[Webkit-unassigned] [Bug 61561] add support for "on demand" webfonts

Mon Jun 13 17:45:45 PDT 2011

https://bugs.webkit.org/show_bug.cgi?id=61561

--- Comment #4 from Brian Stell <bstell at google.com>  2011-06-13 17:45:45 PST ---
My goal is to speed up CJK webfonts. Yuzo's goal in bug 42154 is to speed up CJK fonts. We are both working toward a similar goal but we are going about it in very different ways.

I talked with Yuzo and I believe in bug 42154 the plan is to break up big fonts into subsets of smaller Unicode ranges. These subsets would then be listed out in a CSS font list which the browser would logically reassemble. With his patch only the parts actually used would be downloaded. For a font composed of scripts that are efficiently ordered in Unicode (eg, Latin, Cyrillic, etc.) subsetting by Unicode range makes good sense. Each subset can efficiently cover a script and browser would only need to download the parts actually used.

However, the characters in the Unicode Han (CJK) unification range are not efficiently ordered for Chinese, Japanese, or Korean. The Han unification is ordered in radical-stroke order, not by script or popularity. Popular characters for a given language are somewhat randomly scattered thru the whole range. Each subset in a Unicode range includes many low popularity characters along with a few high popularity characters. To load a page of popular characters would effectively download most of the subsets effectively defeating the goal of smaller downloading. For bug 42154 to be effective we would need to:
1. introduce a concept of 'popular' character ranges
2. add these 'popular' character ranges to the CSS spec
3. subset by 'popular' characters
4. list these in the CSS font family (or make the browser smart enough to request the appropriate subsets).

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