https://bugs.webkit.org/show_bug.cgi?id=122458

Reviewed by Darin Adler.

Line box based inline layout is powerful but also rather slow and memory intensive. Simple line layout
is a compact alternative data structure and fast code path to cover common cases without requiring line
boxes.
        
This patch handles a case single left-aligned text renderer inside flow with no floats. Even this very basic
case is sufficiently common to handle up to 25% of all text lines on some popular new sites. The decision
which path to use is made per block flow (paragraph).
        
Simple line layout aims to produce pixel-exact rendering result when compared to the line box layout.
        
The goal is to handle everything that requires line level access in cases that allow use of simple lines.
This is not quite the case yet. For example selections and outline painting are not supported. In these
cases we seamlessly switch to the line boxes.

The simple line data structure currently uses 12 bytes per line. Lineboxes take ~160 bytes minimum per line.
Laying out the lines is also several times faster as is iterating over them.

* CMakeLists.txt:
* GNUmakefile.list.am:
* WebCore.vcxproj/WebCore.vcxproj:
* WebCore.xcodeproj/project.pbxproj:
* dom/Position.cpp:
(WebCore::Position::upstream):
(WebCore::Position::downstream):
(WebCore::Position::getInlineBoxAndOffset):
        
    Creating positions within a simple line flow causes switch to line boxes.

* editing/TextIterator.cpp:
(WebCore::TextIterator::handleTextNode):
        
    TextIterator traverses line boxes if available. In case simple line case we need to replicate the
    same results (for compatibility but especially to avoid changing test results). This is done here
    by just traversing the string without actually using the layout.

* rendering/RenderBlock.cpp:
(WebCore::RenderBlock::RenderBlock):
(WebCore::RenderBlock::layoutShapeInsideInfo):
* rendering/RenderBlock.h:
* rendering/RenderBlockFlow.cpp:
(WebCore::RenderBlockFlow::layoutInlineChildren):
        
    Select the layout path to use.

(WebCore::RenderBlockFlow::deleteLines):
(WebCore::RenderBlockFlow::hitTestInlineChildren):
(WebCore::RenderBlockFlow::adjustForBorderFit):
(WebCore::RenderBlockFlow::firstLineBaseline):
(WebCore::RenderBlockFlow::inlineBlockBaseline):
(WebCore::RenderBlockFlow::inlineSelectionGaps):
(WebCore::RenderBlockFlow::clearTruncation):
(WebCore::RenderBlockFlow::positionForPointWithInlineChildren):
(WebCore::RenderBlockFlow::addFocusRingRectsForInlineChildren):
(WebCore::RenderBlockFlow::paintInlineChildren):
(WebCore::RenderBlockFlow::hasLines):
(WebCore::RenderBlockFlow::layoutSimpleLines):
        
    Do simple layout.

(WebCore::RenderBlockFlow::deleteLineBoxesBeforeSimpleLineLayout):
(WebCore::RenderBlockFlow::ensureLineBoxes):
        
    This function switches from simple lines to line boxes. The switching can be done outside normal layout.
    This is used to cover some cases that are not yet supported by simple lines (like selections).

* rendering/RenderBlockFlow.h:
(WebCore::RenderBlockFlow::simpleLines):
* rendering/RenderBlockLineLayout.cpp:
(WebCore::RenderBlockFlow::layoutLineBoxes):
        
    Rename the line box layout function.

