gdb/python/guile: check if styling is disabled in Color.escape_sequence

I noticed that the gdb.Color.escape_sequence() method would produce an
escape sequence even when styling is disabled.

I think this is the wrong choice.  Ideally, when styling is
disabled (e.g. with 'set style enabled off'), GDB should not be
producing styled output.

If a GDB extension is using gdb.Color to apply styling to the output,
then currently, the extension should be checking 'show style enabled'
any time Color.escape_sequence() is used.  This means lots of code
duplication, and the possibility that some locations will be missed,
which means disabling styling no longer does what it says.

I propose that Color.escape_sequence() should return the empty string
if styling is disabled.  A Python extension can then do:

  python
  c_none = gdb.Color('none')
  c_red = gdb.Color('red')
  print(c_red.escape_sequence(True)
        + "Text in red."
        + c_none.escape_sequence(True))
  end

If styling is enable this will print some red text.  And if styling is
disabled, then it will print text in the terminal's default color.

I have applied the same fix to the guile API.

I have extended the tests to cover this case.

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

1 files changed, 7 insertions, 2 deletions

diff --git a/gdb/python/py-color.c b/gdb/python/py-color.c
index e208506..3bbd22d 100644
--- a/gdb/python/py-color.c
+++ b/gdb/python/py-color.c
@@ -21,6 +21,7 @@
 #include "python-internal.h"
 #include "py-color.h"
 #include "cli/cli-decode.h"
+#include "cli/cli-style.h"
 
 /* Colorspace constants and their values.  */
 static struct {
@@ -152,8 +153,12 @@ colorpy_escape_sequence (PyObject *self, PyObject *args, PyObject *kwargs)
   /* The argument parsing ensures we have a bool.  */
   gdb_assert (PyBool_Check (is_fg_obj));
 
-  bool is_fg = is_fg_obj == Py_True;
-  std::string s = gdbpy_get_color (self).to_ansi (is_fg);
+  std::string s;
+  if (term_cli_styling ())
+    {
+      bool is_fg = is_fg_obj == Py_True;
+      s = gdbpy_get_color (self).to_ansi (is_fg);
+    }
 
   return host_string_to_python_string (s.c_str ()).release ();
 }