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Report From: Delphi-BCB/Compiler/Delphi/Header Generation [ Add a report in this area ]

Report #: 64326

Status: Open

autocreated handler for OnMouseWheel incompatible with signature of TMouseWheelEvent

Project: C++Builder

Build #: 11.0.2902.10471

Version: 11.0

Submitted By: Sergiy Kanilo

Report Type: Minor failure / Design problem

Date Reported: 7/10/2008 2:05:45 PM

Severity: Infrequently encountered problem

Last Updated: 3/20/2012 2:24:39 AM

Platform: All platforms

Internal Tracking #: 262052

Resolution: None (Resolution Comments)

Resolved in Build: : None

Duplicate of: None

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Description

It seems that the TMouseWheelEvent accepts const reference to the TPoint, and autogenerated handler uses non-const reference
Somehow it is work if handler set using ObjectInspector, but this is impossible if the component created in run-time.

Possible workaround:
create handler with proper signature and assign it in runtime

Steps to Reproduce:

1. create new form
2. in object explorer add handler for OnMouseWheel
3. add something (comment) in the handler (so it is not removed automatically)
4. add line
  OnMouseWheel =FormMouseWheel;
in the constructor:

#include <vcl.h>
#pragma hdrstop
#include "Unit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)

: TForm(Owner)
{

OnMouseWheel =FormMouseWheel;  // ERROR HERE
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormMouseWheel(TObject *Sender, TShiftState Shift,

  int WheelDelta, TPoint &MousePos, bool &Handled)
{

// ...
}
//---------------------------------------------------------------------------

5. compile

[BCC32 Error] Unit1.cpp(15): E2034 Cannot convert 'void (_fastcall * (_closure )(TObject *,TShiftState,int,TPoint &,bool &))(TObject *,TShiftState,int,TPoint &,bool &)' to 'TMouseWheelEvent'

Workarounds

None

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