Add in st-graphics repo

1 files changed, 587 insertions, 190 deletions

diff --git a/st.c b/st.c
index bba90d3..d8e347e 100644
--- a/st.c
+++ b/st.c
@@ -19,6 +19,7 @@
 
 #include "st.h"
 #include "win.h"
+#include "graphics.h"
 
 #if   defined(__linux)
  #include <pty.h>
@@ -35,7 +36,10 @@
 #define ESC_ARG_SIZ   16
 #define STR_BUF_SIZ   ESC_BUF_SIZ
 #define STR_ARG_SIZ   ESC_ARG_SIZ
-#define HISTSIZE      2000
+
+/* PUA character used as an image placeholder */
+#define IMAGE_PLACEHOLDER_CHAR 0x10EEEE
+#define IMAGE_PLACEHOLDER_CHAR_OLD 0xEEEE
 
 /* macros */
 #define IS_SET(flag)		((term.mode & (flag)) != 0)
@@ -43,9 +47,10 @@
 #define ISCONTROLC1(c)		(BETWEEN(c, 0x80, 0x9f))
 #define ISCONTROL(c)		(ISCONTROLC0(c) || ISCONTROLC1(c))
 #define ISDELIM(u)		(u && wcschr(worddelimiters, u))
-#define TLINE(y)		((y) < term.scr ? term.hist[((y) + term.histi - \
-            term.scr + HISTSIZE + 1) % HISTSIZE] : \
-            term.line[(y) - term.scr])
+
+#define TSCREEN term.screen[IS_SET(MODE_ALTSCREEN)]
+#define TLINEOFFSET(y) (((y) + TSCREEN.cur - TSCREEN.off + TSCREEN.size) % TSCREEN.size)
+#define TLINE(y) (TSCREEN.buffer[TLINEOFFSET(y)])
 
 enum term_mode {
 	MODE_WRAP        = 1 << 0,
@@ -113,15 +118,23 @@ typedef struct {
 	int alt;
 } Selection;
 
+/* Screen lines */
+typedef struct {
+	Line* buffer;  /* ring buffer */
+	int size;      /* size of buffer */
+	int cur;       /* start of active screen */
+	int off;       /* scrollback line offset */
+	TCursor sc;    /* saved cursor */
+} LineBuffer;
+
 /* Internal representation of the screen */
 typedef struct {
 	int row;      /* nb row */
 	int col;      /* nb col */
-	Line *line;   /* screen */
-	Line *alt;    /* alternate screen */
-	Line hist[HISTSIZE]; /* history buffer */
-	int histi;    /* history index */
-	int scr;      /* scroll back */
+	int pixw;     /* width of the text area in pixels */
+	int pixh;     /* height of the text area in pixels */
+	LineBuffer screen[2]; /* screen and alternate screen */
+	int linelen;  /* allocated line length */
 	int *dirty;   /* dirtyness of lines */
 	TCursor c;    /* cursor */
 	int ocx;      /* old cursor col */
@@ -192,8 +205,8 @@ static void tnewline(int);
 static void tputtab(int);
 static void tputc(Rune);
 static void treset(void);
-static void tscrollup(int, int, int);
-static void tscrolldown(int, int, int);
+static void tscrollup(int, int);
+static void tscrolldown(int, int);
 static void tsetattr(const int *, int);
 static void tsetchar(Rune, const Glyph *, int, int);
 static void tsetdirt(int, int);
@@ -210,6 +223,8 @@ static void tdeftran(char);
 static void tstrsequence(uchar);
 
 static void drawregion(int, int, int, int);
+static void clearline(Line, Glyph, int, int);
+static Line ensureline(Line);
 
 static void selnormalize(void);
 static void selscroll(int, int);
@@ -220,7 +235,6 @@ static Rune utf8decodebyte(char, size_t *);
 static char utf8encodebyte(Rune, size_t);
 static size_t utf8validate(Rune *, size_t);
 
-static char *base64dec(const char *);
 static char base64dec_getc(const char **);
 
 static ssize_t xwrite(int, const char *, size_t);
@@ -239,6 +253,10 @@ static const uchar utfmask[UTF_SIZ + 1] = {0xC0, 0x80, 0xE0, 0xF0, 0xF8};
 static const Rune utfmin[UTF_SIZ + 1] = {       0,    0,  0x80,  0x800,  0x10000};
 static const Rune utfmax[UTF_SIZ + 1] = {0x10FFFF, 0x7F, 0x7FF, 0xFFFF, 0x10FFFF};
 
+/* Converts a diacritic to a row/column/etc number. The result is 1-base, 0
+ * means "couldn't convert". Defined in rowcolumn_diacritics_helpers.c */
+uint16_t diacritic_to_num(uint32_t code);
+
 ssize_t
 xwrite(int fd, const char *s, size_t len)
 {
@@ -415,11 +433,12 @@ int
 tlinelen(int y)
 {
 	int i = term.col;
+	Line line = TLINE(y);
 
-	if (TLINE(y)[i - 1].mode & ATTR_WRAP)
+	if (line[i - 1].mode & ATTR_WRAP)
 		return i;
 
-	while (i > 0 && TLINE(y)[i - 1].u == ' ')
+	while (i > 0 && line[i - 1].u == ' ')
 		--i;
 
 	return i;
@@ -623,6 +642,12 @@ getsel(void)
 			if (gp->mode & ATTR_WDUMMY)
 				continue;
 
+			if (gp->mode & ATTR_IMAGE) {
+				// TODO: Copy diacritics as well
+				ptr += utf8encode(IMAGE_PLACEHOLDER_CHAR, ptr);
+				continue;
+			}
+
 			ptr += utf8encode(gp->u, ptr);
 		}
 
@@ -722,11 +747,14 @@ sigchld(int a)
 	int stat;
 	pid_t p;
 
-	if ((p = waitpid(pid, &stat, WNOHANG)) < 0)
+	if ((p = waitpid(-1, &stat, WNOHANG)) < 0)
 		die("waiting for pid %hd failed: %s\n", pid, strerror(errno));
 
