QGIS processing scripts, more than one progress bar in the generated GUI?

Question

Since I sometimes have to process cross product of two vector layers with geoprocessing scripts, causing me to use nested loops like

source_count = source_layer.featureCount()
target_count = target_layer.featureCount()
nsource = 1.0
for f_source in source_layer.getFeatures():
    ntarget = 1.0
    for f_target in target_layer.getFeatures():
        #do something
        targetprogress = 100 * (ntarget / target_count)
        ntarget += 1
    sourceprogress = 100  *(nsource / source_count)
    progress.setPercentage(sourceprogress)
    nsource += 1

When both layers consist of, let's say, some ten thousands of features, processing can be extremely time consuming, and to communicate the user that the processing is still alive, it would make sense to have a progress bar for each inner and outer loop.

I don't think this can be achieved with standard processing gui tools, but this combined with some Qt widgets? I'd like to do the processing in a script, not a plugin, in wich's Qt form various QprogressBars would be easy to implement.

Answer 1

You could import the necessary functions into your script with:

from PyQt4.QtGui import QProgressBar
from qgis.gui import QgsMessageBar

Then you can call the progress bar with:

msgBar= iface.messageBar()
pb= QProgressBar()
msgBar.pushWidget(pb, QgsMessageBar().INFO, 0)

and update the value in the progress bar in your loop:

pb.setValue(Your_variable)

However, as you pointed out, updating a progress bar in your inner loop can slow down the process. Cheers,