third_party/WebKit/Source/core/style/GridResolvedPosition.cpp

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "config.h"
   6 #include "core/style/GridResolvedPosition.h"
   7
   8 #include "core/layout/LayoutBox.h"
   9 #include "core/style/GridCoordinate.h"
  10
  11 namespace blink {
  12
  13 static const NamedGridLinesMap& gridLinesForSide(const ComputedStyle& style, GridPositionSide side)
  14 {
  15     return (side == ColumnStartSide || side == ColumnEndSide) ? style.namedGridColumnLines() : style.namedGridRowLines();
  16 }
  17
  18 static inline String implicitNamedGridLineForSide(const String& lineName, GridPositionSide side)
  19 {
  20     return lineName + ((side == ColumnStartSide || side == RowStartSide) ? "-start" : "-end");
  21 }
  22
  23 static bool isValidNamedLineOrArea(const String& lineName, const ComputedStyle& style, GridPositionSide side)
  24 {
  25     const NamedGridLinesMap& gridLineNames = gridLinesForSide(style, side);
  26
  27     return gridLineNames.contains(implicitNamedGridLineForSide(lineName, side)) || gridLineNames.contains(lineName);
  28 }
  29
  30 static GridPositionSide calculateInitialPositionSide(GridTrackSizingDirection direction)
  31 {
  32     return (direction == ForColumns) ? ColumnStartSide : RowStartSide;
  33 }
  34
  35 static GridPositionSide calculateFinalPositionSide(GridTrackSizingDirection direction)
  36 {
  37     return (direction == ForColumns) ? ColumnEndSide : RowEndSide;
  38 }
  39
  40 void GridResolvedPosition::initialAndFinalPositionsFromStyle(const ComputedStyle& gridContainerStyle, const LayoutBox& gridItem, GridTrackSizingDirection direction, GridPosition& initialPosition, GridPosition& finalPosition)
  41 {
  42     initialPosition = (direction == ForColumns) ? gridItem.style()->gridColumnStart() : gridItem.style()->gridRowStart();
  43     finalPosition = (direction == ForColumns) ? gridItem.style()->gridColumnEnd() : gridItem.style()->gridRowEnd();
  44     GridPositionSide initialPositionSide = calculateInitialPositionSide(direction);
  45     GridPositionSide finalPositionSide = calculateFinalPositionSide(direction);
  46
  47     // We must handle the placement error handling code here instead of in the StyleAdjuster because we don't want to
  48     // overwrite the specified values.
  49     if (initialPosition.isSpan() && finalPosition.isSpan())
  50         finalPosition.setAutoPosition();
  51
  52     // Try to early detect the case of non existing named grid lines. This way we could assume later that
  53     // GridResolvedPosition::resolveGrisPositionFromStyle() always return a valid resolved position.
  54     if (initialPosition.isNamedGridArea() && !isValidNamedLineOrArea(initialPosition.namedGridLine(), gridContainerStyle, initialPositionSide))
  55         initialPosition.setAutoPosition();
  56
  57     if (finalPosition.isNamedGridArea() && !isValidNamedLineOrArea(finalPosition.namedGridLine(), gridContainerStyle, finalPositionSide))
  58         finalPosition.setAutoPosition();
  59
  60     // If the grid item has an automatic position and a grid span for a named line in a given dimension, instead treat the grid span as one.
  61     if (initialPosition.isAuto() && finalPosition.isSpan() && !finalPosition.namedGridLine().isNull())
  62         finalPosition.setSpanPosition(1, String());
  63     if (finalPosition.isAuto() && initialPosition.isSpan() && !initialPosition.namedGridLine().isNull())
  64         initialPosition.setSpanPosition(1, String());
  65 }
  66
  67 GridSpan GridResolvedPosition::resolveGridPositionsFromAutoPlacementPosition(const ComputedStyle& gridContainerStyle, const LayoutBox& gridItem, GridTrackSizingDirection direction, const GridResolvedPosition& resolvedInitialPosition)
  68 {
  69     GridPosition initialPosition, finalPosition;
  70     initialAndFinalPositionsFromStyle(gridContainerStyle, gridItem, direction, initialPosition, finalPosition);
  71
  72     GridPositionSide finalPositionSide = calculateFinalPositionSide(direction);
  73
  74     // This method will only be used when both positions need to be resolved against the opposite one.