-	if (pid != p)
+	if (pid != p) {
+		/* reinstall sigchld handler */
+		signal(SIGCHLD, sigchld);
 		return;
+	}
 
 	if (WIFEXITED(stat) && WEXITSTATUS(stat))
 		die("child exited with status %d\n", WEXITSTATUS(stat));
@@ -810,7 +838,7 @@ ttynew(const char *line, char *cmd, const char *out, char **args)
 		break;
 	default:
 #ifdef __OpenBSD__
-		if (pledge("stdio rpath tty proc", NULL) == -1)
+		if (pledge("stdio rpath tty proc exec", NULL) == -1)
 			die("pledge\n");
 #endif
 		close(s);
@@ -826,7 +854,11 @@ ttyread(void)
 {
 	static char buf[BUFSIZ];
 	static int buflen = 0;
-	int ret, written;
+	static int already_processing = 0;
+	int ret, written = 0;
+
+	if (buflen >= LEN(buf))
+		return 0;
 
 	/* append read bytes to unprocessed bytes */
 	ret = read(cmdfd, buf+buflen, LEN(buf)-buflen);
@@ -838,7 +870,24 @@ ttyread(void)
 		die("couldn't read from shell: %s\n", strerror(errno));
 	default:
 		buflen += ret;
-		written = twrite(buf, buflen, 0);
+		if (already_processing) {
+			/* Avoid recursive call to twrite() */
+			return ret;
+		}
+		already_processing = 1;
+		while (1) {
+			int buflen_before_processing = buflen;
+			written += twrite(buf + written, buflen - written, 0);
+			// If buflen changed during the call to twrite, there is
+			// new data, and we need to keep processing, otherwise
+			// we can exit. This will not loop forever because the
+			// buffer is limited, and we don't clean it in this
+			// loop, so at some point ttywrite will have to drop
+			// some data.
+			if (buflen_before_processing == buflen)
+				break;
+		}
+		already_processing = 0;
 		buflen -= written;
 		/* keep any incomplete UTF-8 byte sequence for the next call */
 		if (buflen > 0)
@@ -851,9 +900,6 @@ void
 ttywrite(const char *s, size_t n, int may_echo)
 {
 	const char *next;
-	Arg arg = (Arg) { .i = term.scr };
-
-	kscrolldown(&arg);
 
 	if (may_echo && IS_SET(MODE_ECHO))
 		twrite(s, n, 1);
@@ -884,6 +930,7 @@ ttywriteraw(const char *s, size_t n)
 	fd_set wfd, rfd;
 	ssize_t r;
 	size_t lim = 256;
+	int retries_left = 100;
 
 	/*
 	 * Remember that we are using a pty, which might be a modem line.
@@ -892,6 +939,9 @@ ttywriteraw(const char *s, size_t n)
 	 * FIXME: Migrate the world to Plan 9.
 	 */
 	while (n > 0) {
+		if (retries_left-- <= 0)
+			goto too_many_retries;
+
 		FD_ZERO(&wfd);
 		FD_ZERO(&rfd);
 		FD_SET(cmdfd, &wfd);
@@ -933,11 +983,16 @@ ttywriteraw(const char *s, size_t n)
 
 write_error:
 	die("write error on tty: %s\n", strerror(errno));
+too_many_retries:
+	fprintf(stderr, "Could not write %zu bytes to tty\n", n);
 }
 
 void
 ttyresize(int tw, int th)
 {
+	term.pixw = tw;
+	term.pixh = th;
+
 	struct winsize w;
 
 	w.ws_row = term.row;
@@ -959,12 +1014,15 @@ int
 tattrset(int attr)
 {
 	int i, j;
+	int y = TLINEOFFSET(0);
 
 	for (i = 0; i < term.row-1; i++) {
+		Line line = TSCREEN.buffer[y];
 		for (j = 0; j < term.col-1; j++) {
-			if (term.line[i][j].mode & attr)
+			if (line[j].mode & attr)
 				return 1;
 		}
+		y = (y+1) % TSCREEN.size;
 	}
 
 	return 0;
@@ -986,14 +1044,17 @@ void
 tsetdirtattr(int attr)
 {
 	int i, j;
+	int y = TLINEOFFSET(0);
 
 	for (i = 0; i < term.row-1; i++) {
+		Line line = TSCREEN.buffer[y];
 		for (j = 0; j < term.col-1; j++) {
-			if (term.line[i][j].mode & attr) {
+			if (line[j].mode & attr) {
 				tsetdirt(i, i);
 				break;
 			}
 		}
+		y = (y+1) % TSCREEN.size;
 	}
 }
 
@@ -1006,27 +1067,22 @@ tfulldirt(void)
 void
 tcursor(int mode)
 {
-	static TCursor c[2];
-	int alt = IS_SET(MODE_ALTSCREEN);
-
 	if (mode == CURSOR_SAVE) {
-		c[alt] = term.c;
+		TSCREEN.sc = term.c;
 	} else if (mode == CURSOR_LOAD) {
-		term.c = c[alt];
-		tmoveto(c[alt].x, c[alt].y);
+		term.c = TSCREEN.sc;
+		tmoveto(term.c.x, term.c.y);
 	}
 }
 
 void
 treset(void)
 {
-	uint i;
-
-	term.c = (TCursor){{
-		.mode = ATTR_NULL,
-		.fg = defaultfg,
-		.bg = defaultbg
-	}, .x = 0, .y = 0, .state = CURSOR_DEFAULT};
+	int i, j;
+	Glyph g = (Glyph){.mode = ATTR_NULL,
+			  .fg = defaultfg,
+			  .bg = defaultbg,
+			  .decor = DECOR_DEFAULT_COLOR};
 
 	memset(term.tabs, 0, term.col * sizeof(*term.tabs));
 	for (i = tabspaces; i < term.col; i += tabspaces)
@@ -1038,17 +1094,38 @@ treset(void)
 	term.charset = 0;
 
