Add a backend setting

See #2589

doc/changelog.asciidoc

@@ -51,6 +51,9 @@ Added
 - New back/forward indicator in the statusbar
 - New `bindings.key_mappings` setting to map keys to other keys
 - New `qt_args` setting to pass additional arguments to Qt/Chromium
+- New `backend` setting to select the backend to use (auto/webengine/webkit).
+  Together with the previous setting, this should make wrapper scripts
+  unnecessary.
 
 Changed
 ~~~~~~~

doc/help/settings.asciidoc

@@ -12,6 +12,7 @@
 |<<aliases,aliases>>|Aliases for commands.
 |<<auto_save.interval,auto_save.interval>>|How often (in milliseconds) to auto-save config/cookies/etc.
 |<<auto_save.session,auto_save.session>>|Always restore open sites when qutebrowser is reopened.
+|<<backend,backend>>|The backend to use to display websites.
 |<<bindings.commands,bindings.commands>>|Keybindings mapping keys to commands in different modes.
 |<<bindings.default,bindings.default>>|Default keybindings. If you want to add bindings, modify `bindings.commands` instead.
 |<<bindings.key_mappings,bindings.key_mappings>>|This setting can be used to map keys to other keys.
@@ -285,6 +286,23 @@ Valid values:
 
 Default: empty
 
+[[backend]]
+=== backend
+The backend to use to display websites.
+qutebrowser supports two different web rendering engines / backends, QtWebKit and QtWebEngine.
+QtWebKit is based on WebKit (similar to Safari). It was discontinued by the Qt project with Qt 5.6, but picked up as a well maintained fork: https://github.com/annulen/webkit/wiki - qutebrowser only supports the fork.
+QtWebEngine is Qt's official successor to QtWebKit and based on the Chromium project. It's slightly more resource hungry that QtWebKit and has a couple of missing features in qutebrowser, but is generally the preferred choice.
+
+Type: <<types,String>>
+
+Valid values:
+
+ * +auto+: Automatically select either QtWebEngine or QtWebKit
+ * +webkit+: Force QtWebKit
+ * +webengine+: Force QtWebEngine
+
+Default: +pass:[auto]+
+
 [[bindings.commands]]
 === bindings.commands
 Keybindings mapping keys to commands in different modes.

qutebrowser/config/config.py

@@ -700,12 +700,15 @@ def get_backend(args):
     else:
         webkit_available = qtutils.is_new_qtwebkit()
 
+    str_to_backend = {
+        'webkit': usertypes.Backend.QtWebKit,
+        'webengine': usertypes.Backend.QtWebEngine,
+    }
+
     if args.backend is not None:
-        backends = {
-            'webkit': usertypes.Backend.QtWebKit,
-            'webengine': usertypes.Backend.QtWebEngine,
-        }
-        return backends[args.backend]
+        return str_to_backend[args.backend]
+    elif val.backend != 'auto':
+        return str_to_backend[val.backend]
     elif webkit_available:
         return usertypes.Backend.QtWebKit
     else:

qutebrowser/config/configdata.yml

@@ -101,6 +101,28 @@ qt_args:
     https://peter.sh/experiments/chromium-command-line-switches/ for a list)
     will work.
 
+backend:
+  type:
+    name: String
+    valid_values:
+      - auto: Automatically select either QtWebEngine or QtWebKit
+      - webkit: Force QtWebKit
+      - webengine: Force QtWebEngine
+  default: auto
+  desc: >-
+    The backend to use to display websites.
+
+    qutebrowser supports two different web rendering engines / backends,
+    QtWebKit and QtWebEngine.
+
+    QtWebKit is based on WebKit (similar to Safari). It was discontinued by the
+    Qt project with Qt 5.6, but picked up as a well maintained fork:
+    https://github.com/annulen/webkit/wiki - qutebrowser only supports the fork.
+
+    QtWebEngine is Qt's official successor to QtWebKit and based on the Chromium
+    project. It's slightly more resource hungry that QtWebKit and has a couple
+    of missing features in qutebrowser, but is generally the preferred choice.
+
 ## auto_save
 
 auto_save.interval: