The simplest way to draw a box around a Glyph is to use the Box Glyph. The Box Glyph is a Mono Glyph thus having a child Glyph. It also has an attribute, 'mode', which indicates what type of box to draw. The supported UTF-8 box drawing characters that are support by Forms have the following 'mode' names:
- light: single line box
- heavy: single heavy line box
- double: double lines box
- light_arc: single line box but corners are arcs
- light_double_dash: single dashed line box
- light_double_dash_arc: double dashed lines box
- heavy_double_dash: heavy double dashed lines box
- light_triple_dash: triple line box
- light_triple_dash_arc: triple dashed line box but corners are arcs
- heavy_triple_dash: heavy triple dash lined box
- light_quadruple_dash: light four dashed line box
- light_quadruple_dash_arc: light four dashed line box but corners are arcs
- heavy_quadruple_dash: heavy four dashed line box
- block: character blocks used to make box
- semi_block: character blocks used to make box but corners empty
- triangle_block: box having triangle corners
The Box Glyph has a default 'mode' of 'light'.
Since box drawing characters are simply characters, the size of a Box Glyph is the size of its child Glyph with size width and height plus the size of the box characters, that is, width + 2 and height + 2.
While putting a box around a Glyph or a grouping of Glyphs is useful, it is sometime required/desired to place separate boxes around a number of Glyphs but not have each box being separate, rather having them merge together. The Poly's HPoly and VPoly support this as does the Grid Glyph.
In these cases, the default behavior if the 'mode' attribute is not explicitly set is to not draw any box. If the Glyphs are in box-mode, the 'mode' is set, then boxes are draw around all child Glyphs but only a single character appear between any two neighboring child Glyphs.
In the case of a HPoly in box-mode, its height is what its height would be if it were not in box-mode plus 2, while its width is its non-box-mode width plus 2 for the lines at both ends plus the number of internal box lines being drawn (which depends upon the number of child Glyphs).
A VPoly has similar size considerations when in box-mode.
For a Grid Glyph, since it is kind of like a combined HPoly and VPoly, its size is increased both in width and height by 2 plus for width, the number of its columns minus 1 and for height the number of its rows minus 1.
Now, for both the HPoly and VPoly and for the Grid Glyphs it would be possible to have a larger selection of how box drawing characters are combined, but that level of support would be a much more complicated API. For instance, for a Grid, the exterior horizontal box characters would be heavy dashed, the exterior vertical could be single while the interior lines could be double dashed. Its possible to find the correct joiner characters to make this all work, but at this point it does not seem worth it.