Adding ligatures patch as requested in #4

Makefile

@@ -4,7 +4,11 @@
 
 include config.mk
 
-SRC = st.c x.c
+# Uncomment the line below and the hb.o line further down for the ligatures patch
+#LIGATURES_C = hb.c
+#LIGATURES_H = hb.h
+
+SRC = st.c x.c $(LIGATURES_C)
 OBJ = $(SRC:.c=.o)
 
 all: options st
@@ -25,7 +29,9 @@ patches.h:
 	$(CC) $(STCFLAGS) -c $<
 
 st.o: config.h st.h win.h
-x.o: arg.h config.h st.h win.h
+x.o: arg.h config.h st.h win.h $(LIGATURES_H)
+# Uncomment the below line for the ligatures patch
+#hb.o: st.h
 
 $(OBJ): config.h config.mk patches.h
 
@@ -38,7 +44,7 @@ clean:
 dist: clean
 	mkdir -p st-$(VERSION)
 	cp -R FAQ LEGACY TODO LICENSE Makefile README config.mk\
-		config.def.h st.info st.1 arg.h st.h win.h $(SRC)\
+		config.def.h st.info st.1 arg.h st.h win.h $(LIGATURES_H) $(SRC)\
 		st-$(VERSION)
 	tar -cf - st-$(VERSION) | gzip > st-$(VERSION).tar.gz
 	rm -rf st-$(VERSION)

README.md

@@ -15,6 +15,8 @@ Refer to [https://st.suckless.org/](https://st.suckless.org/) for details on the
 
 ### Changelog:
 
+2020-06-05 - Added the ligatures patch
+
 2020-05-20 - Upgrade to 222876, 2020-05-09, and removed visualbell 1, 2, 3 patches and force redraw after keypress due to incompatibility. Refer to tag [371878](https://github.com/bakkeby/st-flexipatch/tree/371878) if you want to try these out.
 
 2020-04-20 - Upgrade to c279f5, 2020-04-19, and added the force redraw on pselect after key is pressed patch and the externalpipein patch
@@ -93,6 +95,9 @@ Refer to [https://st.suckless.org/](https://st.suckless.org/) for details on the
    - [keyboard-select](https://st.suckless.org/patches/keyboard_select/)
       - allows you to select text on the terminal using keyboard shortcuts
 
+   - [ligatures](https://st.suckless.org/patches/ligatures/)
+      - adds support for drawing ligatures using the Harfbuzz library to transform original text of a single line to a list of glyphs with ligatures included
+
    - [newterm](https://st.suckless.org/patches/newterm/)
       - allows you to spawn a new st terminal using Ctrl-Shift-Return
       - it will have the same CWD (current working directory) as the original st instance

config.mk

@@ -18,13 +18,15 @@ PKG_CONFIG = pkg-config
 # Uncomment this for the themed cursor patch / THEMED_CURSOR_PATCH
 #XCURSOR = -lXcursor
 
-# includes and libs
+# includes and libs, uncomment harfbuzz for the ligatures patch
 INCS = -I$(X11INC) \
        `$(PKG_CONFIG) --cflags fontconfig` \
-       `$(PKG_CONFIG) --cflags freetype2`
+       `$(PKG_CONFIG) --cflags freetype2` \
+#       `$(PKG_CONFIG) --cflags harfbuzz`
 LIBS = -L$(X11LIB) -lm -lrt -lX11 -lutil -lXft ${XRENDER} ${XCURSOR}\
        `$(PKG_CONFIG) --libs fontconfig` \
-       `$(PKG_CONFIG) --libs freetype2`
+       `$(PKG_CONFIG) --libs freetype2` \
+#       `$(PKG_CONFIG) --libs harfbuzz`
 
