Folium map embedded within PyQt displays blank when adding GeoJson to layer [duplicate] - pyqt5

Question

This question already has answers here:
Add a large shapefile to map in python using folium
(1 answer)
Use QWebEngineView to Display Something Larger Than 2MB?
(1 answer)
Closed 12 months ago.
I have PyQt5 app that embeds a folium Map within a QWidget.
Here's a minimal example of the class I wrote :
import folium
import io
from folium.plugins import Draw, MousePosition, HeatMap
from PySide2 import QtWidgets, QtWebEngineWidgets
class FoliumMap(QtWidgets.QWidget):
def __init__(self, parent=None):
QtWidgets.QWidget.__init__(self, parent)
self.layout = QtWidgets.QVBoxLayout()
m = folium.Map(
title='coastlines',
zoom_start=3)
data = io.BytesIO()
m.save(data, close_file=False)
webView = QtWebEngineWidgets.QWebEngineView()
webView.setHtml(data.getvalue().decode())
self.layout.addWidget(webView)
self.setLayout(self.layout)
If i run my program here's what I have :
Now I want to add a GeoJson layer within the __init__ of my class :
folium.GeoJson('data/custom.geo.json', name='coasts').add_to(m)
This results in having a blank Qwidget :
If I save the map under html format I am able to see the layer on my web browser:
Has anyone an idea on why the layer implementation makes the QWidget blank ? And how to fix this ?

Answer 1

The problem seems to be the following command :
webView.setHtml(data.getvalue().decode())
It is said in the Qt documentation that :
Content larger than 2 MB cannot be displayed, because setHtml() converts the provided HTML to percent-encoding and places data: in front of it to create the URL that it navigates to. Thereby, the provided code becomes a URL that exceeds the 2 MB limit set by Chromium. If the content is too large, the loadFinished() signal is triggered with success=false.
My html file weighs 2628 KB > 2MB. So we have to use webView.load() method instead.
This is the way to go :
import folium
import io
from folium.plugins import Draw, MousePosition, HeatMap
from PySide2 import QtWidgets, QtWebEngineWidgets, QtCore
class FoliumMap(QtWidgets.QWidget):
def __init__(self, parent=None):
QtWidgets.QWidget.__init__(self, parent)
self.layout = QtWidgets.QVBoxLayout()
m = folium.Map(
title='coastlines',
zoom_start=3)
url = "C:/MYPATH/TO/map.html"
m.save(url)
webView = QtWebEngineWidgets.QWebEngineView()
html_map = QtCore.QUrl.fromLocalFile(url)
webView.load(html_map)
self.layout.addWidget(webView)
self.setLayout(self.layout)