function Leadtools.Annotations.Rendering.AnnTextUnderlineObjectRenderer()
AnnTextUnderlineObjectRenderer is the default renderer for the following objects:
AnnRenderingEngine creates a new instance of this class and stores it in the AnnRenderingEngine.Renderers dictionary for each of the listed object ids.
This renderer overrides RenderShape to render a thick horizontal line near the bottom of each rectangle in GetRectangles as follows:
This thick line is really a rectangle that has a width equal to the rectangle width.
The height of the line is calculated from multiplying the height of the rectangle by the value of Thickness (0.15 by default which result in a line thickness equal to 15 percent of the rectangle height).
The position the line centered vertically at Position percentage value of the rectangle height (the default value of Position is 0.85 which result in the line centered verticaly at 85 percent of the height).
This thick line is then rendered as a filled rectangle using Fill.