Class TCastleBehavior

Description

Hierarchy

Methods

Properties

Unit

CastleTransform

Declaration

type TCastleBehavior = class(TCastleComponent)

Description

Behaviors can be attached to TCastleTransform to perform specific logic, for example implement creature movement. This implements a simple component-system for TCastleTransform. Using behaviors allows to attach independent functionality like TCastleBillboard, TCastleSoundSource, creature AI and more. CGE provides implementation for some behaviors, and you can create your own too.

You implemement a descendant of TCastleBehavior, typically overriding its Update method, and add it to TCastleTransform by TCastleTransform.AddBehavior. Inside TCastleBehavior, access the TCastleTransform instances by Parent.

The API of TCastleBehavior is deliberately a subset of the TCastleTransform API, for example both have Update method. Using TCastleBehavior is just simpler and more efficient, as TCastleBehavior doesn't have own transformation, children and it cannot render something. If this is too limiting, remember you can always implement more powerful behaviors by creating TCastleTransform descendants instead of TCastleBehavior descendants, and accessing the TCastleTransform.Parent from a child.

Source: transform/castletransform_behavior.inc (line 40).

Hierarchy

TObject
TPersistent
TComponent
TCastleComponent
TCastleBehavior

Show Additional Members: Inherited Protected

Overview

Methods

Protected	`function GetInternalText: String; virtual;`
Protected	`procedure SetInternalText(const Value: String); virtual;`
Protected	`procedure SetName(const Value: TComponentName); override;`
Protected	`procedure TranslateProperties(const TranslatePropertyEvent: TTranslatePropertyEvent); virtual;`
Public	`destructor Destroy; override;`
Public	`procedure CustomSerialization(const SerializationProcess: TSerializationProcess); virtual;`
Public	`function PropertySections(const PropertyName: String): TPropertySections; virtual;`
Public	`procedure SetTransient;`
Public	`procedure AddNonVisualComponent(const NonVisualComponent: TComponent);`
Public	`procedure InsertNonVisualComponent(const Index: Integer; const NonVisualComponent: TComponent);`
Public	`procedure RemoveNonVisualComponent(const NonVisualComponent: TComponent);`
Public	`function NonVisualComponentsIndexOf(const NonVisualComponent: TComponent): Integer;`
Public	`function NonVisualComponentsCount: Integer;`
Public	`function NonVisualComponentsEnumerate: TNonVisualComponentsEnumerator;`
Public	`function ValueIsStreamed: Boolean; virtual;`
Public	`procedure DesignerInfo(const SList: TStrings); virtual;`
Public	`procedure DesignerWarnings(const SList: TStrings); virtual;`
Protected	`procedure Update(const SecondsPassed: Single; var RemoveMe: TRemoveType); virtual;`
Protected	`procedure BeforeRender( const CameraView: TViewVectors; const ParentParentWorldTransformation: TTransformation); virtual;`
Protected	`procedure ParentChanged; virtual; deprecated 'Use ParentAfterAttach / ParentBeforeDetach or WorldAfterAttach / WorldBeforeDetach';`
Protected	`procedure ParentAfterAttach; virtual;`
Protected	`procedure ParentBeforeDetach; virtual;`
Protected	`procedure WorldAfterAttach; virtual;`
Protected	`procedure WorldBeforeDetach; virtual;`
Protected	`function CanAttachToParent(const NewParent: TCastleTransform; out ReasonWhyCannot: String): Boolean; virtual;`
Public	`procedure BeforeDestruction; override;`
Public	`function World: TCastleAbstractRootTransform;`

Properties

Public	`property NonVisualComponents [const Index: Integer]: TComponent read GetNonVisualComponents;`
Public	`property IsLoading: Boolean read FIsLoading;`
Public	`property Parent: TCastleTransform read FParent;`
Public	`property ListenWorldChange: Boolean read FListenWorldChange write SetListenWorldChange;`

Description

Methods

Protected function GetInternalText: String; virtual;

This item is declared in ancestor TCastleComponent.

This item has no description.

Source: base/castleclassutils.pas (line 575).

Protected procedure SetInternalText(const Value: String); virtual;

This item is declared in ancestor TCastleComponent.

