RenderMultiColumnSet.cpp

/*
 * Copyright (C) 2012 Apple Inc.  All rights reserved.
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#include "config.h"
#include "RenderMultiColumnSet.h"

#include "HitTestResult.h"
#include "PaintInfo.h"
#include "RenderMultiColumnFlowThread.h"
#include "RenderMultiColumnBlock.h"

using std::min;
using std::max;

namespace WebCore {

RenderMultiColumnSet::RenderMultiColumnSet(Node* node, RenderFlowThread* flowThread)
    : RenderRegionSet(node, flowThread)
    , m_computedColumnCount(1)
    , m_computedColumnWidth(ZERO_LAYOUT_UNIT)
    , m_computedColumnHeight(ZERO_LAYOUT_UNIT)
{
}

LayoutUnit RenderMultiColumnSet::pageLogicalTopForOffset(LayoutUnit offset) const
{
    LayoutUnit portionLogicalTop = (isHorizontalWritingMode() ? flowThreadPortionRect().y() : flowThreadPortionRect().x());
    unsigned columnIndex = (offset - portionLogicalTop) / computedColumnHeight();
    return portionLogicalTop + columnIndex * computedColumnHeight();
}

void RenderMultiColumnSet::updateLogicalWidth()
{
    // Our logical width starts off matching the column block itself.
    // This width will be fixed up after the flow thread lays out once it is determined exactly how many
    // columns we ended up holding.
    // FIXME: When we add regions support, we'll start it off at the width of the multi-column
    // block in that particular region.
    setLogicalWidth(parentBox()->contentLogicalWidth());
    
    RenderMultiColumnBlock* parentBlock = toRenderMultiColumnBlock(parent());
    setComputedColumnWidthAndCount(parentBlock->columnWidth(), parentBlock->columnCount()); // FIXME: This will eventually vary if we are contained inside regions.
}

void RenderMultiColumnSet::updateLogicalHeight()
{
    // FIXME: This is the only class that overrides updateLogicalHeight. If we didn't have to set computedColumnHeight,
    // we could remove this and make updateLogicalHeight non-virtual. https://bugs.webkit.org/show_bug.cgi?id=96804
    // Make sure our column height is up to date.
    LogicalExtentComputedValues computedValues;
    computeLogicalHeight(0, 0, computedValues);
    setComputedColumnHeight(computedValues.m_extent); // FIXME: Once we make more than one column set, this will become variable.
    
    // Our logical height is always just the height of our columns.
    setLogicalHeight(computedColumnHeight());
}

void RenderMultiColumnSet::computeLogicalHeight(LayoutUnit, LayoutUnit, LogicalExtentComputedValues& computedValues) const
{
    RenderMultiColumnBlock* parentBlock = toRenderMultiColumnBlock(parent());
    computedValues.m_extent = parentBlock->columnHeight();
}

LayoutUnit RenderMultiColumnSet::columnGap() const
{
    if (style()->hasNormalColumnGap())
        return style()->fontDescription().computedPixelSize(); // "1em" is recommended as the normal gap setting. Matches <p> margins.
    return static_cast<int>(style()->columnGap());
}

unsigned RenderMultiColumnSet::columnCount() const
{
    if (!computedColumnHeight())
        return 0;
    
    // Our region rect determines our column count. We have as many columns as needed to fit all the content.
    LayoutUnit logicalHeightInColumns = flowThread()->isHorizontalWritingMode() ? flowThreadPortionRect().height() : flowThreadPortionRect().width();
    return ceil(static_cast<float>(logicalHeightInColumns) / computedColumnHeight());
}

LayoutRect RenderMultiColumnSet::columnRectAt(unsigned index) const
{
    LayoutUnit colLogicalWidth = computedColumnWidth();
    LayoutUnit colLogicalHeight = computedColumnHeight();
    LayoutUnit colLogicalTop = borderBefore() + paddingBefore();
    LayoutUnit colLogicalLeft = borderAndPaddingLogicalLeft();
    int colGap = columnGap();
    if (style()->isLeftToRightDirection())
        colLogicalLeft += index * (colLogicalWidth + colGap);
    else
        colLogicalLeft += contentLogicalWidth() - colLogicalWidth - index * (colLogicalWidth + colGap);

    if (isHorizontalWritingMode())
        return LayoutRect(colLogicalLeft, colLogicalTop, colLogicalWidth, colLogicalHeight);
    return LayoutRect(colLogicalTop, colLogicalLeft, colLogicalHeight, colLogicalWidth);
}

unsigned RenderMultiColumnSet::columnIndexAtOffset(LayoutUnit offset) const
{
    LayoutRect portionRect(flowThreadPortionRect());
    LayoutUnit flowThreadLogicalTop = isHorizontalWritingMode() ? portionRect.y() : portionRect.x();
    LayoutUnit flowThreadLogicalBottom = isHorizontalWritingMode() ? portionRect.maxY() : portionRect.maxX();
    
