[ NoAccessorMethod ]
public bool gtk_primary_button_warps_slider { get; set; }

If the value of this setting is true, clicking the primary button in a Range trough will move the slider, and hence set the range’s value, to the point that you clicked.

If it is false, a primary click will cause the slider/value to move by the range’s page-size towards the point clicked.

Whichever action you choose for the primary button, the other action will be available by holding Shift and primary-clicking, or clicking the middle mouse button.