TLazRegion class

In unit LazRegions

Represents a custom region in the Lazarus LCL.

Declaration

pascal

TLazRegion = class(TFPCustomRegion)

Inheritance

TLazRegion
TFPCustomRegion

Descends from it: TLazRegionWithChilds

Description

TLazRegion is a TFPCustomRegion descendant which represents a region as used in the Lazarus LCL. It is used to implement the clipping region in TLazCanvas, and in custom-drawn windowed LCL controls. The region is composed of TLazRegionPart descendants representing the rectangles, polygons, and ellipses that define the display area on a device. TLazRegion provides overridden methods to query information for the composite display area.

The parts of a region should all be inside valid areas for the region. If a combine operation removes an area in the region, then the area should be removed from all parts for the region. There is no z-order for the Parts, they are all validly inside the region area.

Methods

`Create`	public	Constructor for the class instance.
`Destroy`	public	Destructor for the class instance.
`Assign`	public	Stores values from ASrcRegion in the current class instance.
`Clear`	public	Frees the TLazRegionPart instances in Parts, and clears the list storage.
`CombineWith`	public	Combines the specified source region using the given region operation.
`GetRegionKind`	public	Gets the type of region represented in the class instance.
`IsSimpleRectEmpty`	public	Indicates whether the Rect member contains empty or invalid rectangle coordinates.
`AddPart`	public	Adds the specified part as a subregion in the Parts member.
`AddRectangle`	public	Adds the specified TRect instance to the Parts member.
`AddPolygon`	public	Adds a polygonal area with the specified vertices to the region.
`AddEllipse`	public	Adds an elliptical area with the specified co-vertices to the region.
`SetAsSimpleRectRegion`	public	Sets the area for the region to the specified rectangle.
`AddPartsFromRegion`	public	Adds the region (and any subregions) from ASrcRegion to the current class instance.
`DoChangeToComplexRegion`	public	Adds the value in Rect to the Parts member, and resets the value in IsSimpleRectRegion.
`GetBoundingRect`	public	Gets the bounds for the region as a rectangle.
`IsPointInRegion`	public	Checks whether the specified point is inside the region.

Fields

`Parts`	public	List with the Rectangles, Polygons, and Ellipses that define the display area for the region.
`IsSimpleRectRegion`	public	Indicates whether this region is composed of a single rectangular part.
`Rect`	public	TRect instance with the bounds for the region.

An experiment, built from development snapshots. Not the official Free Pascal or Lazarus documentation.