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Bug 939901 part 5: Honor 'align-content' in flexbox layout, for multi-line flex containers. r=mats

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This commit is contained in:
Daniel Holbert 2013-12-05 10:57:51 -08:00
parent 5739dc64de
commit 42b052e67e
1 changed files with 172 additions and 31 deletions
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203
layout/generic/nsFlexContainerFrame.cpp
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@ -1165,16 +1165,31 @@ private:
// content-box.
class MOZ_STACK_CLASS CrossAxisPositionTracker : public PositionTracker {
public:
CrossAxisPositionTracker(nsFlexContainerFrame* aFlexContainerFrame,
const FlexboxAxisTracker& aAxisTracker,
const nsHTMLReflowState& aReflowState)
: PositionTracker(aAxisTracker.GetCrossAxis()) {}
CrossAxisPositionTracker(nsTArray<FlexLine>& aLines,
uint8_t aAlignContent,
nscoord aContentBoxCrossSize,
bool aIsCrossSizeDefinite,
const FlexboxAxisTracker& aAxisTracker);
// XXXdholbert This probably needs a ResolveStretchedLines() method,
// (which takes an array of SingleLineCrossAxisPositionTracker objects
// and distributes an equal amount of space to each one).
// For now, we just have Reflow directly call
// SingleLineCrossAxisPositionTracker::SetLineCrossSize().
// Advances past the packing space (if any) between two flex lines
void TraversePackingSpace();
// Advances past the given FlexLine
void TraverseLine(FlexLine& aLine) { mPosition += aLine.GetLineCrossSize(); }
private:
// Redeclare the frame-related methods from PositionTracker as private with
// MOZ_DELETE, to be sure (at compile time) that no client code can invoke
// them. (Unlike the other PositionTracker derived classes, this class here
// deals with FlexLines, not with individual FlexItems or frames.)
void EnterMargin(const nsMargin& aMargin) MOZ_DELETE;
void ExitMargin(const nsMargin& aMargin) MOZ_DELETE;
void EnterChildFrame(nscoord aChildFrameSize) MOZ_DELETE;
void ExitChildFrame(nscoord aChildFrameSize) MOZ_DELETE;
nscoord mPackingSpaceRemaining;
uint32_t mNumPackingSpacesRemaining;
uint8_t mAlignContent;
};
// Utility class for managing our position along the cross axis, *within* a
@ -1712,6 +1727,147 @@ MainAxisPositionTracker::TraversePackingSpace()
}
}
CrossAxisPositionTracker::
CrossAxisPositionTracker(nsTArray<FlexLine>& aLines,
uint8_t aAlignContent,
nscoord aContentBoxCrossSize,
bool aIsCrossSizeDefinite,
const FlexboxAxisTracker& aAxisTracker)
: PositionTracker(aAxisTracker.GetCrossAxis()),
mPackingSpaceRemaining(0),
mNumPackingSpacesRemaining(0),
mAlignContent(aAlignContent)
{
MOZ_ASSERT(!aLines.IsEmpty(), "We should have at least 1 line");
if (aIsCrossSizeDefinite && aLines.Length() == 1) {
// "If the flex container has only a single line (even if it's a
// multi-line flex container) and has a definite cross size, the cross
// size of the flex line is the flex container's inner cross size."
// SOURCE: http://dev.w3.org/csswg/css-flexbox/#algo-line-break
// NOTE: This means (by definition) that there's no packing space, which
// means we don't need to be concerned with "align-conent" at all and we
// can return early. This is handy, because this is the usual case (for
// single-line flexbox).
aLines[0].SetLineCrossSize(aContentBoxCrossSize);
return;
}
// NOTE: The rest of this function should essentially match
// MainAxisPositionTracker's constructor, though with FlexLines instead of
// FlexItems, and with the additional value "stretch" (and of course with
// cross sizes instead of main sizes.)
// Figure out how much packing space we have (container's cross size minus
// all the lines' cross sizes)
mPackingSpaceRemaining = aContentBoxCrossSize;
for (uint32_t i = 0; i < aLines.Length(); i++) {
const FlexLine& line = aLines[i];
mPackingSpaceRemaining -= line.GetLineCrossSize();
}
// If packing space is negative, 'space-between' and 'stretch' behave like
// 'flex-start', and 'space-around' behaves like 'center'. In those cases,
// it's simplest to just pretend we have a different 'align-content' value
// and share code.
if (mPackingSpaceRemaining < 0) {
if (mAlignContent == NS_STYLE_ALIGN_CONTENT_SPACE_BETWEEN ||
mAlignContent == NS_STYLE_ALIGN_CONTENT_STRETCH) {
mAlignContent = NS_STYLE_ALIGN_CONTENT_FLEX_START;
} else if (mAlignContent == NS_STYLE_ALIGN_CONTENT_SPACE_AROUND) {
mAlignContent = NS_STYLE_ALIGN_CONTENT_CENTER;
}
}
// Figure out how much space we'll set aside for packing spaces, and advance
// past any leading packing-space.
if (mPackingSpaceRemaining != 0) {
switch (mAlignContent) {
case NS_STYLE_ALIGN_CONTENT_FLEX_START:
// All packing space should go at the end --> nothing to do here.
break;
case NS_STYLE_ALIGN_CONTENT_FLEX_END:
// All packing space goes at the beginning
mPosition += mPackingSpaceRemaining;
break;
case NS_STYLE_ALIGN_CONTENT_CENTER:
// Half the packing space goes at the beginning
mPosition += mPackingSpaceRemaining / 2;
break;
case NS_STYLE_ALIGN_CONTENT_SPACE_BETWEEN:
MOZ_ASSERT(mPackingSpaceRemaining >= 0,
"negative packing space should make us use 'flex-start' "
"instead of 'space-between'");
// 1 packing space between each flex line, no packing space at ends.