  75     ASSERT(initialPosition.shouldBeResolvedAgainstOppositePosition() && finalPosition.shouldBeResolvedAgainstOppositePosition());
  76
  77     GridResolvedPosition resolvedFinalPosition = resolvedInitialPosition;
  78
  79     if (initialPosition.isSpan())
  80         return *resolveGridPositionAgainstOppositePosition(gridContainerStyle, resolvedInitialPosition, initialPosition, finalPositionSide);
  81     if (finalPosition.isSpan())
  82         return *resolveGridPositionAgainstOppositePosition(gridContainerStyle, resolvedInitialPosition, finalPosition, finalPositionSide);
  83
  84     return GridSpan(resolvedInitialPosition, resolvedFinalPosition);
  85 }
  86
  87 PassOwnPtr<GridSpan> GridResolvedPosition::resolveGridPositionsFromStyle(const ComputedStyle& gridContainerStyle, const LayoutBox& gridItem, GridTrackSizingDirection direction)
  88 {
  89     GridPosition initialPosition, finalPosition;
  90     initialAndFinalPositionsFromStyle(gridContainerStyle, gridItem, direction, initialPosition, finalPosition);
  91
  92     GridPositionSide initialPositionSide = calculateInitialPositionSide(direction);
  93     GridPositionSide finalPositionSide = calculateFinalPositionSide(direction);
  94
  95     if (initialPosition.shouldBeResolvedAgainstOppositePosition() && finalPosition.shouldBeResolvedAgainstOppositePosition()) {
  96         // We can't get our grid positions without running the auto placement algorithm.
  97         return nullptr;
  98     }
  99
 100     if (initialPosition.shouldBeResolvedAgainstOppositePosition()) {
 101         // Infer the position from the final position ('auto / 1' or 'span 2 / 3' case).
 102         GridResolvedPosition finalResolvedPosition = resolveGridPositionFromStyle(gridContainerStyle, finalPosition, finalPositionSide);
 103         return resolveGridPositionAgainstOppositePosition(gridContainerStyle, finalResolvedPosition, initialPosition, initialPositionSide);
 104     }
 105
 106     if (finalPosition.shouldBeResolvedAgainstOppositePosition()) {
 107         // Infer our position from the initial position ('1 / auto' or '3 / span 2' case).
 108         GridResolvedPosition initialResolvedPosition = resolveGridPositionFromStyle(gridContainerStyle, initialPosition, initialPositionSide);
 109         return resolveGridPositionAgainstOppositePosition(gridContainerStyle, initialResolvedPosition, finalPosition, finalPositionSide);
 110     }
 111
 112     GridResolvedPosition resolvedInitialPosition = resolveGridPositionFromStyle(gridContainerStyle, initialPosition, initialPositionSide);
 113     GridResolvedPosition resolvedFinalPosition = resolveGridPositionFromStyle(gridContainerStyle, finalPosition, finalPositionSide);
 114
 115     // If 'grid-after' specifies a line at or before that specified by 'grid-before', it computes to 'span 1'.
 116     if (resolvedFinalPosition < resolvedInitialPosition)
 117         resolvedFinalPosition = resolvedInitialPosition;
 118
 119     return adoptPtr(new GridSpan(resolvedInitialPosition, resolvedFinalPosition));
 120 }
 121
 122 size_t GridResolvedPosition::explicitGridColumnCount(const ComputedStyle& gridContainerStyle)
 123 {
 124     return std::min(gridContainerStyle.gridTemplateColumns().size(), kGridMaxTracks);
 125 }
 126
 127 size_t GridResolvedPosition::explicitGridRowCount(const ComputedStyle& gridContainerStyle)
 128 {
 129     return std::min(gridContainerStyle.gridTemplateRows().size(), kGridMaxTracks);
 130 }
 131
 132 size_t GridResolvedPosition::explicitGridSizeForSide(const ComputedStyle& gridContainerStyle, GridPositionSide side)
 133 {
 134     return (side == ColumnStartSide || side == ColumnEndSide) ? explicitGridColumnCount(gridContainerStyle) : explicitGridRowCount(gridContainerStyle);
 135 }
 136
 137 GridResolvedPosition GridResolvedPosition::resolveNamedGridLinePositionFromStyle(const ComputedStyle& gridContainerStyle, const GridPosition& position, GridPositionSide side)
 138 {
 139     ASSERT(!position.namedGridLine().isNull());
 140
 141     const NamedGridLinesMap& gridLinesNames = gridLinesForSide(gridContainerStyle, side);
 142     NamedGridLinesMap::const_iterator it = gridLinesNames.find(position.namedGridLine());
 143     if (it == gridLinesNames.end()) {
 144         if (position.isPositive())
 145             return GridResolvedPosition(0);
 146         const size_t lastLine = explicitGridSizeForSide(gridContainerStyle, side);
 147         return adjustGridPositionForSide(lastLine, side);
 148     }
 149
 150     size_t namedGridLineIndex;
 151     if (position.isPositive())
 152         namedGridLineIndex = std::min<size_t>(position.integerPosition(), it->value.size()) - 1;
 153     else
 154         namedGridLineIndex = std::max<int>(it->value.size() - abs(position.integerPosition()), 0);
 155     return adjustGridPositionForSide(it->value[namedGridLineIndex], side);
 156 }
 157
 158 GridResolvedPosition GridResolvedPosition::resolveGridPositionFromStyle(const ComputedStyle& gridContainerStyle, const GridPosition& position, GridPositionSide side)
 159 {
 160     switch (position.type()) {
 161     case ExplicitPosition: {
 162         ASSERT(position.integerPosition());
 163
 164         if (!position.namedGridLine().isNull())
 165             return resolveNamedGridLinePositionFromStyle(gridContainerStyle, position, side);
 166
 167         // Handle <integer> explicit position.
