Allow inserting Pango markup in text buffers

This has been a very long-standing feature request.

https://bugzilla.gnome.org/show_bug.cgi?id=59390

docs/reference/gtk/gtk3-sections.txt

@@ -3560,6 +3560,7 @@ gtk_text_buffer_insert_range
 gtk_text_buffer_insert_range_interactive
 gtk_text_buffer_insert_with_tags
 gtk_text_buffer_insert_with_tags_by_name
+gtk_text_buffer_insert_markup
 gtk_text_buffer_delete
 gtk_text_buffer_delete_interactive
 gtk_text_buffer_backspace

gtk/gtktextbuffer.c

@@ -4720,3 +4720,182 @@ _gtk_text_buffer_get_text_after (GtkTextBuffer   *buffer,
       break;
     }
 }
+
+static GtkTextTag *
+get_tag_for_attributes (PangoAttrIterator *iter)
+{
+  PangoAttribute *attr;
+  GtkTextTag *tag;
+
+  tag = gtk_text_tag_new (NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_LANGUAGE);
+  if (attr)
+    g_object_set (tag, "language", pango_language_to_string (((PangoAttrLanguage*)attr)->value), NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_FAMILY);
+  if (attr)
+    g_object_set (tag, "family", ((PangoAttrString*)attr)->value, NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_STYLE);
+  if (attr)
+    g_object_set (tag, "style", ((PangoAttrInt*)attr)->value, NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_WEIGHT);
+  if (attr)
+    g_object_set (tag, "weight", ((PangoAttrInt*)attr)->value, NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_VARIANT);
+  if (attr)
+    g_object_set (tag, "variant", ((PangoAttrInt*)attr)->value, NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_STRETCH);
+  if (attr)
+    g_object_set (tag, "stretch", ((PangoAttrInt*)attr)->value, NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_SIZE);
+  if (attr)
+    g_object_set (tag, "size", ((PangoAttrInt*)attr)->value, NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_FONT_DESC);
+  if (attr)
+    g_object_set (tag, "font-desc", ((PangoAttrFontDesc*)attr)->desc, NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_FOREGROUND);
+  if (attr)
+    {
+      PangoColor *color;
+      GdkRGBA rgba;
+     
+      color = &((PangoAttrColor*)attr)->color;
+      rgba.red = color->red / 65535.;
+      rgba.green = color->green / 65535.;
+      rgba.blue = color->blue / 65535.;
+      rgba.alpha = 1.;
+      g_object_set (tag, "foreground-rgba", &rgba, NULL);
+    };
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_BACKGROUND);
+  if (attr)
+    {
+      PangoColor *color;
+      GdkRGBA rgba;
+     
+      color = &((PangoAttrColor*)attr)->color;
+      rgba.red = color->red / 65535.;
+      rgba.green = color->green / 65535.;
+      rgba.blue = color->blue / 65535.;
+      rgba.alpha = 1.;
+      g_object_set (tag, "background-rgba", &rgba, NULL);
+    };
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_UNDERLINE);
+  if (attr)
+    g_object_set (tag, "underline", ((PangoAttrInt*)attr)->value, NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_STRIKETHROUGH);
+  if (attr)
+    g_object_set (tag, "strikethrough", (gboolean) (((PangoAttrInt*)attr)->value != 0), NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_RISE);
+  if (attr)
+    g_object_set (tag, "rise", ((PangoAttrInt*)attr)->value, NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_SCALE);
+  if (attr)
+    g_object_set (tag, "scale", ((PangoAttrFloat*)attr)->value, NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_FALLBACK);
+  if (attr)
+    g_object_set (tag, "fallback", (gboolean) (((PangoAttrInt*)attr)->value != 0), NULL);
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_LETTER_SPACING);
+  if (attr)
+    g_object_set (tag, "letter-spacing", ((PangoAttrInt*)attr)->value, NULL);
+
+  return tag;
+}
+
+static void
+gtk_text_buffer_insert_with_attributes (GtkTextBuffer *buffer,
+                                        GtkTextIter   *iter,
+                                        const gchar   *text,
+                                        PangoAttrList *attributes)
+{
+  GtkTextMark *mark;
+  PangoAttrIterator *attr;
+  GtkTextTagTable *tags;
+
+  g_return_if_fail (GTK_IS_TEXT_BUFFER (buffer));
+
+  if (!attributes)
+    {
+      gtk_text_buffer_insert (buffer, iter, text, -1);
+      return;
+    }
+
+  /* create mark with right gravity */
+  mark = gtk_text_buffer_create_mark (buffer, NULL, iter, FALSE);
+  attr = pango_attr_list_get_iterator (attributes);
+  tags = gtk_text_buffer_get_tag_table (buffer);
+
+  do
+    {
+      GtkTextTag *tag;
+      gint start, end;
+
+      pango_attr_iterator_range (attr, &start, &end);
+
+      if (end == G_MAXINT) /* last chunk */
+        end = start - 1; /* resulting in -1 to be passed to _insert */
+
+      tag = get_tag_for_attributes (attr);
+      gtk_text_tag_table_add (tags, tag);
+
+      gtk_text_buffer_insert_with_tags (buffer, iter, text + start, end - start, tag, NULL);
+
+      gtk_text_buffer_get_iter_at_mark (buffer, iter, mark);
+    }
+  while (pango_attr_iterator_next (attr));
+  
+  gtk_text_buffer_delete_mark (buffer, mark);
+  pango_attr_iterator_destroy (attr);
+} 
+
+/**
+ * gtk_text_buffer_insert_markup:
+ * @buffer: a #GtkTextBuffer
+ * @iter: location to insert the markup
+ * @markup: a nul-terminated UTF-8 string containing [Pango markup][PangoMarkupFormat]
+ * @len: length of @markup in bytes, or -1
+ *
+ * Inserts the text in @markup at position @iter. @markup will be inserted
+ * in its entirety and must be nul-terminated and valid UTF-8. Emits the
+ * #GtkTextBuffer::insert-text signal, possibly multiple times; insertion
+ * actually occurs in the default handler for the signal. @iter will point
+ * to the end of the inserted text on return.
+ *
+ * Since: 3.16
+ */
+void
+gtk_text_buffer_insert_markup (GtkTextBuffer *buffer,
+                               GtkTextIter   *iter,
+                               const gchar   *markup,
+                               gint           len)
+{
+  PangoAttrList *attributes;
+  gchar *text;
+  GError *error = NULL;
+
+  if (!pango_parse_markup (markup, len, 0, &attributes, &text, NULL, &error))
+    {
+      g_warning ("Invalid markup string: %s", error->message);
+      g_error_free (error);
+      return;
+    }
+
+  gtk_text_buffer_insert_with_attributes (buffer, iter, text, attributes);
+
+  pango_attr_list_unref (attributes);
+  g_free (text); 
+}

gtk/gtktextbuffer.h

@@ -236,6 +236,12 @@ void    gtk_text_buffer_insert_with_tags_by_name  (GtkTextBuffer     *buffer,
                                                    const gchar       *first_tag_name,
                                                    ...) G_GNUC_NULL_TERMINATED;
 
+GDK_AVAILABLE_IN_3_16
+void     gtk_text_buffer_insert_markup            (GtkTextBuffer     *buffer,
+                                                   GtkTextIter       *iter,
+                                                   const gchar       *markup,
+                                                   gint               len);
+
 /* Delete from the buffer */
 GDK_AVAILABLE_IN_ALL
 void     gtk_text_buffer_delete             (GtkTextBuffer *buffer,