[Webkit-unassigned] [Bug 20953] Rework the Font handling in QtWebKit

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Wed Oct 8 07:31:39 PDT 2008


hausmann at webkit.org changed:

           What    |Removed                     |Added
                 CC|                            |hausmann at webkit.org

------- Comment #14 from hausmann at webkit.org  2008-10-08 07:31 PDT -------
(In reply to comment #13)
> Has anyone done perf testing to determine wether the fast path makes a
> performance difference for Qt? It might be good to know if this causes a perf
> regression (though perhaps the Qt folks are willing to take the speed hit for
> other reasons).

I don't have hard numbers, but the main problem with the "fast" path is that
it's slower with Qt because we can not provide a proper mapping from characters
to glyphs. There is currently no public API in Qt for that, and as a result of
that the implementation would have to map a character to a "virtual" glyph that
is the unicode value again. When drawing the glyphs we treat them as characters
and pass them as string to Qt to draw the text. That is much more work and uses
more memory than just always going the "complex" path of passing the string
down to the toolkit.

I recall very well how the qt port become significantly faster after Lars
removed the "fast" path for the Qt port.

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