Disable hardware acceleration unconditionally

Riot works just fine without it, and the application will work better
for people using binary drivers (i.e. NVidia) with Flatpak builds. As
a side effect, the memory consumption is slightly lower.

Tested both with WebKitGTK+ 2.14.5 and 2.15.92

Fixes #29

revolt/window.py

@@ -56,6 +56,15 @@ def __init__(self, application, saved_state):
         websettings.set_javascript_can_access_clipboard(True)
         websettings.set_minimum_font_size(12)  # TODO: Make it a setting
         websettings.set_property("enable-mediasource", True)
+
+        # This makes Revolt lighter, and makes things work for people using
+        # binary drivers (i.e. NVidia) with Flatpak build. See issue #29.
+        if hasattr(websettings, "set_hardware_acceleration_policy"):
+            websettings.set_hardware_acceleration_policy(WebKit2.HardwareAccelerationPolicy.NEVER)
+        else:
+            import os
+            os.environ["WEBKIT_DISABLE_COMPOSITING_MODE"] = "1"
+
         self._webview.show_all()
         self.add(self._webview)
         self.__connect_widgets()