Question

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

Asked by: Delphi_developer

Hi

I got a solution on how to draw RichEdit and Bitmap on Canvas. In attached code the bitmap gets drawn at position 10,10. I would like to draw it just below RichEdit, on Canvas. So I need to identify the Height of RichEdit, which gets drawn on Canvas... the height depends on the text and word wrap...

I guess I should get it within PaintRichEditToCanvas procedure, but don't know how exactly.

Please help.

Thank you

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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Asked On
2009-05-21 at 02:52:10ID24427181
Tags

Delphi

,

RichEdit

,

Bitmpap

,

canvas

Topic

Delphi Programming

Participating Experts
1
Points
0
Comments
6

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Answers

 

by: ThievingSixPosted on 2009-05-21 at 04:26:47ID: 24440066

This might be a very good or bad answer but what about ARichEdit.Height?

 

by: Delphi_developerPosted on 2009-05-21 at 04:32:22ID: 24440107

No, this doesn't work. Because before I call I have RichEdit's width and height set to 1, both. This makes sure it is created and it formats all the content as I need it, but it doesn't draw it in real width and height. Then I call PaintRichEditToCanvas and send the RichEdit which actually draws the text as it should, correctly. But originals width and height remain 1.

I hope it makes sense.

 

by: ThievingSixPosted on 2009-05-21 at 04:50:59ID: 24440236

Hmm, OK I see. This might work:

Function TwipsToPixels(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((APoint.X / 1440) * ppiX);
    Result.Y := Round((APoint.X / 1440) * ppiY);
  end else
    Result := Point(0, 0);
End;
 
Function RectToPixels(ADC : HDC; ARect : TRect) : TRect;
Begin
  Result.TopLeft := TwipsToPixels(ADC, ARect.TopLeft);
  Result.BottomRight := TwipsToPixels(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;
    ShowMessage(Format('RichEdit height: %d',[RectToPixels(hdc, ARect).Bottom - RectToPixels(hdc, ARect).Top]));
  end;
  ARichedit.Perform(EM_FORMATRANGE, 1, Longint(@fmtRange));
  { Free cached information }
  ARichedit.Perform(EM_FORMATRANGE, 0, 0);
End;

                                              
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by: Delphi_developerPosted on 2009-05-21 at 05:23:38ID: 24440498

No, this doesn't work. I draw RichEdit on TPanel's Canvas, and the text is drawn in two lines, since the width and height of the Panel is 200x80 (WxH), and all the text doesn't fit in one line.

The height, from a message, is 13. Although it draws 16 pixels as one row.

And one more issue - when I use your message line, it doesn't draw any text - it is blank. When I comment your line, it draws it.

 

by: Delphi_developerPosted on 2009-05-21 at 06:59:36ID: 24441477

Would it be possible to get the height any other way?

This is what I do, before call to PaintRichEditToCanvas:

vRC1 := TrichEdit.Create(Nil);
    vRC1.Width := 1;
    vRC1.Height := 1;
    vRC1.Parent := TPanel(Sender);
    vRC1.Color := TPanel(Sender).Color;

... + formatting text

and now I call PaintRichEditToCanvas

I use W  = 1 and H = 1, because it doesn't work to create 'dummy' Richedit without Parent! So, I set it to be almost invisible. Is it possible to calculate height if I set width to be 200? Text can be in multiple lines.

 

by: Delphi_developerPosted on 2009-05-27 at 10:36:49ID: 24485574

I approached the problem in another way... because I know where the RichEdit's text starts, I draw it's background as clGray, for example, then I move pixel by pixel from top to bottom until I get different color than the background. Now I have the RichEdit's text height.

Anyway, I appreciate your help.

20120131-EE-VQP-002

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