 	for (i = 0; i < 2; i++) {
-		tmoveto(0, 0);
-		tcursor(CURSOR_SAVE);
-		tclearregion(0, 0, term.col-1, term.row-1);
-		tswapscreen();
+		term.screen[i].sc = (TCursor){{
+			.fg = defaultfg,
+			.bg = defaultbg,
+			.decor = DECOR_DEFAULT_COLOR
+		}};
+		term.screen[i].cur = 0;
+		term.screen[i].off = 0;
+		for (j = 0; j < term.row; ++j) {
+			if (term.col != term.linelen)
+				term.screen[i].buffer[j] = xrealloc(term.screen[i].buffer[j], term.col * sizeof(Glyph));
+			clearline(term.screen[i].buffer[j], g, 0, term.col);
+		}
+		for (j = term.row; j < term.screen[i].size; ++j) {
+			free(term.screen[i].buffer[j]);
+			term.screen[i].buffer[j] = NULL;
+		}
 	}
+	tcursor(CURSOR_LOAD);
+	term.linelen = term.col;
+	tfulldirt();
 }
 
 void
 tnew(int col, int row)
 {
-	term = (Term){ .c = { .attr = { .fg = defaultfg, .bg = defaultbg } } };
+	int i;
+	term = (Term){};
+	term.screen[0].buffer = xmalloc(HISTSIZE * sizeof(Line));
+	term.screen[0].size = HISTSIZE;
+	term.screen[1].buffer = NULL;
+	for (i = 0; i < HISTSIZE; ++i) term.screen[0].buffer[i] = NULL;
+
 	tresize(col, row);
 	treset();
 }
@@ -1056,104 +1133,108 @@ tnew(int col, int row)
 void
 tswapscreen(void)
 {
-	Line *tmp = term.line;
-
-	term.line = term.alt;
-	term.alt = tmp;
 	term.mode ^= MODE_ALTSCREEN;
 	tfulldirt();
 }
 
 void
-kscrolldown(const Arg* a)
+kscrollup(const Arg *a)
 {
 	int n = a->i;
 
-	if (n < 0)
-		n = term.row + n;
-
-	if (n > term.scr)
-		n = term.scr;
+	if (IS_SET(MODE_ALTSCREEN))
+		return;
 
-	if (term.scr > 0) {
-		term.scr -= n;
-		selscroll(0, -n);
-		tfulldirt();
-	}
+	if (n < 0) n = (-n) * term.row;
+	if (n > TSCREEN.size - term.row - TSCREEN.off) n = TSCREEN.size - term.row - TSCREEN.off;
+	while (!TLINE(-n)) --n;
+	TSCREEN.off += n;
+	selscroll(0, n);
+	tfulldirt();
 }
 
 void
-kscrollup(const Arg* a)
+kscrolldown(const Arg *a)
 {
+
 	int n = a->i;
 
-	if (n < 0)
-		n = term.row + n;
+	if (IS_SET(MODE_ALTSCREEN))
+		return;
 
-	if (term.scr <= HISTSIZE-n) {
-		term.scr += n;
-		selscroll(0, n);
-		tfulldirt();
-	}
+	if (n < 0) n = (-n) * term.row;
+	if (n > TSCREEN.off) n = TSCREEN.off;
+	TSCREEN.off -= n;
+	selscroll(0, -n);
+	tfulldirt();
 }
 
 void
-tscrolldown(int orig, int n, int copyhist)
+tscrolldown(int orig, int n)
 {
 	int i;
 	Line temp;
 
 	LIMIT(n, 0, term.bot-orig+1);
 
-	if (copyhist) {
-		term.histi = (term.histi - 1 + HISTSIZE) % HISTSIZE;
-		temp = term.hist[term.histi];
-		term.hist[term.histi] = term.line[term.bot];
-		term.line[term.bot] = temp;
+	/* Ensure that lines are allocated */
+	for (i = -n; i < 0; i++) {
+		TLINE(i) = ensureline(TLINE(i));
 	}
 
-	tsetdirt(orig, term.bot-n);
-	tclearregion(0, term.bot-n+1, term.col-1, term.bot);
-
-	for (i = term.bot; i >= orig+n; i--) {
-		temp = term.line[i];
-		term.line[i] = term.line[i-n];
-		term.line[i-n] = temp;
+	/* Shift non-scrolling areas in ring buffer */
+	for (i = term.bot+1; i < term.row; i++) {
+		temp = TLINE(i);
+		TLINE(i) = TLINE(i-n);
+		TLINE(i-n) = temp;
+	}
+	for (i = 0; i < orig; i++) {
+		temp = TLINE(i);
+		TLINE(i) = TLINE(i-n);
+		TLINE(i-n) = temp;
 	}
 
-	if (term.scr == 0)
-		selscroll(orig, n);
+	/* Scroll buffer */
+	TSCREEN.cur = (TSCREEN.cur + TSCREEN.size - n) % TSCREEN.size;
+	/* Clear lines that have entered the view */
+	tclearregion(0, orig, term.linelen-1, orig+n-1);
+	/* Redraw portion of the screen that has scrolled */
+	tsetdirt(orig+n-1, term.bot);
+	selscroll(orig, n);
 }
 
 void
-tscrollup(int orig, int n, int copyhist)
+tscrollup(int orig, int n)
 {
 	int i;
 	Line temp;
 
 	LIMIT(n, 0, term.bot-orig+1);
 
-	if (copyhist) {
-		term.histi = (term.histi + 1) % HISTSIZE;
-		temp = term.hist[term.histi];
-		term.hist[term.histi] = term.line[orig];
-		term.line[orig] = temp;
+	/* Ensure that lines are allocated */
+	for (i = term.row; i < term.row + n; i++) {
+		TLINE(i) = ensureline(TLINE(i));
 	}
 
-	if (term.scr > 0 && term.scr < HISTSIZE)
-		term.scr = MIN(term.scr + n, HISTSIZE-1);
-
-	tclearregion(0, orig, term.col-1, orig+n-1);
-	tsetdirt(orig+n, term.bot);
-
-	for (i = orig; i <= term.bot-n; i++) {
-		temp = term.line[i];
-		term.line[i] = term.line[i+n];
-		term.line[i+n] = temp;
+	/* Shift non-scrolling areas in ring buffer */
+	for (i = orig-1; i >= 0; i--) {
+		temp = TLINE(i);
+		TLINE(i) = TLINE(i+n);
+		TLINE(i+n) = temp;
+	}
+	for (i = term.row-1; i >term.bot; i--) {
+		temp = TLINE(i);
+		TLINE(i) = TLINE(i+n);
+		TLINE(i+n) = temp;
 	}
 