    // Handle the offset being out of range.
    if (offset < flowThreadLogicalTop)
        return 0;
    if (offset >= flowThreadLogicalBottom)
        return columnCount() - 1;
    
    // Just divide by the column height to determine the correct column.
    return static_cast<float>(offset - flowThreadLogicalTop) / computedColumnHeight();
}

LayoutRect RenderMultiColumnSet::flowThreadPortionRectAt(unsigned index) const
{
    LayoutRect portionRect = flowThreadPortionRect();
    if (isHorizontalWritingMode())
        portionRect = LayoutRect(portionRect.x(), portionRect.y() + index * computedColumnHeight(), portionRect.width(), computedColumnHeight());
    else
        portionRect = LayoutRect(portionRect.x() + index * computedColumnHeight(), portionRect.y(), computedColumnHeight(), portionRect.height());
    return portionRect;
}

LayoutRect RenderMultiColumnSet::flowThreadPortionOverflowRect(const LayoutRect& portionRect, unsigned index, unsigned colCount, int colGap) const
{
    // This function determines the portion of the flow thread that paints for the column. Along the inline axis, columns are
    // unclipped at outside edges (i.e., the first and last column in the set), and they clip to half the column
    // gap along interior edges.
    //
    // In the block direction, we will not clip overflow out of the top of the first column, or out of the bottom of
    // the last column. This applies only to the true first column and last column across all column sets.
    //
    // FIXME: Eventually we will know overflow on a per-column basis, but we can't do this until we have a painting
    // mode that understands not to paint contents from a previous column in the overflow area of a following column.
    // This problem applies to regions and pages as well and is not unique to columns.
    bool isFirstColumn = !index;
    bool isLastColumn = index == colCount - 1;
    LayoutRect overflowRect(portionRect);
    if (isHorizontalWritingMode()) {
        if (isFirstColumn) {
            // Shift to the logical left overflow of the flow thread to make sure it's all covered.
            overflowRect.shiftXEdgeTo(min(flowThread()->visualOverflowRect().x(), portionRect.x()));
        } else {
            // Expand into half of the logical left column gap.
            overflowRect.shiftXEdgeTo(portionRect.x() - colGap / 2);
        }
        if (isLastColumn) {
            // Shift to the logical right overflow of the flow thread to ensure content can spill out of the column.
            overflowRect.shiftMaxXEdgeTo(max(flowThread()->visualOverflowRect().maxX(), portionRect.maxX()));
        } else {
            // Expand into half of the logical right column gap.
            overflowRect.shiftMaxXEdgeTo(portionRect.maxX() + colGap / 2);
        }
    } else {
        if (isFirstColumn) {
            // Shift to the logical left overflow of the flow thread to make sure it's all covered.
            overflowRect.shiftYEdgeTo(min(flowThread()->visualOverflowRect().y(), portionRect.y()));
        } else {
            // Expand into half of the logical left column gap.
            overflowRect.shiftYEdgeTo(portionRect.y() - colGap / 2);
        }
        if (isLastColumn) {
            // Shift to the logical right overflow of the flow thread to ensure content can spill out of the column.
            overflowRect.shiftMaxYEdgeTo(max(flowThread()->visualOverflowRect().maxY(), portionRect.maxY()));
        } else {
            // Expand into half of the logical right column gap.
            overflowRect.shiftMaxYEdgeTo(portionRect.maxY() + colGap / 2);
        }
    }
    return overflowRectForFlowThreadPortion(overflowRect, isFirstRegion() && isFirstColumn, isLastRegion() && isLastColumn);
}

void RenderMultiColumnSet::paintReplaced(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
{
    // FIXME: RenderRegions are replaced elements right now and so they only paint in the foreground phase.
    // Columns should technically respect phases and allow for background/float/foreground overlap etc., just like
    // RenderBlocks do. We can't correct this, however, until RenderRegions are changed to actually be
    // RenderBlocks. Note this is a pretty minor issue, since the old column implementation clipped columns
    // anyway, thus making it impossible for them to overlap one another. It's also really unlikely that the columns
    // would overlap another block.
    setRegionObjectsRegionStyle();
    paintColumnRules(paintInfo, paintOffset);
    paintColumnContents(paintInfo, paintOffset);
    restoreRegionObjectsOriginalStyle();
}

void RenderMultiColumnSet::paintColumnRules(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
{
    if (paintInfo.context->paintingDisabled())
        return;

