ScrollBar: fix infinite loop

9e1b044 ("ScrollBar: allow configuring the minimum size") attempted to
simplify QQuickScrollBarAttachedPrivate::scrollHorizontal() and
scrollVertical(), but apparently the new calculation was not identical
since it caused a crash with pixel delta wheel events on macOS. Revert
back to the previous version, as it was before 9e1b044.

Task-number: QTBUG-65784
Change-Id: I4f326c3ba67595429cfbaef491089aa83572f0de
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

1 files changed, 6 insertions, 4 deletions

diff --git a/src/quicktemplates2/qquickscrollbar.cpp b/src/quicktemplates2/qquickscrollbar.cpp
index aa0094aa..67195ba8 100644
--- a/src/quicktemplates2/qquickscrollbar.cpp
+++ b/src/quicktemplates2/qquickscrollbar.cpp
@@ -872,8 +872,9 @@ void QQuickScrollBarAttachedPrivate::scrollHorizontal()
 {
     QQuickFriendlyFlickable *f = reinterpret_cast<QQuickFriendlyFlickable *>(flickable);
 
-    const qreal extent = f->contentWidth() - f->minXExtent();
-    const qreal cx = horizontal->position() * extent;
+    const qreal viewwidth = f->width();
+    const qreal maxxextent = -f->maxXExtent() + f->minXExtent();
+    const qreal cx = horizontal->position() * (maxxextent + viewwidth) - f->minXExtent();
 
     if (!qIsNaN(cx) && !qFuzzyCompare(cx, flickable->contentX()))
         flickable->setContentX(cx);
@@ -883,8 +884,9 @@ void QQuickScrollBarAttachedPrivate::scrollVertical()
 {
     QQuickFriendlyFlickable *f = reinterpret_cast<QQuickFriendlyFlickable *>(flickable);
 
-    const qreal extent = f->contentHeight() - f->minYExtent();
-    const qreal cy = vertical->position() * extent;
+    const qreal viewheight = f->height();
+    const qreal maxyextent = -f->maxYExtent() + f->minYExtent();
+    const qreal cy = vertical->position() * (maxyextent + viewheight) - f->minYExtent();
 
     if (!qIsNaN(cy) && !qFuzzyCompare(cy, flickable->contentY()))
         flickable->setContentY(cy);