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namespace UnityEngine.UI
{
// 布局算法的核心都在这个基类里面
public abstract class HorizontalOrVerticalLayoutGroup : LayoutGroup
{
[SerializeField] protected float m_Spacing = 0;
public float spacing { get { return m_Spacing; } set { SetProperty(ref m_Spacing, value); } }
[SerializeField] protected bool m_ChildForceExpandWidth = true;
public bool childForceExpandWidth { get { return m_ChildForceExpandWidth; } set { SetProperty(ref m_ChildForceExpandWidth, value); } }
[SerializeField] protected bool m_ChildForceExpandHeight = true;
public bool childForceExpandHeight { get { return m_ChildForceExpandHeight; } set { SetProperty(ref m_ChildForceExpandHeight, value); } }
[SerializeField] protected bool m_ChildControlWidth = true;
public bool childControlWidth { get { return m_ChildControlWidth; } set { SetProperty(ref m_ChildControlWidth, value); } }
[SerializeField] protected bool m_ChildControlHeight = true;
public bool childControlHeight { get { return m_ChildControlHeight; } set { SetProperty(ref m_ChildControlHeight, value); } }
// 根据子节点计算得到自身的min, preferred, flexible
protected void CalcAlongAxis(int axis, bool isVertical)
{
float combinedPadding = (axis == 0 ? padding.horizontal : padding.vertical); // padding是left+right, top+bottom
bool controlSize = (axis == 0 ? m_ChildControlWidth : m_ChildControlHeight);
bool childForceExpandSize = (axis == 0 ? childForceExpandWidth : childForceExpandHeight);
float totalMin = combinedPadding; // 所有子节点的min之和
float totalPreferred = combinedPadding; // 所有子节点的preferred之和
float totalFlexible = 0; // 是一个无单位数值，等于所有子节点的flexible值相加
bool alongOtherAxis = (isVertical ^ (axis == 1));
for (int i = 0; i < rectChildren.Count; i++)
{
RectTransform child = rectChildren[i];
float min, preferred, flexible; // 子节点的三个属性值
GetChildSizes(child, axis, controlSize, childForceExpandSize, out min, out preferred, out flexible);
if (alongOtherAxis)
{
totalMin = Mathf.Max(min + combinedPadding, totalMin);
totalPreferred = Mathf.Max(preferred + combinedPadding, totalPreferred);
totalFlexible = Mathf.Max(flexible, totalFlexible);
}
else
{
totalMin += min + spacing;
totalPreferred += preferred + spacing;
// Increment flexible size with element's flexible size.
totalFlexible += flexible;
}
}
// 减去最后一个子节点多加的spacing
if (!alongOtherAxis && rectChildren.Count > 0)
{
totalMin -= spacing;
totalPreferred -= spacing;
}
totalPreferred = Mathf.Max(totalMin, totalPreferred);
// 保存到m_TotalMinSize, m_TotalPreferredSize, m_TotalFlexibleSize
SetLayoutInputForAxis(totalMin, totalPreferred, totalFlexible, axis);
}
protected void SetChildrenAlongAxis(int axis, bool isVertical)
{
float size = rectTransform.rect.size[axis]; // RectTransform大小
bool controlSize = (axis == 0 ? m_ChildControlWidth : m_ChildControlHeight);
bool childForceExpandSize = (axis == 0 ? childForceExpandWidth : childForceExpandHeight);
float alignmentOnAxis = GetAlignmentOnAxis(axis);
bool alongOtherAxis = (isVertical ^ (axis == 1));
if (alongOtherAxis)
{
float innerSize = size - (axis == 0 ? padding.horizontal : padding.vertical); // 容纳子节点的空间
for (int i = 0; i < rectChildren.Count; i++)
{
RectTransform child = rectChildren[i];
float min, preferred, flexible;
GetChildSizes(child, axis, controlSize, childForceExpandSize, out min, out preferred, out flexible);
float requiredSpace = Mathf.Clamp(innerSize, min, flexible > 0 ? size : preferred);
float startOffset = GetStartOffset(axis, requiredSpace);
if (controlSize)
{
SetChildAlongAxis(child, axis, startOffset, requiredSpace);
}
else
{
float offsetInCell = (requiredSpace - child.sizeDelta[axis]) * alignmentOnAxis;
SetChildAlongAxis(child, axis, startOffset + offsetInCell);
}
}
}
else
{
float pos = (axis == 0 ? padding.left : padding.top);
if (GetTotalFlexibleSize(axis) == 0 && GetTotalPreferredSize(axis) < size)
pos = GetStartOffset(axis, GetTotalPreferredSize(axis) - (axis == 0 ? padding.horizontal : padding.vertical));
float minMaxLerp = 0; // 塞进min之后的剩余空间/preferred-min的空间，是子节点从min向preferred扩大的依据
if (GetTotalMinSize(axis) != GetTotalPreferredSize(axis))
minMaxLerp = Mathf.Clamp01((size - GetTotalMinSize(axis)) / (GetTotalPreferredSize(axis) - GetTotalMinSize(axis)));
float itemFlexibleMultiplier = 0; // 塞进preferred之后，进一步塞满剩余空间的依据，即flexible
if (size > GetTotalPreferredSize(axis))
{
if (GetTotalFlexibleSize(axis) > 0)
itemFlexibleMultiplier = (size - GetTotalPreferredSize(axis)) / GetTotalFlexibleSize(axis);
}
for (int i = 0; i < rectChildren.Count; i++)
{
RectTransform child = rectChildren[i];
float min, preferred, flexible;
GetChildSizes(child, axis, controlSize, childForceExpandSize, out min, out preferred, out flexible);
float childSize = Mathf.Lerp(min, preferred, minMaxLerp);
childSize += flexible * itemFlexibleMultiplier;
if (controlSize)
{
// 设置子节点的transform
SetChildAlongAxis(child, axis, pos, childSize);
}
else
{
float offsetInCell = (childSize - child.sizeDelta[axis]) * alignmentOnAxis;
SetChildAlongAxis(child, axis, pos + offsetInCell);
}
pos += childSize + spacing;
}
}
}
// 返回节点的min, prefered, flexible大小
// axis 0是x轴，1是y轴
// controlSize 是否勾选ChildControlSize
// childForceExpand 是否勾选ChildForceExpand
private void GetChildSizes(RectTransform child, int axis, bool controlSize, bool childForceExpand,
out float min, out float preferred, out float flexible)
{
if (!controlSize) // 如果没勾ChildControlSize，那么会忽略
{
min = child.sizeDelta[axis];//sizeDelta这里等价于size，因为动态布局系统里面anchor都是一起的
preferred = min;
flexible = 0;
}
else
{
min = LayoutUtility.GetMinSize(child, axis);
preferred = LayoutUtility.GetPreferredSize(child, axis);
flexible = LayoutUtility.GetFlexibleSize(child, axis);
}
if (childForceExpand)
flexible = Mathf.Max(flexible, 1);
}
#if UNITY_EDITOR
protected override void Reset()
{
base.Reset();
// For new added components we want these to be set to false,
// so that the user's sizes won't be overwritten before they
// have a chance to turn these settings off.
// However, for existing components that were added before this
// feature was introduced, we want it to be on be default for
// backwardds compatibility.
// Hence their default value is on, but we set to off in reset.
m_ChildControlWidth = false;
m_ChildControlHeight = false;
}
#endif
}
}
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