    RenderStyle* blockStyle = toRenderMultiColumnBlock(parent())->style();
    const Color& ruleColor = blockStyle->visitedDependentColor(CSSPropertyWebkitColumnRuleColor);
    bool ruleTransparent = blockStyle->columnRuleIsTransparent();
    EBorderStyle ruleStyle = blockStyle->columnRuleStyle();
    LayoutUnit ruleThickness = blockStyle->columnRuleWidth();
    LayoutUnit colGap = columnGap();
    bool renderRule = ruleStyle > BHIDDEN && !ruleTransparent && ruleThickness <= colGap;
    if (!renderRule)
        return;

    unsigned colCount = columnCount();
    if (colCount <= 1)
        return;

    bool antialias = shouldAntialiasLines(paintInfo.context);

    bool leftToRight = style()->isLeftToRightDirection();
    LayoutUnit currLogicalLeftOffset = leftToRight ? ZERO_LAYOUT_UNIT : contentLogicalWidth();
    LayoutUnit ruleAdd = borderAndPaddingLogicalLeft();
    LayoutUnit ruleLogicalLeft = leftToRight ? ZERO_LAYOUT_UNIT : contentLogicalWidth();
    LayoutUnit inlineDirectionSize = computedColumnWidth();
    BoxSide boxSide = isHorizontalWritingMode()
        ? leftToRight ? BSLeft : BSRight
        : leftToRight ? BSTop : BSBottom;

    for (unsigned i = 0; i < colCount; i++) {
        // Move to the next position.
        if (leftToRight) {
            ruleLogicalLeft += inlineDirectionSize + colGap / 2;
            currLogicalLeftOffset += inlineDirectionSize + colGap;
        } else {
            ruleLogicalLeft -= (inlineDirectionSize + colGap / 2);
            currLogicalLeftOffset -= (inlineDirectionSize + colGap);
        }
       
        // Now paint the column rule.
        if (i < colCount - 1) {
            LayoutUnit ruleLeft = isHorizontalWritingMode() ? paintOffset.x() + ruleLogicalLeft - ruleThickness / 2 + ruleAdd : paintOffset.x() + borderLeft() + paddingLeft();
            LayoutUnit ruleRight = isHorizontalWritingMode() ? ruleLeft + ruleThickness : ruleLeft + contentWidth();
            LayoutUnit ruleTop = isHorizontalWritingMode() ? paintOffset.y() + borderTop() + paddingTop() : paintOffset.y() + ruleLogicalLeft - ruleThickness / 2 + ruleAdd;
            LayoutUnit ruleBottom = isHorizontalWritingMode() ? ruleTop + contentHeight() : ruleTop + ruleThickness;
            IntRect pixelSnappedRuleRect = pixelSnappedIntRectFromEdges(ruleLeft, ruleTop, ruleRight, ruleBottom);
            drawLineForBoxSide(paintInfo.context, pixelSnappedRuleRect.x(), pixelSnappedRuleRect.y(), pixelSnappedRuleRect.maxX(), pixelSnappedRuleRect.maxY(), boxSide, ruleColor, ruleStyle, 0, 0, antialias);
        }
        
        ruleLogicalLeft = currLogicalLeftOffset;
    }
}

void RenderMultiColumnSet::paintColumnContents(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
{
    // For each rectangle, set it as the region rectangle and then let flow thread painting do the rest.
    // We make multiple calls to paintFlowThreadPortionInRegion, changing the rectangles each time.
    unsigned colCount = columnCount();
    if (!colCount)
        return;

    LayoutUnit colGap = columnGap();
    for (unsigned i = 0; i < colCount; i++) {
        // First we get the column rect, which is in our local coordinate space, and we make it physical and apply
        // the paint offset to it. That gives us the physical location that we want to paint the column at.
        LayoutRect colRect = columnRectAt(i);
        flipForWritingMode(colRect);
        colRect.moveBy(paintOffset);
        
        // Next we get the portion of the flow thread that corresponds to this column.
        LayoutRect flowThreadPortion = flowThreadPortionRectAt(i);
        
        // Now get the overflow rect that corresponds to the column.
        LayoutRect flowThreadOverflowPortion = flowThreadPortionOverflowRect(flowThreadPortion, i, colCount, colGap);

