Drawing stylesheets reference the bundled OpenGost Type B TT font by
family name only. The SVG writer inlined the stylesheet text into the
SVG's style tag but never embedded the actual font data, so exported
drawings only rendered with the intended typeface if that font also
happened to be installed at the OS level of whoever opened the file,
silently falling back to a generic font otherwise.
Embed each bundled font as a base64 encoded @font-face rule so drawing
SVGs are self contained and render consistently regardless of the
viewer's installed fonts. Fixes#5433.
Generated with the assistance of an AI coding tool.
Petru Conduraru
6546abca6e