[util] Add hb-shape utility

Like hb-view, but prints out buffer contents.

The output format is kinda cryptic.  Suggestions welcome.
diff --git a/util/view-cairo.cc b/util/view-cairo.cc
index e3c49a4..4671147 100644
--- a/util/view-cairo.cc
+++ b/util/view-cairo.cc
@@ -26,60 +26,10 @@
 
 #include "view-cairo.hh"
 
-
-#ifdef CAIRO_HAS_SVG_SURFACE
-#  include <cairo-svg.h>
-#endif
-#ifdef CAIRO_HAS_PDF_SURFACE
-#  include <cairo-pdf.h>
-#endif
-#ifdef CAIRO_HAS_PS_SURFACE
-#  include <cairo-ps.h>
-#  if CAIRO_VERSION >= CAIRO_VERSION_ENCODE(1,6,0)
-#    define HAS_EPS 1
-
-static cairo_surface_t *
-_cairo_eps_surface_create_for_stream (cairo_write_func_t  write_func,
-				      void               *closure,
-				      double              width,
-				      double              height)
-{
-  cairo_surface_t *surface;
-
-  surface = cairo_ps_surface_create_for_stream (write_func, closure, width, height);
-  cairo_ps_surface_set_eps (surface, TRUE);
-
-  return surface;
-}
-
-#  else
-#    undef HAS_EPS
-#  endif
-#endif
-
-struct line_t {
-  cairo_glyph_t *glyphs;
-  unsigned int num_glyphs;
-  char *utf8;
-  unsigned int utf8_len;
-  cairo_text_cluster_t *clusters;
-  unsigned int num_clusters;
-  cairo_text_cluster_flags_t cluster_flags;
-
-  void finish (void) {
-    if (glyphs)
-      cairo_glyph_free (glyphs);
-    if (clusters)
-      cairo_text_cluster_free (clusters);
-    if (utf8)
-      g_free (utf8);
-  }
-};
-
 void
 view_cairo_t::init (const font_options_t *font_opts)
 {
-  lines = g_array_new (FALSE, FALSE, sizeof (line_t));
+  lines = g_array_new (FALSE, FALSE, sizeof (helper_cairo_line_t));
   scale = double (font_size) / hb_face_get_upem (hb_font_get_face (font_opts->get_font ()));
 }
 
@@ -88,82 +38,8 @@
 			    const char   *text,
 			    unsigned int  text_len)
 {
-  line_t l = {0};
-
-  l.num_glyphs = hb_buffer_get_length (buffer);
-  hb_glyph_info_t *hb_glyph = hb_buffer_get_glyph_infos (buffer, NULL);
-  hb_glyph_position_t *hb_position = hb_buffer_get_glyph_positions (buffer, NULL);
-  l.glyphs = cairo_glyph_allocate (l.num_glyphs + 1);
-
-  if (text) {
-    l.utf8 = g_strndup (text, text_len);
-    l.utf8_len = text_len;
-    l.num_clusters = l.num_glyphs ? 1 : 0;
