Saving a RichEdit to a Metafile

Introduction
Sometimes, you may want to store the contents of a rich edit control in a metafile.

This article outlines an approach that stores this type of control's contents in enhanced metafiles, one page per metafile.

Metafiles are useful when you want the content to be scalable at different resolutions

The following code demonstrates one method to dump the contents of a rich edit control into EMF files (one per page):

 

The Delphi Source Code
unit RichEditEMFPrint; interface uses Windows, SysUtils, RichEdit, commdlg, classes, messages, Comctrls; procedure RichEditToMetaFile(AControl : TRichEdit; AFileName : string); implementation // GetPrinterDC() // returns a printer DC - uses Printer Common Dialog function GetPrinterDC : HDC; var pdlg : TPRINTDLG; begin FillChar(pdlg, sizeof(TPRINTDLG), 0); pdlg.lStructSize := sizeof( TPRINTDLG ); pdlg.Flags := PD_RETURNDC; PrintDlg(pdlg); Result := pdlg.hDC; end; // Get the length, in characters, of the text in the control function GetRTFTextLength(hWndRTF : HWND) : integer; begin Result := SendMessage(hWndRTF, WM_GETTEXTLENGTH, 0, 0 ); end; // RTFToEMF - Tell the control to draw itself on the EMF // Parameters: // hRefDC is used to create the EMF // pszMetaFileName is the file name of the new EMF (can be nil) // prcMeta is the RECT used to in CreateEnhMetaFile(), in 0.01mm // units (should not be nil) // hWndRTF is the control of interest // nStart is the starting character location // pEnd is a integer which receives the position of // the next character to print after this page function RTFToEMF(hRefDC : HDC; pszMetaFileName : LPCTSTR; prcMeta : TRECT; hWndRTF : HWND; nStart : integer; var pEnd : integer) : HENHMETAFILE; var hMetaDC : HDC; fr : FORMATRANGE; nTextPrinted : integer; begin // Create the EMF hMetaDC := CreateEnhMetaFile( hRefDC, pszMetaFileName, @prcMeta, nil ); if( hMetaDC = 0 ) then begin Result := 0; Exit; end; ZeroMemory(@fr, sizeof(fr)); // Set up the page (convert 0.01mm to twips) fr.rcPage.top := prcMeta.left*1440 div 2540; fr.rcPage.left := prcMeta.top*1440 div 2540; fr.rcPage.right := prcMeta.right*1440 div 2540; fr.rcPage.bottom := prcMeta.bottom*1440 div 2540; // Set up no margins all around. fr.rc := fr.rcPage; // Set up the range of text to print as nStart to end of document fr.chrg.cpMin := nStart; fr.chrg.cpMax := -1; fr.hdcTarget := hMetaDC; fr.hdc := fr.hdcTarget; // Tell the control to draw itself on our (meta) DC nTextPrinted := SendMessage(hWndRTF, EM_FORMATRANGE, 1, integer(@(fr))); pEnd := nTextPrinted; Result := CloseEnhMetaFile( hMetaDC ); end; // DumpRTFToPagedEMFs - demonstrates using RTFToEMF() to create an EMF // for each page in an RTF control // Parameters: // hWndRTFControl - the control // szEMFFileTitleBase - base filename for EMF files, number is appended procedure DumpRTFToPagedEMFs(hWndRTFControl : HWND; szEMFFileTitleBase : LPTSTR); var szMetaName : string; nRTFTextLength, nStart, nPage : integer; hRefDC : HDC; rcMeta : TRECT; hEMF : HENHMETAFILE; begin // First, determine how many chars are in the RTF nRTFTextLength := GetRTFTextLength( hWndRTFControl ); // Get a reference DC (based on a printer) hRefDC := GetPrinterDC(); // Set up the meta RECT for 0.01mm units rcMeta := Classes.Rect( 0, 0, GetDeviceCaps(hRefDC, HORZSIZE)*100, GetDeviceCaps(hRefDC, VERTSIZE)*100 ); nPage := 0; nStart := 0; while nStart<nRTFTextLength do // Loop while we've not reached the end of the text in the control begin // construct a file name for this page szMetaName := Format('%s%d.EMF', [szEMFFileTitleBase, nPage]); // call function above to draw this portion of the RTF on the EMF hEMF := RTFToEMF( hRefDC, PChar(szMetaName), rcMeta, hWndRTFControl, nStart, nStart ); // clean up DeleteEnhMetaFile( hEMF ); inc(nPage); if nStart = 0 then break; end; end; procedure RichEditToMetaFile(AControl : TRichEdit; AFileName : string); begin DumpRTFToPagedEMFs(AControl.Handle, PChar(AFileName)); end; end.