TCanvas

type TCanvas = class(TFPCustomCanvas)

protected

  function DoCreateDefaultFont; override;

Creates the TFont instance used as the default font for the canvas.

  function DoCreateDefaultPen; override;

DoCreateDefaultPen - calls TPen.Create to create a default pen.

  function DoCreateDefaultBrush; override;

DoCreateDefaultBrush - calls TBrush.Create to create a default brush.

  procedure SetColor(); override;

Sets the value for the indexed Colors property.

  function GetColor(); override;

Gets the Color for the pixel at the given coordinates as a TFPColor value.

  procedure SetHeight(); override;

SetHeight should never be called for Canvas: raises an exception if it is called.

  function GetHeight; override;

GetHeight - if a handle has been allocated, returns the height from the device size.

  procedure SetWidth(); override;

SetWidth - should never be called; raises an exception if it is called.

  function GetWidth; override;

Gets the value for the Width property.

  procedure SetPenPos(); override;

Moves the pen to the specified position.

  procedure DoLockCanvas; override;

Enters the critical section used to lock the canvas, and calls the inherited method.

  procedure DoUnlockCanvas; override;

Leaves the critical section used to lock the canvas, and calls the inherited method.

  procedure DoTextOut(); override;

DoTextOut calls TextOut for the specified coordinates and string.

  procedure DoGetTextSize(); override;

Calls TextExtent to find the width and height of the specified text.

  function DoGetTextHeight(); override;

DoGetTextHeight calls TextHeight to return the height of the text.

  function DoGetTextWidth(); override;

DoGetTextWidth calls TextWidth to return the width of the given text string.

  procedure DoRectangle(); override;

DoRectangle calls Frame to draw a rectangle in the given bounds.

  procedure DoRectangleFill(); override;

DoRectangleFill calls FillRect to draw a filled rectangle with the given bounds.

  procedure DoRectangleAndFill(); override;

DoRectangleAndFill - calls Rectangle to draw a rectangle and fill it.

  procedure DoEllipse(); override;

Draws an Arc of 360 degrees within the specified Bounds.

  procedure DoEllipseFill(); override;

DoEllipseFill calls Ellipse.

  procedure DoEllipseAndFill(); override;

DoEllipseAndFill calls the inherited DoEllipseAndFill.

  procedure DoPolygon(); override;

DoPolygon calls PolyLine to draw a series of lines through the points.

  procedure DoPolygonFill(); override;

DoPolygonFill calls Polygon for the supplied points.

  procedure DoPolygonAndFill(); override;

DoPolygonAndFill calls inherited method.

  procedure DoPolyline(); override;

DoPolyline calls PolyLine.

  procedure DoPolyBezier(); override;

Performs actions needed to draw a Bézier curve using the specified control points.

  procedure DoFloodFill(); override;

DoFloodFill calls the FloodFill method.

  procedure DoMoveTo(); override;

DoMoveTo calls the MoveTo method.

  procedure DoLineTo(); override;

DoLineTo calls the LineTo method.

  procedure DoLine(); override;

DoLine calls Line to draw from x1, y1 to x2, y2.

  procedure DoCopyRect(); override;

Verifies and copies the source canvas.

  procedure DoDraw(); override;

DoDraw checks that Image is of the right type, makes a local copy, creates the necessary handles and bitmaps for drawing.

  procedure CheckHelper(); override;

Ignored in the current implementation of the class.

  function GetDefaultColor(); virtual;

Gets the default color value for the canvas.

  function GetClipRect; override;

GetClipRect - if an error is encountered in finding the Clipping Rectangle dimensions, sets some defaults anyway.

  procedure SetClipRect(); override;

Sets the value for the ClipRect property.

  function GetClipping; override;

GetClipping returns True if clipping is being performed.

  procedure SetClipping(); override;

SetClipping specifies whether clipping is to be performed.

  function GetPixel(); virtual;

Gets the value for the indexed Pixels property.

  procedure CreateBrush; virtual;

Ensures that the handle for the Brush is valid and configured with the Brush settings.

  procedure CreateFont; virtual;

Ensures that the Font for the canvas is valid and uses the correct color.

  procedure CreateHandle; virtual;

Creates a new Handle for the Canvas.

  procedure CreatePen; virtual;

Ensures that the Pen for the canvas is valid, configured, and positioned.

  procedure CreateRegion; virtual;

Ensures that the handle for the canvas Region is valid.

  procedure DeselectHandles; virtual;

Deselects all sub-handles in the current device context.

  procedure PenChanging(); virtual;

Implements the default OnChanging event handler used for the Pen in the canvas.

  procedure FontChanging(); virtual;

Implements the OnChanging event handler for the Font used on the canvas.

  procedure BrushChanging(); virtual;

Implements the OnChanging event handler for the Brush on the canvas.

  procedure RegionChanging(); virtual;

Implements the OnChanging event handler for the Region on the canvas.

  procedure RealizeAutoRedraw; virtual;

Implements the AutoRedraw feature when enabled.

  procedure RealizeAntialiasing; virtual;

Implements the Anti-aliasing feature for the canvas.

  procedure RequiredState(); virtual;

Ensures that all handles needed for the canvas are valid.

  procedure SetHandle(); virtual;

Sets the value for the Handle property.

  procedure SetInternalPenPos(); virtual;

SetInternalPenPos - specify position for the Pen.

  procedure SetPixel(); virtual;

Sets a value in the indexed Pixels property.

  procedure FreeHandle; virtual;

