Using Delphi 6 code in a modern world.

[ceilingcat]

unit ExtMemo;
    interface
uses
    Windows, Messages, Classes, StdCtrls;
type
    TddgExtendedMemo = class(TMemo)
    private
        FRow: Longint;FColumn: Longint;
        FOnHScroll: TNotifyEvent;
        FOnVScroll: TNotifyEvent;
procedure WMHScroll(var Msg: TWMHScroll); message WM_HSCROLL;
procedure WMVScroll(var Msg: TWMVScroll); message WM_VSCROLL;
procedure SetRow(Value: Longint);
procedure SetColumn(Value: Longint);
function GetRow: Longint;
function GetColumn: Longint;
protected
// Event dispatching methods
procedure HScroll; dynamic;
procedure VScroll; dynamic;
public
    property Row: Longint read GetRow write SetRow;
    property Column: Longint read GetColumn write SetColumn;
published
    property OnHScroll: TNotifyEvent read FOnHScroll write FOnHScroll;
    property OnVScroll: TNotifyEvent read FOnVScroll write FOnVScroll;
end;

implementation

procedure TddgExtendedMemo.WMHScroll(var Msg: TWMHScroll);
begin
    inherited;
    HScroll;
end;
procedure TddgExtendedMemo.WMVScroll(var Msg: TWMVScroll);
begin
    inherited;
    VScroll;
end;
procedure TddgExtendedMemo.HScroll;
    { This is the OnHScroll event dispatch method. It checks to see
    if OnHScroll points to an event handler and calls it if it does. }
begin
    if Assigned(FOnHScroll) then
    FOnHScroll(self);
end;
procedure TddgExtendedMemo.VScroll;
    { This is the OnVScroll event dispatch method. It checks to see
    if OnVScroll points to an event handler and calls it if it does. }
begin
{ if Assigned(FOnVScroll) then }
{ FOnVScroll(self); }
end;
procedure TddgExtendedMemo.SetRow(Value: Longint);
{
{ The EM_LINEINDEX returns the character position of the first }
{ character in the line specified by wParam. The Value is used for }
{ wParam in this instance. Setting SelStart to this return value }
{ positions the caret on the line specified by Value.  }
}
begin
    SelStart := Perform(EM_LINEINDEX, Value, 0);
    FRow := SelStart;
end;
function TddgExtendedMemo.GetRow: Longint;
    { The EM_LINEFROMCHAR returns the line in which the character specified
    by wParam sits. If -1 is passed as wParam, the line number at which
    the caret sits is returned. }
begin
    Result := Perform(EM_LINEFROMCHAR, -1, 0);
end;
procedure TddgExtendedMemo.SetColumn(Value: Longint);
begin
    { Get the length of the current line using the EM_LINELENGTH
    message. This message takes a character position as WParam.
    The length of the line in which that character sits is returned. }
    FColumn := Perform(EM_LINELENGTH, Perform(EM_LINEINDEX, GetRow, 0), 0);
    { If the FColumn is greater than the value passed in, then set
    FColumn to the value passed in }
    if FColumn > Value then
        FColumn := Value;
// Now set SelStart to the newly specified position
    SelStart := Perform(EM_LINEINDEX, GetRow, 0) + FColumn;
end;
function TddgExtendedMemo.GetColumn: Longint;
begin
    { The EM_LINEINDEX message returns the line index of a specified
    character passed in as wParam. When wParam is -1 then it
    returns the index of the current line. Subtracting SelStart from this
    value returns the column position }
    Result := SelStart - Perform(EM_LINEINDEX, -1, 0);
end;
end.

I am using Embarcadero Delphi 10 community edition.
I wanted some code that would add an OnScroll event to a TMemo, and the code I posted here works well. It is not my code. It is from "Borland Delphi 6 Developer's Guide".

However, the TddgExtendedMemo.GetColumn method,and the TddgExtendedMemo.GetRow method do not work. And I would like to know if the code was wrong even in the Dephi 6 era, or if the definition of EM_LINEFROMCHAR, and the definition of EM_LINEINDEX, has changed since Delphi 6.
Comments and/or observations welcomed.

[Norrit]

I'm curious what do not work meens, since the same EM_LINEFROMCHAR and EM_LINEINDEX are used in the SetColumn/SetRow and work.
So if the definitions of this would've changed those setters wouldn't work either.

Therefor I would've guessed that above code should work as normal, therefor the question on what difference do you see in output (what you expect and what you get)

[ceilingcat]

Norrit, thanks for responding. Your comment that the code should work as normal struck a chord. I had added a procedure, not in the original code, and forgot an "inherited" statement. I re-registered the component, and it works as expected. Somethimes I can't see the forest for the trees.