Changing marker shape to ArrowHead using PyQGIS

Question

With the code below I can add a marker to the symbology of a line type layer. But by default, this marker is a circle.

layerName = 'rede_bombas'
vLayer = QgsProject.instance().mapLayersByName(layerName)[0]

ggsl = QgsGeometryGeneratorSymbolLayer.create({})
ggsl.setSymbolType(QgsSymbol.Marker)
ggsl.setGeometryExpression("centroid($geometry)")
ggsl.setColor(QColor('Blue'))
symbol = vLayer.renderer().symbols(QgsRenderContext())[0]
symbol.insertSymbolLayer(1, ggsl)
vLayer.triggerRepaint()

How do I change the marker shape to ArrowHead?

Is it possible to adjust the marker rotation according to the line rotation?

Answer 1

I would recommend using a QgsMarkerLineSymbolLayer rather than a QgsGeometryGeneratorSymbolLayer.

For example:

layerName = 'rede_bombas'
vLayer = QgsProject.instance().mapLayersByName(layerName)[0]

sym = vLayer.renderer().symbol()
arrow_sym = QgsMarkerSymbol.createSimple({'name': 'arrowhead', 'outline_color': 'blue'})
marker_line_symbol_layer = QgsMarkerLineSymbolLayer()
marker_line_symbol_layer.setSubSymbol(arrow_sym)
marker_line_symbol_layer.setPlacement(Qgis.MarkerLinePlacement.SegmentCenter)
sym.appendSymbolLayer(marker_line_symbol_layer)
vLayer.triggerRepaint()

Expected result:

Though not about PyQGIS, this Q & A may be useful, as would the section on Appearance (Symbology) of Vector Layers from the PyQGIS Developer Cookbook.