[UI/TUI] Add support for italic and underline ANSI escape sequences

The ANSI escape sequence translation layer in TUI mode strips italic
or underlined text modes silently. You cannot output text formatted
like that using `TuiWindow.write` in Python at the moment.

Parse the ANSI escape sequences for italic and underlined text into
the `ui_file_style` structure and apply it to the TUI window when
applying styles, similar to preserving the bold/dim state already.

A script like this shows italic and underlined text correctly now.
```python
import gdb

class TestTUIWindow:
    _tui_window: gdb.TuiWindow

    def __init__(self, tui_window: gdb.TuiWindow) -> None:
        self._tui_window = tui_window
        self._tui_window.title = "colors test"

    def render(self) -> None:
        self._tui_window.write("""
\x1b[4mThis is underlined.\x1b[24m And normal text.
\x1b[3mThis is italic.\x1b[23m And normal text.
""", True)

gdb.register_window_type("colortest", TestTUIWindow)
```

And launching it with
```
source the_above_script.py
tui new-layout test colortest 1 cmd 1
layout test
```

Approved-By: Tom Tromey <tom@tromey.com>

6 files changed, 107 insertions, 15 deletions

diff --git a/gdb/testsuite/gdb.base/style.exp b/gdb/testsuite/gdb.base/style.exp
index 47efb64..a6c18d3 100644
--- a/gdb/testsuite/gdb.base/style.exp
+++ b/gdb/testsuite/gdb.base/style.exp
@@ -323,10 +323,10 @@ proc run_style_tests { } {
 	    gdb_test_no_output "set style version background 255"
 	    gdb_test_no_output "set style version foreground #FED210"
 	    gdb_test "show style version background" \
-		"The \033\\\[38;2;254;210;16;48;5;255;22;27m.*\".*version.*\".*style.*\033\\\[m background color is: 255" \
+		"The \033\\\[38;2;254;210;16;48;5;255;22;23;24;27m.*\".*version.*\".*style.*\033\\\[m background color is: 255" \
 		"Version's 256-color background style"
 	    gdb_test "show style version foreground" \
-		"The \033\\\[38;2;254;210;16;48;5;255;22;27m.*\".*version.*\".*style.*\033\\\[m foreground color is: #FED210" \
+		"The \033\\\[38;2;254;210;16;48;5;255;22;23;24;27m.*\".*version.*\".*style.*\033\\\[m foreground color is: #FED210" \
 		"Version's TrueColor foreground style"
 	}
 
@@ -782,7 +782,7 @@ proc test_pagination_cmd_after_quit_styling {} {
 	    -re "^apropos time\r\n" {
 		exp_continue
 	    }
-	    -re "^\033\\\[39;49;1;27m\[^\r\n\]+\r\n" {
+	    -re "^\033\\\[39;49;1;23;24;27m\[^\r\n\]+\r\n" {
 		exp_continue
 	    }
 	    -re "^$::pagination_prompt$" {
@@ -828,7 +828,7 @@ proc test_pagination_cmd_after_quit_styling {} {
     # non-default style that was in use when pagination kicked in
     # above.
     gdb_test "maintenance time" \
-	"^\"\033\\\[39;49;1;27mmaintenance time\033\\\[m\" takes a numeric argument\\."
+	"^\"\033\\\[39;49;1;23;24;27mmaintenance time\033\\\[m\" takes a numeric argument\\."
 }
 
 # Helper for test_pagination_prompt_styling.  Return false if STR, a
@@ -995,20 +995,20 @@ proc test_pagination_continue_styling_1 { length } {
 	    exp_continue
 	}
 
-	-re "^The current logfile is \"\033\\\[32;49;22;27m(?:ax)+\033\\\[m" {
+	-re "^The current logfile is \"\033\\\[32;49;22;23;24;27m(?:ax)+\033\\\[m" {
 	    exp_continue
 	}
 
-	-re "^\r\n\033\\\[32;49;22;27m(?:ax)+\033\\\[m(?=--)" {
+	-re "^\r\n\033\\\[32;49;22;23;24;27m(?:ax)+\033\\\[m(?=--)" {
 	    exp_continue
 	}
 
-	-re "^\r\n\033\\\[32;49;22;27m(?:ax)+(?=--)" {
+	-re "^\r\n\033\\\[32;49;22;23;24;27m(?:ax)+(?=--)" {
 	    set saw_bad_styling true
 	    exp_continue
 	}
 
-	-re "^\r\n\033\\\[32;49;22;27m(?:ax)+\033\\\[m\"\\.\r\n" {
+	-re "^\r\n\033\\\[32;49;22;23;24;27m(?:ax)+\033\\\[m\"\\.\r\n" {
 	    exp_continue
 	}
 
diff --git a/gdb/testsuite/lib/gdb-utils.exp b/gdb/testsuite/lib/gdb-utils.exp
index fe2cfca..c24e7ed 100644
--- a/gdb/testsuite/lib/gdb-utils.exp
+++ b/gdb/testsuite/lib/gdb-utils.exp
@@ -70,6 +70,8 @@ proc style {str style} {
     set fg 39
     set bg 49
     set intensity 22
+    set italic 23
+    set underline 24
     set reverse 27
     switch -exact -- $style {
 	title { set intensity 1 }
@@ -84,7 +86,7 @@ proc style {str style} {
 	line-number { set intensity 2 }
 	none { return $str }
     }
-    return "\033\\\[${fg};${bg};${intensity};${reverse}m${str}\033\\\[m"
+    return "\033\\\[${fg};${bg};${intensity};${italic};${underline};${reverse}m${str}\033\\\[m"
 }
 
