LayoutSize RenderBoxModelObject::relativePositionOffset() const
{
LayoutSize offset = accumulateInFlowPositionOffsets(this);
RenderBlock* containingBlock = this->containingBlock();
// Objects that shrink to avoid floats normally use available line width when computing containing block width. However
// in the case of relative positioning using percentages, we can't do this. The offset should always be resolved using the
// available width of the containing block. Therefore we don't use containingBlockLogicalWidthForContent() here, but instead explicitly
// call availableWidth on our containing block.
if (!style()->left().isAuto()) {
if (!style()->right().isAuto() && !containingBlock->style()->isLeftToRightDirection())
offset.setWidth(-valueForLength(style()->right(), containingBlock->availableWidth()));
else
offset.expand(valueForLength(style()->left(), containingBlock->availableWidth()), 0);
} else if (!style()->right().isAuto()) {
offset.expand(-valueForLength(style()->right(), containingBlock->availableWidth()), 0);
}
// If the containing block of a relatively positioned element does not
// specify a height, a percentage top or bottom offset should be resolved as
// auto. An exception to this is if the containing block has the WinIE quirk
// where <html> and <body> assume the size of the viewport. In this case,
// calculate the percent offset based on this height.
// See <https://bugs.webkit.org/show_bug.cgi?id=26396>.
if (!style()->top().isAuto()
&& (!containingBlock->hasAutoHeightOrContainingBlockWithAutoHeight()
|| !style()->top().isPercent()
|| containingBlock->stretchesToViewport()))
offset.expand(0, valueForLength(style()->top(), containingBlock->availableHeight()));
else if (!style()->bottom().isAuto()
&& (!containingBlock->hasAutoHeightOrContainingBlockWithAutoHeight()
|| !style()->bottom().isPercent()
|| containingBlock->stretchesToViewport()))
offset.expand(0, -valueForLength(style()->bottom(), containingBlock->availableHeight()));
return offset;
}
bool RenderBoxModelObject::hasAutoHeightOrContainingBlockWithAutoHeight() const
{
Length logicalHeightLength = style()->logicalHeight();
if (logicalHeightLength.isAuto())
return true;
// For percentage heights: The percentage is calculated with respect to the height of the generated box's
// containing block. If the height of the containing block is not specified explicitly (i.e., it depends
// on content height), and this element is not absolutely positioned, the value computes to 'auto'.
if (!logicalHeightLength.isPercent() || isOutOfFlowPositioned() || document().inQuirksMode())
return false;
// Anonymous block boxes are ignored when resolving percentage values that would refer to it:
// the closest non-anonymous ancestor box is used instead.
RenderBlock* cb = containingBlock();
while (cb->isAnonymous())
cb = cb->containingBlock();
// Matching RenderBox::percentageLogicalHeightIsResolvableFromBlock() by
// ignoring table cell's attribute value, where it says that table cells violate
// what the CSS spec says to do with heights. Basically we
// don't care if the cell specified a height or not.
if (cb->isTableCell())
return false;
// Match RenderBox::availableLogicalHeightUsing by special casing
// the render view. The available height is taken from the frame.
if (cb->isRenderView())
return false;
if (cb->isOutOfFlowPositioned() && !cb->style()->logicalTop().isAuto() && !cb->style()->logicalBottom().isAuto())
return false;
// If the height of the containing block computes to 'auto', then it hasn't been 'specified explicitly'.
return cb->hasAutoHeightOrContainingBlockWithAutoHeight();
}