Re:meld crashing vnc on starting

[Vasily Galkin <galkin-vv yandex ru>]

Hi!
It looks like some problems with GtkSourceView theme installation - it hasn't "classic.xml" theme installed 
or can't find it.

You may try check something like following in the interactive python-on-NFS_share shell to verify the reason. 
This is output from working install:
Python 2.7.10+ (default, Oct 10 2015, 09:11:24) 
[GCC 5.2.1 20151028] on linux2
Type "help", "copyright", "credits" or "license" for more information.
> > > from gi.repository import GtkSource
__main__:1: PyGIWarning: GtkSource was imported without specifying a version first. Use 
gi.require_version('GtkSource', '3.0') before import to ensure that the right version gets loaded.
> > > GtkSource.StyleSchemeManager.get_default().get_scheme('classic')
<StyleScheme object at 0xf6b24cac (GtkSourceStyleScheme at 0x8804b48)>
> > > GtkSource.StyleSchemeManager.get_default().get_search_path()
['/home/galkinvv/.local/share/gtksourceview-3.0/styles', '/usr/local/share/gtksourceview-3.0/styles', 
'/usr/share/gtksourceview-3.0/styles']
> > > GtkSource.StyleSchemeManager.get_default().get_scheme_ids()
['classic', 'cobalt', 'kate', 'oblivion', 'solarized-dark', 'solarized-light', 'tango']
> > > from gi.repository import Gio
> > > settings = Gio.Settings.new('org.gnome.meld')
> > > settings.get_string('style-scheme')
'classic'

On my system with standard installation I have /usr/share/gtksourceview-3.0/styles/classic.xml file installed 
by libgtksourceview-3.0-common package (built from libgtksourceview).

Also see some python details in comments below.
> Hi Vasily,
>
> The tool is crashing when I open in servers with RealVNC. So, I have tested in servers with TigerVNC and 
> surprisingly it's not crashing. However, the functionality doesn't work:
>
> When I try to open file comparison and select file, the meld is not crashing, but I can see the error in 
> the background:
>
> ** (meld:25229): WARNING **: Error retrieving accessibility bus address: 
> org.freedesktop.DBus.Error.ServiceUnknown: The name org.a11y.Bus was not provided by any .service files
> Gtk-Message: Failed to load module "pk-gtk-module"
> Gtk-Message: Failed to load module "canberra-gtk-module"
> Gtk-Message: Failed to load module "pk-gtk-module"
> Gtk-Message: Failed to load module "canberra-gtk-module"
> GLib-GIO-Message: Using the 'memory' GSettings backend. Your settings will not be saved or shared with 
> other applications.
> Traceback (most recent call last):
> File "/NFS_share/meld/meld_3_16_0/lib/python2.7/site-packages/meld/sourceview.py", line 154, in __init__
> self.on_setting_changed(meldsettings, 'style-scheme')
> File "/NFS_share/meld/meld_3_16_0/lib/python2.7/site-packages/meld/sourceview.py", line 180, in 
> on_setting_changed
> "meld:current-line-highlight", "background")
> File "/NFS_share/meld/meld_3_16_0/lib/python2.7/site-packages/meld/misc.py", line 189, in 
> colour_lookup_with_fallback
> style = source_style.get_style(name)
> AttributeError: 'NoneType' object has no attribute 'get_style'
>
> As you can see, source_style seems to be a None object.
>
> def colour_lookup_with_fallback(name, attribute):
> from meld.settings import meldsettings
> source_style = meldsettings.style_scheme
>
> So meldsettings.style_scheme returns None.
>
> The following is the definition (removed unnecessary declarations here):
>
> meldsettings = MeldSettings()
>
> class MeldSettings(GObject.GObject):
> def __init__(self):
> GObject.GObject.__init__(self)
> self.style_scheme = self._style_scheme_from_gsettings()
>
> def _style_scheme_from_gsettings(self):
> manager = GtkSource.StyleSchemeManager.get_default()
> return manager.get_scheme(settings.get_string('style-scheme'))
>
> I am not much into Python. But as you can see meldsettings=MeldSettings() (there is no argument).
>
> But MeldSettings is expecting an argument GObject.GObject in the definition. How can it be?

This declaration means "class derived from GObject", there is no explicit object with GObject value. The 
"self" argument is 
 
> Ok, let's say argument is not needed and I have done some debugging and found that get_string used in 
> style_scheme_from_gsettings definition is not defined anywhere.
> May be it is due to the warning I am receiving in the beginning:
> ** (meld:25229): WARNING **: Error retrieving accessibility bus address: 
> org.freedesktop.DBus.Error.ServiceUnknown: The name org.a11y.Bus was not provided by any .service files
>
> I found that in a new python shell:
> import meld.settings generates the above error. Is it somehow linked to the get_string method?

settings is Gio.Settings instance and settings.get_string is method of Gio.Settings: 
https://lazka.github.io/pgi-docs/#Gio-2.0/classes/Settings.html#Gio.Settings.get_string
It is not related to
> ** (meld:25229): WARNING **: Error retrieving accessibility bus address: 
> org.freedesktop.DBus.Error.ServiceUnknown: The name org.a11y.Bus was not provided by any .service files
but can be related to 
> GLib-GIO-Message: Using the 'memory' GSettings backend. Your settings will not be saved or shared with 
> other applications.