-	if (term.scr == 0)
-		selscroll(orig, -n);
+	/* Scroll buffer */
+	TSCREEN.cur = (TSCREEN.cur + n) % TSCREEN.size;
+	/* Clear lines that have entered the view */
+	tclearregion(0, term.bot-n+1, term.linelen-1, term.bot);
+	/* Redraw portion of the screen that has scrolled */
+	tsetdirt(orig, term.bot-n+1);
+	selscroll(orig, -n);
 }
 
 void
@@ -1182,7 +1263,7 @@ tnewline(int first_col)
 	int y = term.c.y;
 
 	if (y == term.bot) {
-		tscrollup(term.top, 1, 1);
+		tscrollup(term.top, 1);
 	} else {
 		y++;
 	}
@@ -1194,6 +1275,7 @@ csiparse(void)
 {
 	char *p = csiescseq.buf, *np;
 	long int v;
+	int sep = ';'; /* colon or semi-colon, but not both */
 
 	csiescseq.narg = 0;
 	if (*p == '?') {
@@ -1211,7 +1293,9 @@ csiparse(void)
 			v = -1;
 		csiescseq.arg[csiescseq.narg++] = v;
 		p = np;
-		if (*p != ';' || csiescseq.narg == ESC_ARG_SIZ)
+		if (sep == ';' && *p == ':')
+			sep = ':'; /* allow override to colon once */
+		if (*p != sep || csiescseq.narg == ESC_ARG_SIZ)
 			break;
 		p++;
 	}
@@ -1256,6 +1340,7 @@ tsetchar(Rune u, const Glyph *attr, int x, int y)
 		"⎻", "─", "⎼", "⎽", "├", "┤", "┴", "┬", /* p - w */
 		"│", "≤", "≥", "π", "≠", "£", "·", /* x - ~ */
 	};
+	Line line = TLINE(y);
 
 	/*
 	 * The table is proudly stolen from rxvt.
@@ -1264,25 +1349,43 @@ tsetchar(Rune u, const Glyph *attr, int x, int y)
 	   BETWEEN(u, 0x41, 0x7e) && vt100_0[u - 0x41])
 		utf8decode(vt100_0[u - 0x41], &u, UTF_SIZ);
 
-	if (term.line[y][x].mode & ATTR_WIDE) {
+	if (line[x].mode & ATTR_WIDE) {
 		if (x+1 < term.col) {
-			term.line[y][x+1].u = ' ';
-			term.line[y][x+1].mode &= ~ATTR_WDUMMY;
+			line[x+1].u = ' ';
+			line[x+1].mode &= ~ATTR_WDUMMY;
 		}
-	} else if (term.line[y][x].mode & ATTR_WDUMMY) {
-		term.line[y][x-1].u = ' ';
-		term.line[y][x-1].mode &= ~ATTR_WIDE;
+	} else if (line[x].mode & ATTR_WDUMMY) {
+		line[x-1].u = ' ';
+		line[x-1].mode &= ~ATTR_WIDE;
+	}
+
+	if (u == ' ' && line[x].mode & ATTR_IMAGE &&
+	    tgetisclassicplaceholder(&line[x])) {
+		// This is a workaround: don't overwrite classic placement
+		// placeholders with space symbols (unlike Unicode placeholders
+		// which must be overwritten by anything).
+		line[x].bg = attr->bg;
+		term.dirty[y] = 1;
+		return;
 	}
 
 	term.dirty[y] = 1;
-	term.line[y][x] = *attr;
-	term.line[y][x].u = u;
+	line[x] = *attr;
+	line[x].u = u;
+
+	if (u == IMAGE_PLACEHOLDER_CHAR || u == IMAGE_PLACEHOLDER_CHAR_OLD) {
+		line[x].u = 0;
+		line[x].mode |= ATTR_IMAGE;
+	}
+
+	if (isboxdraw(u))
+		line[x].mode |= ATTR_BOXDRAW;
 }
 
 void
 tclearregion(int x1, int y1, int x2, int y2)
 {
-	int x, y, temp;
+	int x, y, L, S, temp;
 	Glyph *gp;
 
 	if (x1 > x2)
@@ -1290,22 +1393,122 @@ tclearregion(int x1, int y1, int x2, int y2)
 	if (y1 > y2)
 		temp = y1, y1 = y2, y2 = temp;
 
-	LIMIT(x1, 0, term.col-1);
-	LIMIT(x2, 0, term.col-1);
+	LIMIT(x1, 0, term.linelen-1);
+	LIMIT(x2, 0, term.linelen-1);
 	LIMIT(y1, 0, term.row-1);
 	LIMIT(y2, 0, term.row-1);
 
