Determine the value of inline_img_protocol based on the invoking terminal

* Compile out enable_inline_img ifndef USE_IMAGE
* Add enable_inline_img_config for configuration; leave enable_inline_img
  for state
* Make auto-selection of inline_img_protocol the default value of
  enable_inline_img_config

Author: el-remph

display.c

@@ -530,12 +530,14 @@ drawAnchorCursor0(Buffer *buf, AnchorList *al, int hseq, int prevhseq,
 	    int start_pos = an->start.pos;
 	    int end_pos = an->end.pos;
 	    for (i = an->start.pos; i < an->end.pos; i++) {
-	        if (enable_inline_image && (l->propBuf[i] & PE_IMAGE)) {
+#ifdef USE_IMAGE
+		if (enable_inline_image && (l->propBuf[i] & PE_IMAGE)) {
 		    if (start_pos == i)
 			start_pos = i + 1;
 		    else if (end_pos == an->end.pos)
 		        end_pos = i - 1;
 		}
+#endif
 		if (l->propBuf[i] & (PE_IMAGE | PE_ANCHOR | PE_FORM)) {
 		    if (active)
 			l->propBuf[i] |= PE_ACTIVE;

fm.h

@@ -317,11 +317,14 @@ extern int REV_LB[];
 #define EOL(l) (&(l)->ptr[(l)->length])
 #define IS_EOL(p,l) ((p)==&(l)->ptr[(l)->length])
 
+#ifdef USE_IMAGE
+#define INLINE_IMG_AUTO		-1
 #define INLINE_IMG_NONE		0
 #define INLINE_IMG_OSC5379	1
 #define INLINE_IMG_SIXEL	2
 #define INLINE_IMG_ITERM2	3
 #define INLINE_IMG_KITTY	4
+#endif
 
 /* 
  * Types.
@@ -940,7 +943,10 @@ global char *CurrentKeyData;
 global char *CurrentCmdData;
 global char *w3m_reqlog;
 extern char *w3m_version;
-extern int enable_inline_image;
+#ifdef USE_IMAGE
+global unsigned char enable_inline_image init(INLINE_IMG_NONE);
+global signed char enable_inline_image_config init(INLINE_IMG_AUTO);
+#endif
 
 #define DUMP_BUFFER   0x01
 #define DUMP_HEAD     0x02

image.c

@@ -16,7 +16,7 @@ static int image_index = 0;
 
 /* display image */
 
-typedef struct _termialImage {
+typedef struct _terminalImage {
     ImageCache *cache;
     short x;
     short y;
@@ -34,10 +34,15 @@ static pid_t Imgdisplay_pid = 0;
 static int openImgdisplay(void);
 static void closeImgdisplay(void);
 static int getCharSize(void);
+static int inline_img_protocol_autodetect(void);
 
 void
 initImage()
 {
+    enable_inline_image = enable_inline_image_config == INLINE_IMG_AUTO
+	    ? inline_img_protocol_autodetect()
+	    : enable_inline_image_config;
+
     if (activeImage)
 	return;
     if (getCharSize())
@@ -133,6 +138,37 @@ openImgdisplay()
     return FALSE;
 }
 
+static int
+inline_img_protocol_autodetect(void)
+{
+    int result;
+    const char *env_term, *konsole_version;
+
+    if ((env_term = getenv("TERM"))) {
+	if (strcmp(env_term, "xterm-kitty") == 0)
+	    return INLINE_IMG_KITTY;
+	if (strcmp(env_term, "xterm-ghostty") == 0)
+	    return INLINE_IMG_KITTY;
+	/* yaft doesn't correctly respond to \e[c, but is sixel-capable
+	 * anyway. Thanks to hackerb9/lsix */
+	if (strncmp(env_term, "yaft", 4) == 0)
+	    return INLINE_IMG_SIXEL;
+    }
+
+    if ((konsole_version = getenv("KONSOLE_VERSION"))
+	&& strcmp(konsole_version, "220770") >= 0)
+	return INLINE_IMG_KITTY;
+
+    if ((result = img_protocol_test_for_sixel()) != INLINE_IMG_NONE)
+	return result;
+
+    /* If mlterm too old to support sixel, probably supports older OSC5379 */
+    if (env_term && strncmp(env_term, "mlterm", 6) == 0)
+	return INLINE_IMG_OSC5379;
+
+    return INLINE_IMG_NONE;
+}
+
 static void
 closeImgdisplay(void)
 {
@@ -256,6 +292,11 @@ drawImage(void)
 		put_image_iterm2(url, x, y, sw, sh);
 	    } else if (enable_inline_image == INLINE_IMG_KITTY) {
 		put_image_kitty(url, x, y, i->width, i->height, i->sx, i->sy, sw * pixel_per_char, sh * pixel_per_line_i, sw, sh);
+#ifdef DEBUG
+	    } else {
+		fprintf(stderr, "Unrecognised inline image protocol: %d\n",
+			enable_inline_image);
+#endif
 	    }
 
