print_stream: add a new print_line_color() method

This new interface allows printing a line with specified foreground and
background colors.  The implementation avoids printing escape sequences
if the output stream is not a TTY and note that escape sequences are
ignored on Windows.

This initial implementation relies on relatively modern 24-bit color
support which is present in many terminal emulators but may not always
display properly on older or simpler emulators. Windows coloring is
handled with SetConsoleTextAttribute, which offers a "1-bit" color
experience (but it's better than nothing)

This commit is a precursor to adding additional coloring to tshark.

Bug: 5158
Change-Id: Ib2b9d800095a065a4bb60abe0550862cda5539ec
Reviewed-on: https://code.wireshark.org/review/21324
Reviewed-by: Michael Mann <mmann78@netscape.net>

debian/libwireshark0.symbols

@@ -1023,6 +1023,7 @@ libwireshark.so.0 libwireshark0 #MINVER#
  print_finale@Base 1.12.0~rc1
  print_hex_data@Base 1.12.0~rc1
  print_line@Base 1.12.0~rc1
+ print_line_color@Base 2.5.0
  print_preamble@Base 1.12.0~rc1
  print_stream_ps_new@Base 1.12.0~rc1
  print_stream_ps_stdio_new@Base 1.12.0~rc1

epan/print_stream.c

@@ -25,6 +25,7 @@
 #include "config.h"
 
 #include <stdio.h>
+#include <string.h>
 
 #ifdef _WIN32
 #include <windows.h>
@@ -38,6 +39,113 @@
 
 #include <wsutil/file_util.h>
 
+#define TERM_SGR_RESET "\x1B[0m"  /* SGR - reset */
+#define TERM_CSI_EL    "\x1B[K"   /* EL - Erase in Line (to end of line) */
+
+#ifdef _WIN32
+static void
+print_color_escape(FILE *fh, const color_t *fg, const color_t *bg)
+{
+    /* default to white foreground, black background */
+    WORD win_fg_color = FOREGROUND_RED|FOREGROUND_BLUE|FOREGROUND_GREEN;
+    WORD win_bg_color = 0;
+
+    /* Windows seems to offer 1-bit color, so you can't set the red, green, or blue intensities,
+     * you can only set "{foreground, background} contains {red, green, blue}".
+     * So include red, green or blue if the numeric intensity is high enough
+     */
+    if (fg) {
+        if (((fg->red >> 8) & 0xff) >= 0x80)
+        {
+            win_fg_color |= FOREGROUND_RED;
+        }
+        else
+        {
+            win_fg_color &= (~FOREGROUND_RED);
+        }
+        if (((fg->green >> 8) & 0xff) >= 0x80)
+        {
+            win_fg_color |= FOREGROUND_GREEN;
+        }
+        else
+        {
+            win_fg_color &= (~FOREGROUND_GREEN);
+        }
+        if (((fg->blue >> 8) & 0xff) >= 0x80)
+        {
+            win_fg_color |= FOREGROUND_BLUE;
+        }
+        else
+        {
+            win_fg_color &= (~FOREGROUND_BLUE);
+        }
+    }
+
+    if (bg) {
+        if (((bg->red >> 8) & 0xff) >= 0x80)
+        {
+            win_bg_color |= BACKGROUND_RED;
+        }
+        else
+        {
+            win_bg_color &= (~BACKGROUND_RED);
+        }
+        if (((bg->green >> 8) & 0xff) >= 0x80)
+        {
+            win_bg_color |= BACKGROUND_GREEN;
+        }
+        else
+        {
+            win_bg_color &= (~BACKGROUND_GREEN);
+        }
+        if (((bg->blue >> 8) & 0xff) >= 0x80)
+        {
+            win_bg_color |= BACKGROUND_BLUE;
+        }
+        else
+        {
+            win_bg_color &= (~BACKGROUND_BLUE);
+        }
+    }
+
+    SetConsoleTextAttribute((HANDLE)_get_osfhandle(_fileno(fh)), win_fg_color|win_bg_color);
+}
+#else
+static void
+print_color_escape(FILE *fh, const color_t *fg, const color_t *bg)
+{
+    if (fg) {
+        /*
+         * emit 24-bit "true color" escape sequence if output is going to a
+         * tty, the sequence should be ignored by terminals that aren't capable
+         */
+        fprintf(fh, "\x1B[38;2;%u;%u;%um",
+                (fg->red   >> 8) & 0xff,
+                (fg->green >> 8) & 0xff,
+                (fg->blue  >> 8) & 0xff);
+    }
+
+    if (bg) {
+        fprintf(fh, "\x1B[48;2;%u;%u;%um",
+                (bg->red   >> 8) & 0xff,
+                (bg->green >> 8) & 0xff,
+                (bg->blue  >> 8) & 0xff);
+    }
+}
+#endif
+
+static void
+print_color_eol(FILE *fh)
+{
+    /*
+     * Emit CSI EL to extend current background color all the way to EOL,
+     * otherwise we get a ragged right edge of color wherever the newline
+     * occurs.  It's not perfect in every terminal emulator, but it generally
+     * works.
+     */
+    fprintf(fh, "%s\n%s", TERM_CSI_EL, TERM_SGR_RESET);
+}
+
 static FILE *
 open_print_dest(gboolean to_file, const char *dest)
 {
@@ -75,6 +183,15 @@ print_line(print_stream_t *self, int indent, const char *line)
     return (self->ops->print_line)(self, indent, line);
 }
 
