Image displayed as a background of the progress bar. Not all progress bar interfaces support it, some simply ignore it. You can leave it Nil, then we will simply capture screen contents each time the progress bar starts.
Whether the image assigned here is "owned" (that is, "automatically freed") by TProgressUserInterface instance depends on OwnsImage. In any case, we don't modify the image (if we need to resize it to fit the screen size, we do it on a temporary copy).
property BarYPosition: Single read FBarYPosition write FBarYPosition
default DefaultBarYPosition;
Vertical position of the displayed progress bar. This feature is supposed to indicate a suitable free space on the background Image where we can nicely fit the progress bar UI.
Not all progress bar interfaces support it, some simply ignore it.
0 means the middle of progress bar is at the bottom of the image, 1 means at the top. 0.5 indicates the middle, and it's the default.
property ImageBarYPosition: Single read FBarYPosition write FBarYPosition
default DefaultBarYPosition; deprecated;