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Prevent infinite relayout when adding scrollbars

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When one scrollbar is added, this may cause the other to be
needed as well. This change does a second calculation
immediately instead of relying on a signal through a
QueuedConnection.

Task-number: QTBUG-62818
Task-number: QTBUG-56280
Change-Id: Iee9a083e3a6cd3765e6bb9206687a8a6e7f99cff
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>
Reviewed-by: Andy Nichols <andy.nichols@qt.io>
This commit is contained in:
Andy Shaw 2017-12-12 15:53:44 +01:00 committed by Paul Olav Tvete
parent 93dabeba9d
commit 3841a7dd49
2 changed files with 20 additions and 6 deletions
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25
src/widgets/widgets/qabstractscrollarea.cpp
View File

@ -333,17 +333,28 @@ void QAbstractScrollAreaPrivate::setSingleFingerPanEnabled(bool on)
#endif
void QAbstractScrollAreaPrivate::layoutChildren()
{
bool needH = false;
bool needV = false;
layoutChildren_helper(&needH, &needV);
// Call a second time if one scrollbar was needed and not the other to
// check if it needs to readjust accordingly
if (needH != needV)
layoutChildren_helper(&needH, &needV);
}
void QAbstractScrollAreaPrivate::layoutChildren_helper(bool *needHorizontalScrollbar, bool *needVerticalScrollbar)
{
Q_Q(QAbstractScrollArea);
bool htransient = hbar->style()->styleHint(QStyle::SH_ScrollBar_Transient, 0, hbar);
bool needh = (hbarpolicy != Qt::ScrollBarAlwaysOff) && ((hbarpolicy == Qt::ScrollBarAlwaysOn && !htransient)
|| ((hbarpolicy == Qt::ScrollBarAsNeeded || htransient)
&& hbar->minimum() < hbar->maximum() && !hbar->sizeHint().isEmpty()));
bool needh = *needHorizontalScrollbar || ((hbarpolicy != Qt::ScrollBarAlwaysOff) && ((hbarpolicy == Qt::ScrollBarAlwaysOn && !htransient)
|| ((hbarpolicy == Qt::ScrollBarAsNeeded || htransient)
&& hbar->minimum() < hbar->maximum() && !hbar->sizeHint().isEmpty())));
bool vtransient = vbar->style()->styleHint(QStyle::SH_ScrollBar_Transient, 0, vbar);
bool needv = (vbarpolicy != Qt::ScrollBarAlwaysOff) && ((vbarpolicy == Qt::ScrollBarAlwaysOn && !vtransient)
|| ((vbarpolicy == Qt::ScrollBarAsNeeded || vtransient)
&& vbar->minimum() < vbar->maximum() && !vbar->sizeHint().isEmpty()));
bool needv = *needVerticalScrollbar || ((vbarpolicy != Qt::ScrollBarAlwaysOff) && ((vbarpolicy == Qt::ScrollBarAlwaysOn && !vtransient)
|| ((vbarpolicy == Qt::ScrollBarAsNeeded || vtransient)
&& vbar->minimum() < vbar->maximum() && !vbar->sizeHint().isEmpty())));
QStyleOption opt(0);
opt.init(q);
@ -522,6 +533,8 @@ void QAbstractScrollAreaPrivate::layoutChildren()
viewportRect.adjust(left, top, -right, -bottom);
viewport->setGeometry(QStyle::visualRect(opt.direction, opt.rect, viewportRect)); // resize the viewport last
*needHorizontalScrollbar = needh;
*needVerticalScrollbar = needv;
}
/*!

1
src/widgets/widgets/qabstractscrollarea_p.h
View File

@ -95,6 +95,7 @@ public:
void init();
void layoutChildren();
void layoutChildren_helper(bool *needHorizontalScrollbar, bool *needVerticalScrollbar);
// ### Fix for 4.4, talk to Bjoern E or Girish.
virtual void scrollBarPolicyChanged(Qt::Orientation, Qt::ScrollBarPolicy) {}
bool canStartScrollingAt( const QPoint &startPos );