https://bugs.webkit.org/show_bug.cgi?id=116033

Source/WebCore:

Start by setting the column height to the flow thread's height divided
by the number of columns. Then stretch the column height until
contents fits without creating overflowing columns, or until the
maximum allowed column height is reached, whichever comes first. This
may require several layout iterations (but normally only a
couple). For each time we stretch, stretch by the least amount
required to make a difference to which box goes where.

Also make sure that the columns get tall enough to honor orphans
and widows settings.

This change takes some tiny steps in preparing for multiple column
set support. There is also some minor cleanup and bugfixing; see
details below.

Patch by Morten Stenshorne <mstensho@opera.com> on 2013-06-13
Reviewed by David Hyatt.

Tests: fast/multicol/newmulticol/balance-images.html
       fast/multicol/newmulticol/balance-maxheight1.html
       fast/multicol/newmulticol/balance-maxheight2.html
       fast/multicol/newmulticol/balance1.html
       fast/multicol/newmulticol/balance2.html
       fast/multicol/newmulticol/balance3.html
       fast/multicol/newmulticol/balance4.html
       fast/multicol/newmulticol/balance5.html
       fast/multicol/newmulticol/balance6.html
       fast/multicol/newmulticol/balance7.html
       fast/multicol/newmulticol/balance8.html
       fast/multicol/newmulticol/balance9.html
       fast/multicol/newmulticol/cell-shrinkback.html
       fast/multicol/newmulticol/columns-shorthand-parsing.html
       fast/multicol/newmulticol/orphans-and-widows-balance.html
       fast/multicol/newmulticol/single-line.html

* rendering/RenderBlock.cpp:
(WebCore::RenderBlock::adjustForUnsplittableChild):
(WebCore::RenderBlock::setPageBreak):
(WebCore):
(WebCore::RenderBlock::updateMinimumPageHeight):
(WebCore::calculateMinimumPageHeight):
(WebCore::RenderBlock::adjustLinePositionForPagination):
(WebCore::RenderBlock::adjustBlockChildForPagination): If no lines
cross the boundaries, we need to report where blocks cross
instead, so that the column balancer knows how much to stretch
columns if necessary.
* rendering/RenderBlock.h:
* rendering/RenderFlowThread.h:
* rendering/RenderMultiColumnBlock.cpp:
(WebCore::RenderMultiColumnBlock::RenderMultiColumnBlock):
(WebCore::RenderMultiColumnBlock::checkForPaginationLogicalHeightChange):
(WebCore::RenderMultiColumnBlock::relayoutForPagination):
(WebCore::RenderMultiColumnBlock::layoutSpecialExcludedChild):
* rendering/RenderMultiColumnBlock.h:
(WebCore::RenderMultiColumnBlock::columnHeightAvailable):
(WebCore::RenderMultiColumnBlock::requiresBalancing):
(RenderMultiColumnBlock):
* rendering/RenderMultiColumnFlowThread.cpp:
(WebCore::RenderMultiColumnFlowThread::autoGenerateRegionsToBlockOffset):
(WebCore::RenderMultiColumnFlowThread::setPageBreak):
(WebCore):
(WebCore::RenderMultiColumnFlowThread::updateMinimumPageHeight):
* rendering/RenderMultiColumnFlowThread.h:
(RenderMultiColumnFlowThread):
* rendering/RenderMultiColumnSet.cpp: Get rid of
RenderMultiColumnSet::updateLogicalHeight() override. Make
RenderMultiColumnSet behave more like normal blocks, by having
computeLogicalHeight() calculate logical top in addition to
height, just like any other block.
(WebCore::RenderMultiColumnSet::RenderMultiColumnSet):
(WebCore::RenderMultiColumnSet::heightAdjustedForSetOffset): This
method will become more meaningful once we add support for
multiple column sets.
(WebCore):
(WebCore::RenderMultiColumnSet::pageLogicalTopForOffset):
(WebCore::RenderMultiColumnSet::setAndConstrainColumnHeight):
(WebCore::RenderMultiColumnSet::calculateBalancedHeight):
(WebCore::RenderMultiColumnSet::recordSpaceShortage):
(WebCore::RenderMultiColumnSet::updateLogicalWidth):
(WebCore::RenderMultiColumnSet::prepareForLayout):
(WebCore::RenderMultiColumnSet::computeLogicalHeight):
(WebCore::RenderMultiColumnSet::columnCount):
(WebCore::RenderMultiColumnSet::columnIndexAtOffset):
repaintFlowThreadContent() could end up in an infinite loop
because columnIndexAtOffset() could return UINT_MAX
(subtracting 1 from unsigned 0, which columnCount() could return),
which an unsigned integer obviously can never become larger
than. Also always call columnIndexAtOffset() if we want to get the
column index for some offset, rather than doing it on our own
sometimes. To make this work also during layout, we cannot just
return the last column created so far if we're past it, since
adding new columns is exactly what we want to do at this point.
* rendering/RenderMultiColumnSet.h:
(RenderMultiColumnSet):

LayoutTests:

Patch by Morten Stenshorne <mstensho@opera.com> on 2013-06-13
Reviewed by David Hyatt.

* fast/multicol/newmulticol/balance-images-expected.txt: Added.
* fast/multicol/newmulticol/balance-images.html: Added.
* fast/multicol/newmulticol/balance-maxheight1-expected.txt: Added.
* fast/multicol/newmulticol/balance-maxheight1.html: Added.
* fast/multicol/newmulticol/balance-maxheight2-expected.txt: Added.
* fast/multicol/newmulticol/balance-maxheight2.html: Added.
* fast/multicol/newmulticol/balance1-expected.txt: Added.
* fast/multicol/newmulticol/balance1.html: Added.
* fast/multicol/newmulticol/balance2-expected.txt: Added.
* fast/multicol/newmulticol/balance2.html: Added.
* fast/multicol/newmulticol/balance3-expected.txt: Added.
* fast/multicol/newmulticol/balance3.html: Added.
* fast/multicol/newmulticol/balance4-expected.txt: Added.
* fast/multicol/newmulticol/balance4.html: Added.
* fast/multicol/newmulticol/balance5-expected.txt: Added.
* fast/multicol/newmulticol/balance5.html: Added.
* fast/multicol/newmulticol/balance6-expected.txt: Added.
* fast/multicol/newmulticol/balance6.html: Added.
* fast/multicol/newmulticol/balance7-expected.txt: Added.
* fast/multicol/newmulticol/balance7.html: Added.
* fast/multicol/newmulticol/balance8-expected.txt: Added.
* fast/multicol/newmulticol/balance8.html: Added.
* fast/multicol/newmulticol/balance9-expected.txt: Added.
* fast/multicol/newmulticol/balance9.html: Added.
* fast/multicol/newmulticol/cell-shrinkback-expected.html: Added.
* fast/multicol/newmulticol/cell-shrinkback.html: Added.
* fast/multicol/newmulticol/columns-shorthand-parsing-expected.html: Added.
* fast/multicol/newmulticol/columns-shorthand-parsing.html: Added.
* fast/multicol/newmulticol/orphans-and-widows-balance-expected.txt: Added.
* fast/multicol/newmulticol/orphans-and-widows-balance.html: Added.
* fast/multicol/newmulticol/single-line-expected.html: Added.
* fast/multicol/newmulticol/single-line.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@151545 268f45cc-cd09-0410-ab3c-d52691b4dbfc