+	L = TLINEOFFSET(y1);
 	for (y = y1; y <= y2; y++) {
 		term.dirty[y] = 1;
 		for (x = x1; x <= x2; x++) {
-			gp = &term.line[y][x];
+			gp = &TSCREEN.buffer[L][x];
 			if (selected(x, y))
 				selclear();
 			gp->fg = term.c.attr.fg;
 			gp->bg = term.c.attr.bg;
+			gp->decor = term.c.attr.decor;
 			gp->mode = 0;
 			gp->u = ' ';
 		}
+		L = (L + 1) % TSCREEN.size;
+	}
+}
+
+/// Fills a rectangle area with an image placeholder. The starting point is the
+/// cursor. Adds empty lines if needed. The placeholder will be marked as
+/// classic.
+void tcreateimgplaceholder(uint32_t image_id, uint32_t placement_id, int cols,
+			   int rows, char do_not_move_cursor,
+			   Glyph *text_underneath) {
+	for (int row = 0; row < rows; ++row) {
+		int y = term.c.y;
+		term.dirty[y] = 1;
+		for (int col = 0; col < cols; ++col) {
+			int x = term.c.x + col;
+			if (x >= term.col)
+				break;
+			Glyph *gp = &TLINE(y)[x];
+			if (selected(x, y))
+				selclear();
+			if (text_underneath) {
+				Glyph *to_save = gp;
+				// If there is already a classic placeholder,
+				// use the text underneath it. This will leave
+				// holes in images, but at least we are
+				// guaranteed to restore the original text.
+				if (gp->mode & ATTR_IMAGE &&
+				    tgetisclassicplaceholder(gp)) {
+					Glyph *under =
+						gr_get_glyph_underneath_image(
+							tgetimgid(gp),
+							tgetimgplacementid(gp),
+							tgetimgcol(gp),
+							tgetimgrow(gp));
+					if (under)
+						to_save = under;
+				}
+				text_underneath[cols * row + col] = *to_save;
+			}
+			gp->mode = ATTR_IMAGE;
+			gp->u = 0;
+			tsetimgrow(gp, row + 1);
+			tsetimgcol(gp, col + 1);
+			tsetimgid(gp, image_id);
+			tsetimgplacementid(gp, placement_id);
+			tsetimgdiacriticcount(gp, 3);
+			tsetisclassicplaceholder(gp, 1);
+		}
+		// If moving the cursor is not allowed and this is the last line
+		// of the terminal, we are done.
+		if (do_not_move_cursor && y == term.row - 1)
+			break;
+		// Move the cursor down, maybe creating a new line. The x is
+		// preserved (we never change term.c.x in the loop above).
+		if (row != rows - 1)
+			tnewline(/*first_col=*/0);
+	}
+	if (do_not_move_cursor) {
+		// Return the cursor to the original position.
+		tmoveto(term.c.x, term.c.y - rows + 1);
+	} else {
+		// Move the cursor beyond the last column, as required by the
+		// protocol. If the cursor goes beyond the screen edge, insert a
+		// newline to match the behavior of kitty.
+		if (term.c.x + cols >= term.col)
+			tnewline(/*first_col=*/1);
+		else
+			tmoveto(term.c.x + cols, term.c.y);
+	}
+}
+
+void gr_for_each_image_cell(int (*callback)(void *data, Glyph *gp),
+			    void *data) {
+	for (int row = 0; row < term.row; ++row) {
+		for (int col = 0; col < term.col; ++col) {
+			Glyph *gp = &TLINE(row)[col];
+			if (gp->mode & ATTR_IMAGE) {
+				if (callback(data, gp))
+					term.dirty[row] = 1;
+			}
+		}
+	}
+}
+
+void gr_schedule_image_redraw_by_id(uint32_t image_id) {
+	for (int row = 0; row < term.row; ++row) {
+		if (term.dirty[row])
+			continue;
+		for (int col = 0; col < term.col; ++col) {
+			Glyph *gp = &TLINE(row)[col];
+			if (gp->mode & ATTR_IMAGE) {
+				uint32_t cell_image_id = tgetimgid(gp);
+				if (cell_image_id == image_id) {
+					term.dirty[row] = 1;
+					break;
+				}
+			}
+		}
 	}
 }
 
@@ -1320,7 +1523,7 @@ tdeletechar(int n)
 	dst = term.c.x;
 	src = term.c.x + n;
 	size = term.col - src;
-	line = term.line[term.c.y];
+	line = TLINE(term.c.y);
 
 	memmove(&line[dst], &line[src], size * sizeof(Glyph));
 	tclearregion(term.col-n, term.c.y, term.col-1, term.c.y);
@@ -1337,7 +1540,7 @@ tinsertblank(int n)
 	dst = term.c.x + n;
 	src = term.c.x;
 	size = term.col - dst;
-	line = term.line[term.c.y];
+	line = TLINE(term.c.y);
 
 	memmove(&line[dst], &line[src], size * sizeof(Glyph));
 	tclearregion(src, term.c.y, dst - 1, term.c.y);
@@ -1347,14 +1550,14 @@ void
 tinsertblankline(int n)
 {
 	if (BETWEEN(term.c.y, term.top, term.bot))
-		tscrolldown(term.c.y, n, 0);
+		tscrolldown(term.c.y, n);
 }
 
 void
 tdeleteline(int n)
 {
 	if (BETWEEN(term.c.y, term.top, term.bot))
-		tscrollup(term.c.y, n, 0);
+		tscrollup(term.c.y, n);
 }
 
