Printing a richedit with background colour

I'm outputting text from a delphi TRichedit control to a printer. There is a background image, so I'm using the EM_FORMATRANGE with this logic ...

myrichedit.Perform(EM_FORMATRANGE, 1, Longint(@Range));

... and that works fine except that when the text is rendered it always has a white background regardless of the color of the richedit. Any idea why?

EDIT: From comment posted:

Range is a RANGEFORMAT, and is assigned values like this:

Range.hdc := aCanvas.Handle; 
Range.hdcTarget := aCanvas.Handle; 
LogX := GetDeviceCaps(Range.hdc, LOGPIXELSX); 
LogY := GetDeviceCaps(Range.hdc, LOGPIXELSY); 
Range.rc.Left := x * 1440 div LogX; 
Range.rc.Right := (x+re.ClientWidth) * 1440 div LogX; // (1440=twips/inch)
Range.rc.Top := y * 1440 div LogY; 
Range.rc.Bottom := 5000 * 1440 div LogY; // Some bigish number 
Range.rcPage := Range.rc; 
Range.chrg.cpMin := 0; 
Range.chrg.cpMax := -1;

Solution

What I've found is that a solution to this is that you can set the background of individual characters with the code (before adding the text to the richedit) ...

var
  Format: CHARFORMAT2;
begin
...
 myrichedit.SelStart:=myrichedit.GetTextLen;
 FillChar(Format, SizeOf(Format), 0);
 with Format do begin
     cbSize := SizeOf(Format);
     dwMask := CFM_BACKCOLOR;
     crBackColor := charbackgroundcolor;
     myrichedit.Perform(EM_SETCHARFORMAT, SCF_SELECTION, Longint(@Format));
 end;
 myrichedit.SetText:='Hello';

... but to get a background color for the whole block of text then do this to draw the text ...

var
  size : Tsize;
  Range: TFormatRange;
  Rect: TRect;
  LogX, LogY : Integer;
  bm : tbitmap;
  aCanvas : TCanvas;
  ExStyle: DWord;
begin
  aCanvas:=Printer.Canvas;

  Range.hdc := aCanvas.Handle;
  Range.hdcTarget := aCanvas.Handle;

  LogX := GetDeviceCaps(Range.hdc, LOGPIXELSX);
  LogY := GetDeviceCaps(Range.hdc, LOGPIXELSY);

  Range.rc.Left := x * 1440 div LogX;
  Range.rc.Right := (x+myrichedit.ClientWidth) * 1440 div LogX; // (1440=twips/inch)
  Range.rc.Top := y * 1440 div LogY;
  Range.rc.Bottom := 5000 * 1440 div LogY; // Some bigish number
  Range.rcPage := Range.rc;
  Range.chrg.cpMin := 0;
  Range.chrg.cpMax := -1;  
  myrichedit.Perform(EM_FORMATRANGE, 0, Longint(@Range)); // Measure the formatted text
  rect:=Range.rc;
  rect.Left:=Range.rc.Left * LogX div 1440;
  rect.Top:=Range.rc.Top * LogY div 1440;
  rect.Right:=Range.rc.Right * LogX div 1440;
  rect.Bottom:=Range.rc.Bottom * LogY div 1440;
  acanvas.Brush.Color:=myblockcolor;
  acanvas.FillRect(rect); // Fill the background rectangle

  ExStyle := GetWindowLong(re.Handle, GWL_EXSTYLE); // Draw richedit transparently over coloured area
  ExStyle := ExStyle or WS_EX_TRANSPARENT;
  SetWindowLong(re.Handle, GWL_EXSTYLE, ExStyle);
  myrichedit.Perform(EM_FORMATRANGE, 1, Longint(@Range));  
end;