Using Plot() ot PlotOHLC() causes chart vertical scaling to change


I'lm using PlotOHLC() to plot horizontal zones on a chart. I notice that if the plotted approaches about 33% of either the bottom or top edge of the chart, it causes the entire chart to be be rescaled, such that the chart is compressed. This leaves an empty band at the top or bottom of the chart, where no price information is displayed.

I tried using the styleNoRescale option to the PlotOHLC(), but this cased the chart to be displayed referenced to the 0-line. I also tested using Plot(), with no difference.

Is there a way to stop this behaviour?


My simplified code is

zoneListStr = GetTradingZones();
for( j = 0; ( zoneStr = StrExtract( zoneListStr, j ) ) != ""; j++ )
  zoneBottom = StrToNum(StrExtract(zoneStr,0));
  zoneTop = StrToNum(StrExtract(zoneStr,1));
  PlotOHLC(zoneTop, zoneTop, zoneBottom, zoneTop, "", colorDarkBlue, styleCloud);

This chart shows the scaling effect:

This shows the same chart, when the highest PlotOHLC() is omitted: