python - Qt Webengine not loading openstreetmap tiles

Question

I wrote a python test program like this to show openstreetmap:

from PyQt5.QtWidgets import QApplication
from PyQt5.QtCore import QUrl
from PyQt5.QtWebEngineWidgets import QWebEngineView
import sys

def mainPyQt5():
    url = 'file:///./index.html'
    app = QApplication(sys.argv)
    browser = QWebEngineView()
    browser.load(QUrl(url))
    browser.show()
    sys.exit(app.exec_()) 
mainPyQt5()

index.html fetched by QWebEngineView simply calls openstreetmap:

<title>OSM and Leaflet</title>
<link rel = "stylesheet" href = "http://cdn.leafletjs.com/leaflet-0.7.3/leaflet.css"/>
<div id = "map" style = "width: 900px; height: 580px"></div><script src =  "http://cdn.leafletjs.com/leaflet-0.7.3/leaflet.js"></script>
<script>
         // Creating map options
         var mapOptions = {
            center: [45.641174, 9.114828],
            zoom: 10
         }
         
         // Creating a map object
         var map = new L.map('map', mapOptions);
         
         // Creating a Layer object
         var layer = new L.TileLayer('http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png');
         
         // Adding layer to the map
         map.addLayer(layer);
</script>

If I fetch index.html with a ordinary browser the map is shown as expected but if I call the simple python program using QWebEngineView no tiles are downloaded from openstreetmap. If I replace openstreetmap with maps.stamen.com everything is fine both with a browser or the python script.

Answer 1

By default QtWebEngine does not set default headers like popular browsers do. In this case the openstreetmap server needs to know the "Accept-Language" to produce the maps since for example the names of the cities will depend on the language to filter non-browser traffic. The solution is to implement a QWebEngineUrlRequestInterceptor that adds that header:

import os.path
import sys

from PyQt5.QtCore import QUrl
from PyQt5.QtWidgets import QApplication
from PyQt5.QtWebEngineCore import QWebEngineUrlRequestInterceptor
from PyQt5.QtWebEngineWidgets import QWebEngineView


class Interceptor(QWebEngineUrlRequestInterceptor):
    def interceptRequest(self, info):
        info.setHttpHeader(b"Accept-Language", b"en-US,en;q=0.9,es;q=0.8,de;q=0.7")


def mainPyQt5():
    CURRENT_DIR = os.path.dirname(os.path.realpath(__file__))
    filename = os.path.join(CURRENT_DIR, "index.html")
    app = QApplication(sys.argv)
    browser = QWebEngineView()

    interceptor = Interceptor()
    browser.page().profile().setUrlRequestInterceptor(interceptor)

    browser.load(QUrl.fromLocalFile(filename))
    browser.show()
    sys.exit(app.exec_())


if __name__ == "__main__":
    mainPyQt5()