Watch for changes to images on disk

[Kieran Clancy]

OpenLP 1.9.9 (Windows XP Home)

Currently when an image is added to OpenLP, it's copied to another location and the original image is never touched again.

This means that if the original image is ever changed, OpenLP will never pick it up.

I think it could handle this a little more smartly:

1) The original image paths should be stored, and when OpenLP is started, it should check those paths for existence.

2) If the file exists and is a valid image, it should update the currently stored image. If the file does not exist, it should be ignored for the remainder of the session and the copy should be used (just in case it's been added from a weird place that only exists sometimes).

3) If the image existed, OpenLP should use the QT file watching API to watch for modifications/replacements of the image on disk.

4) Whenever an image is modified, OpenLP should run a callback to the original caller which asked for the image data, so that it can decide what to do with the updated image (if anything). For example, it could update the thumbnail shown and also update the preview/live view if it's being used at the time.

As a bonus of all this, it allows for some pretty cool things to be scripted as just changes to images. For example, you could produce a graph/plot of something live and have it update the image every so often by replacing it.

[Jonathan Corwin (j-corwin)]

I think there might already be a fix in the pipeline to address this
https://code.launchpad.net/~googol/openlp/image-queue/+merge/110793

[Tim Bentley (trb143)]

Most of what is the the request is incorrect. OpenLP will use the original copy of the image unless it gets added to a service, saved and then reloaded. At this point it is part of the service and NOT the original.

[Raoul Snyman (raoul-snyman)]

There are far too many problematic outcomes of this. A better solution would be a "refresh" button to reload the selected image from disk.

See bug #1436056