Specifies the delay before the widget will repick (sending enter/leave/motion events when entering/leaving/hovering tagged regions) after scroll operations. The default value is 50 milliseconds. When setting the value to zero (or less than zero) the repick will be done immediately. The higher the responsiveness, the less the display will flicker while the widget is scrolling.
The primary goal is the reduction of flickering. This is especially very useful when the line metric is changing while the mouse is entering/leaving/hovering, this is normally not wanted during a scroll operation, because the screen becomes volatile as long as the scroll operation is not finished.
The default value of 50 ms is in fact incompatible to prior releases, but it shouldn't matter here, because nobody wants flickering, and nobody is using special tricks with a short mouse hovering. Setting the responsiveness to zero restores the old behavior of the text widget.