 int32_t
@@ -1427,6 +1630,7 @@ tsetattr(const int *attr, int l)
 				ATTR_STRUCK     );
 			term.c.attr.fg = defaultfg;
 			term.c.attr.bg = defaultbg;
+			term.c.attr.decor = DECOR_DEFAULT_COLOR;
 			break;
 		case 1:
 			term.c.attr.mode |= ATTR_BOLD;
@@ -1439,6 +1643,20 @@ tsetattr(const int *attr, int l)
 			break;
 		case 4:
 			term.c.attr.mode |= ATTR_UNDERLINE;
+			if (i + 1 < l) {
+				idx = attr[++i];
+				if (BETWEEN(idx, 1, 5)) {
+					tsetdecorstyle(&term.c.attr, idx);
+				} else if (idx == 0) {
+					term.c.attr.mode &= ~ATTR_UNDERLINE;
+					tsetdecorstyle(&term.c.attr, 0);
+				} else {
+					fprintf(stderr,
+						"erresc: unknown underline "
+						"style %d\n",
+						idx);
+				}
+			}
 			break;
 		case 5: /* slow blink */
 			/* FALLTHROUGH */
@@ -1462,6 +1680,7 @@ tsetattr(const int *attr, int l)
 			break;
 		case 24:
 			term.c.attr.mode &= ~ATTR_UNDERLINE;
+			tsetdecorstyle(&term.c.attr, 0);
 			break;
 		case 25:
 			term.c.attr.mode &= ~ATTR_BLINK;
@@ -1489,6 +1708,13 @@ tsetattr(const int *attr, int l)
 		case 49:
 			term.c.attr.bg = defaultbg;
 			break;
+		case 58:
+			if ((idx = tdefcolor(attr, &i, l)) >= 0)
+				tsetdecorcolor(&term.c.attr, idx);
+			break;
+		case 59:
+			tsetdecorcolor(&term.c.attr, DECOR_DEFAULT_COLOR);
+			break;
 		default:
 			if (BETWEEN(attr[i], 30, 37)) {
 				term.c.attr.fg = attr[i] - 30;
@@ -1764,7 +1990,7 @@ csihandle(void)
 			}
 			break;
 		case 1: /* above */
-			if (term.c.y > 1)
+			if (term.c.y > 0)
 				tclearregion(0, 0, term.col-1, term.c.y-1);
 			tclearregion(0, term.c.y, term.c.x, term.c.y);
 			break;
@@ -1792,11 +2018,11 @@ csihandle(void)
 	case 'S': /* SU -- Scroll <n> line up */
 		if (csiescseq.priv) break;
 		DEFAULT(csiescseq.arg[0], 1);
-		tscrollup(term.top, csiescseq.arg[0], 0);
+		tscrollup(term.top, csiescseq.arg[0]);
 		break;
 	case 'T': /* SD -- Scroll <n> line down */
 		DEFAULT(csiescseq.arg[0], 1);
-		tscrolldown(term.top, csiescseq.arg[0], 0);
+		tscrolldown(term.top, csiescseq.arg[0]);
 		break;
 	case 'L': /* IL -- Insert <n> blank lines */
 		DEFAULT(csiescseq.arg[0], 1);
@@ -1860,7 +2086,11 @@ csihandle(void)
 		tcursor(CURSOR_SAVE);
 		break;
 	case 'u': /* DECRC -- Restore cursor position (ANSI.SYS) */
-		tcursor(CURSOR_LOAD);
+		if (csiescseq.priv) {
+			goto unknown;
+		} else {
+			tcursor(CURSOR_LOAD);
+		}
 		break;
 	case ' ':
 		switch (csiescseq.mode[1]) {
@@ -1872,6 +2102,39 @@ csihandle(void)
 			goto unknown;
 		}
 		break;
+	case '>':
+		switch (csiescseq.mode[1]) {
+		case 'q': /* XTVERSION -- Print terminal name and version */
+			len = snprintf(buf, sizeof(buf),
+				       "\033P>|st-graphics(%s)\033\\", VERSION);
+			ttywrite(buf, len, 0);
+			break;
+		default:
+			goto unknown;
+		}
+		break;
+	case 't': /* XTWINOPS -- Window manipulation */
+		switch (csiescseq.arg[0]) {
+		case 14: /* Report text area size in pixels. */
+			len = snprintf(buf, sizeof(buf), "\033[4;%i;%it",
+					term.pixh, term.pixw);
+			ttywrite(buf, len, 0);
+			break;
+		case 16: /* Report character cell size in pixels. */
+			len = snprintf(buf, sizeof(buf), "\033[6;%i;%it",
+					term.pixh / term.row,
+					term.pixw / term.col);
+			ttywrite(buf, len, 0);
+			break;
+		case 18: /* Report the size of the text area in characters. */
+			len = snprintf(buf, sizeof(buf), "\033[8;%i;%it",
+					term.row, term.col);
+			ttywrite(buf, len, 0);
+			break;
+		default:
+			goto unknown;
+		}
+		break;
 	}
 }
 
@@ -2021,8 +2284,27 @@ strhandle(void)
 	case 'k': /* old title set compatibility */
 		xsettitle(strescseq.args[0]);
 		return;
-	case 'P': /* DCS -- Device Control String */
 	case '_': /* APC -- Application Program Command */
+		if (gr_parse_command(strescseq.buf, strescseq.len)) {
+			GraphicsCommandResult *res = &graphics_command_result;
+			if (res->create_placeholder) {
+				tcreateimgplaceholder(
+					res->placeholder.image_id,
+					res->placeholder.placement_id,
+					res->placeholder.columns,
+					res->placeholder.rows,
+					res->placeholder.do_not_move_cursor,
+					res->placeholder.text_underneath);
+			}
+			if (res->response[0])
+				ttywrite(res->response, strlen(res->response),
+					 0);
+			if (res->redraw)
+				tfulldirt();
+			return;
+		}
+		return;
+	case 'P': /* DCS -- Device Control String */
 	case '^': /* PM -- Privacy Message */
 		return;
 	}
@@ -2054,6 +2336,59 @@ strparse(void)
 }
 
 void
+externalpipe(const Arg *arg)
+{
+	int to[2];
+	char buf[UTF_SIZ];
+	void (*oldsigpipe)(int);
+	Glyph *bp, *end;
+	int lastpos, n, newline;
+
+	if (pipe(to) == -1)
+		return;
+
+	switch (fork()) {
+	case -1:
+		close(to[0]);
+		close(to[1]);
+		return;
+	case 0:
+		dup2(to[0], STDIN_FILENO);
+		close(to[0]);
+		close(to[1]);
+		execvp(((char **)arg->v)[0], (char **)arg->v);
+		fprintf(stderr, "st: execvp %s\n", ((char **)arg->v)[0]);
+		perror("failed");
+		exit(0);
+	}
+
+	close(to[0]);
+	/* ignore sigpipe for now, in case child exists early */
+	oldsigpipe = signal(SIGPIPE, SIG_IGN);
+	newline = 0;
+	for (n = 0; n < term.row; n++) {
+		bp = TLINE(n);
+		lastpos = MIN(tlinelen(n) + 1, term.col) - 1;
+		if (lastpos < 0)
+			break;
+		end = &bp[lastpos + 1];
+		for (; bp < end; ++bp)
+			if (xwrite(to[1], buf, utf8encode(bp->u, buf)) < 0)
+				break;
+		if ((newline = TLINE(n)[lastpos].mode & ATTR_WRAP))
+			continue;
+		if (xwrite(to[1], "\n", 1) < 0)
+			break;
+		newline = 0;
+	}
+	if (newline)
+		(void)xwrite(to[1], "\n", 1);
+	close(to[1]);
+	/* restore */
+	signal(SIGPIPE, oldsigpipe);
+}
+
+void
 strdump(void)
 {
 	size_t i;
@@ -2141,7 +2476,7 @@ tdumpline(int n)
 	char buf[UTF_SIZ];
 	const Glyph *bp, *end;
 