(WebCore::RenderBlockFlow::addOverflowFromInlineChildren):
* rendering/RenderText.cpp:
(WebCore::RenderText::deleteLineBoxesBeforeSimpleLineLayout):
(WebCore::RenderText::absoluteRects):
(WebCore::RenderText::absoluteRectsForRange):
(WebCore::RenderText::absoluteQuadsClippedToEllipsis):
(WebCore::RenderText::absoluteQuads):
(WebCore::RenderText::absoluteQuadsForRange):
(WebCore::RenderText::positionForPoint):
(WebCore::RenderText::knownToHaveNoOverflowAndNoFallbackFonts):
(WebCore::RenderText::setSelectionState):
(WebCore::RenderText::setTextWithOffset):
(WebCore::RenderText::ensureLineBoxes):
(WebCore::RenderText::simpleLines):
(WebCore::RenderText::linesBoundingBox):
(WebCore::RenderText::linesVisualOverflowBoundingBox):
(WebCore::RenderText::selectionRectForRepaint):
(WebCore::RenderText::caretMinOffset):
(WebCore::RenderText::caretMaxOffset):
(WebCore::RenderText::countRenderedCharacterOffsetsUntil):
(WebCore::RenderText::containsRenderedCharacterOffset):
(WebCore::RenderText::containsCaretOffset):
(WebCore::RenderText::hasRenderedText):
* rendering/RenderText.h:
* rendering/RenderTreeAsText.cpp:
(WebCore::RenderTreeAsText::writeRenderObject):
(WebCore::writeSimpleLine):
(WebCore::write):
* rendering/SimpleLineLayout.cpp: Added.
(WebCore::SimpleLineLayout::canUseFor):
        
    This check for the cases supported by the simple line layout path.

(WebCore::SimpleLineLayout::isWhitespace):
(WebCore::SimpleLineLayout::skipWhitespaces):
(WebCore::SimpleLineLayout::textWidth):
(WebCore::SimpleLineLayout::createLines):
        
    The main layout functions that breaks text to lines. It only handles the cases allowed by 
    SimpleLineLayout::canUseFor. What it handles it aims to break exactly as line box layout does.

* rendering/SimpleLineLayout.h: Added.
* rendering/SimpleLineLayoutFunctions.cpp: Added.
(WebCore::SimpleLineLayout::paintFlow):
(WebCore::SimpleLineLayout::hitTestFlow):
(WebCore::SimpleLineLayout::collectFlowOverflow):
(WebCore::SimpleLineLayout::computeTextBoundingBox):
* rendering/SimpleLineLayoutFunctions.h: Added.
(WebCore::SimpleLineLayout::computeFlowHeight):
(WebCore::SimpleLineLayout::computeFlowFirstLineBaseline):
(WebCore::SimpleLineLayout::computeFlowLastLineBaseline):
(WebCore::SimpleLineLayout::findTextCaretMinimumOffset):
(WebCore::SimpleLineLayout::findTextCaretMaximumOffset):
(WebCore::SimpleLineLayout::containsTextCaretOffset):
(WebCore::SimpleLineLayout::isTextRendered):
(WebCore::SimpleLineLayout::lineHeightFromFlow):
        
    Support functions called from RenderBlockFlow and RenderText. They are equivalent to
    similar line box functions.

(WebCore::SimpleLineLayout::baselineFromFlow):
* rendering/SimpleLineLayoutResolver.h: Added.
(WebCore::SimpleLineLayout::Resolver::Line::Line):
(WebCore::SimpleLineLayout::Resolver::Line::rect):
(WebCore::SimpleLineLayout::Resolver::Line::baseline):
(WebCore::SimpleLineLayout::Resolver::Line::text):
(WebCore::SimpleLineLayout::Resolver::Iterator::Iterator):
(WebCore::SimpleLineLayout::Resolver::Iterator::operator++):
(WebCore::SimpleLineLayout::Resolver::Iterator::operator--):
(WebCore::SimpleLineLayout::Resolver::Iterator::operator==):
(WebCore::SimpleLineLayout::Resolver::Iterator::operator!=):
(WebCore::SimpleLineLayout::Resolver::Iterator::operator*):
        
    Lazy iterator for deriving line metrics. This keeps the line data structure small as
    we don't need to keep easily derived values around.

(WebCore::SimpleLineLayout::Resolver::Resolver):
(WebCore::SimpleLineLayout::Resolver::size):
(WebCore::SimpleLineLayout::Resolver::begin):
(WebCore::SimpleLineLayout::Resolver::end):
(WebCore::SimpleLineLayout::Resolver::last):
(WebCore::SimpleLineLayout::Resolver::operator[]):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@157950 268f45cc-cd09-0410-ab3c-d52691b4dbfc