The B4XCanvas DrawLine method doesn't behave the same in B4J like in B4A / B4i.
Drawing a thick line starts at the start point and ends at the end point.
In B4J, the line is longer, I think you set the LineCap property to SQUARE by default and in B4A / B4i it's BUTT.
I would prefer having the same behavior for all three products.
Below, the code for the lines, it draws a thick and a small line to show the difference: