Re: [PATCH 00/16] Add styling to the gdb CLI and TUI

[Eli Zaretskii <eliz@gnu.org>]

> From: Tom Tromey <tom@tromey.com>
> Cc: Tom Tromey <tom@tromey.com>,  gdb-patches@sourceware.org
> Date: Fri, 01 Mar 2019 14:03:58 -0700
> 
> Another way would be to just make a new function and implement it
> differently in mingw-hdep.c and in posix-hdep.c.

Here's a working prototype I'm currently testing.  If this
implementation strategy is acceptable, I will post a proper patch
soon.

Thanks for the guidance.

--- ./gdb/cli/cli-style.c~1	2019-02-27 06:51:50.000000000 +0200
+++ ./gdb/cli/cli-style.c	2019-03-03 17:26:34.122234300 +0200
@@ -24,7 +24,7 @@
 
 /* True if styling is enabled.  */
 
-#if defined(_WIN32) || defined (__CYGWIN__)
+#if defined (__MSDOS__) || defined (__CYGWIN__)
 int cli_styling = 0;
 #else
 int cli_styling = 1;
--- ./gdb/mingw-hdep.c~1	2019-02-27 06:51:50.000000000 +0200
+++ ./gdb/mingw-hdep.c	2019-03-03 17:15:24.608418300 +0200
@@ -177,3 +177,166 @@ gdb_select (int n, fd_set *readfds, fd_s
 
