ProDataGrid derives its scroll extent from the current scroll offset, so an
offset that is briefly too large inflates the extent, which permits a larger
offset again. A trackpad reaches that state within a few hundred sub-row
events: instrumented in the running app, a ~1500px list reported 8735px and
kept growing, the thumb collapsed to its minimum, and the end of the list ran
away from the user. A second defect slid the rows sideways by up to 10px - the
star-sized column is measured against the width including the vertical scroll
bar, leaving the grid convinced it has a scroll bar's worth of content to
reach.
Disabling the horizontal scroll bar, giving each grid its own
DefaultRowHeightEstimator, pinning RowHeight, forcing the vertical scroll bar
visible, and disabling scrolling on the template's inner ScrollViewer each
removed a symptom at most; none can break a loop that runs through the scroll
offset, and 12.0.4 is the newest release. A ListBox's virtualizing panel keeps
the extent a function of the items alone. The price is laying out the columns
here - so the header row and the item template have to be kept in step - and
losing sortable, resizable headers.
Assisted-by: Claude:claude-opus-5[1m]:Claude Code
Christoph Wille
16cd684a09