D27110: Fix scrollbar sometimes reappearing when set to 'hidden' and scrolling using the touchpad

[Ferdinand Bachmann]

yrlf created this revision.
Herald added a project: Konsole.
Herald added a subscriber: konsole-devel.
yrlf requested review of this revision.

REVISION SUMMARY
  (patch originally submitted to the bug tracker on this bug: https://bugs.kde.org/show_bug.cgi?id=415508)
  
  Sometimes the scrollbar reappears on the left side of the screen even when the scrollbar is set to 'hidden'.
  This happens when scrolling twice using the touchpad.
  
  Qt 5.14 changed some parts of the `QScrollBar::wheelEvent(QWheelEvent*)` function, which now sometimes calls `QScrollBarPrivate::setTransient(false)`, which calls `QWidget::show()`, which calls `QWidget::setVisible(true)`.
  
  This change works around this new behaviour that results in the QScrollBar not staying hidden when events are propagated to it by setting it to hidden again after each event propagated to the scroll bar.

TEST PLAN
  I tested it on ArchLinux using Sway, with Qt versions 5.13.2, 5.14.0, and 5.14.1, and it seems to work.

REPOSITORY
  R319 Konsole

REVISION DETAIL
  https://phabricator.kde.org/D27110

AFFECTED FILES
  src/TerminalDisplay.cpp
  src/TerminalDisplay.h

To: yrlf
Cc: konsole-devel, cent, EspadaV8, fbampaloukas, thsurrel, ngraham, maximilianocuria, hindenburg
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