On my map canvas I have various point objects spread through several layers. My plan is to 'animate' those objects by a loop from start to a predefined resolution.

By now I'm just testing the algorithm with the vertical positions of the existing objects and an exportCanvas function which saves the canvas as a single image for each step.

Because this method isn't very handy I want to have the output of the loop directly to the canvas - delayed by e.g. 0.5 seconds per step.

result to be
Above is an example of the merged jpg-files to a gif

The problem is that my loop doesn't work very well at all and freezes my QGIS for the whole process time (+delay).
I know that I need some kind of hyperthreading or callback from QGIS to my plugin but at this point I have no clue how to transfer this idea to useful code

Down below: the code so far

# Animation: Button clicked
def btnAnimationClicked(self):       
    rate = 24

    # Werte zum Färben der xyz
    for i in range(0,rate,1):
        self.caller(i, self.callback)

# Animation: Caller
def caller(self, val, func):

# Animation: Callback
def callback(self, i):
    yhi = 5699049523 + 400000 
    ylo = 5696625163
    delta = yhi - ylo
    rate = 24
    ste = delta / rate 

    ubound = ylo + (ste * (i+1))
    lbound = ylo + (ste * i)

    values = (
        ('hi', ubound + 1, yhi, 'red'),
        ('is', lbound, ubound, 'green'),
        ('lo', ylo, lbound - 1, 'yellow'),
    # HaKasten abgestuft färben     
    for layer in QgsMapLayerRegistry.instance().mapLayers().values():
        if layer.name()[0:9] == "xyz_______":    
            ranges = []
            for label, lower, upper, color in values:
                symbol = QgsSymbolV2.defaultSymbol(layer.geometryType())
                rng = QgsRendererRangeV2(lower, upper, symbol, label)
            attribut = 'y'
            renderer = QgsGraduatedSymbolRendererV2(attribut, ranges)
    for layer in qgis.utils.iface.mapCanvas().layers():
    #time.sleep(0.5) # optional

1 Answer 1


With use of the modoule thread (>Python 3.0 _thread) you are able to start new threads inside your programm code.

import thread

# Animation: Button clicked
def btnAnimationClicked(self):            

# Animation: Caller
def caller(self):
    for i in range(0,24,1):

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