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SlateCore\Public\Widgets\SWidget.h
所有Widget的基类，定义如下几类接口：
- keyboard事件接口
- mouse事件接口
- Drag & Drop事件接口
- Paint接口
- 计算widget大小和排列子窗口接口
/**
* Abstract base class for Slate widgets.
*
* STOP. DO NOT INHERIT DIRECTLY FROM WIDGET!
*
* Inheritance:
* Widget is not meant to be directly inherited. Instead consider inheriting from LeafWidget or Panel,
* which represent intended use cases and provide a succinct set of methods which to override.
*
* SWidget is the base class for all interactive Slate entities. SWidget's public interface describes
* everything that a Widget can do and is fairly complex as a result.
*
* Events:
* Events in Slate are implemented as virtual functions that the Slate system will call
* on a Widget in order to notify the Widget about an important occurrence (e.g. a key press)
* or querying the Widget regarding some information (e.g. what mouse cursor should be displayed).
*
* Widget provides a default implementation for most events; the default implementation does nothing
* and does not handle the event.
*
* Some events are able to reply to the system by returning an FReply, FCursorReply, or similar
* object.
*/
class SLATECORE_API SWidget
: public FSlateControlledConstruction,
public TSharedFromThis<SWidget> // Enables 'this->AsShared()'
;
问题列表:
a. FGeometry做什么用？
- SlateCore\Public\Widgets\SPanel.h
/**
* A Panel arranges its child widgets on the screen.
*
* Each child widget should be stored in a Slot. The Slot describes how the individual child should be arranged with
* respect to its parent (i.e. the Panel) and its peers Widgets (i.e. the Panel's other children.)
* For a simple example see StackPanel.
*/
class SLATECORE_API SPanel
: public SWidget
{
public:
/**
* Panels arrange their children in a space described by the AllottedGeometry parameter. The results of the arrangement
* should be returned by appending a FArrangedWidget pair for every child widget. See StackPanel for an example
*
* @param AllottedGeometry The geometry allotted for this widget by its parent.
* @param ArrangedChildren The array to which to add the WidgetGeometries that represent the arranged children.
*/
virtual void OnArrangeChildren( const FGeometry& AllottedGeometry, FArrangedChildren& ArrangedChildren ) const override = 0;
/**
* A Panel's desired size in the space required to arrange of its children on the screen while respecting all of
* the children's desired sizes and any layout-related options specified by the user. See StackPanel for an example.
*
* @return The desired size.
*/
virtual FVector2D ComputeDesiredSize(float) const override = 0;
/**
* All widgets must provide a way to access their children in a layout-agnostic way.
* Panels store their children in Slots, which creates a dilemma. Most panels
* can store their children in a TPanelChildren<Slot>, where the Slot class
* provides layout information about the child it stores. In that case
* GetChildren should simply return the TPanelChildren<Slot>. See StackPanel for an example.
*/
virtual FChildren* GetChildren() override = 0;
public:
/**
* Most panels do not create widgets as part of their implementation, so
* they do not need to implement a Construct()
*/
void Construct() { }
public:
// SWidget overrides
virtual int32 OnPaint( const FPaintArgs& Args, const FGeometry& AllottedGeometry, const FSlateRect& MyCullingRect, FSlateWindowElementList& OutDrawElements, int32 LayerId, const FWidgetStyle& InWidgetStyle, bool bParentEnabled ) const override;
protected:
/**
* Just like OnPaint, but takes already arranged children. Can be handy for writing custom SPanels.
*/
int32 PaintArrangedChildren( const FPaintArgs& Args, const FArrangedChildren& ArrangedChildren, const FGeometry& AllottedGeometry, const FSlateRect& MyCullingRect, FSlateWindowElementList& OutDrawElements, int32 LayerId, const FWidgetStyle& InWidgetStyle, bool bParentEnabled ) const;
protected:
/** Hidden default constructor. */
SPanel( ) { }
public:
virtual void SetVisibility( TAttribute<EVisibility> InVisibility ) override final;
};
Panel接口类, 用于排版子widgets.
