void setMouseWheelZoomRatio(double ratio);

Sets the magnification ratio for each mouse wheel event.

The magnification ratio is applied when the mouse wheel rolls towards the screen. The reciprocal of the ratio is applied when the mouse wheel rolls away from the screen. A ratio larger than 1 means to zoom in when the mouse wheel rolls towards the screen, and to zoom out when the mouse wheel rolls away from the screen. A ratio less than 1 means the opposite behaviour. A ratio equal to 1 disables mouse wheel zooming.

The mouse wheel causes zooming to occur, it will trigger the QChartViewer.viewPortChanged signal.

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