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 nscoord Baseline::SynthesizeBOffsetFromBorderBox(const nsIFrame* aFrame,
  41                                                  WritingMode aWM,
  42                                                  BaselineSharingGroup aGroup) {
  43   nscoord borderBoxSize =
  44       MOZ_UNLIKELY(aWM.IsOrthogonalTo(aFrame->GetWritingMode()))
  45           ? aFrame->ISize(aWM)
  46           : aFrame->BSize(aWM);
  47   if (aGroup == BaselineSharingGroup::First) {
  48     return MOZ_LIKELY(aWM.IsAlphabeticalBaseline()) ? borderBoxSize
  49                                                     : borderBoxSize / 2;
  50   }
  51   MOZ_ASSERT(aGroup == BaselineSharingGroup::Last);
  52   // Round up for central baseline offset, to be consistent with ::First.
  53   auto borderBoxCenter = (borderBoxSize / 2) + (borderBoxSize % 2);
  54   return MOZ_LIKELY(aWM.IsAlphabeticalBaseline()) ? 0 : borderBoxCenter;
  55 }
  56
  57 nscoord Baseline::SynthesizeBOffsetFromContentBox(const nsIFrame* aFrame,
  58                                                   WritingMode aWM,
  59                                                   BaselineSharingGroup aGroup) {
  60   WritingMode wm = aFrame->GetWritingMode();
  61   MOZ_ASSERT(!aWM.IsOrthogonalTo(wm));
  62   const auto bp = aFrame->GetLogicalUsedBorderAndPadding(wm)
  63                       .ApplySkipSides(aFrame->GetLogicalSkipSides())
  64                       .ConvertTo(aWM, wm);
  65
  66   if (MOZ_UNLIKELY(aWM.IsCentralBaseline())) {
  67     nscoord contentBoxBSize = aFrame->BSize(aWM) - bp.BStartEnd(aWM);
  68     if (aGroup == BaselineSharingGroup::First) {
  69       return contentBoxBSize / 2 + bp.BStart(aWM);
  70     }
  71     // Return the same center position as for ::First, but as offset from end:
  72     nscoord halfContentBoxBSize = (contentBoxBSize / 2) + (contentBoxBSize % 2);
  73     return halfContentBoxBSize + 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())
  79                ? bp.BStart(aWM)
  80                : aFrame->BSize(aWM) - bp.BEnd(aWM);
  81   }
  82   // Last baseline for inverted-line content is the block-start content edge,
  83   // as the frame is in effect "flipped" for alignment purposes.
  84   return MOZ_UNLIKELY(aWM.IsLineInverted())
  85              ? aFrame->BSize(aWM) - bp.BStart(aWM)
  86              : bp.BEnd(aWM);
  87 }
  88
  89 }  // namespace mozilla