 # flags
 STCPPFLAGS = -DVERSION=\"$(VERSION)\" -D_XOPEN_SOURCE=600

hb.c

@@ -0,0 +1,136 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <math.h>
+#include <X11/Xft/Xft.h>
+#include <hb.h>
+#include <hb-ft.h>
+
+#include "st.h"
+
+void hbtransformsegment(XftFont *xfont, const Glyph *string, hb_codepoint_t *codepoints, int start, int length);
+hb_font_t *hbfindfont(XftFont *match);
+
+typedef struct {
+	XftFont *match;
+	hb_font_t *font;
+} HbFontMatch;
+
+static int hbfontslen = 0;
+static HbFontMatch *hbfontcache = NULL;
+
+void
+hbunloadfonts()
+{
+	for (int i = 0; i < hbfontslen; i++) {
+		hb_font_destroy(hbfontcache[i].font);
+		XftUnlockFace(hbfontcache[i].match);
+	}
+
+	if (hbfontcache != NULL) {
+		free(hbfontcache);
+		hbfontcache = NULL;
+	}
+	hbfontslen = 0;
+}
+
+hb_font_t *
+hbfindfont(XftFont *match)
+{
+	for (int i = 0; i < hbfontslen; i++) {
+		if (hbfontcache[i].match == match)
+			return hbfontcache[i].font;
+	}
+
+	/* Font not found in cache, caching it now. */
+	hbfontcache = realloc(hbfontcache, sizeof(HbFontMatch) * (hbfontslen + 1));
+	FT_Face face = XftLockFace(match);
+	hb_font_t *font = hb_ft_font_create(face, NULL);
+	if (font == NULL)
+		die("Failed to load Harfbuzz font.");
+
+	hbfontcache[hbfontslen].match = match;
+	hbfontcache[hbfontslen].font = font;
+	hbfontslen += 1;
+
+	return font;
+}
+
+void
+hbtransform(XftGlyphFontSpec *specs, const Glyph *glyphs, size_t len, int x, int y)
+{
+	int start = 0, length = 1, gstart = 0;
+	hb_codepoint_t *codepoints = calloc(len, sizeof(hb_codepoint_t));
+
+	for (int idx = 1, specidx = 1; idx < len; idx++) {
+		if (glyphs[idx].mode & ATTR_WDUMMY) {
+			length += 1;
+			continue;
+		}
+
+		if (specs[specidx].font != specs[start].font || ATTRCMP(glyphs[gstart], glyphs[idx]) || selected(x + idx, y) != selected(x + gstart, y)) {
+			hbtransformsegment(specs[start].font, glyphs, codepoints, gstart, length);
+
+			/* Reset the sequence. */
+			length = 1;
+			start = specidx;
+			gstart = idx;
+		} else {
+			length += 1;
+		}
+
+		specidx++;
+	}
+
+	/* EOL. */
+	hbtransformsegment(specs[start].font, glyphs, codepoints, gstart, length);
+
+	/* Apply the transformation to glyph specs. */
+	for (int i = 0, specidx = 0; i < len; i++) {
+		if (glyphs[i].mode & ATTR_WDUMMY)
+			continue;
+
+		if (codepoints[i] != specs[specidx].glyph)
+			((Glyph *)glyphs)[i].mode |= ATTR_LIGA;
+
+		specs[specidx++].glyph = codepoints[i];
+	}
+
+	free(codepoints);
+}
+
+void
+hbtransformsegment(XftFont *xfont, const Glyph *string, hb_codepoint_t *codepoints, int start, int length)
+{
+	hb_font_t *font = hbfindfont(xfont);
+	if (font == NULL)
+		return;
+
+	Rune rune;
+	ushort mode = USHRT_MAX;
+	hb_buffer_t *buffer = hb_buffer_create();
+	hb_buffer_set_direction(buffer, HB_DIRECTION_LTR);
+
+	/* Fill buffer with codepoints. */
+	for (int i = start; i < (start+length); i++) {
+		rune = string[i].u;
+		mode = string[i].mode;
+		if (mode & ATTR_WDUMMY)
+			rune = 0x0020;
+		hb_buffer_add_codepoints(buffer, &rune, 1, 0, 1);
+	}
+
+	/* Shape the segment. */
+	hb_shape(font, buffer, NULL, 0);
+
+	/* Get new glyph info. */
+	hb_glyph_info_t *info = hb_buffer_get_glyph_infos(buffer, NULL);
+
+	/* Write new codepoints. */
+	for (int i = 0; i < length; i++) {
+		hb_codepoint_t gid = info[i].codepoint;
+		codepoints[start+i] = gid;
+	}
+
+	/* Cleanup. */
+	hb_buffer_destroy(buffer);
+}