-	bp = &term.line[n][0];
+	bp = &TLINE(n)[0];
 	end = &bp[MIN(tlinelen(n), term.col) - 1];
 	if (bp != end || bp->u != ' ') {
 		for ( ; bp <= end; ++bp)
@@ -2368,7 +2703,7 @@ eschandle(uchar ascii)
 		return 0;
 	case 'D': /* IND -- Linefeed */
 		if (term.c.y == term.bot) {
-			tscrollup(term.top, 1, 1);
+			tscrollup(term.top, 1);
 		} else {
 			tmoveto(term.c.x, term.c.y+1);
 		}
@@ -2381,7 +2716,7 @@ eschandle(uchar ascii)
 		break;
 	case 'M': /* RI -- Reverse index */
 		if (term.c.y == term.top) {
-			tscrolldown(term.top, 1, 1);
+			tscrolldown(term.top, 1);
 		} else {
 			tmoveto(term.c.x, term.c.y-1);
 		}
@@ -2528,11 +2863,46 @@ check_control_code:
 	if (selected(term.c.x, term.c.y))
 		selclear();
 
-	gp = &term.line[term.c.y][term.c.x];
+	// wcwidth is broken on some systems, set the width to 0 if it's a known
+	// diacritic used for images.
+	uint16_t num = diacritic_to_num(u);
+	if (num != 0)
+		width = 0;
+	// Set the width to 1 if it's an image placeholder character.
+	if (u == IMAGE_PLACEHOLDER_CHAR || u == IMAGE_PLACEHOLDER_CHAR_OLD)
+		width = 1;
+
+	if (width == 0) {
+		// It's probably a combining char. Combining characters are not
+		// supported, so we just ignore them, unless it denotes the row and
+		// column of an image character.
+		if (term.c.y <= 0 && term.c.x <= 0)
+			return;
+		else if (term.c.x == 0)
+			gp = &TLINE(term.c.y-1)[term.col-1];
+		else if (term.c.state & CURSOR_WRAPNEXT)
+			gp = &TLINE(term.c.y)[term.c.x];
+		else
+			gp = &TLINE(term.c.y)[term.c.x-1];
+		if (num && (gp->mode & ATTR_IMAGE)) {
+			unsigned diaccount = tgetimgdiacriticcount(gp);
+			if (diaccount == 0)
+				tsetimgrow(gp, num);
+			else if (diaccount == 1)
+				tsetimgcol(gp, num);
+			else if (diaccount == 2)
+				tsetimg4thbyteplus1(gp, num);
+			tsetimgdiacriticcount(gp, diaccount + 1);
+		}
+		term.lastc = u;
+		return;
+	}
+
+	gp = &TLINE(term.c.y)[term.c.x];
 	if (IS_SET(MODE_WRAP) && (term.c.state & CURSOR_WRAPNEXT)) {
 		gp->mode |= ATTR_WRAP;
 		tnewline(1);
-		gp = &term.line[term.c.y][term.c.x];
+		gp = &TLINE(term.c.y)[term.c.x];
 	}
 
 	if (IS_SET(MODE_INSERT) && term.c.x+width < term.col) {
@@ -2545,7 +2915,7 @@ check_control_code:
 			tnewline(1);
 		else
 			tmoveto(term.col - width, term.c.y);
-		gp = &term.line[term.c.y][term.c.x];
+		gp = &TLINE(term.c.y)[term.c.x];
 	}
 
 	tsetchar(u, &term.c.attr, term.c.x, term.c.y);
@@ -2576,6 +2946,11 @@ twrite(const char *buf, int buflen, int show_ctrl)
 	Rune u;
 	int n;
 
+	if (TSCREEN.off) {
+		TSCREEN.off = 0;
+		tfulldirt();
+	}
+
 	for (n = 0; n < buflen; n += charsize) {
 		if (IS_SET(MODE_UTF8)) {
 			/* process a complete utf8 char */
@@ -2602,64 +2977,85 @@ twrite(const char *buf, int buflen, int show_ctrl)
 }
 
 void
+clearline(Line line, Glyph g, int x, int xend)
+{
+	int i;
+	g.mode = 0;
+	g.u = ' ';
+	for (i = x; i < xend; ++i) {
+		line[i] = g;
+	}
+}
+
+Line
+ensureline(Line line)
+{
+	if (!line) {
+		line = xmalloc(term.linelen * sizeof(Glyph));
+	}
+	return line;
+}
+
+void
 tresize(int col, int row)
 {
 	int i, j;
 	int minrow = MIN(row, term.row);
 	int mincol = MIN(col, term.col);
+	int linelen = MAX(col, term.linelen);
 	int *bp;
-	TCursor c;
 
-	if (col < 1 || row < 1) {
+	if (col < 1 || row < 1 || row > HISTSIZE) {
 		fprintf(stderr,
 		        "tresize: error resizing to %dx%d\n", col, row);
 		return;
 	}
 
