RichEdit problem on dbcs system

rbuser

Last time i get a 'Invalid Pointer operation' error in tppRichText
component , when the componet set stretch to true.
( I enter some Chinese Character)

And later i use

ppRegisterRichEditClass( tRichEdit );

to avoid the error , No error on Win2K system but having some Win 98/ME
System have infinite loop result.

I try to find out why the error occur only on Win98/ME ?

Finally , i found out that following.

On D5 ComCtrls.Pas;

function TCustomRichEdit.GetSelLength: Integer;
var
CharRange: TCharRange;
begin
SendMessage(Handle, EM_EXGETSEL, 0, Longint(@CharRange));
Result := CharRange.cpMax - CharRange.cpMin;
end;

function TCustomRichEdit.GetSelText: string;
var
Length: Integer;
begin
SetLength(Result, GetSelLength + 1);
Length := SendMessage(Handle, EM_GETSELTEXT, 0, Longint(PChar(Result)));
SetLength(Result, Length);
end;

On Line 'SetLength(Result, GetSelLength + 1); ' , it use GetSelLength to
determine the length need to allocate string length. But in RichEd20.DLL ,
its will return no. of 'character' not byte count. In Westen country , there
are no error occur. But if in DBCS sytsem , those return value will be short
than expect , so the

Length := SendMessage(Handle, EM_GETSELTEXT, 0, Longint(PChar(Result)));

e.g. 'a' will return 1 , but enter 1 Chinese Character , it also return 1
instead of 2.

have't enough space to return value . Error occur.


Below is the modify code i use :

unit PccRichEdit;

interface

Uses StdCtrls,ComCtrls,Controls,Messages,Windows,RichEdit,ppDrwCmd;


Const
EM_GETTEXTLENGTHEX = WM_USER + 95;

const
GTL_DEFAULT = 0; { do the default (return # of
}
GTL_USECRLF = 1; { compute answer using CRLFs for
paragraphs }
GTL_PRECISE = 2; { compute a precise
}
GTL_CLOSE = 4; { fast computation of a "close"
r }
GTL_NUMCHARS = 8; { return the number of
}
GTL_NUMBYTES = 16; { return the number of
}

{ EM_GETTEXTLENGTHEX info; this struct is passed in the wparam of the msg }

type
TGetTextLengthEx = record
flags: DWORD; { flags (see GTL_XXX defines) }
codepage: UINT; { code page for translation }
end;


Type

TppPccRichEdit = class(TppRichEdit)
private

protected
function GetSelText: string; override;

end; {class, TppRichEdit}

implementation

function TppPccRichEdit.GetSelText: string;
Var
TextLenEx: TGetTextLengthEx;
MaxLength , Length: Integer;
begin
with TextLenEx do begin
flags := GTL_NUMBYTES or GTL_CLOSE or GTL_USECRLF ;
codepage := CP_ACP;
end;
MaxLength := Perform(EM_GETTEXTLENGTHEX, WParam(@TextLenEx), 0);
if MaxLength = 0 then
begin
Result := '';
exit;
end;
SetLength(Result, MaxLength);
Length := SendMessage(Handle, EM_GETSELTEXT, 0, Longint(PChar(Result)));
SetLength(Result, Length);
end;

initialization
ppRegisterRichEditClass( tppPccRichEdit );

finalization
ppUnRegisterRichEditClass( tppPccRichEdit );

end.

This time seens everything OK .

Or someone else have another idea?

digitalmetaphors

Thanks for sharing the info. It's really unfortunate that there are
multiple versions of these RichEd dll's which exhibit different behavior.


Cheers,

Jim Bennett
Digital Metaphors