layout/base/Baseline.h

   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 #ifndef LAYOUT_BASE_BASELINE_H_
   6 #define LAYOUT_BASE_BASELINE_H_
   7
   8 #include "nsCoord.h"
   9 #include "mozilla/WritingModes.h"
  10
  11 class nsIFrame;
  12
  13 namespace mozilla {
  14
  15 // https://drafts.csswg.org/css-align-3/#baseline-sharing-group
  16 enum class BaselineSharingGroup : uint8_t {
  17   // NOTE Used as an array index so must be 0 and 1.
  18   First = 0,
  19   Last = 1,
  20 };
  21
  22 class Baseline {
  23  public:
  24   /**
  25    * Synthesize a first(last) inline-axis baseline in aWM based on aFrame's
  26    * margin-box.
  27    *
  28    * An alphabetical baseline is at the end edge of aFrame's margin-box with
  29    * respect to aWM's block-axis, and a central baseline is halfway between the
  30    * start and end edges. (aWM tells which baseline to use.)
  31    * https://drafts.csswg.org/css-align-3/#synthesize-baseline
  32    *
  33    * @note This works only when aFrame's writing-mode is parallel to aWM.
  34    * @param aWM the writing-mode of the alignment context.
  35    * @return an offset from aFrame's border-box start(end) edge in aWM's
  36    *         block-axis for a first(last) baseline, respectively.
  37    */
  38   static nscoord SynthesizeBOffsetFromMarginBox(const nsIFrame* aFrame,
  39                                                 WritingMode aWM,
  40                                                 BaselineSharingGroup);
  41
  42   /**
  43    * Synthesize a first(last) inline-axis baseline in aWM based on aFrame's
  44    * border-box.
  45    *
  46    * An alphabetical baseline is at the end edge of aFrame's border-box with
  47    * respect to aWM's block-axis, and a central baseline is halfway between the
  48    * start and end edges. (aWM tells which baseline to use.)
  49    * https://drafts.csswg.org/css-align-3/#synthesize-baseline
  50    *
  51    * @param aWM the writing-mode of the alignment context.
  52    * @return an offset from aFrame's border-box start(end) edge in aWM's
  53    *         block-axis for a first(last) baseline, respectively.
  54    */
  55   static nscoord SynthesizeBOffsetFromBorderBox(const nsIFrame* aFrame,
  56                                                 WritingMode aWM,
  57                                                 BaselineSharingGroup);
  58
  59   /**
  60    * Synthesize a first(last) inline-axis baseline in aWM based on aFrame's
  61    * content-box.
  62    *
  63    * An alphabetical baseline is at the end edge of aFrame's content-box with
  64    * respect to aWM's block-axis, and a central baseline is halfway between the
  65    * start and end edges. (aWM tells which baseline to use.)
  66    * https://drafts.csswg.org/css-align-3/#synthesize-baseline
  67    *
  68    * @note This works only when aFrame's writing-mode is parallel to aWM.
  69    * @param aWM the writing-mode of the alignment context.
  70    * @return an offset from aFrame's border-box start(end) edge in aWM's
  71    *         block-axis for a first(last) baseline, respectively.
  72    */
  73   static nscoord SynthesizeBOffsetFromContentBox(const nsIFrame* aFrame,
  74                                                  WritingMode aWM,
  75                                                  BaselineSharingGroup);
  76 };
  77
  78 }  // namespace mozilla
  79
  80 #endif  // LAYOUT_BASE_BASELINE_H_