[Overview][Types][Classes][Variables][Index] | Reference for unit 'Printers' (#lcl)

# TPrinterCanvas.Changing

Signals the OnChanging event when the printer status is changed.

## Declaration

Source position: printers.pas line 119

`public procedure TPrinterCanvas.Changing; override;`

## Description

Changing is an overridden procedure used to signal the OnChanging event handler (when assigned) for the canvas. Changing is overridden to ensure that an assigned Printer in the class instance has the value pfPrinting in its internal Flags. This is done by calling the CheckPrinting method in TPrinter, which can raise an EPrinter exception if it does not have the expected value in its Printing property.

Changing calls the inherited method to signal the OnChanging event handler prior to exiting from the method.

## See also

TPrinter.Printing |  | True if the document is currently being printed.
EPrinter |  | Exception raised for errors in TPrinter methods.
TCanvas.Changing |  | Signals the OnChanging event handler (when assigned).
TCanvas.OnChanging |  | Event handler signalled prior to changing the canvas.