mNumPackingSpacesRemaining = aLines.Length() - 1;
break;
case NS_STYLE_ALIGN_CONTENT_SPACE_AROUND: {
MOZ_ASSERT(mPackingSpaceRemaining >= 0,
"negative packing space should make us use 'center' "
"instead of 'space-around'");
// 1 packing space between each flex line, plus half a packing space
// at beginning & end. So our number of full packing-spaces is equal
// to the number of flex lines.
mNumPackingSpacesRemaining = aLines.Length();
// The edges (start/end) share one full packing space
nscoord totalEdgePackingSpace =
mPackingSpaceRemaining / mNumPackingSpacesRemaining;
// ...and we'll use half of that right now, at the start
mPosition += totalEdgePackingSpace / 2;
// ...but we need to subtract all of it right away, so that we won't
// hand out any of it to intermediate packing spaces.
mPackingSpaceRemaining -= totalEdgePackingSpace;
mNumPackingSpacesRemaining--;
break;
}
case NS_STYLE_ALIGN_CONTENT_STRETCH:
// Split space equally between the lines:
MOZ_ASSERT(mPackingSpaceRemaining > 0,
"negative packing space should make us use 'flex-start' "
"instead of 'stretch' (and we shouldn't bother with this "
"code if we have 0 packing space)");
for (uint32_t i = 0; i < aLines.Length(); i++) {
FlexLine& line = aLines[i];
// Our share is the amount of space remaining, divided by the number
// of lines remainig.
nscoord shareOfExtraSpace =
mPackingSpaceRemaining / (aLines.Length() - i);
nscoord newSize = line.GetLineCrossSize() + shareOfExtraSpace;
line.SetLineCrossSize(newSize);
mPackingSpaceRemaining -= shareOfExtraSpace;
}
break;
default:
MOZ_CRASH("Unexpected align-content value");
}
}
}
void
CrossAxisPositionTracker::TraversePackingSpace()
{
if (mNumPackingSpacesRemaining) {
MOZ_ASSERT(mAlignContent == NS_STYLE_ALIGN_CONTENT_SPACE_BETWEEN ||
mAlignContent == NS_STYLE_ALIGN_CONTENT_SPACE_AROUND,
"mNumPackingSpacesRemaining only applies for "
"space-between/space-around");
MOZ_ASSERT(mPackingSpaceRemaining >= 0,
"ran out of packing space earlier than we expected");
// NOTE: This integer math will skew the distribution of remainder
// app-units towards the end, which is fine.
nscoord curPackingSpace =
mPackingSpaceRemaining / mNumPackingSpacesRemaining;
mPosition += curPackingSpace;
mNumPackingSpacesRemaining--;
mPackingSpaceRemaining -= curPackingSpace;
}
}
SingleLineCrossAxisPositionTracker::
SingleLineCrossAxisPositionTracker(const FlexboxAxisTracker& aAxisTracker)
: PositionTracker(aAxisTracker.GetCrossAxis())
@ -2520,16 +2676,6 @@ nsFlexContainerFrame::Reflow(nsPresContext* aPresContext,
lines[lineIdx].ComputeCrossSizeAndBaseline(axisTracker);
}
// Set up state for cross-axis alignment, at a high level (outside the
// scope of a particular flex line)
CrossAxisPositionTracker
crossAxisPosnTracker(this, axisTracker, aReflowState);
// XXXdholbert Once we've got multi-line flexbox support: here, after we've
// computed the cross size of all lines, we need to check if if
// 'align-content' is 'stretch' -- if it is, we need to give each line an
// additional share of our flex container's desired cross-size. (if it's
// not NS_AUTOHEIGHT and there's any cross-size left over to distribute)
bool isCrossSizeDefinite;
const nscoord contentBoxCrossSize =
ComputeFlexContainerCrossSize(aReflowState, axisTracker,
@ -2537,18 +2683,11 @@ nsFlexContainerFrame::Reflow(nsPresContext* aPresContext,
availableHeightForContent,
&isCrossSizeDefinite, aStatus);
if (isCrossSizeDefinite) {
if (lines.Length() == 1) {
// "If the flex container has only a single line (even if it's a multi-line
// flex container) and has a definite cross size, the cross size of the
// flex line is the flex container's inner cross size."
lines[0].SetLineCrossSize(contentBoxCrossSize);
} else {
// XXXdholbert Distribute contentBoxCrossSize among (or around) lines,
// depending on 'align-content' value. (This will be handled in the later
// patch about honoring "align-content".)
}
}
// Set up state for cross-axis alignment, at a high level (outside the
// scope of a particular flex line)
CrossAxisPositionTracker
crossAxisPosnTracker(lines, aReflowState.mStylePosition->mAlignContent,
contentBoxCrossSize, isCrossSizeDefinite, axisTracker);
// Set the flex container's baseline, from its first line's baseline-aligned items.
// (This might give us nscoord_MIN if we don't have any baseline-aligned
@ -2573,6 +2712,8 @@ nsFlexContainerFrame::Reflow(nsPresContext* aPresContext,
// ===============================================
line.PositionItemsInCrossAxis(crossAxisPosnTracker.GetPosition(),
axisTracker);
crossAxisPosnTracker.TraverseLine(line);
crossAxisPosnTracker.TraversePackingSpace();
}
// Before giving each child a final reflow, calculate the origin of the