Author: Jonas Bilinkevicius

How to get a range of text from a TRichEdit without setting a selection

Answer:

Sometimes while using RichEdit you need to get just a part of the text from that 
control, without setting a selection and using the SelText property. The code below 
shows the way to do that :
1   
2   {overrides wrong TTextRange definition in RichEdit.pas}
3   TTextRange = record
4     chrg: TCharRange;
5     lpstrText: PAnsiChar;
6   end;
7   
8   function REGetTextRange(RichEdit: TRichEdit; BeginPos, MaxLength: Integer): string;
9   {RichEdit: RichEdit control
10  BeginPos: absolute  index of first char
11  MaxLength: maximum chars to retrieve}
12  var
13    TextRange: TTextRange;
14  begin
15    if MaxLength > 0 then
16    begin
17      SetLength(Result, MaxLength);
18      with TextRange do
19      begin
20        chrg.cpMin := BeginPos;
21        chrg.cpMax := BeginPos + MaxLength;
22        lpstrText := PChar(Result);
23      end;
24      SetLength(Result, SendMessage(RichEdit.Handle, EM_GETTEXTRANGE, 0,
25        longint(@TextRange)));
26    end
27    else
28      Result := '';
29  end;


This function can be used to extract a word under the current mouse pointer 
position:
30  
31  function RECharIndexByPos(RichEdit: TRichEdit; X, Y: Integer): Integer;
32  { function returns absolute character position for given cursor coordinates}
33  var
34    P: TPoint;
35  begin
36    P := Point(X, Y);
37    Result := SendMessage(RichEdit.Handle, EM_CHARFROMPOS, 0, longint(@P));
38  end;
39  
40  function REExtractWordFromPos(RichEdit: TRichEdit; X, Y: Integer): string;
41  { X, Y: point coordinates in rich edit control }
42  {returns word under current cursor position}
43  var
44    BegPos, EndPos: Integer;
45  begin
46    BegPos := RECharIndexByPos(RichEdit, X, Y);
47    if (BegPos < 0) or
48      (SendMessage(RichEdit.Handle, EM_FINDWORDBREAK,
49      WB_CLASSIFY, BegPos) and (WBF_BREAKLINE or WBF_ISWHITE) < > 0) then
50    begin
51      result := '';
52      exit;
53    end;
54    if SendMessage(RichEdit.Handle, EM_FINDWORDBREAK,
55      WB_CLASSIFY, BegPos - 1) and (WBF_BREAKLINE or WBF_ISWHITE) = 0 then
56      BegPos := SendMessage(RichEdit.Handle, EM_FINDWORDBREAK,
57        WB_MOVEWORDLEFT, BegPos);
58    EndPos := SendMessage(RichEdit.Handle, EM_FINDWORDBREAK,
59      WB_MOVEWORDRIGHT, BegPos);
60    Result := TrimRight(REGetTextRange(RichEdit, BegPos, EndPos - BegPos));
61  end;