When the text is larger than 10000 characters, we now avoid creating
nodes for blocks that go outside the viewport. Each time the text moves
relative to the viewport, we check whether the rectangular area that we
know is "covered" with the text rendered so far is still enough to fill
the viewport; if not, update the whole document: mark all existing SG
nodes dirty, then delete and re-create them.
[ChangeLog][QtQuick][Text] When given large text documents
(QString::size() > 10000), Text and TextEdit now try to avoid populating
scene graph nodes for ranges of text that fall outside the viewport,
which could be a parent item having the ItemIsViewport flag set (such as
a Flickable), or the window's content item. If the viewport is smaller
than the window, you might see lines of text disappearing when they are
scrolled out of the viewport; if that's undesired, either design your UI
so that other items obscure the area beyond the viewport, or set the
clip property to make clipping exact.
Task-number: QTBUG-90734
Change-Id: I9c88885b1ad3c3f24df0f7f322ed82d76b8e07c9
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>
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