Report progress callback

[AndreMiras]

I'm integrating your library to a Kivy graphical application.
I would like the user to know roughly the progress of the process.
I guess this could be achieved with a callback we could pass to the MBTilesBuilder.run() method.

[leplatrem]

Yes, why not. Or you could also poll a class attribute at regular interval. As you prefer...

[AndreMiras]

Thanks @leplatrem, I had a look at which attribute I could poll and I found only two relevant ones.
MBTilesBuilder.nbtiles and TilesManager.rendered.
While MBTilesBuilder.nbtiles gives the number of tiles in total for a given bbox, TilesManager.rendered gives the number of tiles that were downloaded. The problem is that when accessing cached tiles, the rendered counter doesn't get incremented. Which means we do not always get TilesManager.rendered = MBTilesBuilder.nbtiles at the end.
I think I'll probably use your polling method even though I'm not a big fan of polling patterns (compared to callbacks), but I'll inherit MBTilesBuilder to specialise it and always increment a counter on each loop.

[leplatrem]

As you wish !
Don't hesitate to provide a pull-request to introduce your callback ! We'll review it with pleasure ! Especially if it comes with a small test case.
Thanks for your feedback !