 	    continue ;

main.c

@@ -127,8 +127,6 @@ static int searchKeyNum(void);
 #define help() fusage(stdout, 0)
 #define usage() fusage(stderr, 1)
 
-int enable_inline_image;
-
 static void
 fversion(FILE * f)
 {
@@ -719,13 +717,13 @@ main(int argc, char **argv)
 		    set_pixel_per_line = TRUE;
 		}
 	    }
-#endif
 	    else if (!strcmp("-ri", argv[i])) {
 	        enable_inline_image = INLINE_IMG_OSC5379;
 	    }
 	    else if (!strcmp("-sixel", argv[i])) {
 		enable_inline_image = INLINE_IMG_SIXEL;
 	    }
+#endif
 	    else if (!strcmp("-num", argv[i]))
 		showLineNum = TRUE;
 	    else if (!strcmp("-no-proxy", argv[i]))
@@ -6006,11 +6004,13 @@ deleteFiles()
     }
     while ((f = popText(fileToDelete)) != NULL) {
 	unlink(f);
+#ifdef USE_IMAGE
 	if (enable_inline_image == INLINE_IMG_SIXEL && strcmp(f+strlen(f)-4, ".gif") == 0) {
 	    Str firstframe = Strnew_charp(f);
 	    Strcat_charp(firstframe, "-1");
 	    unlink(firstframe->ptr);
         }
+#endif
     }
 }
 

rc.c

@@ -377,6 +377,7 @@ static struct sel_c graphic_char_str[] = {
 
 #ifdef USE_IMAGE
 static struct sel_c inlineimgstr[] = {
+    {N_S(INLINE_IMG_AUTO), N_("auto-select protocol")},
     {N_S(INLINE_IMG_NONE), N_("external command")},
     {N_S(INLINE_IMG_OSC5379), N_("OSC 5379 (mlterm)")},
     {N_S(INLINE_IMG_SIXEL), N_("sixel (img2sixel)")},
@@ -449,7 +450,7 @@ struct param_ptr params1[] = {
      CMT_EXT_IMAGE_VIEWER, NULL},
     {"image_scale", P_SCALE, PI_TEXT, (void *)&image_scale, CMT_IMAGE_SCALE,
      NULL},
-    {"inline_img_protocol", P_INT, PI_SEL_C, (void *)&enable_inline_image,
+    {"inline_img_protocol", P_CHARINT, PI_SEL_C, (void *)&enable_inline_image_config,
      CMT_INLINE_IMG_PROTOCOL, (void *)inlineimgstr},
     {"imgdisplay", P_STRING, PI_TEXT, (void *)&Imgdisplay, CMT_IMGDISPLAY,
      NULL},
@@ -1313,7 +1314,7 @@ sync_with_option(void)
     init_migemo();
 #endif
 #ifdef USE_IMAGE
-    if (fmInitialized && (displayImage || enable_inline_image))
+    if (fmInitialized && (displayImage || enable_inline_image_config))
 	initImage();
 #else
     displayImage = FALSE;	/* XXX */

terms.c

@@ -856,6 +856,112 @@ put_image_sixel(char *url, int x, int y, int w, int h, int sx, int sy, int sw, i
     MOVE(Currentbuf->cursorY,Currentbuf->cursorX);
 }
 
