in neovim statusline.

config.h

@@ -6,6 +6,10 @@
  * font: see http://freedesktop.org/software/fontconfig/fontconfig-user.html
  */
 static char *font = "JetBrains Mono Medium:style=Medium Italic,Italic:pixelsize=14:antialias=true:autohint=true";
+/* Spare fonts */
+static char *font2[] = {
+	"TerminessTTF Nerd Font:pixelsize=14:antialias=true:autohint=true",
+};
 static int borderpx = 0;
 
 /*

x.c

@@ -160,6 +160,8 @@ static void xhints(void);
 static int xloadcolor(int, const char *, Color *);
 static int xloadfont(Font *, FcPattern *);
 static void xloadfonts(char *, double);
+static int xloadsparefont(FcPattern *, int);
+static void xloadsparefonts(void);
 static void xunloadfont(Font *);
 static void xunloadfonts(void);
 static void xsetenv(void);
@@ -310,6 +312,7 @@ zoomabs(const Arg *arg)
 {
 	xunloadfonts();
 	xloadfonts(usedfont, arg->f);
+	xloadsparefonts();
 	cresize(0, 0);
 	redraw();
 	xhints();
@@ -1036,6 +1039,101 @@ xloadfonts(char *fontstr, double fontsize)
 	FcPatternDestroy(pattern);
 }
 
+int
+xloadsparefont(FcPattern *pattern, int flags)
+{
+	FcPattern *match;
+	FcResult result;
+
+	match = FcFontMatch(NULL, pattern, &result);
+	if (!match) {
+		return 1;
+	}
+
+	if (!(frc[frclen].font = XftFontOpenPattern(xw.dpy, match))) {
+		FcPatternDestroy(match);
+		return 1;
+	}
+
+	frc[frclen].flags = flags;
+	/* Believe U+0000 glyph will present in each default font */
+	frc[frclen].unicodep = 0;
+	frclen++;
+
+	return 0;
+}
+
+void
+xloadsparefonts(void)
+{
+	FcPattern *pattern;
+	double sizeshift, fontval;
+	int fc;
+	char **fp;
+
+	if (frclen != 0)
+		die("can't embed spare fonts. cache isn't empty");
+
+	/* Calculate count of spare fonts */
+	fc = sizeof(font2) / sizeof(*font2);
+	if (fc == 0)
+		return;
+
+	/* Allocate memory for cache entries. */
+	if (frccap < 4 * fc) {
+		frccap += 4 * fc - frccap;
+		frc = xrealloc(frc, frccap * sizeof(Fontcache));
+	}
+
+	for (fp = font2; fp - font2 < fc; ++fp) {
+
+		if (**fp == '-')
+			pattern = XftXlfdParse(*fp, False, False);
+		else
+			pattern = FcNameParse((FcChar8 *)*fp);
+
+		if (!pattern)
+			die("can't open spare font %s\n", *fp);
+
+		if (defaultfontsize > 0) {
+			sizeshift = usedfontsize - defaultfontsize;
+			if (sizeshift != 0 &&
+					FcPatternGetDouble(pattern, FC_PIXEL_SIZE, 0, &fontval) ==
+					FcResultMatch) {
+				fontval += sizeshift;
+				FcPatternDel(pattern, FC_PIXEL_SIZE);
+				FcPatternDel(pattern, FC_SIZE);
+				FcPatternAddDouble(pattern, FC_PIXEL_SIZE, fontval);
+			}
+		}
+
+		FcPatternAddBool(pattern, FC_SCALABLE, 1);
+
+		FcConfigSubstitute(NULL, pattern, FcMatchPattern);
+		XftDefaultSubstitute(xw.dpy, xw.scr, pattern);
+
+		if (xloadsparefont(pattern, FRC_NORMAL))
+			die("can't open spare font %s\n", *fp);
+
+		FcPatternDel(pattern, FC_SLANT);
+		FcPatternAddInteger(pattern, FC_SLANT, FC_SLANT_ITALIC);
+		if (xloadsparefont(pattern, FRC_ITALIC))
+			die("can't open spare font %s\n", *fp);
+
+		FcPatternDel(pattern, FC_WEIGHT);
+		FcPatternAddInteger(pattern, FC_WEIGHT, FC_WEIGHT_BOLD);
+		if (xloadsparefont(pattern, FRC_ITALICBOLD))
+			die("can't open spare font %s\n", *fp);
+
+		FcPatternDel(pattern, FC_SLANT);
+		FcPatternAddInteger(pattern, FC_SLANT, FC_SLANT_ROMAN);
+		if (xloadsparefont(pattern, FRC_BOLD))
+			die("can't open spare font %s\n", *fp);
+
+		FcPatternDestroy(pattern);
+	}
+}
+
 void
 xunloadfont(Font *f)
 {
@@ -1148,6 +1246,9 @@ xinit(int cols, int rows)
 	usedfont = (opt_font == NULL)? font : opt_font;
 	xloadfonts(usedfont, 0);
 
+	/* Spare fonts */
+	xloadsparefonts();
+
 	/* colors */
 	xw.cmap = XCreateColormap(xw.dpy, parent, xw.vis, None);
 	xloadcols();