Implement printing with QtWebEngine

CHANGELOG.asciidoc

@@ -23,6 +23,7 @@ Added
 - Userscripts now have a new `$QUTE_COMMANDLINE_TEXT` environment variable, containing the current commandline contents.
 - New `ripbang` userscript to create a searchengine from a duckduckgo bang
 - link:https://github.com/annulen/webkit/wiki[QtWebKit Reloaded] (also called QtWebKit-NG) is now supported.
+- Printing support for QtWebEngine with Qt >= 5.8
 
 Changed
 ~~~~~~~

qutebrowser/browser/browsertab.py

@@ -107,10 +107,20 @@ class AbstractPrinting:
     def check_printer_support(self):
         raise NotImplementedError
 
+    def check_preview_support(self):
+        raise NotImplementedError
+
     def to_pdf(self, filename):
         raise NotImplementedError
 
-    def to_printer(self, printer):
+    def to_printer(self, printer, callback=None):
+        """Print the tab.
+
+        Args:
+            printer: The QPrinter to print to.
+            callback: Called with a boolean
+                      (True if printing succeeded, False otherwise)
+        """
         raise NotImplementedError
 
 

qutebrowser/browser/commands.py

@@ -370,16 +370,23 @@ class CommandDispatcher:
                 tab.printing.check_pdf_support()
             else:
                 tab.printing.check_printer_support()
+            if preview:
+                tab.printing.check_preview_support()
         except browsertab.WebTabError as e:
             raise cmdexc.CommandError(e)
 
         if preview:
+            def print_callback(ok):
+                if not ok:
+                    message.error("Printing failed!")
+
             diag = QPrintPreviewDialog()
             diag.setAttribute(Qt.WA_DeleteOnClose)
             diag.setWindowFlags(diag.windowFlags() |
                                 Qt.WindowMaximizeButtonHint |
                                 Qt.WindowMinimizeButtonHint)
-            diag.paintRequested.connect(tab.printing.to_printer)
+            diag.paintRequested.connect(functools.partial(
+                tab.printing.to_printer, callback=print_callback))
             diag.exec_()
         elif pdf:
             pdf = os.path.expanduser(pdf)
@@ -389,9 +396,14 @@ class CommandDispatcher:
             tab.printing.to_pdf(pdf)
             log.misc.debug("Print to file: {}".format(pdf))
         else:
+            def print_callback(ok):
+                if not ok:
+                    message.error("Printing failed!")
+                diag.deleteLater()
+
             diag = QPrintDialog()
-            diag.setAttribute(Qt.WA_DeleteOnClose)
-            diag.open(lambda: tab.printing.to_printer(diag.printer()))
+            diag.open(lambda:
+                      tab.printing.to_printer(diag.printer(), print_callback))
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
     def tab_clone(self, bg=False, window=False):

qutebrowser/browser/webengine/webenginetab.py

@@ -89,15 +89,21 @@ class WebEnginePrinting(browsertab.AbstractPrinting):
                 "Printing to PDF is unsupported with QtWebEngine on Qt < 5.7")
 
     def check_printer_support(self):
+        if not hasattr(self._widget.page(), 'print'):
+            raise browsertab.WebTabError(
+                "Printing is unsupported with QtWebEngine on Qt < 5.8")
+
+    def check_preview_support(self):
         raise browsertab.WebTabError(
-            "Printing is unsupported with QtWebEngine")
+            "Print previews are unsupported with QtWebEngine")
 
     def to_pdf(self, filename):
         self._widget.page().printToPdf(filename)
 
-    def to_printer(self, printer):
-        # Should never be called
-        assert False
+    def to_printer(self, printer, callback=None):
+        if callback is None:
+            callback = lambda _ok: None
+        self._widget.page().print(printer, callback)
 
 
 class WebEngineSearch(browsertab.AbstractSearch):

qutebrowser/browser/webkit/webkittab.py

@@ -68,13 +68,19 @@ class WebKitPrinting(browsertab.AbstractPrinting):
     def check_printer_support(self):
         self._do_check()
 
+    def check_preview_support(self):
+        self._do_check()
+
     def to_pdf(self, filename):
         printer = QPrinter()
         printer.setOutputFileName(filename)
         self.to_printer(printer)
 
-    def to_printer(self, printer):
+    def to_printer(self, printer, callback):
         self._widget.print(printer)
+        # Can't find out whether there was an error...
+        if callback is not None:
+            callback(True)
 
 
 class WebKitSearch(browsertab.AbstractSearch):