How can I find if there are printers installed (using Delphi)
My program is written in Delphi (object oriented pascal). When I try to print anything I get the message "There is no default printer currently selected." on computers with no printers installed.
To prevent this I want to check if there are any printers installed. Is there any way to check if any printers are ins开发者_JAVA百科talled?
use Printers;
Printer.Printers.Count
gives you the number of printers installed
The comments form the Printers unit in D2007:
{ TPrinter }
{ The printer object encapsulates the printer interface of Windows. A print
job is started whenever any redering is done either through a Text variable
or the printers canvas. This job will stay open until EndDoc is called or
the Text variable is closed. The title displayed in the Print Manager (and
on network header pages) is determined by the Title property.
EndDoc - Terminates the print job (and closes the currently open Text).
The print job will being printing on the printer after a call to EndDoc.
NewPage - Starts a new page and increments the PageNumber property. The
pen position of the Canvas is put back at (0, 0).
Canvas - Represents the surface of the currently printing page. Note that
some printer do not support drawing pictures and the Draw, StretchDraw,
and CopyRect methods might fail.
Fonts - The list of fonts supported by the printer. Note that TrueType
fonts appear in this list even if the font is not supported natively on
the printer since GDI can render them accurately for the printer.
PageHeight - The height, in pixels, of the page.
PageWidth - The width, in pixels, of the page.
PageNumber - The current page number being printed. This is incremented
when ever the NewPage method is called. (Note: This property can also be
incremented when a Text variable is written, a CR is encounted on the
last line of the page).
PrinterIndex - Specifies which printer in the TPrinters list that is
currently selected for printing. Setting this property to -1 will cause
the default printer to be selected. If this value is changed EndDoc is
called automatically.
Printers - A list of the printers installed in Windows.
Title - The title used by Windows in the Print Manager and for network
title pages. }
Here is a code snippet that populates a image combo box with all the printers currently installed:
procedure TMyForm.RefreshPrinterList;
var
I: Integer;
NewItem: TComboExItem;
PPrinterEnumArray, PLocator: PPrinterInfo2;
ArraySize, BufferSize: cardinal;
strBuffer: string;
const
idx_Default_Net_printer = 0;
idx_Net_printer = 1;
idx_Default_Local_printer = 2;
idx_Local_printer = 3;
begin
DefaultPrinterName := getDefaultPrinterName;
cbPrinterList.ItemsEx.Clear;
// S.G. 4/4/2008: list all other printers
// S.G. 4/4/2008: Get the necessary buffer size
ArraySize := 0;
BufferSize := 0;
PPrinterEnumArray := nil;
EnumPrinters(PRINTER_ENUM_LOCAL or PRINTER_ENUM_CONNECTIONS, nil, 2, nil, 0, BufferSize, ArraySize);
PPrinterEnumArray := AllocMem(BufferSize);
try
if EnumPrinters(PRINTER_ENUM_LOCAL or PRINTER_ENUM_CONNECTIONS, nil, 2, PPrinterEnumArray, BufferSize, BufferSize, ArraySize) then
begin
PLocator := PPrinterEnumArray;
if ArraySize > 0 then
begin
for I := 0 to ArraySize - 1 do // Iterate
begin
NewItem := cbPrinterList.ItemsEx.Add;
strBuffer := StrPas(PLocator^.pPrinterName);
UniqueString(strBuffer); // make sure we have a unique string instance and not a pointer
NewItem.Caption := strBuffer;
if AnsiSameText(DefaultPrinterName, strBuffer) then
begin
// default printer
if (PRINTER_ATTRIBUTE_LOCAL AND PLocator^.Attributes) <> 0 then
begin
// Local, default printer
NewItem.ImageIndex := idx_Default_Local_printer;
end
else
begin
// Network default printer
NewItem.ImageIndex := idx_Default_Net_printer;
end;
cbPrinterList.ItemIndex := NewItem.Index;
end
else
begin
// default printer
if (PRINTER_ATTRIBUTE_LOCAL AND PLocator^.Attributes) <> 0 then
begin
// Local, default printer
NewItem.ImageIndex := idx_Local_printer;
end
else
begin
// Network default printer
NewItem.ImageIndex := idx_Net_printer;
end;
end;
Inc(PLocator);
end; // for
end;
end;
finally // wrap up
FreeMem(PPrinterEnumArray);
end; // try/finally
end;
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