[gtk/async-highlight: 1/3] gtk-demo: Move the highlighting to a separate file

[Matthias Clasen <matthiasc src gnome org>]

commit 80cddd4cc1514168a343a9d566406eafeda27f5a
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Aug 13 13:08:57 2020 -0400

    gtk-demo: Move the highlighting to a separate file
    
    Move all the logic related to asynchronous highlighting
    to fontify.c, to keep main.c from becoming too cluttered.

 demos/gtk-demo/fontify.c   | 405 +++++++++++++++++++++++++++++++++++++++++++++
 demos/gtk-demo/fontify.h   |   6 +
 demos/gtk-demo/main.c      | 393 +------------------------------------------
 demos/gtk-demo/meson.build |   1 +
 4 files changed, 413 insertions(+), 392 deletions(-)
---
diff --git a/demos/gtk-demo/fontify.c b/demos/gtk-demo/fontify.c
new file mode 100644
index 0000000000..ce8efe51a7
--- /dev/null
+++ b/demos/gtk-demo/fontify.c
@@ -0,0 +1,405 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "config.h"
+
+#include <gtk/gtk.h>
+#include <glib/gstdio.h>
+
+#include <gio/gunixoutputstream.h>
+#include <fcntl.h>
+
+
+/* This is the guts of gtk_text_buffer_insert_markup,
+ * copied here so we can make an incremental version.
+ */
+static void
+insert_tags_for_attributes (GtkTextBuffer     *buffer,
+                            PangoAttrIterator *iter,
+                            GtkTextIter       *start,
+                            GtkTextIter       *end)
+{
+  GtkTextTagTable *table;
+  PangoAttribute *attr;
+  GtkTextTag *tag;
+  char name[256];
+
+  table = gtk_text_buffer_get_tag_table (buffer);
+
+#define STRING_ATTR(pango_attr_name, attr_name) \
+  attr = pango_attr_iterator_get (iter, pango_attr_name); \
+  if (attr) \
+    { \
+      const char *string = ((PangoAttrString*)attr)->value; \
+      g_snprintf (name, 256, #attr_name "=%s", string); \
+      tag = gtk_text_tag_table_lookup (table, name); \
+      if (!tag) \
+        { \
+          tag = gtk_text_tag_new (name); \
+          g_object_set (tag, #attr_name, string, NULL); \
+          gtk_text_tag_table_add (table, tag); \
+          g_object_unref (tag); \
+        } \
+      gtk_text_buffer_apply_tag (buffer, tag, start, end); \
+    }
+
+#define INT_ATTR(pango_attr_name, attr_name) \
+  attr = pango_attr_iterator_get (iter, pango_attr_name); \
+  if (attr) \
+    { \
+      int value = ((PangoAttrInt*)attr)->value; \
+      g_snprintf (name, 256, #attr_name "=%d", value); \
+      tag = gtk_text_tag_table_lookup (table, name); \
+      if (!tag) \
+        { \
+          tag = gtk_text_tag_new (name); \
+          g_object_set (tag, #attr_name, value, NULL); \
+          gtk_text_tag_table_add (table, tag); \
+          g_object_unref (tag); \
+        } \
+      gtk_text_buffer_apply_tag (buffer, tag, start, end); \
+    }
+
+#define FLOAT_ATTR(pango_attr_name, attr_name) \
+  attr = pango_attr_iterator_get (iter, pango_attr_name); \
+  if (attr) \
+    { \
+      float value = ((PangoAttrFloat*)attr)->value; \
+      g_snprintf (name, 256, #attr_name "=%g", value); \
+      tag = gtk_text_tag_table_lookup (table, name); \
+      if (!tag) \
+        { \
+          tag = gtk_text_tag_new (name); \
+          g_object_set (tag, #attr_name, value, NULL); \
+          gtk_text_tag_table_add (table, tag); \
+          g_object_unref (tag); \
+        } \
+      gtk_text_buffer_apply_tag (buffer, tag, start, end); \
+    }
+
+#define RGBA_ATTR(pango_attr_name, attr_name) \