This item has no description.

Source: base/castleclassutils.pas (line 576).

Protected procedure SetName(const Value: TComponentName); override;

This item is declared in ancestor TCastleComponent.

This item has no description.

Source: base/castleclassutils.pas (line 577).

Protected procedure TranslateProperties(const TranslatePropertyEvent: TTranslatePropertyEvent); virtual;

This item is declared in ancestor TCastleComponent.

Enumerate all properties that are possible to translate in this component. E.g. in TCastleLabel it will return TCastleLabel.Caption, in TCastleEdit it will return TCastleEdit.Text and TCastleEdit.Placeholder.

Returns only non-empty properties, thus assuming that if current (by convention, English) text is empty, then there is no point in translating it. Moreover descendants may define boolean properties to exclude particular text from translating, e.g. TCastleLabel.CaptionTranslate, TCastleEdit.TextTranslate, TCastleEdit.PlaceholderTranslate.

It is not recursive (it doesn't enumerate children properties). Use global TranslateProperties procedure to call this on a hierarchy of TComponent.

You usually don't want to call this method (it is called by other engine routines). But you may find it useful to override this, if you define new component.

Source: base/castleclassutils.pas (line 598).

Public destructor Destroy; override;

This item is declared in ancestor TCastleComponent.

This item has no description.

Source: base/castleclassutils.pas (line 604).

Public procedure CustomSerialization(const SerializationProcess: TSerializationProcess); virtual;

This item is declared in ancestor TCastleComponent.

Override this method to call various methods of SerializationProcess, which in turn allows to serialize/deserialize things that are not published. This allows to serialize/deserialize with more freedom, e.g. to serialize/deserialize some private field.

Source: base/castleclassutils.pas (line 610).

Public function PropertySections(const PropertyName: String): TPropertySections; virtual;

This item is declared in ancestor TCastleComponent.

Section where to show property in the editor.

Source: base/castleclassutils.pas (line 631).

Public procedure SetTransient;

This item is declared in ancestor TCastleComponent.

Ignore this component when serializing parent's TCastleUserInterface.Controls list or TCastleTransform.List, and do not show this component in CGE editor. This simply sets csTransient flag in ComponentStyle.

This is useful for children that are automatically managed by the parent, and should not be modified by user code. For example, TCastleCheckbox is internally composed from TCastleImageControl and TCastleLabel children, but we don't want to serialize or even show these children to user.

Note that if you want to prevent this component from serializing as part of TCastleUserInterface.Controls list or TCastleTransform.List, but you still want it to be visible in CGE editor, then make it a "subcomponent" instead, by SetSubComponent(true).

Note that both csSubComponent and csTransient only disable the component serialization as part of parent's lists enumerated by CustomSerialization (see internal TCastleUserInterface.SerializeChildrenEnumerate , TCastleTransform.SerializeChildrenEnumerate, TCastleTransform.SerializeBehaviorsEnumerate).

If you will make the component published in its own property (which is normal for "subcomponents") then it will be serialized anyway, just as part of it's own property (like TCastleScrollView.ScrollArea). So to really avoid serializing a children component make it csSubComponent and/or csTransient, and do not publish it.

Source: base/castleclassutils.pas (line 663).

Public procedure AddNonVisualComponent(const NonVisualComponent: TComponent);

This item is declared in ancestor TCastleComponent.

Add non-visual component to this component. This is used to organize non-visual components in a tree hierarchy, in CGE designs and editor.

Parameters

RemoveMe: Set this to rtRemove or rtRemoveAndFree to remove this component from Parent after this call finished. rtRemoveAndFree additionally will free this item. Initially it's rtNone when this method is called.

Source: transform/castletransform_behavior.inc (line 52).

Protected procedure BeforeRender( const CameraView: TViewVectors; const ParentParentWorldTransformation: TTransformation); virtual;

Event called right before rendering the parent TCastleTransform. Override this if you have to adjust the parent transformation strictly before the rendering.

