Refactor print handling and fix window.print

On Qt 5.7.1, window.print() caused a CommandError which wasn't handled as the
command was called from accept_navigation_request.

Instead, we now show the dialog in AbstractPrinting and use that directly.

qutebrowser/browser/browsertab.py

@@ -25,7 +25,8 @@ import itertools
 import attr
 from PyQt5.QtCore import pyqtSignal, pyqtSlot, QUrl, QObject, QSizeF, Qt
 from PyQt5.QtGui import QIcon
-from PyQt5.QtWidgets import QWidget, QApplication
+from PyQt5.QtWidgets import QWidget, QApplication, QDialog
+from PyQt5.QtPrintSupport import QPrintDialog
 
 import pygments
 import pygments.lexers
@@ -187,8 +188,9 @@ class AbstractPrinting:
 
     """Attribute of AbstractTab for printing the page."""
 
-    def __init__(self):
+    def __init__(self, tab):
         self._widget = None
+        self._tab = tab
 
     def check_pdf_support(self):
         raise NotImplementedError
@@ -212,6 +214,29 @@ class AbstractPrinting:
         """
         raise NotImplementedError
 
+    def show_dialog(self):
+        """Print with a QPrintDialog."""
+        self.check_printer_support()
+
+        def print_callback(ok):
+            """Called when printing finished."""
+            if not ok:
+                message.error("Printing failed!")
+            diag.deleteLater()
+
+        def do_print():
+            """Called when the dialog was closed."""
+            self.to_printer(diag.printer(), print_callback)
+
+        diag = QPrintDialog(self._tab)
+        if utils.is_mac:
+            # For some reason we get a segfault when using open() on macOS
+            ret = diag.exec_()
+            if ret == QDialog.Accepted:
+                do_print()
+        else:
+            diag.open(do_print)
+
 
 class AbstractSearch(QObject):
 

qutebrowser/browser/commands.py

@@ -25,9 +25,9 @@ import shlex
 import functools
 import typing
 
-from PyQt5.QtWidgets import QApplication, QTabBar, QDialog
+from PyQt5.QtWidgets import QApplication, QTabBar
 from PyQt5.QtCore import pyqtSlot, Qt, QUrl, QEvent, QUrlQuery
-from PyQt5.QtPrintSupport import QPrintDialog, QPrintPreviewDialog
+from PyQt5.QtPrintSupport import QPrintPreviewDialog
 
 from qutebrowser.commands import userscripts, cmdexc, cmdutils, runners
 from qutebrowser.config import config, configdata
@@ -415,27 +415,6 @@ class CommandDispatcher:
         tab.printing.to_pdf(filename)
         log.misc.debug("Print to file: {}".format(filename))
 
-    def _print(self, tab):
-        """Print with a QPrintDialog."""
-        def print_callback(ok):
-            """Called when printing finished."""
-            if not ok:
-                message.error("Printing failed!")
-            diag.deleteLater()
-
-        def do_print():
-            """Called when the dialog was closed."""
-            tab.printing.to_printer(diag.printer(), print_callback)
-
-        diag = QPrintDialog(tab)
-        if utils.is_mac:
-            # For some reason we get a segfault when using open() on macOS
-            ret = diag.exec_()
-            if ret == QDialog.Accepted:
-                do_print()
-        else:
-            diag.open(do_print)
-
     @cmdutils.register(instance='command-dispatcher', name='print',
                        scope='window')
     @cmdutils.argument('count', count=True)
@@ -453,22 +432,15 @@ class CommandDispatcher:
             return
 
         try:
-            if pdf:
-                tab.printing.check_pdf_support()
-            else:
-                tab.printing.check_printer_support()
             if preview:
-                tab.printing.check_preview_support()
+                self._print_preview(tab)
+            elif pdf:
+                self._print_pdf(tab, pdf)
+            else:
+                tab.printing.show_dialog()
         except browsertab.WebTabError as e:
             raise cmdexc.CommandError(e)
 
-        if preview:
-            self._print_preview(tab)
-        elif pdf:
-            self._print_pdf(tab, pdf)
-        else:
-            self._print(tab)
-
     @cmdutils.register(instance='command-dispatcher', scope='window')
     def tab_clone(self, bg=False, window=False):
         """Duplicate the current tab.

qutebrowser/browser/webengine/webenginetab.py

@@ -976,7 +976,7 @@ class WebEngineTab(browsertab.AbstractTab):
                                     tab=self, parent=self)
         self.zoom = WebEngineZoom(tab=self, parent=self)
         self.search = WebEngineSearch(parent=self)
-        self.printing = WebEnginePrinting()
+        self.printing = WebEnginePrinting(tab=self)
         self.elements = WebEngineElements(tab=self)
         self.action = WebEngineAction(tab=self)
         self.audio = WebEngineAudio(parent=self)
@@ -1315,10 +1315,10 @@ class WebEngineTab(browsertab.AbstractTab):
         super()._on_navigation_request(navigation)
 
         if navigation.url == QUrl('qute://print'):
-            command_dispatcher = objreg.get('command-dispatcher',
-                                            scope='window',
-                                            window=self.win_id)
-            command_dispatcher.printpage()
+            try:
+                self.printing.show_dialog()
+            except browsertab.WebTabError as e:
+                message.error(str(e))
             navigation.accepted = False
 
         if not navigation.accepted or not navigation.is_main_frame:

qutebrowser/browser/webkit/webkittab.py

@@ -658,7 +658,7 @@ class WebKitTab(browsertab.AbstractTab):
                                  tab=self, parent=self)
         self.zoom = WebKitZoom(tab=self, parent=self)
         self.search = WebKitSearch(parent=self)
-        self.printing = WebKitPrinting()
+        self.printing = WebKitPrinting(tab=self)
         self.elements = WebKitElements(tab=self)
         self.action = WebKitAction(tab=self)
         self.audio = WebKitAudio(parent=self)