hb.h

@@ -0,0 +1,6 @@
+#include <X11/Xft/Xft.h>
+#include <hb.h>
+#include <hb-ft.h>
+
+void hbunloadfonts();
+void hbtransform(XftGlyphFontSpec *, const Glyph *, size_t, int, int);

patches.def.h

@@ -10,13 +10,13 @@
 /* Patches */
 
 /* The alpha patch adds transparency for the terminal.
+ * You need to uncomment the corresponding line in config.mk to use the -lXrender library
+ * when including this patch.
  * https://st.suckless.org/patches/alpha/
  */
 #define ALPHA_PATCH 0
 
 /* This patch allows st to reize to any pixel size rather than snapping to character width/height.
- * You need to uncomment the corresponding line in config.mk to use the -lXrender library
- * when including this patch.
  * https://st.suckless.org/patches/anysize/
  */
 #define ANYSIZE_PATCH 0
@@ -126,6 +126,17 @@
  */
 #define KEYBOARDSELECT_PATCH 0
 
+/* This patch adds support for drawing ligatures using the Harfbuzz library to transform
+ * original text of a single line to a list of glyphs with ligatures included.
+ * This patch depends on the Harfbuzz library and headers to compile.
+ * You need to uncomment the corresponding line in config.mk to use the harfbuzz library
+ * when including this patch.
+ * You need to uncomment the corresponding lines in Makefile when including this patch.
+ * https://github.com/cog1to/st-ligatures
+ * https://st.suckless.org/patches/ligatures/
+ */
+#define LIGATURES_PATCH 0
+
 /* This patch allows you to spawn a new st terminal using Ctrl-Shift-Return. It will have the
  * same CWD (current working directory) as the original st instance.
  * https://st.suckless.org/patches/newterm/

st.c

@@ -2784,8 +2784,14 @@ draw(void)
 	#if SCROLLBACK_PATCH
 	if (term.scr == 0)
 	#endif // SCROLLBACK_PATCH
+	#if LIGATURES_PATCH
+	xdrawcursor(cx, term.c.y, term.line[term.c.y][cx],
+			term.ocx, term.ocy, term.line[term.ocy][term.ocx],
+			term.line[term.ocy], term.col);
+	#else
 	xdrawcursor(cx, term.c.y, term.line[term.c.y][cx],
 			term.ocx, term.ocy, term.line[term.ocy][term.ocx]);
+	#endif // LIGATURES_PATCH
 	term.ocx = cx;
 	term.ocy = term.c.y;
 	xfinishdraw();

st.h

@@ -12,8 +12,14 @@
 #define DIVCEIL(n, d)		(((n) + ((d) - 1)) / (d))
 #define DEFAULT(a, b)		(a) = (a) ? (a) : (b)
 #define LIMIT(x, a, b)		(x) = (x) < (a) ? (a) : (x) > (b) ? (b) : (x)
+#if LIGATURES_PATCH
+#define ATTRCMP(a, b)		(((a).mode & (~ATTR_WRAP) & (~ATTR_LIGA)) != ((b).mode & (~ATTR_WRAP) & (~ATTR_LIGA)) || \
+				(a).fg != (b).fg || \
+				(a).bg != (b).bg)
+#else
 #define ATTRCMP(a, b)		((a).mode != (b).mode || (a).fg != (b).fg || \
 				(a).bg != (b).bg)
+#endif // LIGATURES_PATCH
 #define TIMEDIFF(t1, t2)	((t1.tv_sec-t2.tv_sec)*1000 + \
 				(t1.tv_nsec-t2.tv_nsec)/1E6)
 #define MODBIT(x, set, bit)	((set) ? ((x) |= (bit)) : ((x) &= ~(bit)))
@@ -36,6 +42,11 @@ enum glyph_attribute {
 	ATTR_WDUMMY     = 1 << 10,
 	#if BOXDRAW_PATCH
 	ATTR_BOXDRAW    = 1 << 11,
+	#if LIGATURES_PATCH
+	ATTR_LIGA       = 1 << 12,
+	#endif // LIGATURES_PATCH
+	#elif LIGATURES_PATCH
+	ATTR_LIGA       = 1 << 11,
 	#endif // BOXDRAW_PATCH
 	ATTR_BOLD_FAINT = ATTR_BOLD | ATTR_FAINT,
 };

