Support kerning with SVG web fonts

https://bugs.webkit.org/show_bug.cgi?id=117540

Reviewed by Stephen Chenney.

Adds the glue to WidthIterator to take advantage of kerning in SVG web fonts.
To supply SVG font kerning with its required text input, the signature of
applyFontTransforms has been extended.

Since SVG font kerning was extremely slow, it has been sped up by replacing
the iteration over all possible kerning definitions with a hash-map based
lookup of the leading symbol to be kerned. The new algorithm provides a
roughly 100x speed-up in SVG font kerning.

Test: fast/text/svg-font-face-with-kerning.html

* platform/graphics/TextRun.h:
(WebCore::TextRun::string):
* platform/graphics/WidthIterator.cpp:
(WebCore::applyFontTransforms):
(WebCore::WidthIterator::advanceInternal):
* rendering/svg/SVGTextRunRenderingContext.cpp:
(WebCore::SVGTextRunRenderingContext::applySVGKerning):
* rendering/svg/SVGTextRunRenderingContext.h:
* svg/SVGFontElement.cpp:
(WebCore::SVGFontElement::invalidateGlyphCache):
(WebCore::SVGFontElement::ensureGlyphCache):
(WebCore::SVGKerningMap::clear):
(WebCore::SVGKerningMap::insert):
(WebCore::stringMatchesUnicodeRange):
(WebCore::stringMatchesGlyphName):
(WebCore::stringMatchesUnicodeName):
(WebCore::matches):
(WebCore::kerningForPairOfStringsAndGlyphs):
(WebCore::SVGFontElement::horizontalKerningForPairOfStringsAndGlyphs):
(WebCore::SVGFontElement::verticalKerningForPairOfStringsAndGlyphs):
* svg/SVGFontElement.h:
(WebCore::SVGKerning::SVGKerning):
(WebCore::SVGKerningMap::isEmpty):
* svg/SVGHKernElement.cpp:
(WebCore::SVGHKernElement::buildHorizontalKerningPair):
* svg/SVGHKernElement.h:
* svg/SVGVKernElement.cpp:
(WebCore::SVGVKernElement::buildVerticalKerningPair):
* svg/SVGVKernElement.h:

Change-Id: I309d05b57df3a85fa9720e56f4ace53d5d1d8cf5
git-svn-id: http://svn.webkit.org/repository/webkit/trunk@156393 268f45cc-cd09-0410-ab3c-d52691b4dbfc
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@digia.com>

0 files changed, 0 insertions, 0 deletions