BCGSuite for MFC
int BCGPChartSmartLabelParams::m_nAngleOffset

Specifies allowed interval, in degrees, of data label angles.

This parameter should be specified in [0, 360] degrees interval. It defines the allowed angles of data labels. The angle is calculated from the default data label angle, which is set using CBCGPChartVisualObject::ShowDataLabels or CBCGPChartSeries::SetDataLabelAngle. For example, if you need to adjust data label angle in interval [-45, +45] degrees, call CBCGPChartVisualObject::ShowDataLabels with -45 and set m_nAngleOffset to 90.