+  attr = pango_attr_iterator_get (iter, pango_attr_name); \
+  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.; \
+      char *str = gdk_rgba_to_string (&rgba); \
+      g_snprintf (name, 256, #attr_name "=%s", str); \
+      g_free (str); \
+      tag = gtk_text_tag_table_lookup (table, name); \
+      if (!tag) \
+        { \
+          tag = gtk_text_tag_new (name); \
+          g_object_set (tag, #attr_name, &rgba, NULL); \
+          gtk_text_tag_table_add (table, tag); \
+          g_object_unref (tag); \
+        } \
+      gtk_text_buffer_apply_tag (buffer, tag, start, end); \
+    }
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_LANGUAGE);
+  if (attr)
+    {
+      const char *language = pango_language_to_string (((PangoAttrLanguage*)attr)->value);
+      g_snprintf (name, 256, "language=%s", language);
+      tag = gtk_text_tag_table_lookup (table, name);
+      if (!tag)
+        {
+          tag = gtk_text_tag_new (name);
+          g_object_set (tag, "language", language, NULL);
+          gtk_text_tag_table_add (table, tag);
+          g_object_unref (tag);
+        }
+      gtk_text_buffer_apply_tag (buffer, tag, start, end);
+    }
+
+  STRING_ATTR (PANGO_ATTR_FAMILY, family)
+  INT_ATTR    (PANGO_ATTR_STYLE, style)
+  INT_ATTR    (PANGO_ATTR_WEIGHT, weight)
+  INT_ATTR    (PANGO_ATTR_VARIANT, variant)
+  INT_ATTR    (PANGO_ATTR_STRETCH, stretch)
+  INT_ATTR    (PANGO_ATTR_SIZE, size)
+
+  attr = pango_attr_iterator_get (iter, PANGO_ATTR_FONT_DESC);
+  if (attr)
+    {
+      PangoFontDescription *desc = ((PangoAttrFontDesc*)attr)->desc;
+      char *str = pango_font_description_to_string (desc);
+      g_snprintf (name, 256, "font-desc=%s", str);
+      g_free (str);
+      tag = gtk_text_tag_table_lookup (table, name);
+      if (!tag)
+        {
+          tag = gtk_text_tag_new (name);
+          g_object_set (tag, "font-desc", desc, NULL);
+          gtk_text_tag_table_add (table, tag);
+          g_object_unref (tag);
+        }
+      gtk_text_buffer_apply_tag (buffer, tag, start, end);
+    }
+
+  RGBA_ATTR   (PANGO_ATTR_FOREGROUND, foreground_rgba)
+  RGBA_ATTR   (PANGO_ATTR_BACKGROUND, background_rgba)
+  INT_ATTR    (PANGO_ATTR_UNDERLINE, underline)
+  RGBA_ATTR   (PANGO_ATTR_UNDERLINE_COLOR, underline_rgba)
+  INT_ATTR    (PANGO_ATTR_OVERLINE, overline)
+  RGBA_ATTR   (PANGO_ATTR_OVERLINE_COLOR, overline_rgba)
+  INT_ATTR    (PANGO_ATTR_STRIKETHROUGH, strikethrough)
+  RGBA_ATTR   (PANGO_ATTR_STRIKETHROUGH_COLOR, strikethrough_rgba)
+  INT_ATTR    (PANGO_ATTR_RISE, rise)
+  FLOAT_ATTR  (PANGO_ATTR_SCALE, scale)
+  INT_ATTR    (PANGO_ATTR_FALLBACK, fallback)
+  INT_ATTR    (PANGO_ATTR_LETTER_SPACING, letter_spacing)
+  STRING_ATTR (PANGO_ATTR_FONT_FEATURES, font_features)
+  INT_ATTR    (PANGO_ATTR_ALLOW_BREAKS, allow_breaks)
+  INT_ATTR    (PANGO_ATTR_SHOW, show_spaces)
+  INT_ATTR    (PANGO_ATTR_INSERT_HYPHENS, insert_hyphens)
+}
+
+typedef struct
+{
+  GtkTextBuffer *buffer;
+  GtkTextIter iter;
+  GtkTextMark *mark;
+  PangoAttrList *attributes;
+  char *text;
+  PangoAttrIterator *attr;
+} MarkupData;
+
+static void
+free_markup_data (MarkupData *mdata)
+{
+  gtk_text_buffer_delete_mark (mdata->buffer, mdata->mark);
+  pango_attr_iterator_destroy (mdata->attr);
+  pango_attr_list_unref (mdata->attributes);
+  g_free (mdata->text);
+  g_object_unref (mdata->buffer);
+  g_free (mdata);
+}
+
+static gboolean
+insert_markup_idle (gpointer data)
+{
+  MarkupData *mdata = data;
