Hello. I already asked this on the PyQt mailing list but I guess it was not the
right place; this is more of a Qt problem. I’m trying to implement a custom URI
scheme handler, in a context where the underlying data will actually be fetched
asynchronously. I reduced the problem to the « minimal » code pasted below
(python 3.5, PyQt 5.8/Qt 5.8). Basically the problem is that when I call
QWebEngineUrlRequestJob.reply() with an instance of my custom QIODevice, I
expect the following:
1. bytesAvailable() is called, returns 0 (no data available yet)
2. The request job waits for readyRead to be emitted
3. The proceeds with bytesAvailable() / readData() until data is exhausted
4. Goto 2, until readChannelFinished is emitted
What actually happens:
1. bytesAvailable() is called, returns 0
2. The request job tries to read 32 Kb nonetheless
3. It gets no data, closes the QIODevice
Did I miss something here ? This happens on both mac OS and Linux. Didn’t try
on Windows yet.
TIA
Jérôme Laheurte
from PyQt5 import QtCore, QtWidgets
from PyQt5.QtWebEngineWidgets import QWebEngineView
from PyQt5.QtWebEngineCore import QWebEngineUrlSchemeHandler
class TestIODevice(QtCore.QIODevice):
def __init__(self):
super().__init__()
self.open(self.ReadOnly | self.Unbuffered)
self._data = b''
QtCore.QTimer.singleShot(1000, self._dataReceived)
def _dataReceived(self):
print('== RECV')
self._data = b'foo'
self.readyRead.emit()
def bytesAvailable(self):
count = len(self._data) + super().bytesAvailable()
print('== AVAIL', count)
return count
def isSequential(self):
return True
def readData(self, maxSize):
print('== READ', maxSize)
data, self._data = self._data[:maxSize], self._data[maxSize:]
return data
def close(self):
print('== CLOSE')
super().close()
class TestHandler(QWebEngineUrlSchemeHandler):
def requestStarted(self, request):
self._dev = TestIODevice() # Must keep ref
request.reply(b'text/plain', self._dev)
class TestWindow(QtWidgets.QMainWindow):
def __init__(self):
super().__init__()
self._view = QWebEngineView(self)
self._handler = TestHandler() # Must keep ref
self._view.page().profile().installUrlSchemeHandler(b'spam',
self._handler)
self._view.setHtml('<html><head><title>Test</title></head><body><img
src="spam:eggs" /></body></html>')
self.setCentralWidget(self._view)
self.show()
self.raise_()
if __name__ == '__main__':
app = QtWidgets.QApplication([])
win = TestWindow()
app.exec_()
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