#6190: Balloons attached to widgets should always be visible even if the widget is longer than a visible viewport

[oleq]

Suggested merge commit message (convention)

Fix (widget): The widget toolbar should always be visible even if the widget is longer than a visible viewport (see #6190).

Fix (table): The table properties balloon should always be visible if the table is longer than a visible viewport. Closes #6190.

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Additional information

• I'm not sure about the name of centeredBalloonPositionForLongWidgets() but there's so much going on in there I'm not sure there's an easy way to express that in simple words.
• At first I wanted centeredBalloonPositionForLongWidgets() to be a part of BalloonPanelView#defaultPositions but I figured (so far) this is a widget-specific behavior so maybe let's keep it in ckeditor5-widget for a while.

[oleq]

@ckeditor/qa-team Can you take a look at this? You can test both scenarios in http://fake.ckeditor.com:8125/ckeditor5-table/tests/manual/tableproperties.html using a very long table (or a very small viewport).

[FilipTokarski]

Desktop browsers & iOS work fine, but on Android the balloon appears halfway when scrolling up:

[oleq]

Desktop browsers & iOS work fine, but on Android the balloon appears halfway when scrolling up:

I guess I'm ready to live with that.

[niegowski]

I'm wondering about the scenario where editor is limited in height with overflow: scroll. If editor would be in the middle of window, then this balloons would be displayed on the edge of the window (could be far away from editor), maybe we should try to stick it to closest scrollable instead of window?

[oleq]

I'm wondering about the scenario where editor is limited in height with overflow: scroll. If editor would be in the middle of window, then this balloons would be displayed on the edge of the window (could be far away from editor), maybe we should try to stick it to closest scrollable instead of window?

That's a bigger topic because it touches all balloons, not only widget balloons. See #5328.