+  gint64 begin;
+
+  begin = g_get_monotonic_time ();
+
+  do
+    {
+      int start, end;
+      int start_offset;
+      GtkTextIter start_iter;
+
+      if (g_get_monotonic_time () - begin > G_TIME_SPAN_MILLISECOND)
+        {
+          g_idle_add (insert_markup_idle, data);
+          return G_SOURCE_REMOVE;
+        }
+
+      pango_attr_iterator_range (mdata->attr, &start, &end);
+
+      if (end == G_MAXINT) /* last chunk */
+        end = start - 1; /* resulting in -1 to be passed to _insert */
+
+      start_offset = gtk_text_iter_get_offset (&mdata->iter);
+      gtk_text_buffer_insert (mdata->buffer, &mdata->iter, mdata->text + start, end - start);
+      gtk_text_buffer_get_iter_at_offset (mdata->buffer, &start_iter, start_offset);
+
+      insert_tags_for_attributes (mdata->buffer, mdata->attr, &start_iter, &mdata->iter);
+
+      gtk_text_buffer_get_iter_at_mark (mdata->buffer, &mdata->iter, mdata->mark);
+    }
+  while (pango_attr_iterator_next (mdata->attr));
+
+  free_markup_data (mdata);
+  return G_SOURCE_REMOVE;
+}
+
+static void
+insert_markup (GtkTextBuffer *buffer,
+               GtkTextIter   *iter,
+               const char    *markup,
+               int            len)
+{
+  char *text;
+  PangoAttrList *attributes;
+  GError *error = NULL;
+  MarkupData *data;
+
+  g_return_if_fail (GTK_IS_TEXT_BUFFER (buffer));
+
+  if (!pango_parse_markup (markup, len, 0, &attributes, &text, NULL, &error))
+    {
+      g_warning ("Invalid markup string: %s", error->message);
+      g_error_free (error);
+      return;
+    }
+
+  if (!attributes)
+    {
+      gtk_text_buffer_insert (buffer, iter, text, -1);
+      g_free (text);
+      return;
+    }
+
+  data = g_new (MarkupData, 1);
+
+  data->buffer = g_object_ref (buffer);
+  data->iter = *iter;
+  data->attributes = attributes;
+  data->text = text;
+
+  /* create mark with right gravity */
+  data->mark = gtk_text_buffer_create_mark (buffer, NULL, iter, FALSE);
+  data->attr = pango_attr_list_get_iterator (attributes);
+
+  insert_markup_idle (data);
+}
+
+static void
+fontify_finish (GObject *source,
+                GAsyncResult *result,
+                gpointer data)
+{
+  GSubprocess *subprocess = G_SUBPROCESS (source);
+  GtkTextBuffer *buffer = data;
+  GBytes *stdout_buf = NULL;
+  GBytes *stderr_buf = NULL;
+  GError *error = NULL;
+
+  if (!g_subprocess_communicate_finish (subprocess,
+                                        result,
+                                        &stdout_buf,
+                                        &stderr_buf,
+                                        &error))
+    {
+      g_clear_pointer (&stdout_buf, g_bytes_unref);
+      g_clear_pointer (&stderr_buf, g_bytes_unref);
+
+      g_warning ("%s", error->message);
+      g_clear_error (&error);
+
+      g_object_unref (subprocess);
+      g_object_unref (buffer);
+      return;
+    }
+
+  if (g_subprocess_get_exit_status (subprocess) != 0)
+    {
+      if (stderr_buf)
+        g_warning ("%s", (char *)g_bytes_get_data (stderr_buf, NULL));
+      g_clear_pointer (&stderr_buf, g_bytes_unref);
+    }
+
+  g_object_unref (subprocess);
+
+  g_clear_pointer (&stderr_buf, g_bytes_unref);
+
+  if (stdout_buf)
+    {
+      char *markup;
+      gsize len;
+      char *p;
+      GtkTextIter start;
+
+      gtk_text_buffer_set_text (buffer, "", 0);
+
+      /* highlight puts a span with font and size around its output,
+       * which we don't want.
