Until now, when we are purging inactive font data, we would just clear the glyph page cache if we had to purge system fallback font. This means that we consilder glyph page cache would only point to fonts from system fonts fallback. When we are handling unicode's in the Private-User-Area (PUA) block, we shouldn't fallback to system fonts searching for a font that can render it, per spec: https://www.w3.org/TR/css-fonts-4/#char-handling-issues Instead, we render the glyph 0 with the last resort font. However, this font is just added to the custom font cache, and its font pointer in the Glyph Page cache is not cleared during memory pressure. We should add this font to the system font fallback set, to make sure that the associated font pointer is removed from the glyph page cache during memory pressure.
<rdar://problem/117805319>
Pull request: https://github.com/apple/WebKit/pull/921
Committed 267815.567@safari-7617-branch (a595ddd8348d): <https://commits.webkit.org/267815.567@safari-7617-branch> Reviewed commits have been landed. Closing PR #921 and removing active labels.
Committed 272231@main (53683ca2146f): <https://commits.webkit.org/272231@main> Reviewed commits have been landed. Closing PR #21900 and removing active labels.