win.h

@@ -28,7 +28,11 @@ enum win_mode {
 
 void xbell(void);
 void xclipcopy(void);
+#if LIGATURES_PATCH
+void xdrawcursor(int, int, Glyph, int, int, Glyph, Line, int);
+#else
 void xdrawcursor(int, int, Glyph, int, int, Glyph);
+#endif // LIGATURES_PATCH
 void xdrawline(Line, int, int, int);
 void xfinishdraw(void);
 void xloadcols(void);

x.c

@@ -19,6 +19,9 @@ char *argv0;
 #include "arg.h"
 #include "st.h"
 #include "win.h"
+#if LIGATURES_PATCH
+#include "hb.h"
+#endif // LIGATURES_PATCH
 
 #if THEMED_CURSOR_PATCH
 #include <X11/Xcursor/Xcursor.h>
@@ -1216,6 +1219,11 @@ xunloadfont(Font *f)
 void
 xunloadfonts(void)
 {
+	#if LIGATURES_PATCH
+	/* Clear Harfbuzz font cache. */
+	hbunloadfonts();
+	#endif // LIGATURES_PATCH
+
 	/* Free the loaded fonts in the font cache.  */
 	while (frclen > 0)
 		XftFontClose(xw.dpy, frc[--frclen].font);
@@ -1449,7 +1457,11 @@ xmakeglyphfontspecs(XftGlyphFontSpec *specs, const Glyph *glyphs, int len, int x
 		mode = glyphs[i].mode;
 
 		/* Skip dummy wide-character spacing. */
+		#if LIGATURES_PATCH
+		if (mode & ATTR_WDUMMY)
+		#else
 		if (mode == ATTR_WDUMMY)
+		#endif // LIGATURES_PATCH
 			continue;
 
 		/* Determine font for glyph if different from previous glyph. */
@@ -1570,6 +1582,11 @@ xmakeglyphfontspecs(XftGlyphFontSpec *specs, const Glyph *glyphs, int len, int x
 		numspecs++;
 	}
 
+	#if LIGATURES_PATCH
+	/* Harfbuzz transformation for ligatures. */
+	hbtransform(specs, glyphs, len, x, y);
+	#endif // LIGATURES_PATCH
+
 	return numspecs;
 }
 
@@ -1780,14 +1797,24 @@ xdrawglyph(Glyph g, int x, int y)
 }
 
 void
+#if LIGATURES_PATCH
+xdrawcursor(int cx, int cy, Glyph g, int ox, int oy, Glyph og, Line line, int len)
+#else
 xdrawcursor(int cx, int cy, Glyph g, int ox, int oy, Glyph og)
+#endif // LIGATURES_PATCH
 {
 	Color drawcol;
 
 	/* remove the old cursor */
 	if (selected(ox, oy))
 		og.mode ^= ATTR_REVERSE;
+	#if LIGATURES_PATCH
+	/* Redraw the line where cursor was previously.
+	 * It will restore the ligatures broken by the cursor. */
+	xdrawline(line, 0, oy, len);
+	#else
 	xdrawglyph(og, ox, oy);
+	#endif // LIGATURES_PATCH
 
 	if (IS_SET(MODE_HIDE))
 		return;