xF: push huge logs directly to external editors

At around 10 megabytes, processing starts taking quite long.

It might be a good idea to remove the log view altogether now;
it's only there because we copied other frontends.

xF.c

@@ -422,7 +422,8 @@ struct log_view
 	char *buffer_name;                   ///< Stamp: the buffer we want logs for
 
 	bool visible;                        ///< We see the log rather than backlog
-	ARRAY (struct buffer_line *, lines)  ///< Log split into display lines
+	struct buffer_line **lines;          ///< Log split into display lines
+	size_t lines_len;                    ///< Number of lines
 	int offset;                          ///< XUI pixels above the bottom
 };
 
@@ -1123,6 +1124,9 @@ app_process_completion_response
 
 // ~~~ Log request ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+static bool app_launch_external_editor (const char *template_name,
+	const char *contents, size_t contents_len, bool viewing_transcript);
+
 static void
 log_view_request_start (struct log_view *self, uint32_t request_seq,
 	const char *buffer_name)
@@ -1149,7 +1153,7 @@ log_view_hide (struct log_view *self)
 		buffer_line_destroy (self->lines[i]);
 	free (self->lines);
 	self->lines = NULL;
-	self->lines_len = self->lines_alloc = 0;
+	self->lines_len = 0;
 	self->offset = 0;
 }
 
@@ -1161,19 +1165,18 @@ log_view_free (struct log_view *self)
 }
 
 static void
-log_view_show (struct log_view *self, char *text_owned)
+log_view_show (struct log_view *self, const char *text)
 {
 	log_view_hide (self);
+
 	struct strv lines = strv_make ();
-	cstr_split (text_owned, "\r\n", true, &lines);
-	free (text_owned);
-	ARRAY_INIT (self->lines);
+	cstr_split (text, "\r\n", true, &lines);
+	self->lines = xcalloc (lines.len, sizeof *self->lines);
 	for (size_t i = 0; i < lines.len; i++)
 	{
 		struct buffer_line *line = xcalloc (1, sizeof *line);
 		buffer_line_add_item (line, lines.vector[i], -1, -1, 0);
 		buffer_line_finalize (line);
-		ARRAY_RESERVE (self->lines, 1);
 		self->lines[self->lines_len++] = line;
 	}
 	strv_free (&lines);
@@ -1186,10 +1189,15 @@ app_process_log_response (const struct relay_response_data_buffer_log *response)
 	if (g.buffer_current && g.log.buffer_name
 	 && !strcmp (g.buffer_current->buffer_name, g.log.buffer_name))
 	{
-		log_view_show (&g.log,
-			utf8_validate ((const char *) response->log, response->log_len)
-				? xstrndup ((const char *) response->log, response->log_len)
-				: xstrdup ("Log is not valid UTF-8."));
+		// We're not that performant with layouting.
+		const char *log = (const char *) response->log;
+		if (response->log_len > 1 << 20)
+			app_launch_external_editor
+				("log.XXXXXX.txt", log, response->log_len, true);
+		else if (!utf8_validate (log, response->log_len))
+			print_error ("log is not valid UTF-8");
+		else
+			log_view_show (&g.log, log);
 	}
 	log_view_request_reset (&g.log);
 	g.log.offset = 0;
@@ -3796,42 +3804,25 @@ transcript_text_visit (enum transcript_visit_kind kind,
 }
 
 static bool
-app_launch_external_editor (bool view_transcript)
+app_launch_external_editor (const char *template_name,
+	const char *contents, size_t contents_len, bool viewing_transcript)
 {
 	if (g.editor_running_for || !g.buffer_current)
 		return false;
 
-	char *contents = NULL;
-	size_t contents_len = 0;
-	const char *template_name = "input.XXXXXX.txt";
-	if (view_transcript)
-	{
-		struct str text = str_make ();
-		app_walk_transcript (time (NULL), transcript_text_visit, &text);
-		contents_len = text.len;
-		contents = str_steal (&text);
-		template_name = "transcript.XXXXXX.txt";
-	}
-	else
-	{
-		contents = app_editor_text ();
-		contents_len = strlen (contents);
-	}
-
 	struct error *err = NULL;
 	char *filename = app_external_editor_make_file (template_name,
 		contents, contents_len, &err);
-	free (contents);
 	if (!filename)
 	{
-		print_error ("failed to prepare input for editing: %s", err->message);
+		print_error ("failed to prepare editor contents: %s", err->message);
 		error_free (err);
 		return false;
 	}
 
 	g.editor_running_for = xstrdup (g.buffer_current->buffer_name);
 	g.editor_filename = filename;
-	g.editor_shows_transcript = view_transcript;
+	g.editor_shows_transcript = viewing_transcript;
 	xui_invalidate ();
 
 	if (!app_external_editor_launch (&err))
@@ -3844,6 +3835,27 @@ app_launch_external_editor (bool view_transcript)
 	return true;
 }
 
+static bool
+app_launch_input_editor (void)
+{
+	char *contents = app_editor_text ();
+	bool result = app_launch_external_editor ("input.XXXXXX.txt",
+		contents, strlen (contents), false);
+	free (contents);
+	return result;
+}
+
+static bool
+app_launch_transcript_editor (void)
+{
+	struct str text = str_make ();
+	app_walk_transcript (time (NULL), transcript_text_visit, &text);
+	bool result = app_launch_external_editor ("transcript.XXXXXX.txt",
+		text.str, text.len, true);
+	str_free (&text);
+	return result;
+}
+
 // ~~~ Action and mouse dispatch ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 static const enum line_editor_action g_editor_actions[] =
@@ -3942,9 +3954,9 @@ app_process_action (enum action action)
 	case ACTION_LOG:
 		return app_toggle_log ();
 	case ACTION_EDIT_INPUT:
-		return app_launch_external_editor (false);
+		return app_launch_input_editor ();
 	case ACTION_VIEW_TRANSCRIPT:
-		return app_launch_external_editor (true);
+		return app_launch_transcript_editor ();
 	case ACTION_OPEN:
 		return app_open_last_link ();
 	case ACTION_FORMAT: