[LV2] Implement UI:sizeConstraints extension

[David Robillard]

On Sat, 2020-05-30 at 16:45 +0300, Vladimir Sadovnikov wrote:

> The problem is, as I've described, that for different GTK versions
> (Ubuntu vs 
> openSUSE) we get the bad result.
> 
> Moreover, the latest Ardour 6 on my system shows the following window
> while the 
> child window is pretty OK:
> 
> https://imgur.com/VlPvl2d
> 
> As you understand, by manipulating controls plugin's child window
> became a bit 
> larger.
> 
> If the host could control the size of the parent window by itself,
> the problem 
> wouldn't occur ever.

Yes, well, if hosts/plugins didn't have any bugs then they wouldn't
have any bugs ;)

I of course agree all of this stuff should work, my point is that it's
clear at this point that abusing ui:resize to avoid implementing window
things properly is what caused this mess, in the grand scheme of
things.

So, I am working on a simple no-toolkit plugin that does everything
correctly from a window system POV, and fixing suil/hosts
correspondingly.  So far, this seems to work well, and also means
proper examples to test with can be in lv2kit, which avoids this
nightmare of complex plugins and hosts and frameworks working around
each other's bugs with yet more bugs.  It's super clear that this is a
real problem now, and grafting on more half-baked extensions will only
make it worse.

In short, there are two future options here:

1) The above works out, and extensions to hack around broken window
hints/etc are proven to be unnecessary.  In which case, not only will
no hints extension be added, but ui:resize will be deprecated, and
everything is much simpler, particularly for plugin authors.

2) It doesn't and can't work for some concrete reason, and we have to
add something to work around that.

We'll see.

-- 
dr