+       */
+      markup = g_bytes_unref_to_data (stdout_buf, &len);
+      for (p = markup + strlen ("<span "); *p != '>'; p++) *p = ' ';
+
+      gtk_text_buffer_get_start_iter (buffer, &start);
+      insert_markup (buffer, &start, markup, len);
+   }
+
+  g_object_unref (buffer);
+}
+
+void
+fontify (const char    *format,
+         GtkTextBuffer *source_buffer)
+{
+  GSubprocess *subprocess;
+  char *format_arg;
+  GtkSettings *settings;
+  char *theme;
+  gboolean prefer_dark;
+  const char *style_arg;
+  const char *text;
+  GtkTextIter start, end;
+  GBytes *bytes;
+  GError *error = NULL;
+
+  settings = gtk_settings_get_default ();
+  g_object_get (settings,
+                "gtk-theme-name", &theme,
+                "gtk-application-prefer-dark-theme", &prefer_dark,
+                NULL);
+
+  if (prefer_dark || strcmp (theme, "HighContrastInverse") == 0)
+    style_arg = "--style=edit-vim-dark";
+  else
+    style_arg = "--style=edit-kwrite";
+
+  g_free (theme);
+
+  format_arg = g_strconcat ("--syntax=", format, NULL);
+  subprocess = g_subprocess_new (G_SUBPROCESS_FLAGS_STDIN_PIPE |
+                                 G_SUBPROCESS_FLAGS_STDOUT_PIPE |
+                                 G_SUBPROCESS_FLAGS_STDERR_PIPE,
+                                 &error,
+                                 "highlight",
+                                 format_arg,
+                                 "--out-format=pango",
+                                 style_arg,
+                                 NULL);
+  g_free (format_arg);
+
+  if (!subprocess)
+    {
+      if (g_error_matches (error, G_SPAWN_ERROR, G_SPAWN_ERROR_NOENT))
+        {
+          static gboolean warned = FALSE;
+
+          if (!warned)
+            {
+              warned = TRUE;
+              g_message ("For syntax highlighting, install the “highlight” program");
+            }
+        }
+      else
+        g_warning ("%s", error->message);
+
+      g_clear_error (&error);
+
+      return;
+    }
+
+  gtk_text_buffer_get_bounds (source_buffer, &start, &end);
+  text = gtk_text_buffer_get_text (source_buffer, &start, &end, TRUE);
+  bytes = g_bytes_new_static (text, strlen (text));
+
+  /* Work around https://gitlab.gnome.org/GNOME/glib/-/issues/2182 */
+  if (G_IS_UNIX_OUTPUT_STREAM (g_subprocess_get_stdin_pipe (subprocess)))
+    {
+      GOutputStream *stdin_pipe = g_subprocess_get_stdin_pipe (subprocess);
+      int fd = g_unix_output_stream_get_fd (G_UNIX_OUTPUT_STREAM (stdin_pipe));
+      fcntl (fd, F_SETFL, O_NONBLOCK);
+    }
+
+  g_subprocess_communicate_async (subprocess,
+                                  bytes,
+                                  NULL,
+                                  fontify_finish,
+                                  g_object_ref (source_buffer));
+}
diff --git a/demos/gtk-demo/fontify.h b/demos/gtk-demo/fontify.h
new file mode 100644
index 0000000000..9a4df072ab
--- /dev/null
+++ b/demos/gtk-demo/fontify.h
@@ -0,0 +1,6 @@
+#pragma once
+
+#include <gtk/gtk.h>
+
+void fontify (const char    *format,
+              GtkTextBuffer *buffer);
diff --git a/demos/gtk-demo/main.c b/demos/gtk-demo/main.c
index d22a673e94..3da97c54d8 100644