-    for (unsigned int i = 1; i < l.num_glyphs; i++)
-      if (hb_glyph[i].cluster != hb_glyph[i-1].cluster)
-	l.num_clusters++;
-    l.clusters = cairo_text_cluster_allocate (l.num_clusters);
-  } else {
-    l.utf8_len = 0;
-    l.num_clusters = 0;
-  }
-
-  if ((l.num_glyphs && !l.glyphs) ||
-      (l.utf8_len && !l.utf8) ||
-      (l.num_clusters && !l.clusters))
-  {
-    l.finish ();
-    return;
-  }
-
-  hb_position_t x = 0, y = 0;
-  int i;
-  for (i = 0; i < (int) l.num_glyphs; i++)
-  {
-    l.glyphs[i].index = hb_glyph[i].codepoint;
-    l.glyphs[i].x = ( hb_position->x_offset + x) * scale;
-    l.glyphs[i].y = (-hb_position->y_offset + y) * scale;
-    x +=  hb_position->x_advance;
-    y += -hb_position->y_advance;
-
-    hb_position++;
-  }
-  l.glyphs[i].index = 0;
-  l.glyphs[i].x = x;
-  l.glyphs[i].y = y;
-
-  if (l.num_clusters) {
-    memset ((void *) l.clusters, 0, l.num_clusters * sizeof (l.clusters[0]));
-    bool backward = HB_DIRECTION_IS_BACKWARD (hb_buffer_get_direction (buffer));
-    l.cluster_flags = backward ? CAIRO_TEXT_CLUSTER_FLAG_BACKWARD : (cairo_text_cluster_flags_t) 0;
-    unsigned int cluster = 0;
-    if (!l.num_glyphs)
-      goto done;
-    l.clusters[cluster].num_glyphs++;
-    if (backward) {
-      for (i = l.num_glyphs - 2; i >= 0; i--) {
-	if (hb_glyph[i].cluster != hb_glyph[i+1].cluster) {
-	  g_assert (hb_glyph[i].cluster > hb_glyph[i+1].cluster);
-	  l.clusters[cluster].num_bytes += hb_glyph[i].cluster - hb_glyph[i+1].cluster;
-	  cluster++;
-	}
-	l.clusters[cluster].num_glyphs++;
-      }
-      l.clusters[cluster].num_bytes += text_len - hb_glyph[0].cluster;
-    } else {
-      for (i = 1; i < (int) l.num_glyphs; i++) {
-	if (hb_glyph[i].cluster != hb_glyph[i-1].cluster) {
-	  g_assert (hb_glyph[i].cluster > hb_glyph[i-1].cluster);
-	  l.clusters[cluster].num_bytes += hb_glyph[i].cluster - hb_glyph[i-1].cluster;
-	  cluster++;
-	}
-	l.clusters[cluster].num_glyphs++;
-      }
-      l.clusters[cluster].num_bytes += text_len - hb_glyph[i - 1].cluster;
-    }
-  }
-
-done:
+  helper_cairo_line_t l;
+  helper_cairo_line_from_buffer (&l, buffer, text, text_len, scale);
   g_array_append_val (lines, l);
 }
 
