Propagate the maximum length of the characters buffer to the TextRun, even when we're only processing a substring.
eg. in RenderText, when we're measuring:
'len' glyphs starting from 'text()->characters() + start', then there's a remaining length of 'textLength() - start' that we're not processing.
When integrating SVG Fonts with the GlyphPage concept this information is needed to properly handle ligatures.
Currently this is done by a special floatWidthUsingSVGFont that takes an "int& extraCharsAvailable" parameter.
This generalizes the concept.
Created attachment 96852 [details]
Created attachment 96855 [details]
Fix win/wx build.
Comment on attachment 96855 [details]
LGTM. Please think about renaming m_len to a more meaningful name in a follow up patch. r=me
Landed in r88613.