--- a/demos/gtk-demo/main.c
+++ b/demos/gtk-demo/main.c
@@ -8,10 +8,8 @@
 #include <gtk/gtk.h>
 #include <glib/gstdio.h>
 
-#include <gio/gunixoutputstream.h>
-#include <fcntl.h>
-
 #include "demos.h"
+#include "fontify.h"
 
 static GtkWidget *info_view;
 static GtkWidget *source_view;
@@ -237,395 +235,6 @@ activate_run (GSimpleAction *action,
   gtk_demo_run (demo, window);
 }
 
-static void
-insert_tags_for_attributes (GtkTextBuffer     *buffer,
-                            PangoAttrIterator *iter,
-                            GtkTextIter       *start,
-                            GtkTextIter       *end)
-{
-  GtkTextTagTable *table;
-  PangoAttribute *attr;
-  GtkTextTag *tag;
-  char name[256];
-
-  table = gtk_text_buffer_get_tag_table (buffer);
-
-#define STRING_ATTR(pango_attr_name, attr_name) \
-  attr = pango_attr_iterator_get (iter, pango_attr_name); \
-  if (attr) \
-    { \
-      const char *string = ((PangoAttrString*)attr)->value; \
-      g_snprintf (name, 256, #attr_name "=%s", string); \
-      tag = gtk_text_tag_table_lookup (table, name); \
-      if (!tag) \
-        { \
-          tag = gtk_text_tag_new (name); \
-          g_object_set (tag, #attr_name, string, NULL); \
-          gtk_text_tag_table_add (table, tag); \
-          g_object_unref (tag); \
-        } \
-      gtk_text_buffer_apply_tag (buffer, tag, start, end); \
-    }
-
-#define INT_ATTR(pango_attr_name, attr_name) \
-  attr = pango_attr_iterator_get (iter, pango_attr_name); \
-  if (attr) \
-    { \
-      int value = ((PangoAttrInt*)attr)->value; \
-      g_snprintf (name, 256, #attr_name "=%d", value); \
-      tag = gtk_text_tag_table_lookup (table, name); \
-      if (!tag) \
-        { \
-          tag = gtk_text_tag_new (name); \
-          g_object_set (tag, #attr_name, value, NULL); \
-          gtk_text_tag_table_add (table, tag); \
-          g_object_unref (tag); \
-        } \
-      gtk_text_buffer_apply_tag (buffer, tag, start, end); \
-    }
-
-#define FLOAT_ATTR(pango_attr_name, attr_name) \
-  attr = pango_attr_iterator_get (iter, pango_attr_name); \
-  if (attr) \
-    { \
-      float value = ((PangoAttrFloat*)attr)->value; \
-      g_snprintf (name, 256, #attr_name "=%g", value); \
-      tag = gtk_text_tag_table_lookup (table, name); \
-      if (!tag) \
-        { \
-          tag = gtk_text_tag_new (name); \
-          g_object_set (tag, #attr_name, value, NULL); \
-          gtk_text_tag_table_add (table, tag); \
-          g_object_unref (tag); \
-        } \
-      gtk_text_buffer_apply_tag (buffer, tag, start, end); \
-    }
-
-#define RGBA_ATTR(pango_attr_name, attr_name) \
-  attr = pango_attr_iterator_get (iter, pango_attr_name); \
-  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.; \
-      char *str = gdk_rgba_to_string (&rgba); \
-      g_snprintf (name, 256, #attr_name "=%s", str); \
-      g_free (str); \
-      tag = gtk_text_tag_table_lookup (table, name); \
-      if (!tag) \
-        { \
-          tag = gtk_text_tag_new (name); \
-          g_object_set (tag, #attr_name, &rgba, NULL); \
-          gtk_text_tag_table_add (table, tag); \
-          g_object_unref (tag); \
-        } \