 168         if (position.isPositive())
 169             return adjustGridPositionForSide(position.integerPosition() - 1, side);
 170
 171         size_t resolvedPosition = abs(position.integerPosition()) - 1;
 172         const size_t endOfTrack = explicitGridSizeForSide(gridContainerStyle, side);
 173
 174         // Per http://lists.w3.org/Archives/Public/www-style/2013Mar/0589.html, we clamp negative value to the first line.
 175         if (endOfTrack < resolvedPosition)
 176             return GridResolvedPosition(0);
 177
 178         return adjustGridPositionForSide(endOfTrack - resolvedPosition, side);
 179     }
 180     case NamedGridAreaPosition:
 181     {
 182         // First attempt to match the grid area's edge to a named grid area: if there is a named line with the name
 183         // ''<custom-ident>-start (for grid-*-start) / <custom-ident>-end'' (for grid-*-end), contributes the first such
 184         // line to the grid item's placement.
 185         String namedGridLine = position.namedGridLine();
 186         ASSERT(isValidNamedLineOrArea(namedGridLine, gridContainerStyle, side));
 187
 188         const NamedGridLinesMap& gridLineNames = gridLinesForSide(gridContainerStyle, side);
 189         NamedGridLinesMap::const_iterator implicitLineIter = gridLineNames.find(implicitNamedGridLineForSide(namedGridLine, side));
 190         if (implicitLineIter != gridLineNames.end())
 191             return adjustGridPositionForSide(implicitLineIter->value[0], side);
 192
 193         // Otherwise, if there is a named line with the specified name, contributes the first such line to the grid
 194         // item's placement.
 195         NamedGridLinesMap::const_iterator explicitLineIter = gridLineNames.find(namedGridLine);
 196         if (explicitLineIter != gridLineNames.end())
 197             return adjustGridPositionForSide(explicitLineIter->value[0], side);
 198
 199         // If none of the above works specs mandate us to treat it as auto BUT we should have detected it before calling
 200         // this function in GridResolvedPosition::resolveGridPositionsFromStyle(). We should be also covered by the
 201         // ASSERT at the beginning of this block.
 202         ASSERT_NOT_REACHED();
 203         return GridResolvedPosition(0);
 204     }
 205     case AutoPosition:
 206     case SpanPosition:
 207         // 'auto' and span depend on the opposite position for resolution (e.g. grid-row: auto / 1 or grid-column: span 3 / "myHeader").
 208         ASSERT_NOT_REACHED();
 209         return GridResolvedPosition(0);
 210     }
 211     ASSERT_NOT_REACHED();
 212     return GridResolvedPosition(0);
 213 }
 214
 215 PassOwnPtr<GridSpan> GridResolvedPosition::resolveGridPositionAgainstOppositePosition(const ComputedStyle& gridContainerStyle, const GridResolvedPosition& resolvedOppositePosition, const GridPosition& position, GridPositionSide side)
 216 {
 217     if (position.isAuto())
 218         return GridSpan::create(resolvedOppositePosition, resolvedOppositePosition);
 219
 220     ASSERT(position.isSpan());
 221     ASSERT(position.spanPosition() > 0);
 222
 223     if (!position.namedGridLine().isNull()) {
 224         // span 2 'c' -> we need to find the appropriate grid line before / after our opposite position.
 225         return resolveNamedGridLinePositionAgainstOppositePosition(gridContainerStyle, resolvedOppositePosition, position, side);
 226     }
 227
 228     return GridSpan::createWithSpanAgainstOpposite(resolvedOppositePosition, position, side);
 229 }
 230
 231 PassOwnPtr<GridSpan> GridResolvedPosition::resolveNamedGridLinePositionAgainstOppositePosition(const ComputedStyle& gridContainerStyle, const GridResolvedPosition& resolvedOppositePosition, const GridPosition& position, GridPositionSide side)
 232 {
 233     ASSERT(position.isSpan());
 234     ASSERT(!position.namedGridLine().isNull());
 235     // Negative positions are not allowed per the specification and should have been handled during parsing.
 236     ASSERT(position.spanPosition() > 0);
 237
 238     const NamedGridLinesMap& gridLinesNames = gridLinesForSide(gridContainerStyle, side);
 239     NamedGridLinesMap::const_iterator it = gridLinesNames.find(position.namedGridLine());
 240
 241     // If there is no named grid line of that name, we resolve the position to 'auto' (which is equivalent to 'span 1' in this case).
 242     // See http://lists.w3.org/Archives/Public/www-style/2013Jun/0394.html.
 243     if (it == gridLinesNames.end())
 244         return GridSpan::create(resolvedOppositePosition, resolvedOppositePosition);
 245
 246     return GridSpan::createWithNamedSpanAgainstOpposite(resolvedOppositePosition, position, side, it->value);
 247 }
 248
 249 } // namespace blink