 # gdb_get_bp_addr num
diff --git a/gdb/tui/tui-io.c b/gdb/tui/tui-io.c
index 1b4cc82..c97e8fd 100644
--- a/gdb/tui/tui-io.c
+++ b/gdb/tui/tui-io.c
@@ -319,6 +319,8 @@ tui_apply_style (WINDOW *w, ui_file_style style)
   wattron (w, A_NORMAL);
   wattroff (w, A_BOLD);
   wattroff (w, A_DIM);
+  wattroff (w, A_ITALIC);
+  wattroff (w, A_UNDERLINE);
   wattroff (w, A_REVERSE);
   if (last_color_pair != -1)
     wattroff (w, COLOR_PAIR (last_color_pair));
@@ -366,6 +368,12 @@ tui_apply_style (WINDOW *w, ui_file_style style)
       gdb_assert_not_reached ("invalid intensity");
     }
 
+  if (style.is_italic ())
+    wattron (w, A_ITALIC);
+
+  if (style.is_underline ())
+    wattron (w, A_UNDERLINE);
+
   if (style.is_reverse ())
     wattron (w, A_REVERSE);
 
diff --git a/gdb/ui-style.c b/gdb/ui-style.c
index c8f2e11..9a58e4d 100644
--- a/gdb/ui-style.c
+++ b/gdb/ui-style.c
@@ -290,6 +290,16 @@ ui_file_style::to_ansi () const
       else
 	result.append (std::to_string (m_intensity));
       result.push_back (';');
+      if (m_italic)
+	result.append ("3");
+      else
+	result.append ("23");
+      result.push_back (';');
+      if (m_underline)
+	result.append ("4");
+      else
+	result.append ("24");
+      result.push_back (';');
       if (m_reverse)
 	result.push_back ('7');
       else
@@ -435,6 +445,14 @@ ui_file_style::parse (const char *buf, size_t *n_read)
 	      /* Dim.  */
 	      m_intensity = DIM;
 	      break;
+	    case 3:
+	      /* Italic.  */
+	      m_italic = true;
+	      break;
+	    case 4:
+	      /* Underline.  */
+	      m_underline = true;
+	      break;
 	    case 7:
 	      /* Reverse.  */
 	      m_reverse = true;
@@ -446,6 +464,14 @@ ui_file_style::parse (const char *buf, size_t *n_read)
 	      /* Normal.  */
 	      m_intensity = NORMAL;
 	      break;
+	    case 23:
+	      /* Non-italic.  */
+	      m_italic = false;
+	      break;
+	    case 24:
+	      /* Non-underline.  */
+	      m_underline = false;
+	      break;
 	    case 27:
 	      /* Inverse off.  */
 	      m_reverse = false;
diff --git a/gdb/ui-style.h b/gdb/ui-style.h
index f61152f..1ea3556 100644
--- a/gdb/ui-style.h
+++ b/gdb/ui-style.h
@@ -266,7 +266,9 @@ struct ui_file_style
     return (m_foreground == other.m_foreground
 	    && m_background == other.m_background
 	    && m_intensity == other.m_intensity
-	    && m_reverse == other.m_reverse);
+	    && m_reverse == other.m_reverse
+	    && m_italic == other.m_italic
+	    && m_underline == other.m_underline);
   }
 
   bool operator!= (const ui_file_style &other) const
@@ -284,7 +286,9 @@ struct ui_file_style
     return (m_foreground == NONE
 	    && m_background == NONE
 	    && m_intensity == NORMAL
-	    && !m_reverse);
+	    && !m_reverse
+	    && !m_italic
+	    && !m_underline);
   }
 
   /* Return true if this style specified reverse display; false
@@ -330,6 +334,32 @@ struct ui_file_style
     return m_intensity;
   }
 
+  /* Return true if this style specified italic display; false
+     otherwise.  */
+  bool is_italic () const
+  {
+    return m_italic;
+  }
+
+  /* Set/clear the italic display flag.  */
+  void set_italic (bool italic)
+  {
+    m_italic = italic;
+  }
+
+  /* Return true if this style specified underline display; false
+     otherwise.  */
+  bool is_underline () const
+  {
+    return m_underline;
+  }
+
+  /* Set/clear the underline display flag.  */
+  void set_underline (bool underline)
+  {
+    m_underline = underline;
+  }
+
   /* Parse an ANSI escape sequence in BUF, modifying this style.  BUF
      must begin with an ESC character.  Return true if an escape
      sequence was successfully parsed; false otherwise.  In either
@@ -351,6 +381,8 @@ private:
   color m_foreground = NONE;
   color m_background = NONE;
   intensity m_intensity = NORMAL;
+  bool m_italic = false;
+  bool m_underline = false;
   bool m_reverse = false;
 };
 
