Draw RichEdit on Canvas - How To Get RichEdit's Drawn Height?

unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ComCtrls, ExtCtrls, RichEdit, jpeg;
 
type
  // Add this as the first type in your unit to make the Canvas property public for TPanel...
  TPanel = class(ExtCtrls.TPanel)
    protected
     FOnPaint : TNotifyEvent;
     Procedure Paint; Override;
    public
     Property Canvas;
     Property OnPaint : TNotifyEvent read FOnPaint write FOnPaint;
  end;
 
  TForm1 = class(TForm)
    Panel1: TPanel;
    Image1: TImage;
    RichEdit1: TRichEdit;
    procedure FormCreate(Sender: TObject);
    procedure RichEdit1Change(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    procedure Panel1Paint(Sender: TObject);
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
 
Function PixelsToTwips(ADC : HDC; APoint : TPoint) : TPoint;
var ppiX, ppiY : Integer;
begin
  ppiX := GetDeviceCaps(ADC, LOGPIXELSX);
  ppiY := GetDeviceCaps(ADC, LOGPIXELSY);
  if (ppiX <> 0) and (ppiY <> 0) then begin
    Result.X := Round(1440 / ppiX * APoint.X);
    Result.Y := Round(1440 / ppiY * APoint.Y);
  end else
    Result := Point(0, 0);
End;
 
Function RectToTwips(ADC : HDC; ARect : TRect) : TRect;
Begin
  Result.TopLeft := PixelsToTwips(ADC, ARect.TopLeft);
  Result.BottomRight := PixelsToTwips(ADC, ARect.BottomRight);
End;
 
Procedure PaintRichEditToCanvas(ARichEdit : TRichEdit; ACanvas : TCanvas; ARect : TRect);
var fmtRange: TFormatRange;
begin
  FillChar(fmtRange, SizeOf(fmtRange), 0);
  with fmtRange do begin
    hDC := ACanvas.Handle;
    hdcTarget := hDC;
    rcPage := RectToTwips(hdc, ARect);
    rc := RectToTwips(hdc, ARect);
    chrg.cpMin := 0;
    chrg.cpMax := ARichEdit.GetTextLen;
  end;
  ARichedit.Perform(EM_FORMATRANGE, 1, Longint(@fmtRange));
  { Free cached information }
  ARichedit.Perform(EM_FORMATRANGE, 0, 0);
End;
 
 
{ TPanel }
 
procedure TPanel.Paint;
begin
  inherited;
  if Assigned(FOnPaint) then FOnPaint(Self);
end;
 
{ TForm1 }
 
procedure TForm1.FormCreate(Sender: TObject);
begin
  Panel1.OnPaint := Panel1Paint;
end;
 
procedure TForm1.Panel1Paint(Sender: TObject);
var aText : TBitmap;
begin
  // Paint the image
  Panel1.Canvas.Draw(10, 10, Image1.Picture.Graphic);
  // Paint the text...
  aText := TBitmap.Create;
  aText.Width := Panel1.Width;
  aText.Height := Panel1.Height;
  aText.PixelFormat := pf32bit;
  aText.Canvas.Brush.Color := clWhite;
  aText.Canvas.Pen.Color := clWhite;
  aText.Canvas.Rectangle(0, 0, aText.Width, aText.Height);
  aText.TransparentColor := clWhite;
  aText.Transparent := True;
  try
    PaintRichEditToCanvas(RichEdit1, aText.Canvas, Rect(0, 0, aText.Width-1, aText.Height-1));
    Panel1.Canvas.Draw(0, 0, aText);
  finally
    aText.Free;
  end;
end;
 
procedure TForm1.RichEdit1Change(Sender: TObject);
begin
  Panel1.Repaint;
end;
 
end.

                                  

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