Po Lu <luangruo@yahoo.com> writes:

> Thierry Volpiatto <thievol@posteo.net> writes:
>
>> Po Lu <luangruo@yahoo.com> writes:
>>
>>> Thierry Volpiatto <thievol@posteo.net> writes:
>>>
>>>> Here the command fails if you specify the workspace, it works only with
>>>> "worspace0".
>>>
>>> But that's because you only have workspace 1 displayed, right?
>>
>> No, if emacs is on workspace0 and I use:
>> "/backdrop/screen0/monitoreDP/workspace0/last-image"
>> wallpaper is modified as expected. 
>>
>> Then if emacs is on workspace2 and I use:
>> "/backdrop/screen0/monitoreDP/workspace2/last-image"
>> Command exit with 0 status but wallpaper is not modified, but if I use:
>> "/backdrop/screen0/monitoreDP/workspace0/last-image" again (always from
>> workspace2), wallpaper is modified as expected.
>>
>> I can verify this with this command which monitor the desktop change:
>>
>>     xfconf-query -c xfce4-desktop -m
>>
>>     => Commencer à surveiller le canal « xfce4-desktop » :
>>
>> then I go to workspace4, modify wallpaper with mouse and the usual xfce
>> interface for this, go back in workspace1 an look at output:
>> I have now:
>>
>>     Commencer à surveiller le canal « xfce4-desktop » :
>>
>>     définir: /backdrop/screen0/monitoreDP/workspace0/last-image
>>
>> unfortunately this command is interactive :-(
>
> But here is how Thunar, the XFCE file manager, sets the backdrop:
>
>           image_path_prop = g_strdup_printf("/backdrop/screen%d/monitor%s/workspace%d/last-image", screen_nr, monitor_name, workspace);
>           image_style_prop = g_strdup_printf("/backdrop/screen%d/monitor%s/workspace%d/image-style", screen_nr, monitor_name, workspace);
>  
> where `workspace' is:
>
>   GdkWindow *root;
>   gulong     bytes_after_ret = 0;
>   gulong     nitems_ret = 0;
>   guint     *prop_ret = NULL;
>   Atom       _NET_CURRENT_DESKTOP;
>   Atom       _WIN_WORKSPACE;
>   Atom       type_ret = None;
>   gint       format_ret;
>   gint       ws_num = 0;


My command starts working with workspace specified when I use an async
process (start-process) instead of call-process, so with wallpaper-set it should work as
expected.
However the functions to extract infos about screen, monitor and
workspace are working only when (display-graphic-p) is non nil.

-- 
Thierry