+gboolean
+print_line_color(print_stream_t *self, int indent, const char *line, const color_t *fg, const color_t *bg)
+{
+    if (self->ops->print_line_color)
+        return (self->ops->print_line_color)(self, indent, line, fg, bg);
+    else
+        return (self->ops->print_line)(self, indent, line);
+}
+
 /* Insert bookmark */
 gboolean
 print_bookmark(print_stream_t *self, const gchar *name, const gchar *title)
@@ -108,21 +225,24 @@ typedef struct {
 
 #define MAX_INDENT    160
 
+/* returns TRUE if the print succeeded, FALSE if there was an error */
 static gboolean
-print_line_text(print_stream_t *self, int indent, const char *line)
+print_line_color_text(print_stream_t *self, int indent, const char *line, const color_t *fg, const color_t *bg)
 {
-    static char  spaces[MAX_INDENT];
+    static char spaces[MAX_INDENT];
     size_t ret;
-
     output_text *output = (output_text *)self->data;
     unsigned int num_spaces;
+    gboolean emit_color = self->isatty && (fg != NULL || bg != NULL);
 
     /* should be space, if NUL -> initialize */
-    if (!spaces[0]) {
-        int i;
+    if (!spaces[0])
+        memset(spaces, ' ', sizeof(spaces));
 
-        for (i = 0; i < MAX_INDENT; i++)
-            spaces[i] = ' ';
+    if (emit_color) {
+        print_color_escape(output->fh, fg, bg);
+        if (ferror(output->fh))
+            return FALSE;
     }
 
     /* Prepare the tabs for printing, depending on tree level */
@@ -153,11 +273,22 @@ print_line_text(print_stream_t *self, int indent, const char *line)
         } else {
             fputs(line, output->fh);
         }
-        putc('\n', output->fh);
+
+        if (emit_color)
+            print_color_eol(output->fh);
+        else
+            putc('\n', output->fh);
     }
+
     return !ferror(output->fh);
 }
 
+static gboolean
+print_line_text(print_stream_t *self, int indent, const char *line)
+{
+    return print_line_color_text(self, indent, line, NULL, NULL);
+}
+
 static gboolean
 new_page_text(print_stream_t *self)
 {
@@ -185,7 +316,8 @@ static const print_stream_ops_t print_text_ops = {
     NULL,            /* bookmark */
     new_page_text,
     NULL,            /* finale */
-    destroy_text
+    destroy_text,
+    print_line_color_text,
 };
 
 static print_stream_t *
@@ -368,7 +500,8 @@ static const print_stream_ops_t print_ps_ops = {
     print_bookmark_ps,
     new_page_ps,
     print_finale_ps,
-    destroy_ps
+    destroy_ps,
+    NULL, /* print_line_color */
 };
 
 static print_stream_t *

epan/print_stream.h

@@ -27,6 +27,8 @@
 
 #include "ws_symbol_export.h"
 
+#include <wsutil/color.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif /* __cplusplus */
@@ -46,6 +48,7 @@ typedef struct print_stream_ops {
 	gboolean (*new_page)(struct print_stream *self);
 	gboolean (*print_finale)(struct print_stream *self);
 	gboolean (*destroy)(struct print_stream *self);
+	gboolean (*print_line_color)(struct print_stream *self, int indent, const char *line, const color_t *fg, const color_t *bg);
 } print_stream_ops_t;
 
 typedef struct print_stream {
@@ -68,6 +71,15 @@ WS_DLL_PUBLIC gboolean new_page(print_stream_t *self);
 WS_DLL_PUBLIC gboolean print_finale(print_stream_t *self);
 WS_DLL_PUBLIC gboolean destroy_print_stream(print_stream_t *self);
 
+/*
+ * equivalent to print_line(), but if the stream supports text coloring then
+ * the output text will also be colored with the given foreground and
+ * background
+ *
+ * returns TRUE if the print was successful, FALSE otherwise
+ */
+WS_DLL_PUBLIC gboolean print_line_color(print_stream_t *self, int indent, const char *line, const color_t *fg, const color_t *bg);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */