Added a destructor to MPlotColorLegend. Using Instruments with the Leaks/Allocations combo I found that MPlotColorLegend::MPlotColorLegend() was leaking quite a bit. Turns out it was new-ing its signal source but not cleaning it up. Added destructor with a call to deleteLater for the signal source. Did a basic check to make sure it wasn't deleted in any other way and did a basic test. Appears to be fine.