TCanvas

type TCanvas = class(TFPCustomCanvas)

protected

  function DoCreateDefaultFont; override;

DoCreateDefaultFont - calls TFont.Create to create a default fomt

  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;

SetColor converts the specified FPColor to a Color and applies it to the pixels at x, y

  function GetColor(); override;

GetColor - finds the Color of the pixels at x, y and returns the value converted to a FPColor

  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;

GetWidth - if a handle has been allocated, returns the width from the device size

  procedure SetPenPos(); override;

SetPenPos moves pen to specified position

  procedure DoLockCanvas; override;

DoLockCanvas - enters critical locking section then calls inherited method

  procedure DoUnlockCanvas; override;

DoUnlockCanvas - leaves the critical locking section then calls inherited method

  procedure DoTextOut(); override;

DoTextOut calls TextOut for the specified coordinates and string

  procedure DoGetTextSize(); override;

DoGetTextSize calls TextExtent to find width and height of specified text string

  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;

DoEllipse draws an Arc of 360 degrees within given Bounds, making an ellipse

  procedure DoEllipseFill(); override;

DoEllipseFill calls Ellipse

  procedure DoEllipseAndFill(); override;

DoEllipseAndFill - calls 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 suppied points

  procedure DoPolygonAndFill(); override;

DoPolygonAndFill calls inherited method

  procedure DoPolyline(); override;

DoPolyline calls PolyLine

  procedure DoFloodFill(); override;

DoFloodFill calls FloodFill

  procedure DoMoveTo(); override;

DoMoveTo calls MoveTo

  procedure DoLineTo(); override;

DoLineTo calls LineTo

  procedure DoLine(); override;

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

  procedure DoCopyRect(); override;

DoCopyRect checks that SrcCanvas is of correct type then copies coordinates and calls CopyRect

  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;

CheckHelper - ignored by current class

  function GetDefaultColor(); virtual;

  function GetClipRect; override;

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

  procedure SetClipRect(); override;

  function GetClipping; override;

GetClipping returns True if clipping is being performed

  procedure SetClipping(); override;

SetClipping specifies (via boolean argument) whether clipping is to be performed

  function GetPixel(); virtual;

GetPixel - retuns the colour of the pixel at the specified location

  procedure CreateBrush; virtual;

CreateBrush creates necessary handles, sets up local defaults for style, hatching, background colour

  procedure CreateFont; virtual;

  procedure CreateHandle; virtual;

CreateHandle - greates a new Handle for the Canvas

  procedure CreatePen; virtual;

CreatePen sets up local handles and defaults for Pen creation, sets initial position of Pen

  procedure CreateRegion; virtual;

CreateRegion - creates a rectangular region for the Canvas

  procedure DeselectHandles; virtual;

DeselectHandles - remove from group of selected handles

  procedure PenChanging(); virtual;

PenChanging - software emulation for call to OnChanging event for Pen

  procedure FontChanging(); virtual;

FontChanging - software emulation for call to OnChanging event for Font

  procedure BrushChanging(); virtual;

BrushChanging - software emulation for call to OnChanging event for Brush

  procedure RegionChanging(); virtual;

RegionChanging - software emulation for call to OnChanging event for Region

  procedure RealizeAutoRedraw; virtual;

RealizeAutoRedraw - implement the AutoDraw feature

  procedure RealizeAntialiasing; virtual;

RealizeAntialiasing - implement the Anti-aliasing feature

  procedure RequiredState(); virtual;

RequiredState - the set of Canvas State required (csHandleValid, csFontValid, csPenvalid, csBrushValid, csRegionValid)

  procedure SetHandle(); virtual;

SetHandle - specify a Handle

  procedure SetInternalPenPos(); virtual;

SetInternalPenPos - specify position for the Pen

  procedure SetPixel(); virtual;

SetPixel - specify a colour for the stated pixel

  procedure FreeHandle; virtual;

FreeHandle - release a Handle

public

  constructor Create;

Create - constructor for TCanvas: calls inherited Create and sets defaults for many properties and actions

  destructor Destroy; override;

Destroy - destructor for TCanvas: frees handles and region, calls inherited Destroy, sets font, pen and brush resources to nil

  procedure Lock; virtual;

