Read dictionaries from /usr/share/qt on Qt >= 5.10

Fixes #3759
Supersedes #3762
See #2939, #4003

doc/changelog.asciidoc

@@ -87,6 +87,9 @@ Changed
   browsing.
 - When a prompt is opened in insert/passthrough mode, the mode is restored
   after closing the prompt.
+- On Qt 5.10 or newer, dictionaries are now read from the qutebrowser data
+  directory (e.g. `~/.local/share/qutebrowser`) instead of `/usr/share/qt`.
+  Existing dictionaries are copied over.
 
 Fixed
 ~~~~~

qutebrowser/browser/webengine/spell.py

@@ -22,9 +22,11 @@
 import glob
 import os
 import re
+import os.path
+import shutil
 
 from PyQt5.QtCore import QLibraryInfo
-from qutebrowser.utils import log, message
+from qutebrowser.utils import log, message, standarddir, qtutils
 
 dict_version_re = re.compile(r".+-(?P<version>[0-9]+-[0-9]+?)\.bdic")
 
@@ -39,9 +41,12 @@ def version(filename):
     return tuple(int(n) for n in match.group('version').split('-'))
 
 
-def dictionary_dir():
+def dictionary_dir(old=False):
     """Return the path (str) to the QtWebEngine's dictionaries directory."""
-    datapath = QLibraryInfo.location(QLibraryInfo.DataPath)
+    if qtutils.version_check('5.10', compiled=False) and not old:
+        datapath = standarddir.data()
+    else:
+        datapath = QLibraryInfo.location(QLibraryInfo.DataPath)
     return os.path.join(datapath, 'qtwebengine_dictionaries')
 
 
@@ -73,3 +78,15 @@ def local_filename(code):
     """
     all_installed = local_files(code)
     return os.path.splitext(all_installed[0])[0] if all_installed else None
+
+
+def init():
+    if qtutils.version_check('5.10', compiled=False):
+        new_dir = dictionary_dir()
+        old_dir = dictionary_dir(old=True)
+        os.environ['QTWEBENGINE_DICTIONARIES_PATH'] = new_dir
+        try:
+            if os.path.exists(old_dir) and not os.path.exists(new_dir):
+                shutil.copytree(old_dir, new_dir)
+        except OSError:
+            log.misc.exception("Failed to copy old dictionaries")

qutebrowser/browser/webengine/webenginesettings.py

@@ -298,6 +298,8 @@ def init(args):
             not hasattr(QWebEnginePage, 'setInspectedPage')):  # only Qt < 5.11
         os.environ['QTWEBENGINE_REMOTE_DEBUGGING'] = str(utils.random_port())
 
+    spell.init()
+
     _init_profiles()
     config.instance.changed.connect(_update_settings)
 

scripts/dictcli.py

@@ -36,6 +36,7 @@ import attr
 sys.path.insert(0, os.path.join(os.path.dirname(__file__), os.pardir))
 from qutebrowser.browser.webengine import spell
 from qutebrowser.config import configdata
+from qutebrowser.utils import standarddir
 
 
 API_URL = 'https://chromium.googlesource.com/chromium/deps/hunspell_dictionaries.git/+/master/'
@@ -257,6 +258,8 @@ def remove_old(languages):
 def main():
     if configdata.DATA is None:
         configdata.init()
+    standarddir.init(None)
+
     parser = get_argparser()
     argv = sys.argv[1:]
     args = parser.parse_args(argv)