-      gtk_text_buffer_apply_tag (buffer, tag, start, end); \
-    }
-
-  attr = pango_attr_iterator_get (iter, PANGO_ATTR_LANGUAGE);
-  if (attr)
-    {
-      const char *language = pango_language_to_string (((PangoAttrLanguage*)attr)->value);
-      g_snprintf (name, 256, "language=%s", language);
-      tag = gtk_text_tag_table_lookup (table, name);
-      if (!tag)
-        {
-          tag = gtk_text_tag_new (name);
-          g_object_set (tag, "language", language, NULL);
-          gtk_text_tag_table_add (table, tag);
-          g_object_unref (tag);
-        }
-      gtk_text_buffer_apply_tag (buffer, tag, start, end);
-    }
-
-  STRING_ATTR (PANGO_ATTR_FAMILY, family)
-  INT_ATTR    (PANGO_ATTR_STYLE, style)
-  INT_ATTR    (PANGO_ATTR_WEIGHT, weight)
-  INT_ATTR    (PANGO_ATTR_VARIANT, variant)
-  INT_ATTR    (PANGO_ATTR_STRETCH, stretch)
-  INT_ATTR    (PANGO_ATTR_SIZE, size)
-
-  attr = pango_attr_iterator_get (iter, PANGO_ATTR_FONT_DESC);
-  if (attr)
-    {
-      PangoFontDescription *desc = ((PangoAttrFontDesc*)attr)->desc;
-      char *str = pango_font_description_to_string (desc);
-      g_snprintf (name, 256, "font-desc=%s", str);
-      g_free (str);
-      tag = gtk_text_tag_table_lookup (table, name);
-      if (!tag)
-        {
-          tag = gtk_text_tag_new (name);
-          g_object_set (tag, "font-desc", desc, NULL);
-          gtk_text_tag_table_add (table, tag);
-          g_object_unref (tag);
-        }
-      gtk_text_buffer_apply_tag (buffer, tag, start, end);
-    }
-
-  RGBA_ATTR   (PANGO_ATTR_FOREGROUND, foreground_rgba)
-  RGBA_ATTR   (PANGO_ATTR_BACKGROUND, background_rgba)
-  INT_ATTR    (PANGO_ATTR_UNDERLINE, underline)
-  RGBA_ATTR   (PANGO_ATTR_UNDERLINE_COLOR, underline_rgba)
-  INT_ATTR    (PANGO_ATTR_OVERLINE, overline)
-  RGBA_ATTR   (PANGO_ATTR_OVERLINE_COLOR, overline_rgba)
-  INT_ATTR    (PANGO_ATTR_STRIKETHROUGH, strikethrough)
-  RGBA_ATTR   (PANGO_ATTR_STRIKETHROUGH_COLOR, strikethrough_rgba)
-  INT_ATTR    (PANGO_ATTR_RISE, rise)
-  FLOAT_ATTR  (PANGO_ATTR_SCALE, scale)
-  INT_ATTR    (PANGO_ATTR_FALLBACK, fallback)
-  INT_ATTR    (PANGO_ATTR_LETTER_SPACING, letter_spacing)
-  STRING_ATTR (PANGO_ATTR_FONT_FEATURES, font_features)
-  INT_ATTR    (PANGO_ATTR_ALLOW_BREAKS, allow_breaks)
-  INT_ATTR    (PANGO_ATTR_SHOW, show_spaces)
-  INT_ATTR    (PANGO_ATTR_INSERT_HYPHENS, insert_hyphens)
-}
-
-typedef struct
-{
-  GtkTextBuffer *buffer;
-  GtkTextIter iter;
-  GtkTextMark *mark;
-  PangoAttrList *attributes;
-  char *text;
-  PangoAttrIterator *attr;
-} MarkupData;
-
-static void
-free_markup_data (MarkupData *mdata)
-{
-  gtk_text_buffer_delete_mark (mdata->buffer, mdata->mark);
-  pango_attr_iterator_destroy (mdata->attr);
-  pango_attr_list_unref (mdata->attributes);
-  g_free (mdata->text);
-  g_object_unref (mdata->buffer);
-  g_free (mdata);
-}
-
-static gboolean
-insert_markup_idle (gpointer data)
-{
-  MarkupData *mdata = data;
-  gint64 begin;
-
-  begin = g_get_monotonic_time ();
-
-  do
-    {
-      int start, end;
-      int start_offset;
-      GtkTextIter start_iter;
-
-      if (g_get_monotonic_time () - begin > G_TIME_SPAN_MILLISECOND)
-        {
-          g_idle_add (insert_markup_idle, data);
