layout/base/LayoutConstants.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /* constants used throughout the Layout module */
   8
   9 #ifndef LayoutConstants_h___
  10 #define LayoutConstants_h___
  11
  12 #include "mozilla/EnumSet.h"
  13 #include "nsSize.h"  // for NS_MAXSIZE
  14 #include "Units.h"
  15
  16 /**
  17  * Constant used to indicate an unconstrained size.
  18  *
  19  * NOTE: The constants defined in this file are semantically used as symbolic
  20  *       values, so user should not depend on the underlying numeric values. If
  21  *       new specific use cases arise, define a new constant here.
  22  */
  23 #define NS_UNCONSTRAINEDSIZE NS_MAXSIZE
  24
  25 // NS_AUTOOFFSET is assumed to have the same value as NS_UNCONSTRAINEDSIZE.
  26 #define NS_AUTOOFFSET NS_UNCONSTRAINEDSIZE
  27
  28 // +1 is to avoid clamped huge margin values being processed as auto margins
  29 #define NS_AUTOMARGIN (NS_UNCONSTRAINEDSIZE + 1)
  30
  31 #define NS_INTRINSIC_ISIZE_UNKNOWN nscoord_MIN
  32
  33 namespace mozilla {
  34
  35 /**
  36  * Bit-flags to pass to various functions that compute sizes like
  37  * nsIFrame::ComputeSize().
  38  */
  39 enum class ComputeSizeFlag : uint8_t {
  40   /**
  41    * Set if the frame is in a context where non-replaced blocks should
  42    * shrink-wrap (e.g., it's floating, absolutely positioned, or
  43    * inline-block).
  44    */
  45   ShrinkWrap,
  46
  47   /**
  48    * Set if this is a grid measuring reflow, to prevent stretching.
  49    */
  50   IsGridMeasuringReflow,
  51
  52   /**
  53    * Indicates that we should clamp the margin-box min-size to the given CB
  54    * size.  This is used for implementing the grid area clamping here:
  55    * https://drafts.csswg.org/css-grid/#min-size-auto
  56    */
  57   IClampMarginBoxMinSize,  // clamp in our inline axis
  58   BClampMarginBoxMinSize,  // clamp in our block axis
  59
  60   /**
  61    * The frame is stretching (per CSS Box Alignment) and doesn't have an
  62    * Automatic Minimum Size in the indicated axis.
  63    * (may be used for both flex/grid items, but currently only used for Grid)
  64    * https://drafts.csswg.org/css-grid/#min-size-auto
  65    * https://drafts.csswg.org/css-align-3/#valdef-justify-self-stretch
  66    */
  67   IApplyAutoMinSize,  // only has an effect when eShrinkWrap is false
  68 };
  69 using ComputeSizeFlags = mozilla::EnumSet<ComputeSizeFlag>;
  70
  71 /**
  72  * The fallback size of width is 300px and the aspect-ratio is 2:1, based on
  73  * CSS2 section 10.3.2 and CSS Sizing Level 3 section 5.1:
  74  * https://drafts.csswg.org/css2/visudet.html#inline-replaced-width
  75  * https://drafts.csswg.org/css-sizing-3/#intrinsic-sizes
  76  */
  77 inline constexpr CSSIntCoord kFallbackIntrinsicWidthInPixels(300);
  78 inline constexpr CSSIntCoord kFallbackIntrinsicHeightInPixels(150);
  79 inline constexpr CSSIntSize kFallbackIntrinsicSizeInPixels(
  80     kFallbackIntrinsicWidthInPixels, kFallbackIntrinsicHeightInPixels);
  81
  82 inline constexpr nscoord kFallbackIntrinsicWidth =
  83     kFallbackIntrinsicWidthInPixels * AppUnitsPerCSSPixel();
  84 inline constexpr nscoord kFallbackIntrinsicHeight =
  85     kFallbackIntrinsicHeightInPixels * AppUnitsPerCSSPixel();
  86 inline constexpr nsSize kFallbackIntrinsicSize(kFallbackIntrinsicWidth,
  87                                                kFallbackIntrinsicHeight);
  88
  89 /**
  90  * This is used in some nsLayoutUtils functions.
  91  * Declared here so that fewer files need to include nsLayoutUtils.h.
  92  */
  93 enum class IntrinsicISizeType { MinISize, PrefISize };
  94
  95 enum class ContentRelevancyReason {
  96   // If the content of this Frame is on screen or nearly on screen.
  97   Visible,
  98
  99   // If this Frame's element has focus in its subtree.
 100   FocusInSubtree,
 101
 102   // If this Frame's content is part of a selection.
 103   Selected,
 104 };
 105 using ContentRelevancy = EnumSet<ContentRelevancyReason, uint8_t>;
 106
 107 }  // namespace mozilla
 108
 109 #endif  // LayoutConstants_h___