Class TSFNode

Construct a field allowing any children class. Suitable only for special cases. For example, in instantiated prototypes, we must initially just allow all children, otherwise valid prototypes with SFNode/MFNode would cause warnings when parsing.

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Constructor that takes a list of allowed children classes. Note that we copy the contents of AAllowedChildrenClasses, not the reference.

Constructor that allows as children any implementor of given functionality.

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This item has no description. Showing description inherited from TX3DField.ParseXMLAttribute.

Parse field value from X3D XML encoded attribute.

Implementation in this class creates a Lexer to parse the string, and calls ParseXMLAttributeLexer.

This item has no description. Showing description inherited from TX3DField.ParseXMLElement.

Parse field's value from XML Element children. This is used to read SFNode / MFNode field value inside <field> (for interface declaration default field value) and <fieldValue> inside <ProtoInstance>.

This item has no description. Showing description inherited from TX3DField.EqualsDefaultValue.

Whether the value is equal to default. Returns always False in TX3DField, descendants should override it. It is used when writing the field value to X3D file (values that are default do not have to be written, ever).

This item has no description. Showing description inherited from TX3DField.Equals.

True if the SecondValue object has exactly the same type and properties. For this class, this returns just (SecondValue.Name = Name).

All descendants (that add some property that should be compared) should override this like

Result := (inherited Equals(SecondValue)) and
  (SecondValue is TMyType) and
  (TMyType(SecondValue).MyProperty = MyProperty);

The floating-point fields may be compared with a small epsilon tolerance by this method.

Note that this *doesn't* compare the default values of two fields instances. This compares only the current values of two fields instances, and eventually some other properties that affect parsing (like names for TSFEnum and TSFBitMask) or allowed future values (like TSFFloat.MustBeNonnegative).

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This item has no description. Showing description inherited from TX3DField.AssignValue.

Copies the current field value. Contrary to TPersistent.Assign, this doesn't copy the rest of properties.

After setting, our ValueFromIsClause is always changed to False. You can manually change it to True, if this copy indeed was done following "IS" clause.

Descendants implementors notes:

In this class, implementation takes care of setting our ValueFromIsClause to False. In descendants, you should do like

if Source is <appropriate class> then
begin
  inherited;
  Value := Source.value;
end else
  AssignValueRaiseInvalidClass(Source);

This item has no description. Showing description inherited from TX3DField.AssignDefaultValueFromValue.

Set field's default value from the current value.

Note that for now this doesn't guarantee that every possible field's value can be stored as default value. In case of trouble, it will silently record "no default is known" information, so e.g. EqualsDefaultValue will always return False. Our default value mechanisms are sometimes limited, not every value can be a default value. For example, for multiple-valued nodes, we usually cannot save arrays longer than one as default value. This is not a problem, since X3D specification doesn't specify too long default values. But it may be a problem for prototypes, since then user can assign any value as default value. May be corrected in the future.

This item has no description. Showing description inherited from TX3DField.UnassignDefaultValue.

Remove default value, recording that "no default is known". In effect EqualsDefaultValue will always return False.

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Field type in X3D, like 'SFString' or 'MFInt32'. As for VRML/X3D interface declaration statements. In base TX3DField class, this returns XFAny (name indicating any type, used by instantreality and us).

This item has no description. Showing description inherited from TX3DField.CreateEvent.

Create TX3DEvent descendant suitable as exposed event for this field.

Checks is the Child allowed as a value of this SFNode, and makes WritelnWarning if not.

Check is allowed is done looking at AllowedChildrenAll and AllowedChildren properties.

Child must not be Nil.

WritelnWarning message will suggest that this Child is used as value of this node. In other words, you should only pass as Child a node that you want to assign as Value to this field, otherwise WritelnWarning message will be a little unsensible.

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Calls Func for our Value, assuming it's set (non-nil). The main use for this is to simplify implementation of TX3DNode.DirectEnumerateActive overrides in TX3DNode descendants.

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Default value of SFNode field.

While X3D specification says for all SFNode fields that their default value is NULL, this is not necessarily true for PROTO SFNode fiels. So we have to take into account that any DefaultValue is possible.

Note that this doesn't have to be Nil, but will be irrelevant if not DefaultValueExists. (Once I had an idea to automatically set DefaultValue to Nil when DefaultValueExists is set to False, but this was uncomfortable (like "what to do when DefaultValue is assigned non-nil when DefaultValueExists is false?").)

Freeing of this is automatically managed, just like the normal Value property. This means that you can simply set DefaultValue to Nil or some existing node, and eventual memory deallocation of previous DefaultValue node (if unused) will happen automatically.

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VRML node containing this field. May be Nil if unknown, in special cases.

Note that this property is exactly the same as TX3DFieldOrEvent.ParentNode, contains always the same value. But this is declared as TX3DNode, so it's more comfortable.

Use weak links to deal with cycles in the X3D graph.

Marking a field as a weak link can only be done when the field value is empty, right when the field is created, in TX3DNode.CreateNode descendant.

Being a weak link means two things:

1. The nodes inside a weak link are not enumerated when traversing the X3D graph in any way. This includes TX3DNode.EnumerateNodes, TX3DNode.Traverse and all others. Nodes implementing TX3DNode.DirectEnumerateActive should also omit these fields.

2. A weak link does not create a reference count preventing the node from being freed (or freeing it automatically when ref count drops to zero). Instead, weak links merely observe the nodes, and automatically set their value to Nil when the node gets freed.

If effect, this avoids loops when enumerating (and avoids recursive loops in reference counts, which would cause memory leaks), but use this only when you know that the node must occur somewhere else in the X3D graph anyway (or it's OK to ignore it). For example, this is useful for TGeneratedShadowMapNode.Light, as we know that the light must occur somewhere else in the graph anyway to be useful.

Automatically use WeakLink if field would contain a node cycle. Using WeakLink=true allows to handle node cycles, like common in VRML/X3D

DEF Xxx Transform {
  children [
    ...
    Script {
      ...
      inputOutput SFNode someField USE Xxx
    }
  ]
}

When AutomaticWeakLink, the given field contents may, but don't have to, be a node cycle – we only use WeakLink when necessary.

Use this only for fields that are not enumerated by DirectEnumerateActive, Traverse etc., otherwise you create a cycle in nodes that we generally cannot handle.

Called when Value changes. Called before the change is actually done, right after we know that new value is different than old value.