+static int
+have_img2sixel(void)
+{
+    pid_t child_pid;
+    int wstatus;
+
+    if (getenv("W3M_IMG2SIXEL"))
+	return TRUE;
+
+    switch (child_pid = fork()) {
+    case -1:
+	return FALSE;
+    case 0:
+	close(STDOUT_FILENO);
+	close(STDERR_FILENO);
+	execlp("img2sixel", "img2sixel", "--version", NULL);
+	/* if exec fails */
+	_exit(-1);
+    default:
+	return
+#ifdef HAVE_WAITPID
+	    waitpid(child_pid, &wstatus, 0) != -1
+#else
+	    wait(&wstatus) != -1
+#endif
+	    && WIFEXITED(wstatus)
+	    && WEXITSTATUS(wstatus) == 0;
+    }
+}
+
+/*
+ * NB: in theory, user input could be snarfed up with the read(2); in practice,
+ * only museum pieces have such low latency, so we should get the device
+ * attributes (and only the device attributes) immediately. If ever this becomes
+ * an issue (which it won't), ungetch(3) can be used on any extraneous input
+ */
+int
+img_protocol_test_for_sixel(void)
+{
+    static const char errstr[] = "Can't get terminal attributes";
+    size_t response_size = 256, len = 0;
+    char *response = GC_MALLOC_ATOMIC(response_size);
+
+    /* request tty send primary device attributes */
+    write(tty, "\033[c", 3);
+
+    /* loop until we get the whole response */
+    for (; response; response = GC_REALLOC(response, response_size *= 2)) {
+	ssize_t nchars_read;
+	int nret;
+	fd_set fds;
+	/* wait 0.2s (from get_pixel_per_char()) for input */
+	struct timeval timeout = { 0, 0.2 * 1000000 };
+	FD_ZERO(&fds);
+	FD_SET(tty, &fds);
+	if ((nret = select(tty + 1, &fds, NULL, NULL, &timeout)) <= 0) {
+	    fprintf(stderr, "%s: %s\n",
+		errstr, nret == 0 ? "timed out" : strerror(errno));
+	    return INLINE_IMG_NONE;
+	}
+
+	nchars_read = read(tty, response + len, response_size - len - 1);
+	if (nchars_read < 0) {
+	    perror(errstr);
+	    return INLINE_IMG_NONE;
+	}
+
+	/* first useful iteration; validate response */
+	if (nchars_read + len >= 3 && memcmp(response, "\033[?", 3) != 0) {
+	    fputs("Malformed terminal attributes\n", stderr);
+	    return INLINE_IMG_NONE;
+	}
+
+	/* NUL-terminate the terminal response */
+	{
+	    char *ptr = memchr(response + len, 'c', nchars_read);
+	    if (ptr) {
+		ptr[1] = '\0';
+		break;
+	    }
+	}
+
+	/* if we can't find 'c', then the response is incomplete; try again */
+	len += (size_t)nchars_read;
+    }
+
+    /* separate the response parameters by ';' and look for '4' */
+    if (response) {
+	char *ptr = response;
+	while ((ptr = strchr(ptr, ';'))) {
+	    if (*++ptr != '4')
+		continue;
+	    switch (*++ptr) {
+	    case ';':
+	    case 'c':
+		if (have_img2sixel())
+		    return INLINE_IMG_SIXEL;
+	    }
+	}
+    } else
+	perror(errstr);
+
+    /* default */
+    return INLINE_IMG_NONE;
+}
+
 int
 get_pixel_per_cell(int *ppc, int *ppl)
 {

terms.h

@@ -35,6 +35,7 @@ extern void put_image_osc5379(char *url, int x, int y, int w, int h, int sx, int
 extern void put_image_sixel(char *url, int x, int y, int w, int h, int sx, int sy, int sw, int sh, int n_terminal_image);
 extern void put_image_iterm2(char *url, int x, int y, int w, int h);
 extern void put_image_kitty(char *url, int x, int y, int w, int h, int sx, int sy, int sw, int sh, int c, int r);
+extern int img_protocol_test_for_sixel(void);
 extern int get_pixel_per_cell(int *ppc, int *ppl);
 #endif