Select auto to automatically select fill methods. If the whole layer is transparent, then "filling the whole area" method will be used otherwise the "filling non-transparent area" method will be used.
Select "The whole area" to fill the whole layer with the selected color or texture without paying attention to whether part of the layer is transparent.
Select this option to fill the non-transparent part of the layer only.
Select this option to preview the results in real-time.
Click OK to apply the color or texture to the selected layer.
Cancel filling color or texture.