Use of get_bounding_box is not safe for certain fonts

[kevinjwalters]

The documentation informs the user that there needs to be a get_bounding_box method on the font. There are fonts which do meet this criteria but may return None. Fonts loaded using adafruit_bitmap_font have a return value that depends on the content of a bdf file:

https://github.com/adafruit/Adafruit_CircuitPython_Bitmap_Font/blob/master/adafruit_bitmap_font/bdf.py#L67-L79

There are two sequence dereferences in the code currently for [1] from get_bounding_box() which won't handle this elegantly and will confuse users who are not intimately familiar with the content of the bdf file. Perhaps many/all bdf files include this data, though?

I'm a hardcore terminalio.FONT user myself, I only noticed this as part of a discussion in Adafruit Forums: Centre text string on TFTFeatherwing with @wildestpixel

[kmatch98]

According to the BDF file specification, This parameter FONTBOUNDINGBOX is required, see snippet below. Should this raise an exception if the item is missing?

I agree that it’s a bit obtuse to users about what get_bounding_box means. Maybe these item names could be refigured with slighty descriptive names, maybe something like:

font.glyph_max_x = font. get_bounding_box[0]
font.glyph_max_y = font.get_bounding_box[1]
font.glyph_max_x_offset = font.get_bounding_box[2]
font.glyph_max_y_offset = font.get_bounding_box[3]

[kevinjwalters]

Perhaps this should be punted over to https://github.com/adafruit/Adafruit_CircuitPython_Bitmap_Font then?

[jposada202020]

Fix by #43 . Closing