[gtk/demo-highlighting] gtk-demo: Modernize source highlighting

[Matthias Clasen <matthiasc src gnome org>]

commit 05255bfc90310445dae52683ce45729e599d078b
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Aug 7 09:21:29 2020 -0400

    gtk-demo: Modernize source highlighting
    
    Drop the homegrown highlighting code, and just use highlight
    to produce Pango markup.
    
    When using an external highlighter, we can also highlight css,
    xml, headers, at least.

 demos/gtk-demo/main.c | 447 +++++++++++---------------------------------------
 1 file changed, 93 insertions(+), 354 deletions(-)
---
diff --git a/demos/gtk-demo/main.c b/demos/gtk-demo/main.c
index 95541fcfd9..1589b3d4bc 100644
--- a/demos/gtk-demo/main.c
+++ b/demos/gtk-demo/main.c
@@ -234,373 +234,106 @@ activate_run (GSimpleAction *action,
   gtk_demo_run (demo, window);
 }
 
-/* Stupid syntax highlighting.
- *
- * No regex was used in the making of this highlighting.
- * It should only work for simple cases.  This is good, as
- * that's all we should have in the demos.
- */
-/* This code should not be used elsewhere, except perhaps as an example of how
- * to iterate through a text buffer.
- */
-enum {
-  STATE_NORMAL,
-  STATE_IN_COMMENT
-};
-
-static const char *tokens[] =
-{
-  "/*",
-  "\"",
-  NULL
-};
-
-static const char *types[] =
+static GBytes *
+fontify_text (const char *format,
+              const char *text)
 {
-  "static",
-  "const ",
-  "void",
-  " int ",
-  " char ",
-  "char ",
-  "float",
-  "double",
-  "gint8",
-  "gint16",
-  "gint32",
-  "guint",
-  "guint8",
-  "guint16",
-  "guint32",
-  "guchar",
-  "glong",
-  "gboolean" ,
-  "gshort",
-  "gushort",
-  "gulong",
-  "gpointer",
-  "NULL",
-  "GList",
-  "GSList",
-  "FALSE",
-  "TRUE",
-  "FILE ",
-  "GtkColorSelection ",
-  "GtkWidget ",
-  "GtkButton ",
-  "GdkColor ",
-  "GdkRectangle ",
-  "GdkEventExpose ",
-  "GdkGC ",
-  "GdkPixbufLoader ",
-  "GdkPixbuf ",
-  "GError",
-  "size_t",
-  "GtkAboutDialog ",
-  "GtkAction ",
-  "GtkActionEntry ",
-  "GtkRadioActionEntry ",
-  "GtkIconFactory ",
-  "GtkTextBuffer ",
-  "GtkStatusbar ",
-  "GtkTextIter ",
-  "GtkTextMark ",
-  "GdkEventWindowState ",
-  "GtkActionGroup ",
-  "GtkUIManager ",
-  "GtkRadioAction ",
-  "GtkActionClass ",
-  "GtkToggleActionEntry ",
-  "GtkAssistant ",
-  "GtkBuilder ",
-  "GtkSizeGroup ",
-  "GtkTreeModel ",
-  "GtkTreeSelection ",
-  "GdkDisplay ",
-  "GdkScreen ",
-  "GdkSurface ",
-  "GdkEventButton ",
-  "GdkCursor ",
-  "GtkTreeIter ",
-  "GtkTreeViewColumn ",
-  "GdkDisplayManager ",
-  "GdkClipboard ",
-  "GtkIconSize ",
-  "GtkImage ",
-  "GdkDragContext ",
-  "GtkSelectionData ",
-  "GtkDialog ",
-  "GtkMenuItem ",
-  "GtkListStore ",
-  "GtkCellLayout ",
-  "GtkCellRenderer ",
-  "GtkTreePath ",
-  "GtkTreeStore ",
-  "GtkEntry ",
-  "GtkEditable ",
-  "GtkEditableInterface ",
-  "GdkPixmap ",
-  "GdkEventConfigure ",
-  "GdkEventMotion ",
-  "GdkModifierType ",
-  "GtkEntryCompletion ",
-  "GtkToolItem ",
-  "GDir ",
-  "GtkIconView ",
-  "GtkCellRendererText ",
-  "GtkContainer ",
-  "GtkPaned ",
-  "GtkPrintOperation ",
-  "GtkPrintContext ",
-  "cairo_t ",
-  "PangoLayout "
-  "PangoFontDescription ",
-  "PangoRenderer ",
-  "PangoMatrix ",
-  "PangoContext ",
-  "PangoLayout ",
-  "GtkToggleButton ",
-  "GString ",
-  "GtkIconSize ",
-  "GtkTreeView ",
-  "GtkTextTag ",
-  "GdkEvent ",
-  "GdkEventKey ",
-  "GtkTextView ",
-  "GdkBitmap ",
-  "GtkTextChildAnchor ",
-  "GArray ",
-  "GtkCellEditable ",
-  "GtkCellRendererToggle ",
-  NULL
-};
-
-static const char *control[] =
-{
-  " if ",
-  " while ",
-  " else",
-  " do ",
-  " for ",
-  "?",
-  ":",
-  "return ",
-  "goto ",
-  NULL
-};
-void
-parse_chars (char        *text,
-             char       **end_ptr,
-             int         *state,
-             const char **tag,
-             gboolean     start)
-{
-  int i;
-  char *next_token;
-
-  /* Handle comments first */
-  if (*state == STATE_IN_COMMENT)
+  GSubprocess *subprocess;
+  static gboolean warned = FALSE;
+  GBytes *stdin_buf;
+  GBytes *stdout_buf = NULL;
+  GBytes *stderr_buf = NULL;
+  GError *error = NULL;
+  char *format_arg;
+
+  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",
+                                 NULL);
+  g_free (format_arg);
+
+  if (!subprocess)
     {
-      *end_ptr = strstr (text, "*/");
-      if (*end_ptr)
+      if (!warned)
         {
-          *end_ptr += 2;
-          *state = STATE_NORMAL;
-          *tag = "comment";
+          g_warning ("%s", error->message);
+          warned = TRUE;
         }
-      return;
+      g_clear_error (&error);
+
+      return NULL;
     }
 