        // Do the paint with the computed rects.
        flowThread()->paintFlowThreadPortionInRegion(paintInfo, this, flowThreadPortion, flowThreadOverflowPortion, colRect.location());
    }
}

bool RenderMultiColumnSet::nodeAtPoint(const HitTestRequest& request, HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction action)
{
    LayoutPoint adjustedLocation = accumulatedOffset + location();

    // Check our bounds next. For this purpose always assume that we can only be hit in the
    // foreground phase (which is true for replaced elements like images).
    // FIXME: Once we support overflow, we need to intersect with that and not with the bounds rect.
    LayoutRect boundsRect = borderBoxRectInRegion(locationInContainer.region());
    boundsRect.moveBy(adjustedLocation);
    if (!visibleToHitTesting() || action != HitTestForeground || !locationInContainer.intersects(boundsRect))
        return false;
    
    // The point is in one specific column. Since columns can't overlap, we don't ever have to test
    // multiple columns. Put the 
    
    // FIXME: It would be nice to jump right to the specific column by just doing math on the point. Since columns
    // can't overlap, we shouldn't have to walk every column like this. The old column code walked all the columns, though,
    // so this is no worse. We'd have to watch out for rect-based hit testing, though, which actually could overlap
    // multiple columns.
    LayoutUnit colGap = columnGap();
    unsigned colCount = columnCount();
    for (unsigned i = 0; i < colCount; i++) {
        // First we get the column rect, which is in our local coordinate space, and we make it physical and apply
        // the hit test offset to it. That gives us the physical location that we want to paint the column at.
        LayoutRect colRect = columnRectAt(i);
        flipForWritingMode(colRect);
        colRect.moveBy(adjustedLocation);
        
        // Next we get the portion of the flow thread that corresponds to this column.
        LayoutRect flowThreadPortion = flowThreadPortionRectAt(i);
        
        // Now get the overflow rect that corresponds to the column.
        LayoutRect flowThreadOverflowPortion = flowThreadPortionOverflowRect(flowThreadPortion, i, colCount, colGap);

        // Do the hit test with the computed rects.
        if (flowThread()->hitTestFlowThreadPortionInRegion(this, flowThreadPortion, flowThreadOverflowPortion, request, result, locationInContainer, colRect.location()))
            return true;
    }
    
    updateHitTestResult(result, locationInContainer.point() - toLayoutSize(adjustedLocation));
    return !result.addNodeToRectBasedTestResult(node(), request, locationInContainer, boundsRect);
}

void RenderMultiColumnSet::repaintFlowThreadContent(const LayoutRect& repaintRect, bool immediate) const
{
    // Figure out the start and end columns and only check within that range so that we don't walk the
    // entire column set. Put the repaint rect into flow thread coordinates by flipping it first.
    LayoutRect flowThreadRepaintRect(repaintRect);
    flowThread()->flipForWritingMode(flowThreadRepaintRect);
    
    // Now we can compare this rect with the flow thread portions owned by each column. First let's
    // just see if the repaint rect intersects our flow thread portion at all.
    LayoutRect clippedRect(flowThreadRepaintRect);
    clippedRect.intersect(RenderRegion::flowThreadPortionOverflowRect());
    if (clippedRect.isEmpty())
        return;
    
    // Now we know we intersect at least one column. Let's figure out the logical top and logical
    // bottom of the area we're repainting.
    LayoutUnit repaintLogicalTop = isHorizontalWritingMode() ? flowThreadRepaintRect.y() : flowThreadRepaintRect.x();
    LayoutUnit repaintLogicalBottom = (isHorizontalWritingMode() ? flowThreadRepaintRect.maxY() : flowThreadRepaintRect.maxX()) - 1;
    
    unsigned startColumn = columnIndexAtOffset(repaintLogicalTop);
    unsigned endColumn = columnIndexAtOffset(repaintLogicalBottom);
    
    LayoutUnit colGap = columnGap();
    unsigned colCount = columnCount();
    for (unsigned i = startColumn; i <= endColumn; i++) {
        LayoutRect colRect = columnRectAt(i);
        
        // Get the portion of the flow thread that corresponds to this column.
        LayoutRect flowThreadPortion = flowThreadPortionRectAt(i);
        
        // Now get the overflow rect that corresponds to the column.
        LayoutRect flowThreadOverflowPortion = flowThreadPortionOverflowRect(flowThreadPortion, i, colCount, colGap);

        // Do a repaint for this specific column.
        repaintFlowThreadContentRectangle(repaintRect, immediate, flowThreadPortion, flowThreadOverflowPortion, colRect.location());
    }
}

const char* RenderMultiColumnSet::renderName() const
{    
    return "RenderMultiColumnSet";
}

}