-          return G_SOURCE_REMOVE;
-        }
-
-      pango_attr_iterator_range (mdata->attr, &start, &end);
-
-      if (end == G_MAXINT) /* last chunk */
-        end = start - 1; /* resulting in -1 to be passed to _insert */
-
-      start_offset = gtk_text_iter_get_offset (&mdata->iter);
-      gtk_text_buffer_insert (mdata->buffer, &mdata->iter, mdata->text + start, end - start);
-      gtk_text_buffer_get_iter_at_offset (mdata->buffer, &start_iter, start_offset);
-
-      insert_tags_for_attributes (mdata->buffer, mdata->attr, &start_iter, &mdata->iter);
-
-      gtk_text_buffer_get_iter_at_mark (mdata->buffer, &mdata->iter, mdata->mark);
-    }
-  while (pango_attr_iterator_next (mdata->attr));
-
-  free_markup_data (mdata);
-  return G_SOURCE_REMOVE;
-}
-
-static void
-insert_markup (GtkTextBuffer *buffer,
-               GtkTextIter   *iter,
-               const char    *markup,
-               int            len)
-{
-  char *text;
-  PangoAttrList *attributes;
-  GError *error = NULL;
-  MarkupData *data;
-
-  g_return_if_fail (GTK_IS_TEXT_BUFFER (buffer));
-
-  if (!pango_parse_markup (markup, len, 0, &attributes, &text, NULL, &error))
-    {
-      g_warning ("Invalid markup string: %s", error->message);
-      g_error_free (error);
-      return;
-    }
-
-  if (!attributes)
-    {
-      gtk_text_buffer_insert (buffer, iter, text, -1);
-      g_free (text);
-      return;
-    }
-
-  data = g_new (MarkupData, 1);
-
-  data->buffer = g_object_ref (buffer);
-  data->iter = *iter;
-  data->attributes = attributes;
-  data->text = text;
-
-  /* create mark with right gravity */
-  data->mark = gtk_text_buffer_create_mark (buffer, NULL, iter, FALSE);
-  data->attr = pango_attr_list_get_iterator (attributes);
-
-  insert_markup_idle (data);
-}
-
-static void
-fontify_finish (GObject *source,
-                GAsyncResult *result,
-                gpointer data)
-{
-  GSubprocess *subprocess = G_SUBPROCESS (source);
-  GtkTextBuffer *buffer = data;
-  GBytes *stdout_buf = NULL;
-  GBytes *stderr_buf = NULL;
-  GError *error = NULL;
-
-  if (!g_subprocess_communicate_finish (subprocess,
-                                        result,
-                                        &stdout_buf,
-                                        &stderr_buf,
-                                        &error))
-    {
-      g_clear_pointer (&stdout_buf, g_bytes_unref);
-      g_clear_pointer (&stderr_buf, g_bytes_unref);
-
-      g_warning ("%s", error->message);
-      g_clear_error (&error);
-
-      g_object_unref (subprocess);
-      g_object_unref (buffer);
-      return;
-    }
-
-  if (g_subprocess_get_exit_status (subprocess) != 0)
-    {
-      if (stderr_buf)
-        g_warning ("%s", (char *)g_bytes_get_data (stderr_buf, NULL));
-      g_clear_pointer (&stderr_buf, g_bytes_unref);
-    }
-
-  g_object_unref (subprocess);
-
-  g_clear_pointer (&stderr_buf, g_bytes_unref);
-
-  if (stdout_buf)
-    {
-      char *markup;
-      gsize len;
-      char *p;
-      GtkTextIter start;
-
-      gtk_text_buffer_set_text (buffer, "", 0);
-
-      /* highlight puts a span with font and size around its output,
-       * which we don't want.