-  *tag = NULL;
-  *end_ptr = NULL;
+  stdin_buf = g_bytes_new_static (text, strlen (text));
 
-  /* check for comment */
-  if (!strncmp (text, "/*", 2))
+  if (!g_subprocess_communicate (subprocess,
+                                 stdin_buf,
+                                 NULL,
+                                 &stdout_buf,
+                                 &stderr_buf,
+                                 &error))
     {
-      *end_ptr = strstr (text, "*/");
-      if (*end_ptr)
-        *end_ptr += 2;
-      else
-        *state = STATE_IN_COMMENT;
-      *tag = "comment";
-      return;
-    }
+      g_clear_pointer (&stdin_buf, g_bytes_unref);
+      g_clear_pointer (&stdout_buf, g_bytes_unref);
+      g_clear_pointer (&stderr_buf, g_bytes_unref);
 
-  /* check for preprocessor defines */
-  if (*text == '#' && start)
-    {
-      *end_ptr = NULL;
-      *tag = "preprocessor";
-      return;
-    }
+      g_warning ("%s", error->message);
+      g_clear_error (&error);
 
-  /* functions */
-  if (start && * text != '\t' && *text != ' ' && *text != '{' && *text != '}')
-    {
-      if (strstr (text, "("))
-        {
-          *end_ptr = strstr (text, "(");
-          *tag = "function";
-          return;
-        }
+      return NULL;
     }
-  /* check for types */
-  for (i = 0; types[i] != NULL; i++)
-    if (!strncmp (text, types[i], strlen (types[i])) ||
-        (start && types[i][0] == ' ' && !strncmp (text, types[i] + 1, strlen (types[i]) - 1)))
-      {
-        *end_ptr = text + strlen (types[i]);
-        *tag = "type";
-        return;
-      }
-
-  /* check for control */
-  for (i = 0; control[i] != NULL; i++)
-    if (!strncmp (text, control[i], strlen (control[i])))
-      {
-        *end_ptr = text + strlen (control[i]);
-        *tag = "control";
-        return;
-      }
-
-  /* check for string */
-  if (text[0] == '"')
-    {
-      int maybe_escape = FALSE;
 
