Quickly draw an array of lines into the specified window "windowPtr". "xy" is a
two-row vector containing the x and y coordinates of the line segments: Pairs of
consecutive columns define (x,y) positions of the starts and ends of line
segments. All positions are relative to "center" (default center is [0 0]).
"width" is either a scalar with the global width for all lines in pixels
(default is 1), or a vector with one separate width value for each separate
line. "colors" is either a single global color argument for all lines, or an
array of rgb or rgba color values for each line, where each column corresponds
to the color of the corresponding line start or endpoint in the xy position
argument. If you specify different colors for the start- and endpoint of a line
segment, PTB will generate a smooth transition of colors along the line via
linear interpolation. The default color is white if colors is omitted. "smooth"
is a flag that determines whether lines should be smoothed: 0 (default) no
smoothing, 1 smoothing (with anti-aliasing). If you use smoothing, you'll also
need to set a proper blending mode with
Screen('
BlendFunction').