Add tool to display emergency log message full-screen on boot failure.

src/basic/terminal-util.c

@@ -1535,3 +1535,18 @@ void get_log_colors(int priority, const char **on, const char **off, const char
                         *highlight = ansi_highlight_red();
         }
 }
+
+int set_terminal_cursor_position(int fd, unsigned int row, unsigned int column) {
+        int r;
+        char cursor_position[STRLEN("\x1B[") + DECIMAL_STR_MAX(int) * 2 + STRLEN(";H") + 1];
+
+        assert(fd >= 0);
+
+        xsprintf(cursor_position, "\x1B[%u;%uH", row, column);
+
+        r = loop_write(fd, cursor_position, SIZE_MAX, /* do_poll = */false);
+        if (r < 0)
+                return log_warning_errno(r, "Failed to set cursor position, ignoring: %m");
+
+        return 0;
+}

src/basic/terminal-util.h

@@ -68,6 +68,9 @@
 #define ANSI_HIGHLIGHT_YELLOW_FALLBACK           "\x1B[0;1;33m"
 #define ANSI_HIGHLIGHT_YELLOW_FALLBACK_UNDERLINE "\x1B[0;1;4;33m"
 
+/* Background colors */
+#define ANSI_BACKGROUND_BLUE "\x1B[44m"
+
 /* Reset/clear ANSI styles */
 #define ANSI_NORMAL "\x1B[0m"
 
@@ -82,6 +85,7 @@
 
 int reset_terminal_fd(int fd, bool switch_to_text);
 int reset_terminal(const char *name);
+int set_terminal_cursor_position(int fd, unsigned int row, unsigned int column);
 
 int open_terminal(const char *name, int mode);