/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ /* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ /* Utility code for performing CSS Box Alignment */ #include "CSSAlignUtils.h" namespace mozilla { static nscoord SpaceToFill(WritingMode aWM, const LogicalSize& aSize, nscoord aMargin, LogicalAxis aAxis, nscoord aCBSize) { nscoord size = aAxis == eLogicalAxisBlock ? aSize.BSize(aWM) : aSize.ISize(aWM); return aCBSize - (size + aMargin); } nscoord CSSAlignUtils::AlignJustifySelf(uint8_t aAlignment, LogicalAxis aAxis, AlignJustifyFlags aFlags, nscoord aBaselineAdjust, nscoord aCBSize, const ReflowInput& aRI, const LogicalSize& aChildSize) { MOZ_ASSERT(aAlignment != NS_STYLE_ALIGN_AUTO, "auto values should have resolved already"); MOZ_ASSERT(aAlignment != NS_STYLE_ALIGN_LEFT && aAlignment != NS_STYLE_ALIGN_RIGHT, "caller should map that to the corresponding START/END"); // Promote aFlags to convenience bools: const bool isOverflowSafe = !!(aFlags & AlignJustifyFlags::eOverflowSafe); const bool isSameSide = !!(aFlags & AlignJustifyFlags::eSameSide); // Map some alignment values to 'start' / 'end'. switch (aAlignment) { case NS_STYLE_ALIGN_SELF_START: // align/justify-self: self-start aAlignment = MOZ_LIKELY(isSameSide) ? NS_STYLE_ALIGN_START : NS_STYLE_ALIGN_END; break; case NS_STYLE_ALIGN_SELF_END: // align/justify-self: self-end aAlignment = MOZ_LIKELY(isSameSide) ? NS_STYLE_ALIGN_END : NS_STYLE_ALIGN_START; break; // flex-start/flex-end are the same as start/end, in most contexts. // (They have special behavior in flex containers, so flex containers // should map them to some other value before calling this method.) case NS_STYLE_ALIGN_FLEX_START: aAlignment = NS_STYLE_ALIGN_START; break; case NS_STYLE_ALIGN_FLEX_END: aAlignment = NS_STYLE_ALIGN_END; break; } // XXX try to condense this code a bit by adding the necessary convenience // methods? (bug 1209710) // Get the item's margin corresponding to the container's start/end side. const LogicalMargin margin = aRI.ComputedLogicalMargin(); WritingMode wm = aRI.GetWritingMode(); nscoord marginStart, marginEnd; if (aAxis == eLogicalAxisBlock) { if (MOZ_LIKELY(isSameSide)) { marginStart = margin.BStart(wm); marginEnd = margin.BEnd(wm); } else { marginStart = margin.BEnd(wm); marginEnd = margin.BStart(wm); } } else { if (MOZ_LIKELY(isSameSide)) { marginStart = margin.IStart(wm); marginEnd = margin.IEnd(wm); } else { marginStart = margin.IEnd(wm); marginEnd = margin.IStart(wm); } } const auto& styleMargin = aRI.mStyleMargin->mMargin; bool hasAutoMarginStart; bool hasAutoMarginEnd; if (aFlags & AlignJustifyFlags::eIgnoreAutoMargins) { // (Note: ReflowInput will have treated "auto" margins as 0, so we // don't need to do anything special to avoid expanding them.) hasAutoMarginStart = hasAutoMarginEnd = false; } else if (aAxis == eLogicalAxisBlock) { hasAutoMarginStart = styleMargin.GetBStartUnit(wm) == eStyleUnit_Auto; hasAutoMarginEnd = styleMargin.GetBEndUnit(wm) == eStyleUnit_Auto; } else { /* aAxis == eLogicalAxisInline */ hasAutoMarginStart = styleMargin.GetIStartUnit(wm) == eStyleUnit_Auto; hasAutoMarginEnd = styleMargin.GetIEndUnit(wm) == eStyleUnit_Auto; } // https://drafts.csswg.org/css-align-3/#overflow-values // This implements <overflow-position> = 'safe'. // And auto-margins: https://drafts.csswg.org/css-grid/#auto-margins if ((MOZ_UNLIKELY(isOverflowSafe) && aAlignment != NS_STYLE_ALIGN_START) || hasAutoMarginStart || hasAutoMarginEnd) { nscoord space = SpaceToFill(wm, aChildSize, marginStart + marginEnd, aAxis, aCBSize); // XXX we might want to include == 0 here as an optimization - // I need to see what the baseline/last baseline code looks like first. if (space < 0) { // "Overflowing elements ignore their auto margins and overflow // in the end directions" aAlignment = NS_STYLE_ALIGN_START; } else if (hasAutoMarginEnd) { aAlignment = hasAutoMarginStart ? NS_STYLE_ALIGN_CENTER : (isSameSide ? NS_STYLE_ALIGN_START : NS_STYLE_ALIGN_END); } else if (hasAutoMarginStart) { aAlignment = isSameSide ? NS_STYLE_ALIGN_END : NS_STYLE_ALIGN_START; } } // Determine the offset for the child frame (its border-box) which will // achieve the requested alignment. nscoord offset = 0; switch (aAlignment) { case NS_STYLE_ALIGN_BASELINE: case NS_STYLE_ALIGN_LAST_BASELINE: if (MOZ_LIKELY(isSameSide == (aAlignment == NS_STYLE_ALIGN_BASELINE))) { offset = marginStart + aBaselineAdjust; } else { nscoord size = aAxis == eLogicalAxisBlock ? aChildSize.BSize(wm) : aChildSize.ISize(wm); offset = aCBSize - (size + marginEnd) - aBaselineAdjust; } break; case NS_STYLE_ALIGN_STRETCH: MOZ_FALLTHROUGH; // ComputeSize() deals with it case NS_STYLE_ALIGN_START: offset = marginStart; break; case NS_STYLE_ALIGN_END: { nscoord size = aAxis == eLogicalAxisBlock ? aChildSize.BSize(wm) : aChildSize.ISize(wm); offset = aCBSize - (size + marginEnd); break; } case NS_STYLE_ALIGN_CENTER: { nscoord size = aAxis == eLogicalAxisBlock ? aChildSize.BSize(wm) : aChildSize.ISize(wm); offset = (aCBSize - size + marginStart - marginEnd) / 2; break; } default: MOZ_ASSERT_UNREACHABLE("unknown align-/justify-self value"); } return offset; } } // namespace mozilla