TFPCanvasHelper

type TFPCanvasHelper = class(TPersistent)

protected

  function GetAllocated; virtual;

GetAllocated returns True if the canvas is allocated (assigned)

  procedure SetFlags(); virtual;

SetFlags - stores specified boolean values in index-nominated flags

  function GetFlags(); virtual;

GetFlags - returns the boolean value of the specified flag

  procedure CheckAllocated();

CheckAllocated - check whether the canvas is allocated, and if ValueNeeded if True, raises an exception if not allocated

  procedure SetFixedCanvas();

SetFixedCanvas - specifies whether the canvas is to be fixed

  procedure DoAllocateResources; virtual;

DoAllocateResources - procedure for allocating resources

  procedure DoDeAllocateResources; virtual;

DoDeAllocateResources - procedure for deallocationg resources

  procedure DoCopyProps(); virtual;

DoCopyProps - copies properties from another Canvas Helper

  procedure SetFPColor(); virtual;

SetFPColor - specify the colour using the FreePascal list

  procedure Changing; dynamic;

Changing - software emulation of a call to the OnChanging event

  procedure Changed; dynamic;

Changed - software emulation of a call to the OnChange event

  procedure Lock;

Lock the canvas so it can't be changed

  procedure UnLock;

UnLock a previously locked canvas

public

  constructor Create; virtual;

Create - constructor for TFPCanvasHelper: calls inherited Create then sets properties Canvas to nil, FixedCanvas and Allocated to False

  destructor Destroy; override;

Destroy - destructor for TFPCanvasHelper: de-allocates resources then calls inherited Destroy

  procedure AllocateResources();

AllocateResources - prepare helper for use

  procedure DeallocateResources;

DeallocateResources - free all resources used by this helper

  property Allocated: Boolean; [r]

If True, then helper has been Allocated

  property FixedCanvas: Boolean; [r]

FixedCanvas - properties cannot be changed when allocated

  property Canvas: TFPCustomCanvas; [r]

Canvas for which the helper is allocated

  property FPColor: TFPColor; [rw]

FPColor - colour of the helper

  property OnChanging: TNotifyEvent; [rw]

OnChanging - event handler while change is occurring

  property OnChange: TNotifyEvent; [rw]

OnChange - event handler when a change has occurred

  property DelayAllocate: Boolean; [rw]

DelayAllocate - if True, then allocation is to be delayed

end;

TFPCanvasHelper

TFPCanvasHelper - FreePascal base class providing utilities for drawing and painting canvases

TPersistent

TObject