Bug 871: Fall back to 16 colors if color_mode is unsupported.

There may currently be no way to select an unsupported mode,
but the next commit will change that.

src/terminal/color.c

@@ -301,6 +301,9 @@ set_term_color(struct screen_char *schar, struct color_pair *pair,
 		}
 		break;
 
+	default:
+		/* If the desired color mode was not compiled in,
+		 * use 16 colors.  */
 	case COLOR_MODE_16:
 		/* Decrease the range of the 16 palette to not include
 		 * bright colors. */
@@ -386,6 +389,9 @@ set_term_color(struct screen_char *schar, struct color_pair *pair,
 	case COLOR_MODE_TRUE_COLOR:
 		return;
 #endif
+	default:
+		/* If the desired color mode was not compiled in,
+		 * use 16 colors.  */
 	case COLOR_MODE_MONO:
 	case COLOR_MODE_16:
 		set_term_color16(schar, flags, fg, bg);

src/terminal/screen.c

@@ -612,7 +612,15 @@ add_char16(struct string *screen, struct screen_driver *driver,
 
 		add_bytes_to_string(screen, "\033[0", 3);
 
-		if (driver->color_mode == COLOR_MODE_16) {
+		/* @update_screen_driver has set @driver->color_mode
+		 * according to terminal-type-specific options.
+		 * The caller of @add_char16 has already partially
+		 * checked it, but there are still these possibilities:
+		 * - COLOR_MODE_MONO.  Then don't show colors, but
+		 *   perhaps use the standout attribute.
+		 * - COLOR_MODE_16.  Use 16 colors.
+		 * - An unsupported color mode.  Use 16 colors.  */
+		if (driver->color_mode != COLOR_MODE_MONO) {
 			unsigned char code[6] = ";30;40";
 			unsigned char bgcolor = TERM_COLOR_BACKGROUND_16(ch->color);
 
@@ -956,6 +964,9 @@ redraw_screen(struct terminal *term)
 	if (!init_string(&image)) return;
 
 	switch (driver->color_mode) {
+	default:
+		/* If the desired color mode was not compiled in,
+		 * use 16 colors.  */
 	case COLOR_MODE_MONO:
 	case COLOR_MODE_16:
 		add_chars(&image, term, driver, &state, add_char16, compare_bg_color_16, compare_fg_color_16);
@@ -977,7 +988,6 @@ redraw_screen(struct terminal *term)
 #endif
 	case COLOR_MODES:
 	case COLOR_MODE_DUMP:
-	default:
 		INTERNAL("Invalid color mode (%d).", driver->color_mode);
 		return;
 	}

src/viewer/dump/dump.c

@@ -132,6 +132,9 @@ dump_formatted(int fd, struct download *download, struct cache_entry *cached)
 	case COLOR_MODE_MONO: /* FIXME: inversion */
 		dump_to_file(formatted.document, fd);
 		break;
+	default:
+		/* If the desired color mode was not compiled in,
+		 * use 16 colors.  */
 	case COLOR_MODE_16:
 		dump_to_file_16(formatted.document, fd);
 		break;
@@ -150,8 +153,6 @@ dump_formatted(int fd, struct download *download, struct cache_entry *cached)
 		dump_to_file_true_color(formatted.document, fd);
 		break;
 #endif
-	default:
-		break;
 	}
 
 	detach_formatted(&formatted);