@@ -173,20 +49,12 @@
   render (font_opts);
 
   for (unsigned int i = 0; i < lines->len; i++) {
-    line_t &line = g_array_index (lines, line_t, i);
+    helper_cairo_line_t &line = g_array_index (lines, helper_cairo_line_t, i);
     line.finish ();
   }
-
   g_array_unref (lines);
 }
 
-double
-view_cairo_t::line_width (unsigned int i)
-{
-  line_t &line = g_array_index (lines, line_t, i);
-  return line.glyphs[line.num_glyphs].x * scale;
-}
-
 void
 view_cairo_t::get_surface_size (cairo_scaled_font_t *scaled_font,
 				double *w, double *h)
@@ -199,252 +67,29 @@
      + font_extents.descent
      + ((int) lines->len - 1) * font_extents.height;
   *w = 0;
-  for (unsigned int i = 0; i < lines->len; i++)
-    *w = MAX (*w, line_width (i));
+  for (unsigned int i = 0; i < lines->len; i++) {
+    helper_cairo_line_t &line = g_array_index (lines, helper_cairo_line_t, i);
+    double line_width = line.get_width ();
+    *w = MAX (*w, line_width);
+  }
 
   *w += margin.l + margin.r;
   *h += margin.t + margin.b;
 }
 
-cairo_scaled_font_t *
-view_cairo_t::create_scaled_font (const font_options_t *font_opts)
-{
-  hb_font_t *font = hb_font_reference (font_opts->get_font ());
-
-  cairo_font_face_t *cairo_face;
-  FT_Face ft_face = hb_ft_font_get_face (font);
-  if (!ft_face)
-    /* This allows us to get some boxes at least... */
-    cairo_face = cairo_toy_font_face_create ("@cairo:sans",
-					     CAIRO_FONT_SLANT_NORMAL,
-					     CAIRO_FONT_WEIGHT_NORMAL);
-  else
-    cairo_face = cairo_ft_font_face_create_for_ft_face (ft_face, 0);
-  cairo_matrix_t ctm, font_matrix;
-  cairo_font_options_t *font_options;
-
-  cairo_matrix_init_identity (&ctm);
-  cairo_matrix_init_scale (&font_matrix,
-			   font_size, font_size);
-  font_options = cairo_font_options_create ();
-  cairo_font_options_set_hint_style (font_options, CAIRO_HINT_STYLE_NONE);
-  cairo_font_options_set_hint_metrics (font_options, CAIRO_HINT_METRICS_OFF);
-
-  cairo_scaled_font_t *scaled_font = cairo_scaled_font_create (cairo_face,
-							       &font_matrix,
-							       &ctm,
-							       font_options);
-
-  cairo_font_options_destroy (font_options);
-  cairo_font_face_destroy (cairo_face);
-
-  static cairo_user_data_key_t key;
-  if (cairo_scaled_font_set_user_data (scaled_font,
-				       &key,
-				       (void *) font,
-				       (cairo_destroy_func_t) hb_font_destroy))
-    hb_font_destroy (font);
-
-  return scaled_font;
-}
-
-struct finalize_closure_t {
-  void (*callback)(finalize_closure_t *);
-  cairo_surface_t *surface;
-  cairo_write_func_t write_func;
-  void *closure;
-};
-static cairo_user_data_key_t finalize_closure_key;
-
-#ifdef CAIRO_HAS_PNG_FUNCTIONS
-
-static void
-finalize_png (finalize_closure_t *closure)
-{
-  cairo_status_t status;
-  status = cairo_surface_write_to_png_stream (closure->surface,
-					      closure->write_func,
-					      closure->closure);
-  if (status != CAIRO_STATUS_SUCCESS)
-    fail (FALSE, "Failed to write output: %s",
-	  cairo_status_to_string (status));
-}
-
-static cairo_surface_t *
-_cairo_png_surface_create_for_stream (cairo_write_func_t write_func,
-				      void *closure,
-				      double width,
-				      double height,
-				      cairo_content_t content)
-{
-  cairo_surface_t *surface;
-  int w = ceil (width);
-  int h = ceil (height);
-
-  switch (content) {
-    case CAIRO_CONTENT_ALPHA:
-      surface = cairo_image_surface_create (CAIRO_FORMAT_A8, w, h);
-      break;
-    default:
-    case CAIRO_CONTENT_COLOR:
-      surface = cairo_image_surface_create (CAIRO_FORMAT_RGB24, w, h);
-      break;
-    case CAIRO_CONTENT_COLOR_ALPHA:
-      surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, w, h);
-      break;
-  }
-  cairo_status_t status = cairo_surface_status (surface);
-  if (status != CAIRO_STATUS_SUCCESS)
-    fail (FALSE, "Failed to create cairo surface: %s",
-	  cairo_status_to_string (status));
-
-  finalize_closure_t *png_closure = g_new0 (finalize_closure_t, 1);
-  png_closure->callback = finalize_png;
-  png_closure->surface = surface;
-  png_closure->write_func = write_func;
-  png_closure->closure = closure;
-
-  if (cairo_surface_set_user_data (surface,
-				   &finalize_closure_key,
-				   (void *) png_closure,
-				   (cairo_destroy_func_t) g_free))
-    g_free ((void *) closure);
-
-  return surface;
-}
-
-#endif
-
 void
 view_cairo_t::render (const font_options_t *font_opts)
 {
-  cairo_scaled_font_t *scaled_font = create_scaled_font (font_opts);
+  cairo_scaled_font_t *scaled_font = helper_cairo_create_scaled_font (font_opts, font_size);
   double w, h;
   get_surface_size (scaled_font, &w, &h);
-  cairo_t *cr = create_context (w, h);
+  cairo_t *cr = helper_cairo_create_context (w, h, this, this);
   cairo_set_scaled_font (cr, scaled_font);
   cairo_scaled_font_destroy (scaled_font);
 
   draw (cr);
 