Lock the canvas, making it unavailble 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;

Refresh the drawing of the Canvas

  procedure Changing; virtual;

Changing - software emulation of a call to the OnChanging event

  procedure Changed; virtual;

Changed - software emulation of a call to the OnChange event

  procedure SaveHandleState; virtual;

SaveHandleState - stores the state of the Handle

  procedure RestoreHandleState; virtual;

RestoreHandleState - retrieves the saved state of the Handle

  procedure Arc();

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

  procedure Chord();

Chord draws a filled Chord-shape on the canvas

  procedure CopyRect(); virtual;

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

  procedure Draw(); virtual;

Draw - copies bounds from SrcGraphic, then calls StretchDraw to perform the drawing

  procedure DrawFocusRect(); virtual;

DrawFocusRect - draws a focused rectangle at the specified position

  procedure StretchDraw(); virtual;

StretchDraw - uses the Draw method of the source graphic ( TGraphic)

  procedure Ellipse();

Ellipse draws a filled circle or ellipse on the canvas

  procedure FillRect();

FillRect - draw a filled rectangle in the specified coordinate space

  procedure FloodFill(); virtual;

FloodFill flood-fills an area with the given colour, starting from the specified point; uses the FloodFill method for the current interface or widget set

  procedure Frame3d(); virtual;

Frame3d - produce a frame with 3-D effect (with bevelled edges etc) in the specified rectangle

  procedure Frame();

Produce a Frame or border around the specified rectangle using a Pen

  procedure FrameRect();

FrameRect - produce a border around the specified rectangle using a Brush

  function GetTextMetrics(); virtual;

  procedure GradientFill();

GradientFill - fill the specified rectangle with the specified colours in a gradient with the specified direction

  procedure RadialPie(); virtual;

RadialPie uses Pie to draw a filled pie-shaped wedge on the canvas

  procedure Pie(); virtual;

Pie draws a filled Pie-shaped wedge on the canvas

  procedure PolyBezier();

Polybezier draws cubic Bezier curves

  procedure Polygon();

Polygon draws a closed, many-sided shape on the canvas, using the value of Pen

  procedure Polyline();

Polyline connects a set of points on the canvas

  procedure Rectangle();

Draws a Rectangle at the specified coordinates

  procedure RoundRect();

RoundRect - draws a rectangle at the specified position, with corners rounded by the factors RX, RY

  procedure TextOut(); virtual;

Writes the Text string at the position X, Y on the canvas and leaves the pen at the end of the text; uses the ExtUTF8Out method of the current interface or widget set

  procedure TextRect();

Writes Text string within a specified rectangle, according to predefined Style

  function TextExtent(); virtual;

TextExtent - returns the total size of the specified text

  function TextHeight(); virtual;

TextHeight - returns the height of the specified text

  function TextWidth(); virtual;

TextWidth - returns the width of the specified text

  function HandleAllocated; virtual;

HandleAllocated - returns True if a handle has been allocated

  function GetUpdatedHandle(); virtual;

GetUpdatedHandle - returns the value of the updated Handle

  property Pixels: TColor; [rw]

The colour of the Pixels located at the specified position

  property Handle: HDC; [rw]

The operating system Handle for this object

  property TextStyle: TTextStyle; [rw]

The TextStyle to be used in this Canvas

published

  property AntialiasingMode: TAntialiasingMode; [rw]

AntialiasingMode - anti-aliasing on, off or don't care

  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 to be used for painting this Canvas

  property CopyMode: TCopymode; [rw]

The CopyMode to be used (arbitrary number)

  property Font: TFont; [rw]

The Font to be used for text in this canvas

  property Height: Integer; [r]

The Height of the canvas

  property Pen: TPen; [rw]

The Pen to be used for writing in this canvas

  property Region: TRegion; [rw]

The Regionwhere the Canvas is located

  property Width: Integer; [r]

The Width of the Canvas

  property OnChange: TNotifyEvent; [rw]

Event handler for a change in the canvas

  property OnChanging: TNotifyEvent; [rw]

Event handler while canvas is changing

end;

TCanvas

TCanvas - where most of the drawing is performed

TFPCustomCanvas

TPersistent

TObject