Frees the Handle for the canvas.

public

  constructor Create;

Constructor for the class instance.

  destructor Destroy; override;

Destructor for the class instance.

  procedure Lock; virtual;

Lock the canvas, making it unavailable for drawing.

  function TryLock;

TryLock - examines the Lock state, and performs Lock if necessary.

  procedure Unlock; virtual;

Unlock or release a previously locked Canvas.

  procedure Refresh; virtual;

Sets Pen, Brush, and Font handles to their default values.

  procedure Changing; virtual;

Signals the OnChanging event handler (when assigned).

  procedure Changed; virtual;

Signals the OnChange event handler (when assigned).

  procedure SaveHandleState; virtual;

Stores the state for the Handle in the canvas.

  procedure RestoreHandleState; virtual;

Restores the previous Handle state for the canvas.

  procedure Arc();

Use Arc to draw an elliptically curved line with the current Pen.

  procedure ArcTo(); virtual;

Draws an elliptically curved line and updates the Pen position.

  procedure AngleArc();

Draws an arc over a specified angle along the circumference of a circle.

  procedure BrushCopy(); virtual;

Copies part of a bitmap to a rectangle on the canvas and replaces the transparent color with the canvas Brush color.

  procedure Chord();

Draw a filled chord shape starting and finishing at the specified angular positions on the circumference.

  procedure CopyRect(); virtual;

Copies the rectangle found at Source in SrcCanvas to the destination position in Dest.

  procedure Draw(); virtual;

Draws the image content in SrcGraphic on the canvas at the specified position.

  procedure DrawFocusRect(); virtual;

Draws a focus rectangle around the specified rectangle on the canvas.

  procedure StretchDraw(); virtual;

Expands or contracts the specific graphic content to fit the specified destination rectangle on the canvas.

  procedure Ellipse();

Draws a filled ellipse (or circle) on the canvas.

  procedure FillRect();

Fills a rectangular area on the canvas using the current Brush settings.

  procedure FloodFill(); virtual;

Fills an area at the specified coordinates with the current Brush for the canvas.

  procedure Frame3d();

Draws a frame for the specified rectangle with a 3-dimensional appearance.

  procedure Frame();

Draws a frame or border around the specified rectangle using the Pen for the canvas.

  procedure FrameRect();

Draws a border around the specified rectangle with the Brush for the canvas.

  function GetTextMetrics(); virtual;

Gets text metrics for the canvas font.

  procedure GradientFill();

Fills a rectangle with a color gradient using the specified colors in a given direction.

  procedure RadialPie(); virtual;

RadialPie draws a filled pie-shaped wedge on the canvas with specified start and end coordinates, and starting and ending angular positions.

  procedure Pie(); virtual;

Pie draws a filled Pie-shaped wedge on the canvas.

  procedure PolyBezier();

Polybezier draws cubic Bézier curves.

  procedure Polygon();

Draws a closed, many-sided shape using the Pen for the canvas.

  procedure Polyline();

Draws a line which connects a set of points on the canvas.

  procedure Rectangle();

Draws a Rectangle with the specified coordinates.

  procedure RoundRect();

Draws a rectangle with rounded (or radiused) corners at the specified position.

  procedure TextOut(); virtual;

Writes text at the specified position on the canvas.

  procedure TextRect();

Draws text on the canvas at the specified location using the given style.

  function TextExtent(); virtual;

Calculates the width and height for the specified Text using the Font for the canvas.

  function TextHeight(); virtual;

Gets the height for the specified text using the canvas Font.

  function TextWidth(); virtual;

Gets the width for the specified text using the canvas Font.

  function TextFitInfo();

Gets the number of characters that fit in the specified maximum width.

  function HandleAllocated; virtual;

Checks whether the Handle has been allocated for the canvas.

  function GetUpdatedHandle(); virtual;

Checks the required canvas states and gets the updated Handle for the canvas.

  property Pixels []: TColor; [rw]

The color of the Pixels located at the specified position.

  property Handle: HDC; [rw]

Handle (or device context) for the drawing surface.

  property TextStyle: TTextStyle; [rw]

Text style attributes used to draw text on the canvas.

published

  property AntialiasingMode: TAntialiasingMode; [rw]

Controls anti-aliasing for canvas drawing operations.

  property AutoRedraw: Boolean; [rw]

AutoRedraw - if True, the Canvas is to be redrawn automatically after each change or update.

  property Brush: TBrush; [rw]

The Brush used to paint on the Canvas.

  property CopyMode: TCopymode; [rw]

Indicates the raster operation used to combine pixel colors on the drawing surface.

  property Font: TFont; [rw]

Contains the Font used to render text on the drawing surface.

  property Height: Integer; [r]

Height of the canvas.

  property Pen: TPen; [rw]

The Pen to be used for writing in this canvas.

  property Region: TRegion; [rw]

The Region where the Canvas is located.

  property Width: Integer; [r]

The Width of the Canvas.

  property OnChange: TNotifyEvent; [rw]

Event handler signalled after a change to the canvas.

  property OnChanging: TNotifyEvent; [rw]

Event handler signalled prior to changing the canvas.

end;

TCanvas

Implements a drawing surface for a visual control or bitmap image.

TFPCustomCanvas

TObject

TSharedRasterImage

Implements a reference counted raster image that may be shared between controls.

TGraphicControl.Canvas

A clipped window into the parent Canvas.

TCustomControl.Canvas

The drawing surface for the control.

TControlCanvas

Base class which provides a canvas property used in graphic controls.