-       */
-      markup = g_bytes_unref_to_data (stdout_buf, &len);
-      for (p = markup + strlen ("<span "); *p != '>'; p++) *p = ' ';
-
-      gtk_text_buffer_get_start_iter (buffer, &start);
-      insert_markup (buffer, &start, markup, len);
-   }
-
-  g_object_unref (buffer);
-}
-
-void
-fontify (const char    *format,
-         GtkTextBuffer *source_buffer)
-{
-  GSubprocess *subprocess;
-  char *format_arg;
-  GtkSettings *settings;
-  char *theme;
-  gboolean prefer_dark;
-  const char *style_arg;
-  const char *text;
-  GtkTextIter start, end;
-  GBytes *bytes;
-  GError *error = NULL;
-
-  settings = gtk_settings_get_default ();
-  g_object_get (settings,
-                "gtk-theme-name", &theme,
-                "gtk-application-prefer-dark-theme", &prefer_dark,
-                NULL);
-
-  if (prefer_dark || strcmp (theme, "HighContrastInverse") == 0)
-    style_arg = "--style=edit-vim-dark";
-  else
-    style_arg = "--style=edit-kwrite";
-
-  g_free (theme);
-
-  format_arg = g_strconcat ("--syntax=", format, NULL);
-  subprocess = g_subprocess_new (G_SUBPROCESS_FLAGS_STDIN_PIPE |
-                                 G_SUBPROCESS_FLAGS_STDOUT_PIPE |
-                                 G_SUBPROCESS_FLAGS_STDERR_PIPE,
-                                 &error,
-                                 "highlight",
-                                 format_arg,
-                                 "--out-format=pango",
-                                 style_arg,
-                                 NULL);
-  g_free (format_arg);
-
-  if (!subprocess)
-    {
-      if (g_error_matches (error, G_SPAWN_ERROR, G_SPAWN_ERROR_NOENT))
-        {
-          static gboolean warned = FALSE;
-
-          if (!warned)
-            {
-              warned = TRUE;
-              g_message ("For syntax highlighting, install the “highlight” program");
-            }
-        }
-      else
-        g_warning ("%s", error->message);
-
-      g_clear_error (&error);
-
-      return;
-    }
-
-  gtk_text_buffer_get_bounds (source_buffer, &start, &end);
-  text = gtk_text_buffer_get_text (source_buffer, &start, &end, TRUE);
-  bytes = g_bytes_new_static (text, strlen (text));
-
-  /* Work around https://gitlab.gnome.org/GNOME/glib/-/issues/2182 */
-  if (G_IS_UNIX_OUTPUT_STREAM (g_subprocess_get_stdin_pipe (subprocess)))
-    {
-      GOutputStream *stdin_pipe = g_subprocess_get_stdin_pipe (subprocess);
-      int fd = g_unix_output_stream_get_fd (G_UNIX_OUTPUT_STREAM (stdin_pipe));
-      fcntl (fd, F_SETFL, O_NONBLOCK);
-    }
-
-  g_subprocess_communicate_async (subprocess,
-                                  bytes,
-                                  NULL,
-                                  fontify_finish,
-                                  g_object_ref (source_buffer));
-}
-
 static GtkWidget *
 display_image (const char  *format,
                const char  *resource,
diff --git a/demos/gtk-demo/meson.build b/demos/gtk-demo/meson.build
index 3cf3762d77..2ef7a443aa 100644
--- a/demos/gtk-demo/meson.build
+++ b/demos/gtk-demo/meson.build
@@ -93,6 +93,7 @@ demos = files([
 gtkdemo_deps = [ libgtk_dep, ]
 
 extra_demo_sources = files(['main.c',
+                            'fontify.c',
                             'gtkfishbowl.c',
                             'fontplane.c',
                             'gtkgears.c',