Offset RenderEditablePaintOffsetNeededCallback(ViewportDimensions dimensions, Rect caretRect)

Signature for the callback used by RenderEditable to determine the paint offset when the dimensions of the render box change.

The return value should be the new paint offset to use.

Used by RenderEditable.onPaintOffsetUpdateNeeded.

Source 

typedef Offset RenderEditablePaintOffsetNeededCallback(ViewportDimensions dimensions, Rect caretRect);