-  finalize_closure_t *closure = (finalize_closure_t *)
-				cairo_surface_get_user_data (cairo_get_target (cr),
-							     &finalize_closure_key);
-  if (closure)
-    closure->callback (closure);
-
-  cairo_status_t status = cairo_status (cr);
-  if (status != CAIRO_STATUS_SUCCESS)
-    fail (FALSE, "Failed: %s",
-	  cairo_status_to_string (status));
-  cairo_destroy (cr);
-}
-
-static cairo_status_t
-stdio_write_func (void                *closure,
-		  const unsigned char *data,
-		  unsigned int         size)
-{
-  FILE *fp = (FILE *) closure;
-
-  while (size) {
-    size_t ret = fwrite (data, 1, size, fp);
-    size -= ret;
-    data += ret;
-    if (size && ferror (fp))
-      fail (FALSE, "Failed to write output: %s", strerror (errno));
-  }
-
-  return CAIRO_STATUS_SUCCESS;
-}
-
-cairo_t *
-view_cairo_t::create_context (double w, double h)
-{
-  cairo_surface_t *(*constructor) (cairo_write_func_t write_func,
-				   void *closure,
-				   double width,
-				   double height) = NULL;
-  cairo_surface_t *(*constructor2) (cairo_write_func_t write_func,
-				    void *closure,
-				    double width,
-				    double height,
-				    cairo_content_t content) = NULL;
-
-  const char *extension = output_format;
-  if (!extension)
-    extension = "png";
-  if (0)
-    ;
-  #ifdef CAIRO_HAS_PNG_FUNCTIONS
-    else if (0 == strcasecmp (extension, "png"))
-      constructor2 = _cairo_png_surface_create_for_stream;
-  #endif
-  #ifdef CAIRO_HAS_SVG_SURFACE
-    else if (0 == strcasecmp (extension, "svg"))
-      constructor = cairo_svg_surface_create_for_stream;
-  #endif
-  #ifdef CAIRO_HAS_PDF_SURFACE
-    else if (0 == strcasecmp (extension, "pdf"))
-      constructor = cairo_pdf_surface_create_for_stream;
-  #endif
-  #ifdef CAIRO_HAS_PS_SURFACE
-    else if (0 == strcasecmp (extension, "ps"))
-      constructor = cairo_ps_surface_create_for_stream;
-   #ifdef HAS_EPS
-    else if (0 == strcasecmp (extension, "eps"))
-      constructor = _cairo_eps_surface_create_for_stream;
-   #endif
-  #endif
-
-
-  unsigned int fr, fg, fb, fa, br, bg, bb, ba;
-  br = bg = bb = ba = 255;
-  sscanf (back + (*back=='#'), "%2x%2x%2x%2x", &br, &bg, &bb, &ba);
-  fr = fg = fb = 0; fa = 255;
-  sscanf (fore + (*fore=='#'), "%2x%2x%2x%2x", &fr, &fg, &fb, &fa);
-
-  cairo_content_t content;
-  if (!annotate && ba == 255 && br == bg && bg == bb && fr == fg && fg == fb)
-    content = CAIRO_CONTENT_ALPHA;
-  else if (ba == 255)
-    content = CAIRO_CONTENT_COLOR;
-  else
-    content = CAIRO_CONTENT_COLOR_ALPHA;
-
-  cairo_surface_t *surface;
-  FILE *f = get_file_handle ();
-  if (constructor)
-    surface = constructor (stdio_write_func, f, w, h);
-  else if (constructor2)
-    surface = constructor2 (stdio_write_func, f, w, h, content);
-  else
-    fail (FALSE, "Unknown output format `%s'", extension);
-
-  cairo_t *cr = cairo_create (surface);
-  content = cairo_surface_get_content (surface);
-
-  switch (content) {
-    case CAIRO_CONTENT_ALPHA:
-      cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
-      cairo_set_source_rgba (cr, 1., 1., 1., br / 255.);
-      cairo_paint (cr);
-      cairo_set_source_rgba (cr, 1., 1., 1.,
-			     (fr / 255.) * (fa / 255.) + (br / 255) * (1 - (fa / 255.)));
-      break;
-    default:
-    case CAIRO_CONTENT_COLOR:
-    case CAIRO_CONTENT_COLOR_ALPHA:
-      cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
-      cairo_set_source_rgba (cr, br / 255., bg / 255., bb / 255., ba / 255.);
-      cairo_paint (cr);
-      cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
-      cairo_set_source_rgba (cr, fr / 255., fg / 255., fb / 255., fa / 255.);
-      break;
-  }
-
-  cairo_surface_destroy (surface);
-  return cr;
+  helper_cairo_destroy_context (cr);
 }
 
 void
@@ -457,7 +102,7 @@
   cairo_translate (cr, margin.l, margin.t);
   for (unsigned int i = 0; i < lines->len; i++)
   {
-    line_t &l = g_array_index (lines, line_t, i);
+    helper_cairo_line_t &l = g_array_index (lines, helper_cairo_line_t, i);
 
     if (i)
       cairo_translate (cr, 0, line_space);