RFR: 8291908: VirtualFlow creates unneeded empty cells

Thu Aug 4 14:36:55 UTC 2022

When calculating the viewportOffset, we now already take into account that cells will have to shift.

This prevents the creation of temporary empty cells in the layout phase.
One test needed to be fixed, since the number of invocations to updateItem() was hardcoded (and it
is decreased by this commit).

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Commit messages:
 - When calculating the viewportOffset, we now already take into account that cells will have to shift.

Changes: https://git.openjdk.org/jfx/pull/863/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=863&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291908
  Stats: 40 lines in 3 files changed: 38 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jfx/pull/863.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/863/head:pull/863

PR: https://git.openjdk.org/jfx/pull/863