Frequently Asked Questions
Simultaneous printing to multiple printers
Question:
Is it possible to print to more than one printer at a given time?
Answer:
Yes! The following example demonstrates how to print to more than
one printer at a given time. The exmple does not use TPrinter, since
TPrinter does not support printing to multiple printers at a given
time.
Example:
unit multiprn;
interface
{$IFDEF WIN32}
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls,
Forms, Dialogs, StdCtrls;
{$ELSE}
uses
SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics,
Controls, Forms, Dialogs, StdCtrls;
{$ENDIF}
type
TForm1 = class(TForm)
Button1: TButton;
ListBox1: TListBox;
ListBox2: TListBox;
ListBox3: TListBox;
procedure FormCreate(Sender: TObject);
procedure ListBox1Click(Sender: TObject);
procedure ListBox2Click(Sender: TObject);
procedure ListBox3Click(Sender: TObject);
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
procedure GetTheListOfPrinters;
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.DFM}
type
PdcArray = ^TdcArray;
TdcArray = array[0..0] of hdc;
procedure TForm1.GetTheListOfPrinters;
var
p : pChar;
p2 : pChar;
i : integer;
sDriver : string;
sPort : string;
begin
GetMem(p, 32767);
p2 := p;
{Get a list of the printer names from the win.ini file.}
{The list will be a buffer filled with strings, each seperated}
{by a null character, with the final string terminated with}
{a two null characters}
if GetProfileString('devices', nil, '',p, 32767) <> 0 then begin
{loop though the null terminated strings. We know we}
{have reached the end when p2 equals a null character}
while p2^ <> #0 do begin
ListBox1.Items.Add(StrPas(p2));
{increment the pointer past the null to get the next string}
p2 := @p2[lStrLen(p2) + 1];
end;
end;
GetMem(p2, 32767);
{Get the driver and port names for each printer found}
for i := 0 to (ListBox1.Items.Count - 1) do begin
StrPCopy(p2, ListBox1.Items[i]);
if GetProfileString('devices', p2, '',p, 32767) <> 0 then begin
sDriver := StrPas(p);
sPort := sDriver;
{The driver is the portion of the string before the comma}
Delete(sDriver, Pos(',', sDriver), Length(sDriver));
{The port is the portion of the string after the comma}
Delete(sPort, 1, Pos(',', sPort));
ListBox2.Items.Add(sDriver);
ListBox3.Items.Add(sPort);
end;
end;
FreeMem(p2, 32767);
FreeMem(p, 32767);
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
GetTheListOfPrinters;
{Allow the user to select multiple printers}
ListBox1.MultiSelect := true;
ListBox2.MultiSelect := true;
ListBox3.MultiSelect := true;
end;
procedure TForm1.ListBox1Click(Sender: TObject);
var
i : integer;
begin
{Select same indexes in ListBoxs 2 and 3 as are selected in Listbox1}
for i := 0 to ListBox1.Items.Count - 1 do begin
ListBox2.Selected[i] := ListBox1.Selected[i];
ListBox3.Selected[i] := ListBox1.Selected[i]
end;
end;
procedure TForm1.ListBox2Click(Sender: TObject);
var
i : integer;
begin
{Select same indexes in ListBoxs 1 and 3 as are selected in Listbox2}
for i := 0 to ListBox2.Items.Count - 1 do begin
ListBox1.Selected[i] := ListBox2.Selected[i];
ListBox3.Selected[i] := ListBox2.Selected[i]
end;
end;
procedure TForm1.ListBox3Click(Sender: TObject);
var
i : integer;
begin
{Select same indexes in ListBoxs 1 and 2 as are selected in Listbox3}
for i := 0 to ListBox3.Items.Count - 1 do begin
ListBox1.Selected[i] := ListBox3.Selected[i];
