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 /* Utility code for performing CSS Box Alignment */
8
9 #include "CSSAlignUtils.h"
10 #include "ReflowInput.h"
11
12 namespace mozilla {
13
SpaceToFill(WritingMode aWM,const LogicalSize & aSize,nscoord aMargin,LogicalAxis aAxis,nscoord aCBSize)14 static nscoord SpaceToFill(WritingMode aWM, const LogicalSize& aSize,
15 nscoord aMargin, LogicalAxis aAxis,
16 nscoord aCBSize) {
17 nscoord size = aSize.Size(aAxis, aWM);
18 return aCBSize - (size + aMargin);
19 }
20
AlignJustifySelf(const StyleAlignFlags & aAlignment,LogicalAxis aAxis,AlignJustifyFlags aFlags,nscoord aBaselineAdjust,nscoord aCBSize,const ReflowInput & aRI,const LogicalSize & aChildSize)21 nscoord CSSAlignUtils::AlignJustifySelf(const StyleAlignFlags& aAlignment,
22 LogicalAxis aAxis,
23 AlignJustifyFlags aFlags,
24 nscoord aBaselineAdjust,
25 nscoord aCBSize, const ReflowInput& aRI,
26 const LogicalSize& aChildSize) {
27 MOZ_ASSERT(aAlignment != StyleAlignFlags::AUTO,
28 "auto values should have resolved already");
29 MOZ_ASSERT(aAlignment != StyleAlignFlags::LEFT &&
30 aAlignment != StyleAlignFlags::RIGHT,
31 "caller should map that to the corresponding START/END");
32
33 // Promote aFlags to convenience bools:
34 const bool isOverflowSafe = !!(aFlags & AlignJustifyFlags::OverflowSafe);
35 const bool isSameSide = !!(aFlags & AlignJustifyFlags::SameSide);
36
37 StyleAlignFlags alignment = aAlignment;
38 // Map some alignment values to 'start' / 'end'.
39 if (alignment == StyleAlignFlags::SELF_START) {
40 // align/justify-self: self-start
41 alignment =
42 MOZ_LIKELY(isSameSide) ? StyleAlignFlags::START : StyleAlignFlags::END;
43 } else if (alignment == StyleAlignFlags::SELF_END) {
44 alignment =
45 MOZ_LIKELY(isSameSide) ? StyleAlignFlags::END : StyleAlignFlags::START;
46 // flex-start/flex-end are the same as start/end, in most contexts.
47 // (They have special behavior in flex containers, so flex containers
48 // should map them to some other value before calling this method.)
49 } else if (alignment == StyleAlignFlags::FLEX_START) {
50 alignment = StyleAlignFlags::START;
51 } else if (alignment == StyleAlignFlags::FLEX_END) {
52 alignment = StyleAlignFlags::END;
53 }
54
55 // XXX try to condense this code a bit by adding the necessary convenience
56 // methods? (bug 1209710)
57
58 // Get the item's margin corresponding to the container's start/end side.
59 const LogicalMargin margin = aRI.ComputedLogicalMargin();
60 WritingMode wm = aRI.GetWritingMode();
61 nscoord marginStart, marginEnd;
62 if (aAxis == eLogicalAxisBlock) {
63 if (MOZ_LIKELY(isSameSide)) {
64 marginStart = margin.BStart(wm);
65 marginEnd = margin.BEnd(wm);
66 } else {
67 marginStart = margin.BEnd(wm);
68 marginEnd = margin.BStart(wm);
69 }
70 } else {
71 if (MOZ_LIKELY(isSameSide)) {
72 marginStart = margin.IStart(wm);
73 marginEnd = margin.IEnd(wm);
74 } else {
75 marginStart = margin.IEnd(wm);
76 marginEnd = margin.IStart(wm);
77 }
78 }
79
80 const auto& styleMargin = aRI.mStyleMargin->mMargin;
81 bool hasAutoMarginStart;
82 bool hasAutoMarginEnd;
83 if (aFlags & AlignJustifyFlags::IgnoreAutoMargins) {
84 // (Note: ReflowInput will have treated "auto" margins as 0, so we
85 // don't need to do anything special to avoid expanding them.)
86 hasAutoMarginStart = hasAutoMarginEnd = false;
87 } else if (aAxis == eLogicalAxisBlock) {
88 hasAutoMarginStart = styleMargin.GetBStart(wm).IsAuto();
89 hasAutoMarginEnd = styleMargin.GetBEnd(wm).IsAuto();
90 } else { /* aAxis == eLogicalAxisInline */
91 hasAutoMarginStart = styleMargin.GetIStart(wm).IsAuto();
92 hasAutoMarginEnd = styleMargin.GetIEnd(wm).IsAuto();
93 }
94
95 // https://drafts.csswg.org/css-align-3/#overflow-values
96 // This implements <overflow-position> = 'safe'.
97 // And auto-margins: https://drafts.csswg.org/css-grid/#auto-margins
98 if ((MOZ_UNLIKELY(isOverflowSafe) && alignment != StyleAlignFlags::START) ||
99 hasAutoMarginStart || hasAutoMarginEnd) {
100 nscoord space =
101 SpaceToFill(wm, aChildSize, marginStart + marginEnd, aAxis, aCBSize);
102 // XXX we might want to include == 0 here as an optimization -
103 // I need to see what the baseline/last baseline code looks like first.
104 if (space < 0) {
105 // "Overflowing elements ignore their auto margins and overflow
106 // in the end directions"
107 alignment = StyleAlignFlags::START;
108 } else if (hasAutoMarginEnd) {
109 alignment = hasAutoMarginStart ? StyleAlignFlags::CENTER
110 : (isSameSide ? StyleAlignFlags::START
111 : StyleAlignFlags::END);
112 } else if (hasAutoMarginStart) {
113 alignment = isSameSide ? StyleAlignFlags::END : StyleAlignFlags::START;
114 }
115 }
116
117 // Determine the offset for the child frame (its border-box) which will
118 // achieve the requested alignment.
119 nscoord offset = 0;
120 if (alignment == StyleAlignFlags::BASELINE ||
121 alignment == StyleAlignFlags::LAST_BASELINE) {
122 if (MOZ_LIKELY(isSameSide == (alignment == StyleAlignFlags::BASELINE))) {
123 offset = marginStart + aBaselineAdjust;
124 } else {
125 nscoord size = aChildSize.Size(aAxis, wm);
126 offset = aCBSize - (size + marginEnd) - aBaselineAdjust;
127 }
128 } else if (alignment == StyleAlignFlags::STRETCH ||
129 alignment == StyleAlignFlags::START) {
130 // ComputeSize() deals with stretch
131 offset = marginStart;
132 } else if (alignment == StyleAlignFlags::END) {
133 nscoord size = aChildSize.Size(aAxis, wm);
134 offset = aCBSize - (size + marginEnd);
135 } else if (alignment == StyleAlignFlags::CENTER) {
136 nscoord size = aChildSize.Size(aAxis, wm);
137 offset = (aCBSize - size + marginStart - marginEnd) / 2;
138 } else {
139 MOZ_ASSERT_UNREACHABLE("unknown align-/justify-self value");
140 }
141
142 return offset;
143 }
144
145 } // namespace mozilla
146