Compared to adjusting the parent transformation in e.g. Update, adjusting the parent transformation here has advantages:

There's no 1-frame delay between moving the thing that causes the change (like camera) and updating the thing that reacts to it (like a transformation with a billboard).
We adjust transformation before rendering each occurrence of TCastleTransform in the viewport tree. This matters if given TCastleTransform may occur multiple times in the viewport tree, directly or through TCastleTransformReference.
We adjust transformation before each render, so things are OK if given TCastleTransform is present in multiple viewports (see https://castle-engine.io/multiple_viewports_to_display_one_world).

For example, adjusting the TCastleTransform done by the TCastleBillboard is done using this method. The transformation in this case is determined by the camera and parent's parent transformation. The transformation has to be applied without any delay (even a 1-frame delay would be visible, as artifacts caused by billboard not perfectly aligned with the camera would be visible – blending sort along camera direction in sort3D is not perfect if billboard doesn't exactly match camera direction). And the transformation with billboard may be present in multiple viewports and/or multiple times in the same viewport tree.

Parameters

CameraView: Current camera vectors, in world coordinates, used to render the scene now.
ParentParentWorldTransformation: World transformation of the parent of the parent of this behavior. The name is kind of convoluted, but consistent: When the parent of this behavior has exactly one parent TCastleTransform (not zero, not more) then ParentParentWorldTransformation.Transform is equivalent to Parent.Parent.WorldTransform.

Source: transform/castletransform_behavior.inc (line 103).

Protected procedure ParentChanged; virtual; deprecated 'Use ParentAfterAttach / ParentBeforeDetach or WorldAfterAttach / WorldBeforeDetach';

Warning: this symbol is deprecated: Use ParentAfterAttach / ParentBeforeDetach or WorldAfterAttach / WorldBeforeDetach

Called after Parent changed, at the end of TCastleTransform.AddBehavior, TCastleTransform.RemoveBehavior.

Source: transform/castletransform_behavior.inc (line 109).

Protected procedure ParentAfterAttach; virtual;

Called after Parent changed, e.g. at the end of TCastleTransform.AddBehavior.

Source: transform/castletransform_behavior.inc (line 113).

Protected procedure ParentBeforeDetach; virtual;

Called before Parent changed, e.g. at the beginning of TCastleTransform.RemoveBehavior.

This is also called at the destruction of behavior (more precisely from BeforeDestruction now). Even in this case, we guarantee that Parent is still valid during this call, and not in half-destroyed state. Before the actual destructor of TCastleBehavior we do BeforeParentDetach and BeforeWorldDetach and set Parent to Nil.

Source: transform/castletransform_behavior.inc (line 122).

Protected procedure WorldAfterAttach; virtual;

Called after Parent became part of World. Called only if ListenWorldChange is True.

Source: transform/castletransform_behavior.inc (line 126).

Protected procedure WorldBeforeDetach; virtual;

Called before Parent stops being part of World. Called only if ListenWorldChange is True.

Source: transform/castletransform_behavior.inc (line 136).

Protected function CanAttachToParent(const NewParent: TCastleTransform; out ReasonWhyCannot: String): Boolean; virtual;

Check can this behavior be added to NewParent. When this returns False, it has to set also ReasonWhyCannot. When overriding this, you can use e.g. this code to make sure we are the only behavior of given class:

function TCastleBillboard.CanAttachToParent(const NewParent: TCastleTransform;
  out ReasonWhyCannot: String): Boolean;
begin
  Result := inherited;
  if not Result then Exit;

  if NewParent.FindBehavior(TCastleBillboard) <> nil then
  begin
    ReasonWhyCannot := 'Only one TCastleBillboard behavior can be added to a given TCastleTransform';
    Result := false;
  end;
end;

Source: transform/castletransform_behavior.inc (line 158).

Public procedure BeforeDestruction; override;

This item has no description.

Source: transform/castletransform_behavior.inc (line 161).

Public function World: TCastleAbstractRootTransform;

Reference to the root transformation (typically matching the TCastleViewport.Items value) corresponding to the parent of this behavior.

May be Nil if the behavior is not yet added to the parent TCastleTransform, or when the TCastleTransform is not yet part of the TCastleAbstractRootTransform (which means that TCastleTransform is not added to the viewport yet). You can use ListenWorldChange and override WorldBeforeDetach, WorldAfterAttach to be notified when this changes.

Source: transform/castletransform_behavior.inc (line 184).