About switching host while space is opened

[tinchodias]

In BlParallelUniverse, closeSpaceSynchronously: and detachSpaceSynchronously: share most part of code (we should reuse more) BUT ALSO, the diff smells to bug:

Left: closeSpaceSynchronously: - Right: detachSpaceSynchronously:

When are they used?

• closeSpaceSynchronously:, when a space is closed.
• detachSpaceSynchronously when a space is opened and you change the host (like switch from a SDL2 window to a Morphic window on the fly, while it's open). This is not usual, so this is the candidate to be buggy (it should be adapt to what happens in close).

In fact, I didn't know this was implemented. I knew that switching host was working but when you show, then close, then change host, and send show again... I mean, when it is closed you can switch host right now.

Foe exmaple, this is implemented but buggy:

space := BlSpace new.
space host: BlMorphicWindowHost new.
space root background: Color random.
space extent: 200 asPoint.
space show.

"wait, and evaluate:"
space host: BlOSWindowSDL2Host new.

[tinchodias]

Something similar happens in the counterpart operations: open and attach:

Left: openSpaceSynchronously: - Right: attachSpaceSynchronously:

It's error prone to have this semi-duplicated code, and attachSpaceSynchronously: is only used in the case if switching hosts.

[tinchodias]

• I don't find traces of tests on this feature.

[tinchodias]

I added a note in a line added in openSpaceSynchronously: in PR #619

[tinchodias]

Fixed with e2550e8 + 47df523 + 0a80636.

I'm missing an automatized test yet.
Tested manually with:

space := BlSpace new.
space host: BlMorphicWindowHost new.
space root background: Color random.
space extent: 400 asPoint.
space title: 'hello'.
space show.

"wait, and evaluate:"
space host: BlOSWindowSDL2Host new.

"wait, and evaluate:"
space useMorphicHost 

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