which cannot run in background tasks
This is not fantastic UX, but we have lots of constraints here:
- The algorithm dialog itself cannot be made modal. There's child
widgets (such as the point and extent parameter widgets) which
interact with the main QGIS window.
- There is no reliable way in Qt to make a dialog modal after
it's shown (e.g. make it modal only when the algorithm is
running). Trust me - I've tried everything, and all approaches
break with some corner case.
- For non-background algorithms, we must have processEvents calls
in order to show the algorithm feedback and progress to users,
and detect cancel button clicks. Yet these processEvents calls
means that users can interact with other parts of QGIS, e.g.
removing layers from a project, and other operations which
could cause the algorithm to crash. So we MUST have some modal
dialog in order to block interactions outside of allowing
the cancel button clicks/progress repainting.
I've tried many approaches, but this is the only one which
works reliably...
Originally the background colour defaulted to white with no transparency for areas without vector data. I have added an alpha channel to the geotiff and set it zero (full transparency) for areas with no vector data. This could be optional, in case the user wants a solid background.
the algorithm dialog instead of immediately executing same alg
This allows users to edit the parameters before re-running,
which is a more common user-operation (e.g. changing the
input layer, changing a parameter value "oops, that buffer
was a bit too big....").
If someone wants to exactly re-run the algorithm without changes
it's only one extra click anyway...
Adds processing.createAlgorithmDialog and
processing.execAlgorithmDialog. These methods can be used
to create and execute algorithm dialogs for a specified algorithm,
optionally pre-populated with a given set of (non-default) parameter
values.
