How to auto-start a pyQGIS thread?

Question

having build some (two) minor plugins, it's now time for me to link a few (perl-) applications to qgis. As there is no perl-interface in qgis I thought the best way to link both worlds together is a kind of messaging system. It should work like tis:

• the perl-app sends a message to a certain folder
• qgis starts a separete loop which looks every second, whether there is an incoming message in that folder
• Qgis performs the necessary stuff an deletes the message again.
• Or vice versa.

My question is how to start such a loop in qgis and how to do this at qgis-startup.

By the way - is there a possibility to "automate" QGis from external python applications? And if so is there any example code?

Thanks and regards

Answer 1

You can do this with a plugin, using a QTimer.

In the init method of the plugin:

self.timer = QTimer()
self.timer.timeout.connect(self.timer_fired)
self.timer.start(10000)

Then define the timer_fired method:

def timer_fired(self):
    QMessageBox.information(None, "Timer", "Timer Fired")

In this example, QGIS will popup a message box every 10 seconds. For this to work, obviously QGIS must be running and your plugin loaded.