ListBox2.Selected[i] := ListBox3.Selected[i]
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
var
dcs : PdcArray; {a pointer to an array of hdc's}
dcsCount : integer; {count of valad hdc's}
dc : hdc; {test hdc}
i : integer; {couning variable}
pPrinter : pChar; {pointer to a printer name}
pDriver : pChar; {pointer to a printer driver filename}
pPort : pChar; {pointer to a port}
DocInfo: TDocInfo; {document information for the spooler}
{$IFDEF WIN32}
osv : TOSVERSIONINFO; {to test for Windows NT}
{$ENDIF}
begin
{If there are no printers selected then exit}
if ListBox1.SelCount = 0 then exit;
{If Range Checking is on then rember the setting and turn it off}
{This will allow use to access the dcs[i] array past element zero}
{without a compiler or runtime error}
{$IFOPT R+}
{$DEFINE CKRANGE}
{$R-}
{$ENDIF}
{Allocate the array of dcs}
GetMem(dcs, sizeof(hdc) * ListBox1.SelCount);
dcsCount := 0;
{Loop though the printers that are selected and create dc's for each}
for i := 0 to (ListBox1.Items.Count - 1) do begin
{Loop through the list box to find the selected printers}
if ListBox1.Selected[i] then begin
{Allocate and get the Printer, Driver and port from the listboxs}
{in the form of a null terminated string}
GetMem(pPrinter, Length(ListBox1.Items[i]) + 1);
GetMem(pDriver, Length(ListBox2.Items[i]) + 1);
GetMem(pPort, Length(ListBox3.Items[i]) + 1);
StrPCopy(pPrinter, ListBox1.Items[i]);
StrPCopy(pDriver, ListBox2.Items[i]);
StrPCopy(pPort, ListBox3.Items[i]);
{Attempt to create a dc - notes 1) Not all printers can}
{support multiple dc's at one time. 2) CreateDc requires}
{different parameters if Win32 andor Win32 under NT.}
{Sixteen bit win apps get standard handling}
{$IFDEF WIN32}
GetVersionEx(osv);
if osv.dwPlatformId = VER_PLATFORM_WIN32_NT then
dc := CreateDc(pDriver, pPrinter, nil, nil) else
dc := CreateDc(nil, pPrinter, nil, nil);
{$ELSE}
dc := CreateDc(pDriver, pPrinter, pPort, nil);
{$ENDIF}
FreeMem(pPrinter, Length(ListBox1.Items[i]));
FreeMem(pDriver, Length(ListBox2.Items[i]));
FreeMem(pPort, Length(ListBox3.Items[i]));
{If the dc is valid, then lets save it to our array}
{and increment our count}
if dc <> 0 then begin
dcs^[dcsCount] := dc;
inc(dcsCOunt);
end;
end;
end;
{If we ended up with a valid array of dc's then let's print}
if dcsCount > 0 then begin
{Fill Out the DocInfo structure for the spooler}
{and start a document for each printer}
GetMem(DocInfo.lpszDocName, 32);
for i := 0 to (dcsCount - 1) do begin
FillChar(DocInfo, sizeof(DocInfo), #0);
DocInfo.cbSize := SizeOf(DocInfo);
StrPCopy(DocInfo.lpszDocName, 'Test Doc' + IntToStr(i));
StartDoc(dcs^[i], DocInfo);
end;
FreeMem(DocInfo.lpszDocName, 32);
{Start a page for each printer}
for i := 0 to (dcsCount - 1) do
StartPage(dcs^[i]);
{Print something}
for i := 0 to (dcsCount - 1) do
TextOut(dcs^[i], 200, 200, 'Test', 4);
{End a page for each printer}
for i := 0 to (dcsCount - 1) do
EndPage(dcs^[i]);
{End the document for each printer}
for i := 0 to (dcsCount - 1) do
EndDoc(dcs^[i]);
{Delete the dc for each printer}
for i := 0 to (dcsCount - 1) do
DeleteDc(dcs^[i]);
end; {dcsCount}
{Free our array of printers}
FreeMem(dcs, sizeof(hdc) * ListBox1.SelCount);
{If range checking was on when we started then turn it back on}
{$IFDEF CKRANGE}
{$UNDEF CKRANGE}
{$R+}
{$ENDIF}
end;
end.
LiveJournal
PhotoFile