   return num_ready;
 }
+
+/* Zero if not yet initialized, 1 if stdout is a console device, else -1.  */
+static int mingw_console_initialized;
+
+/* Handle to stdout . */
+static HANDLE hstdout = INVALID_HANDLE_VALUE;
+
+/* Text attribute to use for normal text (the "none" pseudo-color).  */
+static SHORT  norm_attr;
+
+/* The most recently applied style.  */
+static ui_file_style last_style;
+
+/* Alternative for the libc 'fputs' which handles embedded SGR
+   sequences in support of styling.  */
+
+int
+gdb_console_fputs (const char *linebuf, FILE *fstream)
+{
+  if (!mingw_console_initialized)
+    {
+      hstdout = (HANDLE)_get_osfhandle (fileno (fstream));
+      DWORD cmode;
+      CONSOLE_SCREEN_BUFFER_INFO csbi;
+
+      if (hstdout != INVALID_HANDLE_VALUE
+	  && GetConsoleMode (hstdout, &cmode) != 0
+	  && GetConsoleScreenBufferInfo (hstdout, &csbi))
+	{
+	  norm_attr = csbi.wAttributes;
+	  mingw_console_initialized = 1;
+	}
+      else if (hstdout != INVALID_HANDLE_VALUE)
+	mingw_console_initialized = -1; /* valid, but not a console device */
+    }
+  /* If our stdout is not a console device, let the default 'fputs'
+     handle the task. */
+  if (mingw_console_initialized <= 0)
+    return 0;
+
+  /* Mapping between 8 ANSI colors and Windows console attributes.  */
+  static int fg_color[] = {
+    0,					/* black */
+    FOREGROUND_RED,			/* red */
+    FOREGROUND_GREEN,			/* green */
+    FOREGROUND_GREEN | FOREGROUND_RED,	/* yellow */
+    FOREGROUND_BLUE,			/* blue */
+    FOREGROUND_BLUE | FOREGROUND_RED,	/* magenta */
+    FOREGROUND_BLUE | FOREGROUND_GREEN, /* cyan */
+    FOREGROUND_RED | FOREGROUND_GREEN | FOREGROUND_BLUE /* gray */
+  };
+  static int bg_color[] = {
+    0,					/* black */
+    BACKGROUND_RED,			/* red */
+    BACKGROUND_GREEN,			/* green */
+    BACKGROUND_GREEN | BACKGROUND_RED,	/* yellow */
+    BACKGROUND_BLUE,			/* blue */
+    BACKGROUND_BLUE | BACKGROUND_RED,	/* magenta */
+    BACKGROUND_BLUE | BACKGROUND_GREEN, /* cyan */
+    BACKGROUND_RED | BACKGROUND_GREEN | BACKGROUND_BLUE /* gray */
+  };
+
+  ui_file_style style = last_style;
+  unsigned char c;
+  size_t n_read;
+
+  for ( ; (c = *linebuf) != 0; linebuf += n_read)
+    {
+      if (c == '\033')
+	{
+	  fflush (fstream);
+	  bool parsed = style.parse (linebuf, &n_read);
+	  if (n_read <= 0)	/* should never happen */
+	    n_read = 1;
+	  if (!parsed)
+	    {
+	      /* This means we silently swallow SGR sequences we
+		 cannot parse.  */
+	      continue;
+	    }
+	  /* Colors.  */
+	  const ui_file_style::color &fg = style.get_foreground ();
+	  const ui_file_style::color &bg = style.get_background ();
+	  int fgcolor, bgcolor, bright, inverse;
+	  if (fg.is_none ())
+	    fgcolor = norm_attr & 15;
+	  else
+	    fgcolor = fg_color[fg.get_value () & 15];
+	  if (bg.is_none ())
+	    bgcolor = norm_attr & (15 << 4);
+	  else
+	    bgcolor = bg_color[bg.get_value () & 15];
+
+	  /* Intensity.  */
+	  switch (style.get_intensity ())
+	    {
+	    case ui_file_style::NORMAL:
+	    case ui_file_style::DIM:
+	      bright = 0;
+	      break;
+	    case ui_file_style::BOLD:
+	      bright = 1;
+	      break;
+	    default:
+	      gdb_assert_not_reached ("invalid intensity");
+	    }
+
+	  /* Inverse video.  */
+	  if (style.is_reverse ())
+	    inverse = 1;
+	  else
+	    inverse = 0;
+
+	  /* Construct the attribute.  */
+	  if (inverse)
+	    {
+	      int t = fgcolor;
+	      fgcolor = (bgcolor >> 4);
+	      bgcolor = (t << 4);
+	    }
+	  if (bright)
+	    fgcolor |= FOREGROUND_INTENSITY;
+
+	  SHORT attr = (bgcolor & (15 << 4)) | (fgcolor & 15);
+
+	  /* Apply the attribute.  */
+	  SetConsoleTextAttribute (hstdout, attr);
+	}
+      else
+	{
+	  /* When we are about to write newline, we need to clear to
+	     EOL with the normal attribute, to avoid spilling the
+	     colors to the next screen line.  We assume here that no
+	     non-default attribute extends beyond the newline.  */
+	  if (c == '\n')
+	    {
+	      DWORD nchars;
+	      COORD start_pos;
+	      DWORD written;
+	      CONSOLE_SCREEN_BUFFER_INFO csbi;
+
+	      fflush (fstream);
+	      GetConsoleScreenBufferInfo (hstdout, &csbi);
+
+	      if (csbi.wAttributes != norm_attr)
+		{
+		  start_pos = csbi.dwCursorPosition;
+		  nchars = csbi.dwSize.X - start_pos.X;
+
+		  FillConsoleOutputAttribute (hstdout, norm_attr, nchars,
+					      start_pos, &written);
+		  FillConsoleOutputCharacter (hstdout, ' ', nchars,
+					      start_pos, &written);
+		}
+	    }
+	  fputc (c, fstream);
+	  n_read = 1;
+	}
+    }
+
+  last_style = style;
+  return 1;
+}
--- ./gdb/posix-hdep.c~1	2019-02-27 06:51:50.000000000 +0200
+++ ./gdb/posix-hdep.c	2019-03-03 17:34:32.870539500 +0200
@@ -30,3 +30,11 @@ gdb_select (int n, fd_set *readfds, fd_s
 {
   return select (n, readfds, writefds, exceptfds, timeout);
 }
+
+/* Host-dependent console fputs method.  POSIX platforms always return
+   zero, to use the default C 'fputs'.  */
+int
+gdb_console_fputs (const char *buf, FILE *f)
+{
+  return 0;
+}
--- ./gdb/ui-file.c~1	2019-02-27 06:51:50.000000000 +0200
+++ ./gdb/ui-file.c	2019-03-03 17:32:02.526701100 +0200
@@ -236,6 +236,12 @@ stdio_file::write_async_safe (const char
 void
 stdio_file::puts (const char *linebuffer)
 {
+  /* This host-dependent function (with implementations in
+     posix-hdep.c and mingw-hdep.c) is given the opportunity to
+     process the output first in host-dependent way.  If it does, it
+     should return non-zero, to avoid calling fputs below.  */
+  if (gdb_console_fputs (linebuffer, m_file))
+    return;
   /* Calling error crashes when we are called from the exception framework.  */
   if (fputs (linebuffer, m_file))
     {
--- ./gdb/ui-file.h~1	2019-02-27 06:51:50.000000000 +0200
+++ ./gdb/ui-file.h	2019-03-03 17:40:00.605222700 +0200
@@ -101,6 +101,8 @@
 
 extern long ui_file_read (struct ui_file *file, char *buf, long length_buf);
 
+extern int gdb_console_fputs (const char *, FILE *);
+
 /* A std::string-based ui_file.  Can be used as a scratch buffer for
    collecting output.  */
 
--- ./gdb/utils.c~1	2019-02-27 06:51:50.000000000 +0200
+++ ./gdb/utils.c	2019-03-03 17:39:30.222675900 +0200
@@ -1456,8 +1456,18 @@ can_emit_style_escape (struct ui_file *s
       || !ui_file_isatty (stream))
     return false;
   const char *term = getenv ("TERM");
+  /* Windows doesn't by default define $TERM, but can support styles
+     regardless.  */
+#ifndef _WIN32
   if (term == nullptr || !strcmp (term, "dumb"))
     return false;
+#else
+  /* But if they do define $TERM, let us behave the same as on Posix
+     platforms, for the benefit of programs which invoke GDB as their
+     back-end.  */
+  if (term && !strcmp (term, "dumb"))
+    return false;
+#endif
   return true;
 }