https://bugs.webkit.org/show_bug.cgi?id=121416

Source/WebCore:

Reviewed by David Hyatt.

Tests: mathml/presentation/mo-minus.html
       mathml/presentation/mo-stacked-glyphs.html
       mathml/presentation/mo-stretchy-vertical-bar.html
       mathml/very-large-stretchy-operators.html

MathML stretched operators by both modifying the width of the operator
and adding children to the operator node in the render tree.

Instead we make the operator width equal to the widest glyph possible that we use
to represent the operator.  Additionally instead of rendering stretchy glyphs via
stacked operator pieces in separate render tree nodes, keep only one node for the
glyph, and use a custom paint method to paint the stacked representation.

With this patch, rendering seems roughly equivalent on Mac and markedly better
on Linux.

* css/mathml.css:
Not sure what this line-height:0 was here for, but it caused bugs with the new code

* mathml/MathMLTextElement.cpp:
(WebCore::MathMLTextElement::attach):
(WebCore):
(WebCore::MathMLTextElement::childrenChanged):
Need to update the anonymous render tree below <mo> elements when their
children change or when the renderer is first attached.

* mathml/MathMLTextElement.h:
(MathMLTextElement):
* rendering/mathml/RenderMathMLBlock.cpp:
(WebCore::RenderMathMLBlock::RenderMathMLBlock):
* rendering/mathml/RenderMathMLBlock.h:
Now that the preferred width doesn't depend on the height, we don't
need to override computePreferredLogicalWidths at all.

* rendering/mathml/RenderMathMLFenced.cpp:
(WebCore::RenderMathMLFenced::makeFences):
(WebCore::RenderMathMLFenced::styleDidChange):
Need to update the anonymous renderers for the anonymous RenderMathMLOperators.

* rendering/mathml/RenderMathMLOperator.cpp:
(WebCore::RenderMathMLOperator::expandedStretchHeight):
Store the non-expanded stretch height so that we can detect when the height
actually changed.

(WebCore::RenderMathMLOperator::stretchToHeight):
Only update the style on the anonymous render tree since this is called
from RenderMathMLRow::layout

(WebCore::RenderMathMLOperator::styleDidChange):
(WebCore::RenderMathMLOperator::glyphBoundsForCharacter): A helper to get glyph boundaries.
(WebCore::RenderMathMLOperator::glyphHeightForCharacter): Ditto for glyph width.
(WebCore::RenderMathMLOperator::advanceForCharacter): The advance is different from the width,
and we want the width of the operator to be the advance instead of the tight bounding width.
(WebCore::RenderMathMLOperator::computePreferredLogicalWidths): Use the max of all possible glyphs
we can use to render this operator.
(WebCore::RenderMathMLOperator::computeLogicalHeight): Return the stretched operator height, if appropriate.
(WebCore::RenderMathMLOperator::updateFromElement): We add a child for rendering the non-scaled
version of the glyph.
(WebCore::RenderMathMLOperator::firstCharacterForStretching): Helper to figure out what character
is the character used for stretching operations.
(WebCore::RenderMathMLOperator::findAcceptableStretchyCharacter): Helper to find an acceptable set
of glyph pieces for stretching characters.
(WebCore::RenderMathMLOperator::updateStyle): Resize the operator to the appropriate height and hide
the child if we are using the stretchy style.
(WebCore::RenderMathMLOperator::firstLineBoxBaseline):
(WebCore::RenderMathMLOperator::paintCharacter): Helper to paint a single character component of the
stretchy glyph.
(WebCore::RenderMathMLOperator::fillWithExtensionGlyph): Helper to paint the extender glue between
features of the stretchy glyph.
(WebCore::RenderMathMLOperator::paint): Properly paint stretchy glyphs.
* rendering/mathml/RenderMathMLOperator.h: Update method declarations.

LayoutTests:

Patch by Frédéric Wang <fred.wang@free.fr> on 2013-10-04
Reviewed by David Hyatt.

Add some reftests for stretchy operators.

* TestExpectations: The remaining MathML pixel tests are broken by this patch.
* LayoutTests/platform/gtk/TestExpectations:
* LayoutTests/platform/mac/TestExpectations:
* LayoutTests/platform/win/TestExpectations:
* mathml/presentation/mo-minus.html: Added.
* mathml/presentation/mo-stacked-glyphs-expected.html: Added.
* mathml/presentation/mo-stacked-glyphs.html: Added.
* mathml/presentation/mo-stretchy-vertical-bar-expected-mismatch.html: Added.
* mathml/presentation/mo-stretchy-vertical-bar.html: Added.
* mathml/very-large-stretchy-operators-expected.txt: Added.
* mathml/very-large-stretchy-operators.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@157070 268f45cc-cd09-0410-ab3c-d52691b4dbfc