Make sure external schemes are clickable via hints

This issue was probably introduced in 545539f28d
- with JavaScript, we can't "click" on an external link.

There might be a better solution using
QWebEngineSettings::setUnknownUrlSchemePolicy(QWebEngineSettings::AllowAllUnknownUrlSchemes)
temporarily when using hints with PyQt 5.11.

Fixes #2833

qutebrowser/browser/webelem.py

@@ -307,6 +307,10 @@ class AbstractWebElement(collections.abc.MutableMapping):
         href_tags = ['a', 'area', 'link']
         return self.tag_name() in href_tags and 'href' in self
 
+    def _requires_user_interaction(self):
+        """Return True if clicking this element needs user interaction."""
+        raise NotImplementedError
+
     def _mouse_pos(self):
         """Get the position to click/hover."""
         # Click the center of the largest square fitting into the top/left
@@ -405,7 +409,7 @@ class AbstractWebElement(collections.abc.MutableMapping):
             return
 
         if click_target == usertypes.ClickTarget.normal:
-            if self.is_link():
+            if self.is_link() and not self._requires_user_interaction():
                 log.webelem.debug("Clicking via JS click()")
                 self._click_js(click_target)
             elif self.is_editable(strict=True):

qutebrowser/browser/webengine/webengineelem.py

@@ -27,7 +27,7 @@ from PyQt5.QtGui import QMouseEvent
 from PyQt5.QtWidgets import QApplication
 from PyQt5.QtWebEngineWidgets import QWebEngineSettings
 
-from qutebrowser.utils import log, javascript
+from qutebrowser.utils import log, javascript, urlutils
 from qutebrowser.browser import webelem
 
 
@@ -198,6 +198,13 @@ class WebEngineElement(webelem.AbstractWebElement):
         if self.is_text_input() and self.is_editable():
             self._js_call('move_cursor_to_end')
 
+    def _requires_user_interaction(self):
+        baseurl = self._tab.url()
+        url = self.resolve_url(baseurl)
+        if url is None:
+            return True
+        return url.scheme() not in urlutils.WEBENGINE_SCHEMES
+
     def _click_editable(self, click_target):
         # WORKAROUND for https://bugreports.qt.io/browse/QTBUG-58515
         ev = QMouseEvent(QMouseEvent.MouseButtonPress, QPoint(0, 0),

qutebrowser/browser/webkit/webkitelem.py

@@ -305,6 +305,9 @@ class WebKitElement(webelem.AbstractWebElement):
         if self.is_text_input() and self.is_editable():
             self._tab.caret.move_to_end_of_document()
 
+    def _requires_user_interaction(self):
+        return False
+
     def _click_editable(self, click_target):
         ok = self._elem.evaluateJavaScript('this.focus(); true;')
         if ok:

qutebrowser/utils/urlutils.py

@@ -39,6 +39,21 @@ from qutebrowser.browser.network import pac
 # https://github.com/qutebrowser/qutebrowser/issues/108
 
 
+# URL schemes supported by QtWebEngine
+WEBENGINE_SCHEMES = [
+    'about',
+    'data',
+    'file',
+    'filesystem',
+    'ftp',
+    'http',
+    'https',
+    'javascript',
+    'ws',
+    'wss',
+]
+
+
 class InvalidUrlError(ValueError):
 
     """Error raised if a function got an invalid URL.