-      *end_ptr = text + 1;
-      *tag = "string";
-      while (**end_ptr != '\000')
-        {
-          if (**end_ptr == '\"' && !maybe_escape)
-            {
-              *end_ptr += 1;
-              return;
-            }
-          if (**end_ptr == '\\')
-            maybe_escape = TRUE;
-          else
-            maybe_escape = FALSE;
-          *end_ptr += 1;
-        }
-      return;
-    }
+  g_bytes_unref (stdin_buf);
 
-  /* not at the start of a tag.  Find the next one. */
-  for (i = 0; tokens[i] != NULL; i++)
+  if (g_subprocess_get_exit_status (subprocess) != 0)
     {
-      next_token = strstr (text, tokens[i]);
-      if (next_token)
-        {
-          if (*end_ptr)
-            *end_ptr = (*end_ptr<next_token)?*end_ptr:next_token;
-          else
-            *end_ptr = next_token;
-        }
-    }
+      if (stderr_buf)
+        g_warning ("%s", (char *)g_bytes_get_data (stderr_buf, NULL));
 
-  for (i = 0; types[i] != NULL; i++)
-    {
-      next_token = strstr (text, types[i]);
-      if (next_token)
-        {
-          if (*end_ptr)
-            *end_ptr = (*end_ptr<next_token)?*end_ptr:next_token;
-          else
-            *end_ptr = next_token;
-        }
+      g_clear_pointer (&stdout_buf, g_bytes_unref);
     }
 
-  for (i = 0; control[i] != NULL; i++)
-    {
-      next_token = strstr (text, control[i]);
-      if (next_token)
-        {
-          if (*end_ptr)
-            *end_ptr = (*end_ptr<next_token)?*end_ptr:next_token;
-          else
-            *end_ptr = next_token;
-        }
-    }
+  g_clear_pointer (&stderr_buf, g_bytes_unref);
+
+  g_object_unref (subprocess);
+
+  return stdout_buf;
 }
 
-/* While not as cool as c-mode, this will do as a quick attempt at highlighting */
 void
-fontify (GtkTextBuffer *source_buffer)
+fontify (const char    *format,
+         GtkTextBuffer *source_buffer)
 {
-  GtkTextIter start_iter, next_iter, tmp_iter;
-  int state;
+  GtkTextIter start, end;
   char *text;
-  char *start_ptr, *end_ptr;
-  const char *tag;
-
-  gtk_text_buffer_create_tag (source_buffer, "source",
-                              "font", "monospace",
-                              NULL);
-  gtk_text_buffer_create_tag (source_buffer, "comment",
-                              "foreground", "DodgerBlue",
-                              NULL);
-  gtk_text_buffer_create_tag (source_buffer, "type",
-                              "foreground", "ForestGreen",
-                              NULL);
-  gtk_text_buffer_create_tag (source_buffer, "string",
-                              "foreground", "RosyBrown",
-                              "weight", PANGO_WEIGHT_BOLD,
-                              NULL);
-  gtk_text_buffer_create_tag (source_buffer, "control",
-                              "foreground", "purple",
-                              NULL);
-  gtk_text_buffer_create_tag (source_buffer, "preprocessor",
-                              "style", PANGO_STYLE_OBLIQUE,
-                              "foreground", "burlywood4",
-                              NULL);
-  gtk_text_buffer_create_tag (source_buffer, "function",
-                              "weight", PANGO_WEIGHT_BOLD,
-                              "foreground", "DarkGoldenrod4",
-                              NULL);
-
-  gtk_text_buffer_get_bounds (source_buffer, &start_iter, &tmp_iter);
-  gtk_text_buffer_apply_tag_by_name (source_buffer, "source", &start_iter, &tmp_iter);
-
-  state = STATE_NORMAL;
+  GBytes *bytes;
 
-  gtk_text_buffer_get_iter_at_offset (source_buffer, &start_iter, 0);
+  gtk_text_buffer_get_bounds (source_buffer, &start, &end);
+  text = gtk_text_buffer_get_text (source_buffer, &start, &end, TRUE);
 
