layout/base/Baseline.cpp

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #include "Baseline.h"
   6 #include "nsIFrame.h"
   7
   8 namespace mozilla {
   9
  10 nscoord Baseline::SynthesizeBOffsetFromMarginBox(const nsIFrame* aFrame,
  11                                                  WritingMode aWM,
  12                                                  BaselineSharingGroup aGroup) {
  13   MOZ_ASSERT(!aWM.IsOrthogonalTo(aFrame->GetWritingMode()));
  14   auto margin = aFrame->GetLogicalUsedMargin(aWM);
  15   if (aGroup == BaselineSharingGroup::First) {
  16     if (aWM.IsAlphabeticalBaseline()) {
  17       // First baseline for inverted-line content is the block-start margin
  18       // edge, as the frame is in effect "flipped" for alignment purposes.
  19       return MOZ_UNLIKELY(aWM.IsLineInverted())
  20                  ? -margin.BStart(aWM)
  21                  : aFrame->BSize(aWM) + margin.BEnd(aWM);
  22     }
  23     nscoord marginBoxCenter = (aFrame->BSize(aWM) + margin.BStartEnd(aWM)) / 2;
  24     return marginBoxCenter - margin.BStart(aWM);
  25   }
  26   MOZ_ASSERT(aGroup == BaselineSharingGroup::Last);
  27   if (aWM.IsAlphabeticalBaseline()) {
  28     // Last baseline for inverted-line content is the block-start margin edge,
  29     // as the frame is in effect "flipped" for alignment purposes.
  30     return MOZ_UNLIKELY(aWM.IsLineInverted())
  31                ? aFrame->BSize(aWM) + margin.BStart(aWM)
  32                : -margin.BEnd(aWM);
  33   }
  34   // Round up for central baseline offset, to be consistent with ::First.
  35   nscoord marginBoxSize = aFrame->BSize(aWM) + margin.BStartEnd(aWM);
  36   nscoord marginBoxCenter = (marginBoxSize / 2) + (marginBoxSize % 2);
  37   return marginBoxCenter - margin.BEnd(aWM);
  38 }
  39
  40 enum class BoxType { Border, Padding, Content };
  41
  42 template <BoxType aType>
  43 static nscoord SynthesizeBOffsetFromInnerBox(const nsIFrame* aFrame,
  44                                              WritingMode aWM,
  45                                              BaselineSharingGroup aGroup) {
  46   WritingMode wm = aFrame->GetWritingMode();
  47   MOZ_ASSERT_IF(aType != BoxType::Border, !aWM.IsOrthogonalTo(wm));
  48   const nscoord borderBoxSize = MOZ_UNLIKELY(aWM.IsOrthogonalTo(wm))
  49                                     ? aFrame->ISize(aWM)
  50                                     : aFrame->BSize(aWM);
  51   const LogicalMargin bp = ([&] {
  52     switch (aType) {
  53       case BoxType::Border:
  54         return LogicalMargin(aWM);
  55       case BoxType::Padding:
  56         return aFrame->GetLogicalUsedBorder(wm)
  57             .ApplySkipSides(aFrame->GetLogicalSkipSides())
  58             .ConvertTo(aWM, wm);
  59       case BoxType::Content:
  60         return aFrame->GetLogicalUsedBorderAndPadding(wm)
  61             .ApplySkipSides(aFrame->GetLogicalSkipSides())
  62             .ConvertTo(aWM, wm);
  63     }
  64     MOZ_CRASH();
  65   })();
  66   if (MOZ_UNLIKELY(aWM.IsCentralBaseline())) {
  67     nscoord boxBSize = borderBoxSize - bp.BStartEnd(aWM);
  68     if (aGroup == BaselineSharingGroup::First) {
  69       return boxBSize / 2 + bp.BStart(aWM);
  70     }
  71     // Return the same center position as for ::First, but as offset from end:
  72     nscoord halfBoxBSize = (boxBSize / 2) + (boxBSize % 2);
  73     return halfBoxBSize + bp.BEnd(aWM);
  74   }
  75   if (aGroup == BaselineSharingGroup::First) {
  76     // First baseline for inverted-line content is the block-start content
  77     // edge, as the frame is in effect "flipped" for alignment purposes.
  78     return MOZ_UNLIKELY(aWM.IsLineInverted()) ? bp.BStart(aWM)
  79                                               : borderBoxSize - bp.BEnd(aWM);
  80   }
  81   // Last baseline for inverted-line content is the block-start content edge,
  82   // as the frame is in effect "flipped" for alignment purposes.
  83   return MOZ_UNLIKELY(aWM.IsLineInverted()) ? borderBoxSize - bp.BStart(aWM)
  84                                             : bp.BEnd(aWM);
  85 }
  86
  87 nscoord Baseline::SynthesizeBOffsetFromContentBox(const nsIFrame* aFrame,
  88                                                   WritingMode aWM,
  89                                                   BaselineSharingGroup aGroup) {
  90   return SynthesizeBOffsetFromInnerBox<BoxType::Content>(aFrame, aWM, aGroup);
  91 }
  92
  93 nscoord Baseline::SynthesizeBOffsetFromPaddingBox(const nsIFrame* aFrame,
  94                                                   WritingMode aWM,
  95                                                   BaselineSharingGroup aGroup) {
  96   return SynthesizeBOffsetFromInnerBox<BoxType::Padding>(aFrame, aWM, aGroup);
  97 }
  98
  99 nscoord Baseline::SynthesizeBOffsetFromBorderBox(const nsIFrame* aFrame,
 100                                                  WritingMode aWM,
 101                                                  BaselineSharingGroup aGroup) {
 102   return SynthesizeBOffsetFromInnerBox<BoxType::Border>(aFrame, aWM, aGroup);
 103 }
 104
 105 }  // namespace mozilla