Performance issue with QtCharts::QXYSeries

I have 155 objects each containing 11 QtCharts::QLineSeries. So this makes a total of 1705 QLineSeries objects. The current design accumulates points every second up to 86400 points to contain a range of 24h.

At each second, I'm adding a point to all 1705 series object.

When I launch my program and start collecting data, CPU usage is at around 20%. After about an hour, processor usage saturates at 100%.

I think that I suffer from a realloc bomb. When my Series point capacity is reached, all 1705 series will reallocate at the same time.

I have 2 suggestions for this class:

1. You should allow a QXYSeries user to call reserve() on the underneath QVector. (perhaps by adding QXYSeries::reserve() method
2. You should make it hard to misuse your class by deprecating points() method. I was exhaustively using it without being aware of the performance cost that I was paying using it...