Dropping X11 VCL backend

[Luboš Luňák]

On Tuesday 29 of December 2020, Chris Sherlock wrote:
> Hi all,
>
> I am interested in knowing the future of the X11 VCL backend now that we
> have a Skia backend.

 Just to avoid any possible confusion, I'd like to point out that 'X11 VCL 
backend' is ambiguous, because VCL backends may themselves have backends. 
Each VCL backend is supposed to handle its platform's windows, fonts, drawing 
and whatnot, but some of them defer the drawing to plugable backends. So 
the 'gen' VCL backend is sort of the X11 VCL backend, selected by 
SAL_USE_VCLPLUGIN=gen, but it has different SalGraphicsImpl backends that 
draw using X11, Skia or until recently GL (LO has inherited from OOo also its 
fine tradition of definitely not making things simple, right?).

 So when you say X11 VCL backend, I presume you mean the X11 drawing backend, 
not the X11 VCL backend itself. Skia is just a drawing backend and doesn't 
have its own VCL backend, it's used by the 'gen' or 'win' VCL backends.

> Are there any plans afoot to remove it and just go 
> with the Skia backend?

 I'm not aware of anything specific.

> If not, may I ask the reason? It seems maintenance heavy.

 I think the reason is that it does not seem maintenance heavy. What are the 
specific reasons that you do find it otherwise? The X11 drawing code had 
relatively few commits in the last year if I exclude all the generic cleanup 
changes and my Skia-related commits.

 Also, X11 is the stable lowest common denominator, i.e. the safe fallback, 
which may be another reason to keep it.

> If we are, do we have a potential release where we believe that Skia is
> stable enough to use and remove the X11 backend?

 We apparently believe that Skia is stable enough to be the default on our 
largest platform, for both 7.0 and 7.1. Unless users are disabling it in 
masses, presumably it is stable enough to use (although admittedly a default 
is not the same as removing other options, so I'm unsure about the "and 
remove" part).

 But if the reason for wanting to remove the X11 code is XRender (lack 
thereof), then it might be simpler to hard-require XRender and let X11 be.

-- 
 Luboš Luňák
 l.lunak at collabora.com