statistics: refactor QSG memory management

The code was wrong, because it deleted the ChartItems in the
main UI thread, not the render thread. This would delete the
QSG nodes in the UI thread and then crash on mobile.

Therefore refactor this part of the code by adding the
items to be deleted to a list that will be deleted by the
render thread.

As a drop in replacement of std::unique_ptr, implement
a silly ChartItemPtr class, which auto-initializes to null.

This turns the deterministic and easily controlled memory
management into a steaming pile of insanity. Obviously,
this can be made much more elegant, but this has to do for now.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

1 files changed, 3 insertions, 0 deletions

diff --git a/stats/statsaxis.cpp b/stats/statsaxis.cpp
index 5c4f0403e..7af41c14b 100644
--- a/stats/statsaxis.cpp
+++ b/stats/statsaxis.cpp
@@ -159,6 +159,9 @@ void StatsAxis::setSize(double sizeIn)
 {
 	size = sizeIn;
 
+	// Ticks (and labels) should probably be reused. For now, clear them.
+	for (Tick &tick: ticks)
+		view.deleteChartItem(tick.item);
 	labels.clear();
 	ticks.clear();
 	updateLabels();