https://bugzilla.wikimedia.org/show_bug.cgi?id=56346

--- Comment #73 from Philippe Verdy <[email protected]> ---
Also the "missinglyph" item of the SVG is just mapped with an advance-width
equal to the space character; it has no path for the glyph itself, where it
should have a path drawing an empty box in that space.

The unselectable glyphs seem to come from an incomplete conversion tool, that
does not know really how to map the glyphs selectable by OpenType features into
the necessary mappings for making them selectable by the SVG font.

An SVG font cannnot use OpenType feature, because it lacks the logic included
in the OpneType renderers to select these features. OpenType features have
implicit selection rules from the script and character properties. Then each
feature adds GSUB and GPOS rules for mapping glyph definitions. In an SVG font,
all the implicit rules must be mapped (the only exception supported by current
relase of the SVG font spec being the Arabic joining type). This means that
Indic script cannot work with simple one-to-one mappings of a character code to
a glyph, with their required features. You need to map Unicode strings (not
characters) into a SVG glyph definition to support the equivalent of contextual
substitutions, and use the "hkern" (or "vkern") definitions to support the
equivalent of OpneType GSUB (for contextual positioning).

I think that the tool used to convert OpenType fonts to SVG font is
insufficient for "complex scripts" (those that have REQUIRED features needed;
see the OpenType specfiications). This means that extra manual tweaking are
needed in the SVG font to make it work correctly (the existing tool is not
doing things properly with its one-to-one character-to-glyph mappings, and its
bogous unselectable zero-to-one mappings).

For this project, just uploading the generated fonts into the MediaWiki
repository is clearly not enough, there should exist a full project containing
or documenting the build tools used to perform these conversions.

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