TLazCanvas class

In unit LazCanvas

Implements a canvas which masks differences between FCL and LCL canvas classes.

Declaration

pascal

TLazCanvas = class(TFPImageCanvas)

Inheritance

TLazCanvas
TFPImageCanvas

Description

TLazCanvas is an FCL TFPImageCanvas descendant. TLazCanvas extends the ancestor class to support stretching filters and features found in the TCanvas class from the LCL. TLazCanvas also fixes various small problems and incompatibilities between TFPImageCanvas versions, making the interface smoother and more consistent.

TLazCanvas is used in the implementation of custom-drawn widgetset classes, and provides a device context used to perform drawing operations for a control.

There are several useful examples using TLazCanvas on the Lazarus Wiki at:

Developing with Graphics

Properties

`AssignedPen`	public	Pen assigned to the canvas.
`AssignedBrush`	public	Brush assigned to the canvas.
`AssignedFont`	public	Font assigned to the canvas.
`BaseWindowOrg`	public	Base window origin for the canvas.
`WindowOrg`	public	Window origin for the canvas.

Methods

`SetColor`	protected	Sets the color for the pixel at the specified coordinates.
`DoCreateDefaultFont`	protected	Creates the custom font used as the default for the canvas.
`DoRectangle`	protected	Adjusts the fcl-image coordinate system to be compatible with coordinates used in TCanvas.
`DoRectangleFill`	protected	Adjusts the FCL image rectangle to be LCL compatible and draws a filled rectangle on the canvas.
`DoPolygonFill`	protected	Implements a polygon fill algorithm not present in fcl-image prior to FPC version 3.2.3.
`DoLine`	protected	Draws a line using the specified coordinates and Pen for the canvas.
`DoCopyRect`	protected	Performs actions needed to copy a source rectangle from the specified canvas.
`DoDraw`	protected	Performs actions needed to draws the specified image at the given coordinates using AlphaBlending.
`create`	public	Constructor for the class instance.
`destroy`	public	Destructor for the class instance.
`SetLazClipRegion`	public	Sets the value in the ClipRegion property.
`SaveState`	public	Saves the current canvas state in the GraphicStateList member.
`RestoreState`	public	Restores the canvas to the state stored at the specified position.
`ResetCanvasState`	public	Sets the canvas to the default values/state used in the LCL TCanvas class.
`AlphaBlend`	public	Alpha blends the specified content from the source canvas onto the canvas instance.
`AlphaBlendIgnoringDestPixels`	public	Performs an AlphaBlend operation assuming a white background.
`AlphaBlend_Image`	public	AlphaBlends the specified image onto the canvas.
`DoDrawImage`	public	Calls DoDraw for the specified image and coordinates.
`CanvasCopyRect`	public	Copies the contents of a supported image format in ASource to the canvas.
`FillColor`	public	Fills the entire drawing area with the specified color.
`Polygon`	public	Overloaded method which adds support for the non-zero winding rule.
`AssignPenData`	public	Sets the Pen data for the canvas.
`AssignBrushData`	public	Sets the Brush data for the canvas.
`AssignFontData`	public	Sets the Font data for the canvas.

Fields

`HasNoImage`	public	Indicates if a valid image was provided in the constructor.
`NativeDC`	public	Native device context for the canvas.
`ExtraFontData`	public	Member with extra FreeType font data from the canvas or device context.
`ImageFormat`	public	Member with the TLazCanvasImageFormat instance used to speed up drawing.
`SelectedBitmap`	public	Member with the GDI Handle for an image.

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