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 // Layout context under which the baseline is being exported to.
  23 enum class BaselineExportContext : uint8_t {
  24   LineLayout = 0,
  25   Other = 1,
  26 };
  27
  28 class Baseline {
  29  public:
  30   /**
  31    * Synthesize a first(last) inline-axis baseline in aWM based on aFrame's
  32    * margin-box.
  33    *
  34    * An alphabetical baseline is at the end edge of aFrame's margin-box with
  35    * respect to aWM's block-axis, and a central baseline is halfway between the
  36    * start and end edges. (aWM tells which baseline to use.)
  37    * https://drafts.csswg.org/css-align-3/#synthesize-baseline
  38    *
  39    * @note This works only when aFrame's writing-mode is parallel to aWM.
  40    * @param aWM the writing-mode of the alignment context.
  41    * @return an offset from aFrame's border-box start(end) edge in aWM's
  42    *         block-axis for a first(last) baseline, respectively.
  43    */
  44   static nscoord SynthesizeBOffsetFromMarginBox(const nsIFrame* aFrame,
  45                                                 WritingMode aWM,
  46                                                 BaselineSharingGroup);
  47
  48   /**
  49    * Synthesize a first(last) inline-axis baseline in aWM based on aFrame's
  50    * border-box.
  51    *
  52    * An alphabetical baseline is at the end edge of aFrame's border-box with
  53    * respect to aWM's block-axis, and a central baseline is halfway between the
  54    * start and end edges. (aWM tells which baseline to use.)
  55    * https://drafts.csswg.org/css-align-3/#synthesize-baseline
  56    *
  57    * @param aWM the writing-mode of the alignment context.
  58    * @return an offset from aFrame's border-box start(end) edge in aWM's
  59    *         block-axis for a first(last) baseline, respectively.
  60    */
  61   static nscoord SynthesizeBOffsetFromBorderBox(const nsIFrame* aFrame,
  62                                                 WritingMode aWM,
  63                                                 BaselineSharingGroup);
  64   /**
  65    * As above, but using the content box.
  66    */
  67   static nscoord SynthesizeBOffsetFromContentBox(const nsIFrame*, WritingMode,
  68                                                  BaselineSharingGroup);
  69   /**
  70    * As above, but using the padding box.
  71    */
  72   static nscoord SynthesizeBOffsetFromPaddingBox(const nsIFrame*, WritingMode,
  73                                                  BaselineSharingGroup);
  74 };
  75
  76 }  // namespace mozilla
  77
  78 #endif  // LAYOUT_BASE_BASELINE_H_