-  next_iter = start_iter;
-  while (gtk_text_iter_forward_line (&next_iter))
+  bytes = fontify_text (format, text);
+  if (bytes)
     {
-      gboolean start = TRUE;
-      start_ptr = text = gtk_text_iter_get_text (&start_iter, &next_iter);
-
-      do
-        {
-          parse_chars (start_ptr, &end_ptr, &state, &tag, start);
-
-          start = FALSE;
-          if (end_ptr)
-            {
-              tmp_iter = start_iter;
-              gtk_text_iter_forward_chars (&tmp_iter, end_ptr - start_ptr);
-            }
-          else
-            {
-              tmp_iter = next_iter;
-            }
-          if (tag)
-            gtk_text_buffer_apply_tag_by_name (source_buffer, tag, &start_iter, &tmp_iter);
+      const char *markup;
+      gsize len;
 
-          start_iter = tmp_iter;
-          start_ptr = end_ptr;
-        }
-      while (end_ptr);
-
-      g_free (text);
-      start_iter = next_iter;
+      markup = g_bytes_get_data (bytes, &len);
+      gtk_text_buffer_delete (source_buffer, &start, &end);
+      gtk_text_buffer_insert_markup (source_buffer, &start, markup, len);
+      g_bytes_unref (bytes);
     }
+
+  g_free (text);
 }
 
 static GtkWidget *
-display_image (const char *resource)
+display_image (const char *format,
+               const char *resource)
 {
   GtkWidget *sw, *image;
 
@@ -614,7 +347,8 @@ display_image (const char *resource)
 }
 
 static GtkWidget *
-display_text (const char *resource)
+display_text (const char *format,
+              const char *resource)
 {
   GtkTextBuffer *buffer;
   GtkWidget *textview, *sw;
@@ -641,8 +375,10 @@ display_text (const char *resource)
 
   buffer = gtk_text_buffer_new (NULL);
   gtk_text_buffer_set_text (buffer, g_bytes_get_data (bytes, NULL), g_bytes_get_size (bytes));
-  if (g_str_has_suffix (resource, ".c"))
-    fontify (buffer);
+
+  if (format)
+    fontify (format, buffer);
+
   gtk_text_view_set_buffer (GTK_TEXT_VIEW (textview), buffer);
 
   g_bytes_unref (bytes);
@@ -657,7 +393,8 @@ display_text (const char *resource)
 }
 
 static GtkWidget *
-display_video (const char *resource)
+display_video (const char *format,
+               const char *resource)
 {
   GtkWidget *video;
 
@@ -684,18 +421,20 @@ display_nothing (const char *resource)
 
 static struct {
   const char *extension;
-  GtkWidget * (* display_func) (const char *resource);
+  const char *format;
+  GtkWidget * (* display_func) (const char *format,
+                                const char *resource);
 } display_funcs[] = {
-  { ".gif", display_image },
-  { ".jpg", display_image },
-  { ".png", display_image },
-  { ".c", display_text },
-  { ".css", display_text },
-  { ".glsl", display_text },
-  { ".h", display_text },
-  { ".txt", display_text },
-  { ".ui", display_text },
-  { ".webm", display_video }
+  { ".gif", NULL, display_image },
+  { ".jpg", NULL, display_image },
+  { ".png", NULL, display_image },
+  { ".c", "c", display_text },
+  { ".css", "css", display_text },
+  { ".glsl", NULL, display_text },
+  { ".h", "c", display_text },
+  { ".txt", NULL, display_text },
+  { ".ui", "xml", display_text },
+  { ".webm", NULL, display_video }
 };
 
 static void
@@ -725,7 +464,7 @@ add_data_tab (const char *demoname)
         }
 
       if (j < G_N_ELEMENTS(display_funcs))
-        widget = display_funcs[j].display_func (resource_name);
+        widget = display_funcs[j].display_func (display_funcs[j].format, resource_name);
       else
         widget = display_nothing (resource_name);
 
@@ -920,7 +659,7 @@ load_file (const char *demoname,
 
   g_strfreev (lines);
 
-  fontify (source_buffer);
+  fontify ("c", source_buffer);
 
   gtk_text_buffer_end_irreversible_action (source_buffer);
   gtk_text_view_set_buffer (GTK_TEXT_VIEW (source_view), source_buffer);