Our first task is to let the user add a new track while in the track editing mode. This involves defining a new map tool, which we will call AddTrackTool. Before we start implementing the
AddTrackTool class, however, we're going to create a mixin class that provides various helper methods for our map tools. We'll call this mixin class MapToolMixin.
Here is our initial implementation of the MapToolMixin class, which should be placed near the top of your mapTools.py module:
class MapToolMixin
def setLayer(self, layer):
self.layer = layer
def transformCoordinates(self, screenPt):
return (self.toMapCoordinates(screenPt),
self.toLayerCoordinates(self.layer, screenPt))
def calcTolerance(self, pos):
pt1 = QPoint(pos.x(), pos.y())
pt2 = QPoint(pos.x() + 10, pos.y())
mapPt1,layerPt1 = self.transformCoordinates(pt1)
mapPt2,layerPt2 = self.transformCoordinates(pt2)
tolerance = layerPt2.x() ...