diff --git a/gdb/unittests/style-selftests.c b/gdb/unittests/style-selftests.c
index f2a37bb..7cb42a1 100644
--- a/gdb/unittests/style-selftests.c
+++ b/gdb/unittests/style-selftests.c
@@ -38,6 +38,8 @@ run_tests ()
   SELF_CHECK (style.get_foreground ().is_none ());
   SELF_CHECK (style.get_background ().is_none ());
   SELF_CHECK (style.get_intensity () == ui_file_style::NORMAL);
+  SELF_CHECK (!style.is_italic ());
+  SELF_CHECK (!style.is_underline ());
   SELF_CHECK (!style.is_reverse ());
   SELF_CHECK (style.to_ansi () == "\033[m");
 
@@ -47,6 +49,8 @@ run_tests ()
   SELF_CHECK (style.get_foreground ().is_none ());
   SELF_CHECK (style.get_background ().is_none ());
   SELF_CHECK (style.get_intensity () == ui_file_style::NORMAL);
+  SELF_CHECK (!style.is_italic ());
+  SELF_CHECK (!style.is_underline ());
   SELF_CHECK (!style.is_reverse ());
   /* This particular case does not round-trip identically, but the
      difference is unimportant.  */
@@ -57,8 +61,10 @@ run_tests ()
   SELF_CHECK (style.get_foreground ().is_none ());
   SELF_CHECK (style.get_background ().is_none ());
   SELF_CHECK (style.get_intensity () == ui_file_style::NORMAL);
+  SELF_CHECK (!style.is_italic ());
+  SELF_CHECK (!style.is_underline ());
   SELF_CHECK (style.is_reverse ());
-  SELF_CHECK (style.to_ansi () == "\033[39;49;22;7m");
+  SELF_CHECK (style.to_ansi () == "\033[39;49;22;23;24;7m");
 
   style = ui_file_style ();
   SELF_CHECK (style.parse ("\033[32;1m", &n_read));
@@ -67,8 +73,22 @@ run_tests ()
   SELF_CHECK (style.get_foreground ().get_value () == ui_file_style::GREEN);
   SELF_CHECK (style.get_background ().is_none ());
   SELF_CHECK (style.get_intensity () == ui_file_style::BOLD);
+  SELF_CHECK (!style.is_italic ());
+  SELF_CHECK (!style.is_underline ());
   SELF_CHECK (!style.is_reverse ());
-  SELF_CHECK (style.to_ansi () == "\033[32;49;1;27m");
+  SELF_CHECK (style.to_ansi () == "\033[32;49;1;23;24;27m");
+
+  style = ui_file_style ();
+  SELF_CHECK (style.parse ("\033[32;2;3;4m", &n_read));
+  SELF_CHECK (n_read == 11);
+  SELF_CHECK (style.get_foreground ().is_basic ());
+  SELF_CHECK (style.get_foreground ().get_value () == ui_file_style::GREEN);
+  SELF_CHECK (style.get_background ().is_none ());
+  SELF_CHECK (style.get_intensity () == ui_file_style::DIM);
+  SELF_CHECK (style.is_italic ());
+  SELF_CHECK (style.is_underline ());
+  SELF_CHECK (!style.is_reverse ());
+  SELF_CHECK (style.to_ansi () == "\033[32;49;2;3;4;27m");
 
   style = ui_file_style ();
   SELF_CHECK (style.parse ("\033[38;5;112;48;5;249m", &n_read));
@@ -80,8 +100,10 @@ run_tests ()
   style.get_background ().get_rgb (rgb);
   CHECK_RGB (0xb2, 0xb2, 0xb2);
   SELF_CHECK (style.get_intensity () == ui_file_style::NORMAL);
+  SELF_CHECK (!style.is_italic ());
+  SELF_CHECK (!style.is_underline ());
   SELF_CHECK (!style.is_reverse ());
-  SELF_CHECK (style.to_ansi () == "\033[38;5;112;48;5;249;22;27m");
+  SELF_CHECK (style.to_ansi () == "\033[38;5;112;48;5;249;22;23;24;27m");
 
   style = ui_file_style ();
   SELF_CHECK (style.parse ("\033[38;2;83;84;85;48;2;0;1;254;2;7m", &n_read));
@@ -93,8 +115,10 @@ run_tests ()
   style.get_background ().get_rgb (rgb);
   CHECK_RGB (0, 1, 254);
   SELF_CHECK (style.get_intensity () == ui_file_style::DIM);
+  SELF_CHECK (!style.is_italic ());
+  SELF_CHECK (!style.is_underline ());
   SELF_CHECK (style.is_reverse ());
-  SELF_CHECK (style.to_ansi () == "\033[38;2;83;84;85;48;2;0;1;254;2;7m");
+  SELF_CHECK (style.to_ansi () == "\033[38;2;83;84;85;48;2;0;1;254;2;23;24;7m");
 }
 
 } /* namespace style */