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// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "third_party/blink/renderer/core/layout/ng/ng_relative_utils.h"
#include "base/optional.h"
#include "third_party/blink/renderer/core/layout/ng/geometry/ng_physical_offset.h"
#include "third_party/blink/renderer/core/layout/ng/geometry/ng_physical_size.h"
#include "third_party/blink/renderer/core/style/computed_style.h"
#include "third_party/blink/renderer/platform/length_functions.h"
namespace blink {
// Returns the child's relative position wrt the containing fragment.
NGPhysicalOffset ComputeRelativeOffset(const ComputedStyle& child_style,
WritingMode container_writing_mode,
TextDirection container_direction,
NGPhysicalSize container_size) {
NGPhysicalOffset offset;
if (child_style.GetPosition() != EPosition::kRelative)
return offset;
base::Optional<LayoutUnit> left, right, top, bottom;
if (!child_style.Left().IsAuto())
left = ValueForLength(child_style.Left(), container_size.width);
if (!child_style.Right().IsAuto())
right = ValueForLength(child_style.Right(), container_size.width);
if (!child_style.Top().IsAuto())
top = ValueForLength(child_style.Top(), container_size.height);
if (!child_style.Bottom().IsAuto())
bottom = ValueForLength(child_style.Bottom(), container_size.height);
// Common case optimization
if (!left && !right && !top && !bottom)
return offset;
// Implements confict resolution rules from spec:
// https://www.w3.org/TR/css-position-3/#rel-pos
if (!left && !right) {
left = LayoutUnit();
right = LayoutUnit();
}
if (!left)
left = -right.value();
if (!right)
right = -left.value();
if (!top && !bottom) {
top = LayoutUnit();
bottom = LayoutUnit();
}
if (!top)
top = -bottom.value();
if (!bottom)
bottom = -top.value();
if (IsHorizontalWritingMode(container_writing_mode)) {
if (IsLtr(container_direction))
offset.left = left.value();
else
offset.left = -right.value();
offset.top = top.value();
} else {
if (IsLtr(container_direction))
offset.top = top.value();
else
offset.top = -bottom.value();
offset.left = left.value();
}
return offset;
}
} // namespace blink
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