Printing html using QWebEngineView fails (PyQt5)

Koenux · 5 Mar 2020, 13:40

Hello everyone,

I'm trying to get print html code which is generated by my application, but unfortunately I can't get it to work.
The print preview shows the page but the quality looks bad, all I get is a corrupted PDF file and it is kinda slow. I had it working for years with PyQt4.x.

The code where I call my printer class:

	def _print(self, preview=False, PDF=False):
		if(not self.printer.readyState):
			print('printer class not ready yet.')
			return;

		tpl = '<html><head></head><body>Test</body></html>';

		self.printer.load();
		self.printer.forceLandscape = True;
		self.printer.fontfamily = str(self.cfg.value('fontsettings_0_font'))
		self.printer.fontsize = str(self.cfg.value('fontsettings_0_size'))
		self.printer.preview = preview;
		self.printer.pdf = PDF;
		self.printer.setHtml(tpl);
		self.printer.print();

The printer class (printer.py)

from typing import List

try:
	import sys, os, locale, subprocess
	from PyQt5.QtGui import *
	from PyQt5.QtCore import *
	from PyQt5.QtNetwork import *	
	from PyQt5.QtPrintSupport import QPrinter, QPrintPreviewDialog, QPrintDialog
	from PyQt5 import QtSql, QtGui
	from PyQt5.QtWidgets import QWidget, QDialog, QTextEdit

	from PyQt5.QtWebEngineWidgets import QWebEngineView,QWebEnginePage,QWebEngineSettings


except ImportError as msg:
	print("Exception: Couldn't import all required modules:\n-> ImportError: ", msg)
	sys.exit()

locale.setlocale(locale.LC_ALL, '')
locale.setlocale(locale.LC_NUMERIC, '')
	

class printer(QWidget):
	# Initialize printer class
	def __init__(self, parent=None):
		QWidget.__init__(self);
		self.parent = parent;
		self.pagecounter=-1;
		self.html="";
		self.preview=""
		self.m_page = None
		self.m_inPrintPreview = False
		self.page = QWebEnginePage();
		self.progress = 0;
		self.waiting = False;


		# tasklist
		self.readyState = True;

		self.defaultPageMargins=[float(self.parent.cfg.value('page_margin_rawdec_left')) \
		, float(self.parent.cfg.value('page_margin_rawdec_top')) \
		, float(self.parent.cfg.value('page_margin_rawdec_right')) \
		, float(self.parent.cfg.value('page_margin_rawdec_bottom')) \
		, int(self.parent.cfg.value('page_margin_rawdec_unit'))];
		

	def setPageMargins(self,a,b,c,d,e):
		self.pageMargins=[a,b,c,d,e];
		
	
	# Load printer for new job
	def load(self):
		self.fontfamily='Sans'
		self.fontsize='12'
		self.progress = 0;
		self.pages = [];
		self.pagecounter=-1;
		self.forceLandscape=False;
		self.pageMargins=self.defaultPageMargins;

	def readyTask(self):
		self.readyState = True;


	def pageSetup(self):
		ps = QPageSetupDialog(self.printer,self.doc);
		ps.open();



	def openPDF(self, filename="output.pdf"):
		if os.name == 'mac':
			subprocess.call(['open', filename])
		elif os.name == 'nt':
			subprocess.call(['start', filename], shell=True)
		elif os.name == 'posix':
			subprocess.call(['xdg-open', filename])


	def setHtml(self, html):
		self.page.setHtml(html)

	def pageloaded(self):
		print('webviewloaded')
		if(self.waiting):
			self.waiting = False;
			return self.print();

	def pageprogress(self,progress):
		print(progress)
		self.progress = progress;

	@property
	def page(self):
 		return self.m_page

	@page.setter
	def page(self, page):
		if isinstance(page, QWebEnginePage):
			self.m_page = page
			self.page.printRequested.connect(self.printPreview)
			self.page.loadFinished.connect(self.pageloaded)
			self.page.loadProgress.connect(self.pageprogress);

		else:
			raise TypeError("page must be a QWebEnginePage")


	def getPrinter(self):
		pm = self.pageMargins;
		printer = QPrinter(QPrinter.HighResolution)
		printer.setPageSize(QPrinter.A4);
		printer.setFullPage (True); # must be before set margin
		printer.setPageMargins(pm[0],pm[1],pm[2],pm[3], pm[4]);

		# Landscape or Portraitself.webview.show();
		if self.forceLandscape:
			printer.setOrientation(QPrinter.Landscape);
			self.forceLandscape=False;
		else:
			printer.setOrientation(QPrinter.Portrait);

		return printer;




	@pyqtSlot()
	def print(self):
		if(self.progress is not 100):
			self.waiting = True;
			print('waiting...')
			print(self.progress)
			return;

		print('ok')

		if(self.preview):
			return self.printPreview();


		printer = self.getPrinter();

		# PDF
		tmpfile=None;
		if(self.pdf):
			tmpfile = QTemporaryFile();
			if(tmpfile.open()):
				print(tmpfile)
				printer.setOutputFormat(QPrinter.PdfFormat)
				printer.setOutputFileName(tmpfile.fileName())
				return self.printDocument(printer,tmpfile)
			else:
				debug().critical("NoesAdmin printer.py couldn't open a temporary file.")
				return False;

		# Print dialog
		dialog = QPrintDialog(printer, self.page.view())
		if dialog.exec_() != QDialog.Accepted:
			self.readyTask();
			return
		self.printDocument(printer, tmpfile)

	@pyqtSlot()
	def printPreview(self):
		if self.page is None:
			return
		if self.m_inPrintPreview:
			return
		self.m_inPrintPreview = True

		printer = self.getPrinter();
		preview = QPrintPreviewDialog(printer,self.page.view())
		preview.paintRequested.connect(self.printDocument);

		if preview.exec_() != QDialog.Accepted:
			self.readyTask();
		self.m_inPrintPreview = False

	@pyqtSlot(QPrinter)
	def printDocument(self, printer, tmpfile=None):
		result = False
		loop = QEventLoop()
		self.parent.changeStatusBar('Printjob loading...');
		
		def printPreview(sucess):
			nonlocal result
			result = sucess
			loop.quit()
	
		self.page.print(printer,printPreview)
		loop.exec_()
		if not result:
			print('no result')
			painter = QPainter()
			if painter.begin(printer):
				font = painter.font()
				font.setPixelSize(20)
				painter.setFont(font)
				painter.drawText(QPointF(10, 25), "Could not generate print preview.")
				painter.end()
		self.readyTask();
		self.parent.readyStatusBar();


		if self.pdf and tmpfile:
			print('PDF print opening....');
			self.openPDF(tmpfile.fileName())

I tried to use QTextDocument as an alternative for QWebEngineView which worked perfectly fine except for the lack of support for modern html and css and I had trouble with the page size, so I rather use webengine if possible.

Does anyone have an idea where it goes wrong? Sorry if the code is a bit messy.

Thanks!

(Qt 5.12.5 - Python 3.7.7)

Koenux · wrote on 4 May 2020, 09:54

I've got a bit further than yesterday with this issue. I went back to the example on this website:
http://quabr.com:8182/59438021/how-do-i-create-a-print-preview-of-qwebengineview-in-pyqt5

The problem has to do something with:

printer = QPrinter(QPrinter.HighResolution)

When I use QPrinter() without the HighResolution part, everything works as expected. I didn't realise that the example had the same problem since it calls the printPreview method which doesn't have the resolution part.

Is this a bug in (Py)Qt?

Since my problem is fixed, I'm will mark it as solved.