-	/*
-	 * slide screen to keep cursor where we expect it -
-	 * tscrollup would work here, but we can optimize to
-	 * memmove because we're freeing the earlier lines
-	 */
-	for (i = 0; i <= term.c.y - row; i++) {
-		free(term.line[i]);
-		free(term.alt[i]);
+	/* Shift buffer to keep the cursor where we expect it */
+	if (row <= term.c.y) {
+		term.screen[0].cur = (term.screen[0].cur - row + term.c.y + 1) % term.screen[0].size;
+	}
+
+	/* Resize and clear line buffers as needed */
+	if (linelen > term.linelen) {
+		for (i = 0; i < term.screen[0].size; ++i) {
+			if (term.screen[0].buffer[i]) {
+				term.screen[0].buffer[i] = xrealloc(term.screen[0].buffer[i], linelen * sizeof(Glyph));
+				clearline(term.screen[0].buffer[i], term.c.attr, term.linelen, linelen);
+			}
+		}
+		for (i = 0; i < minrow; ++i) {
+			term.screen[1].buffer[i] = xrealloc(term.screen[1].buffer[i], linelen * sizeof(Glyph));
+			clearline(term.screen[1].buffer[i], term.c.attr, term.linelen, linelen);
+		}
+	}
+	/* Allocate all visible lines for regular line buffer */
+	for (j = term.screen[0].cur, i = 0; i < row; ++i, j = (j + 1) % term.screen[0].size)
+	{
+		if (!term.screen[0].buffer[j]) {
+			term.screen[0].buffer[j] = xmalloc(linelen * sizeof(Glyph));
+		}
+		if (i >= term.row) {
+			clearline(term.screen[0].buffer[j], term.c.attr, 0, linelen);
+		}
 	}
-	/* ensure that both src and dst are not NULL */
-	if (i > 0) {
-		memmove(term.line, term.line + i, row * sizeof(Line));
-		memmove(term.alt, term.alt + i, row * sizeof(Line));
+	/* Resize alt screen */
+	term.screen[1].cur = 0;
+	term.screen[1].size = row;
+	for (i = row; i < term.row; ++i) {
+		free(term.screen[1].buffer[i]);
 	}
-	for (i += row; i < term.row; i++) {
-		free(term.line[i]);
-		free(term.alt[i]);
+	term.screen[1].buffer = xrealloc(term.screen[1].buffer, row * sizeof(Line));
+	for (i = term.row; i < row; ++i) {
+		term.screen[1].buffer[i] = xmalloc(linelen * sizeof(Glyph));
+		clearline(term.screen[1].buffer[i], term.c.attr, 0, linelen);
 	}
 
 	/* resize to new height */
-	term.line = xrealloc(term.line, row * sizeof(Line));
-	term.alt  = xrealloc(term.alt,  row * sizeof(Line));
 	term.dirty = xrealloc(term.dirty, row * sizeof(*term.dirty));
 	term.tabs = xrealloc(term.tabs, col * sizeof(*term.tabs));
 
-	for (i = 0; i < HISTSIZE; i++) {
-		term.hist[i] = xrealloc(term.hist[i], col * sizeof(Glyph));
-		for (j = mincol; j < col; j++) {
-			term.hist[i][j] = term.c.attr;
-			term.hist[i][j].u = ' ';
-		}
-	}
-
-	/* resize each row to new width, zero-pad if needed */
-	for (i = 0; i < minrow; i++) {
-		term.line[i] = xrealloc(term.line[i], col * sizeof(Glyph));
-		term.alt[i]  = xrealloc(term.alt[i],  col * sizeof(Glyph));
-	}
-
-	/* allocate any new rows */
-	for (/* i = minrow */; i < row; i++) {
-		term.line[i] = xmalloc(col * sizeof(Glyph));
-		term.alt[i] = xmalloc(col * sizeof(Glyph));
-	}
+	/* fix tabstops */
 	if (col > term.col) {
 		bp = term.tabs + term.col;
 
@@ -2669,26 +3065,16 @@ tresize(int col, int row)
 		for (bp += tabspaces; bp < term.tabs + col; bp += tabspaces)
 			*bp = 1;
 	}
+
 	/* update terminal size */
 	term.col = col;
 	term.row = row;
+	term.linelen = linelen;
 	/* reset scrolling region */
 	tsetscroll(0, row-1);
 	/* make use of the LIMIT in tmoveto */
 	tmoveto(term.c.x, term.c.y);
-	/* Clearing both screens (it makes dirty all lines) */
-	c = term.c;
-	for (i = 0; i < 2; i++) {
-		if (mincol < col && 0 < minrow) {
-			tclearregion(mincol, 0, col - 1, minrow - 1);
-		}
-		if (0 < col && minrow < row) {
-			tclearregion(0, minrow, col - 1, row - 1);
-		}
-		tswapscreen();
-		tcursor(CURSOR_LOAD);
-	}
-	term.c = c;
+	tfulldirt();
 }
 
 void
@@ -2700,15 +3086,20 @@ resettitle(void)
 void
 drawregion(int x1, int y1, int x2, int y2)
 {
-	int y;
+	int y, L;
 
-	for (y = y1; y < y2; y++) {
-		if (!term.dirty[y])
-			continue;
+	xstartimagedraw(term.dirty, term.row);
 
-		term.dirty[y] = 0;
-		xdrawline(TLINE(y), x1, y, x2);
+	L = TLINEOFFSET(y1);
+	for (y = y1; y < y2; y++) {
+		if (term.dirty[y]) {
+			term.dirty[y] = 0;
+			xdrawline(TSCREEN.buffer[L], x1, y, x2);
+		}
+		L = (L + 1) % TSCREEN.size;
 	}
+
+	xfinishimagedraw();
 }
 
 void
@@ -2722,16 +3113,16 @@ draw(void)
 	/* adjust cursor position */
 	LIMIT(term.ocx, 0, term.col-1);
 	LIMIT(term.ocy, 0, term.row-1);
-	if (term.line[term.ocy][term.ocx].mode & ATTR_WDUMMY)
+	if (TLINE(term.ocy)[term.ocx].mode & ATTR_WDUMMY)
 		term.ocx--;
-	if (term.line[term.c.y][cx].mode & ATTR_WDUMMY)
+	if (TLINE(term.c.y)[cx].mode & ATTR_WDUMMY)
 		cx--;
 
 	drawregion(0, 0, term.col, term.row);
-	if (term.scr == 0)
-		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);
+	if (TSCREEN.off == 0)
+		xdrawcursor(cx, term.c.y, TLINE(term.c.y)[cx],
+				term.ocx, term.ocy, TLINE(term.ocy)[term.ocx],
+				TLINE(term.ocy), term.col);
 	term.ocx = cx;
 	term.ocy = term.c.y;
 	xfinishdraw();
@@ -2745,3 +3136,9 @@ redraw(void)
 	tfulldirt();
 	draw();
 }
+
+Glyph
+getglyphat(int col, int row)
+{
+	return TLINE(row)[col];
+}