FILL_BEGIN_TO_END:null = 0
The progress bar fills from begin to end horizontally, according to the language direction. If [method Control.is_layout_rtl] returns false, it fills from left to right, and if it returns true, it fills from right to left.
FILL_END_TO_BEGIN:null = 1
The progress bar fills from end to begin horizontally, according to the language direction. If [method Control.is_layout_rtl] returns false, it fills from right to left, and if it returns true, it fills from left to right.
FILL_TOP_TO_BOTTOM:null = 2
The progress fills from top to bottom.
FILL_BOTTOM_TO_TOP:null = 3
The progress fills from bottom to top.