Loading RTF text from database into TRichEdit

问题:

I am currently in the process of migrating our software solution from Delphi 7 to 2010. Mostly the changes have been simple and there are only a small amount of hurdles left to go.

On a form we use a TRichEdit which displayed rtf text grabbed from a blob field in a MSSQL db. This is how it worked in Delphi 7:

//Get RTF text from Blob field using TADOQuery
rtfStream := sql.CreateBlobStream(sql.FieldByName('rtftext'), BmRead) as TMemoryStream;

//Load into TRichEdit
RichEdit.PlainText := False;
RichEdit.Lines.LoadFromStream(rtfStream);

This would display the RTF as expected in the TRichEdit component, but the same code in Delphi 2010 displays the RTF as plain text with tabs between each character. I assume this has a lot to do with the change from Ansi to Unicode, but I haven't had any luck rectifying the problem.

Any help getting this to work would be much appreciated. Thanks

回答1:

Okay I figured it out.

For loading the rtf text:

//Get the data from the database as AnsiString
rtfString := sql.FieldByName('rtftext').AsAnsiString;

//Write the string into a stream
stream := TMemoryStream.Create;
stream.Clear;
stream.Write(PAnsiChar(rtfString)^, Length(rtfString));
stream.Position := 0;

//Load the stream into the RichEdit
RichEdit.PlainText := False;
RichEdit.Lines.LoadFromStream(stream);

stream.Free;

For saving the rtf text:

//Save to stream
stream := TMemoryStream.Create;
stream.Clear;

RichEdit.Lines.SaveToStream(stream);
stream.Position := 0;

//Read from the stream into an AnsiString (rtfString)
if (stream.Size > 0) then begin
    SetLength(rtfString, stream.Size);
    if (stream.Read(rtfString[1], stream.Size) <= 0) then
        raise EStreamError.CreateFmt('End of stream reached with %d bytes left to read.', [stream.Size]);
end;

stream.Free;

//Save to database
sql.FieldByName('rtftext').AsAnsiString := rtfString;

This took me way too long to figure out :) I guess I have learned one thing though... if something goes wrong in Delphi 2010, its usually related to unicode ;)

回答2:

When PlainText is False, LoadFromStream() first attempts to load the RTF code, and if that fails then LoadFromStream() attempts to load the stream again as plain text. That has always been the case in all Delphi versions. With the introduction of Unicode, I suppose something could have broken in LoadFromStream()'s EM_STREAMIN callback handler. I suggest you step into LoadFromStream()'s actual source code with the debugger and see what is really happening.