Add a content.desktop_capture setting

See #2939

doc/help/settings.asciidoc

@@ -116,6 +116,7 @@
 |<<content.cookies.accept,content.cookies.accept>>|Which cookies to accept.
 |<<content.cookies.store,content.cookies.store>>|Store cookies.
 |<<content.default_encoding,content.default_encoding>>|Default encoding to use for websites.
+|<<content.desktop_capture,content.desktop_capture>>|Allow websites to share screen content.
 |<<content.dns_prefetch,content.dns_prefetch>>|Try to pre-fetch DNS entries to speed up browsing.
 |<<content.frame_flattening,content.frame_flattening>>|Expand each subframe to its contents.
 |<<content.geolocation,content.geolocation>>|Allow websites to request geolocations.
@@ -1551,6 +1552,21 @@ Type: <<types,String>>
 
 Default: +pass:[iso-8859-1]+
 
+[[content.desktop_capture]]
+=== content.desktop_capture
+Allow websites to share screen content.
+On Qt < 5.10, a dialog box is always displayed, even if this is set to "true".
+
+Type: <<types,BoolAsk>>
+
+Valid values:
+
+ * +true+
+ * +false+
+ * +ask+
+
+Default: +pass:[ask]+
+
 [[content.dns_prefetch]]
 === content.dns_prefetch
 Try to pre-fetch DNS entries to speed up browsing.

qutebrowser/browser/webengine/webenginesettings.py

@@ -110,6 +110,11 @@ class WebEngineSettings(websettings.AbstractSettings):
             Attr(QWebEngineSettings.WebGLEnabled),
         'content.local_storage':
             Attr(QWebEngineSettings.LocalStorageEnabled),
+        'content.desktop_capture':
+            Attr(QWebEngineSettings.ScreenCaptureEnabled,
+                 converter=lambda val: True if val == 'ask' else val),
+            # 'ask' is handled via the permission system, or a hardcoded
+            # dialog on Qt < 5.10
 
         'input.spatial_navigation':
             Attr(QWebEngineSettings.SpatialNavigationEnabled),

qutebrowser/browser/webengine/webenginetab.py

@@ -699,6 +699,23 @@ class _WebEnginePermissions(QObject):
             QWebEnginePage.MediaVideoCapture: 'record video',
             QWebEnginePage.MediaAudioVideoCapture: 'record audio/video',
         }
+        try:
+            options.update({
+                QWebEnginePage.DesktopVideoCapture:
+                    'content.desktop_capture',
+                QWebEnginePage.DesktopAudioVideoCapture:
+                    'content.desktop_capture',
+            })
+            messages.update({
+                QWebEnginePage.DesktopVideoCapture:
+                    'capture your desktop',
+                QWebEnginePage.DesktopAudioVideoCapture:
+                    'capture your desktop and audio',
+            })
+        except AttributeError:
+            # Added in Qt 5.10
+            pass
+
         assert options.keys() == messages.keys()
 
         page = self._widget.page()

qutebrowser/config/configdata.yml

@@ -305,6 +305,15 @@ content.windowed_fullscreen:
   desc: >-
     Limit fullscreen to the browser window (does not expand to fill the screen).
 
+content.desktop_capture:
+  type: BoolAsk
+  default: ask
+  desc: >-
+    Allow websites to share screen content.
+
+    On Qt < 5.10, a dialog box is always displayed, even if this is set to
+    "true".
+
 content.developer_extras:
   deleted: true