Status of LO embedding inside other processes windows?

[Robert Marcano]

Thanks for replying.

On 02/22/2018 07:10 AM, Michael Stahl wrote:
> On 21.02.2018 16:55, Robert Marcano wrote:
>> Greetings. I have been playing with the developers guide example [1] for
>> embedding LO inside a Java window (Swing toolkit). The example works on
>> a Windows host, but on Linux I found the following problems (in the
>> order I found)
>>
>> 1- When the host Java application is running on a Wayland session (Java
>> Swing is still an X11 program), there is a crash. IIRC LO still is a X11
>> based application (or at least the Fedora compiled version is using the
>> X11 GTK back-end)
>>
>> 2- Switched to an X11 desktop session, there was no crash this time, but
>> the document was not shown embedded on the Java window, it was a
>> floating window with no window controls, unresponsive to the user.
>>
>> 3- Run the same application with the environment variable
>> SAL_USE_VCLPLUGIN=gtk in order to force the LO GTK2 back-end. The
>> document is embedded on the Java window as expected, but keyboard input
>> is not possible on the document or the controls, mouse actions works,
>> for example, I can change fonts using the mouse, but can't write
>> anything on the font combobox nor the document. New LO dialogs opened
>> from that document, keyboard input works.
>>
>> 4- Trying with SAL_USE_VCLPLUGIN=gen and keyboard input now works, but
>> with the outdated look of that LO VCL backend :(
>>
>> So now the possible reasons that came to my head for each case:
>>
>> 1- Some confusion between Java being X11 and LO trying to do some
>> Wayland thing?
> 
> by default the "gtk3" vclplug will use Wayland if available.  probably
> this won't work if the Java connects to X11 instead.  there is some
> environment var GDK_BACKEND=x11 that can be used to force it.

GDK_BACKEND=x11 helps with not crashing on the Wayland session.

> 
>> 2- Java has a GTK Look and Feel/theme that loads GTK2 (the example
>> application does not load that theme) , I am under the impression that
>> if LO is loading GTK3, they are on different processes, so should not be
>> any conflict here.
> 
> AFAIK GTK 2 and GTK 3 cannot coexist in the same process, due to some
> naming conflict of GObjects or so...

What I find weird is that there is no GTK libraries loaded on the 
process space of the Java example (verified checking /proc/<pid>/maps), 
even when running the example in-place (not on an independent top level 
window)

> 
>> 3- Now both processes should be using GTK2, but the problems with
>> keyboard input is a blocker
> 
> that sounds like a bug somewhere.  (unlikely to get fixed any time soon
> given this is quite an esoteric use-case.)

LibreOffice online and if IIRC the Android viewer are more invested on 
using LibreOfficeKit, I think I should investigate that. My knowledge of 
what can be done with LibreOfficeKit tell me I can have an headless 
process rendering to a shared buffer and use that to draw on my Java 
process.

Is this a better long term strategy?

> 
>> 4- Everything running without conflicting libraries/protocols (Wayland
>> vs X11 or GTK3 vs GTK2) and work, but the look and feel!!!!!!
>>
>> Now, when running the example with a no inline option, everything works
>> fine, even when GTK2 and GTK3 are mixed. Wish to have an option to
>> create the new document top level window as a child of the Java window,
>> it is a pain for user that the document can go to the back of the
>> "caller" window. Any hints if this is possible between two processes
>> like Java and LO?
> 
> so does that option run LO as a separate process? yes, that would avoid
> some of these issues, but as you found you get different issues instead :-/
>