vtl: check if server's docroot matches ardour's config

NOTE: this breaks backwards compatibility with icsd and
harvid < 0.3.0 which do not report their settings.

It may also conflict with harvid running on localhost in a chroot.

Ideally this will be a warning only.
That the user can choose to ignore this and should get the option
to stop the video-server and re-start it using a different docroot.

gtk2_ardour/ardour_ui.cc

@@ -3439,6 +3439,11 @@ ARDOUR_UI::start_video_server (Gtk::Window* float_window, bool popup_msg)
 		}
 		if (timeout <= 0) {
 			warning << _("Video-server was started but does not respond to requests...") << endmsg;
+		} else {
+			if (!ARDOUR_UI::instance()->video_timeline->check_server_docroot()) {
+				delete video_server_process;
+				video_server_process = 0;
+			}
 		}
 	}
 	return true;

gtk2_ardour/video_timeline.cc

@@ -553,6 +553,39 @@ VideoTimeLine::check_server ()
 	return ok;
 }
 
+bool
+VideoTimeLine::check_server_docroot ()
+{
+	bool ok = true;
+	char url[1024];
+	std::vector<std::vector<std::string> > lines;
+
+	if (video_server_url.find("/localhost:") == string::npos) {
+		return true;
+	}
+	snprintf(url, sizeof(url), "%s%src?format=csv"
+			, video_server_url.c_str()
+			, (video_server_url.length()>0 && video_server_url.at(video_server_url.length()-1) == '/')?"":"/"
+			);
+	char *res=curl_http_get(url, NULL);
+	if (!res) {
+		return false;
+	}
+
+	ParseCSV(std::string(res), lines);
+	if (   lines.empty()
+			|| lines.at(0).empty()
+			|| lines.at(0).at(0) != video_get_docroot(Config)) {
+		warning << string_compose(
+				_("Video-server docroot mismatch. Ardour: '%1', video-server: '%2'. This usually means that the video server was not started by ardour and uses a different document-root."),
+				video_get_docroot(Config), lines.at(0).at(0))
+		<< endmsg;
+		ok = false; // TODO allow to override
+	}
+	free(res);
+	return ok;
+}
+
 void
 VideoTimeLine::gui_update(std::string const & t) {
 	/* this is to be called via GuiUpdate() only. */

gtk2_ardour/video_timeline.h

@@ -86,6 +86,7 @@ class VideoTimeLine : public sigc::trackable, public ARDOUR::SessionHandlePtr, p
 
 	bool found_xjadeo () { return ((_xjadeo_bin.empty())?false:true); }
 	bool check_server ();
+	bool check_server_docroot ();
 	void flush_local_cache ();
 	void vmon_update ();
 	void flush_cache ();