TImage - MOUSE SCROLL WHEEL
lazarus / 7-LCL

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Boshu · 2006-04-06 09:06

Hi!

...
  protected
  PROCEDURE MOUSEMOVE(SHIFT:TSHIFTSTATE;X,Y:LONGINT);OVERRIDE;
  PROCEDURE
MOUSEDOWN(BUTTON:TMOUSEBUTTON;SHIFT:TSHIFTSTATE;X,Y:LONGINT);OVERRIDE;
  PROCEDURE
MOUSEUP(BUTTON:TMOUSEBUTTON;SHIFT:TSHIFTSTATE;X,Y:LONGINT);OVERRIDE;
  public
....

These are the procedures i use to intercept mouse events in a custom
TImage.
I can't find the procedure triggered by mouse wheel events. Is it
implemented? If it's not then please reply this message in order to
add it to Mantis.

Bye!

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felipemdc · 2006-05-24 13:30

You can handle those messages yourself. First you need to rebuild
lazarus putting this as commandline option:

-dPassWin32MessagesToLCL

Now you can modify and use this sample code:

{*******************************************************************
*  TMainWindow.WndProc ()
*
*  DESCRIPTION:    Window function of the main window.
*                  Only handles manually the messages for the taskbar
icon.
*                  Other messages are forwarded to the Component
Library
*
*  PARAMETERS:     Standard window function parameters
*
*  RETURNS:        Nothing
*
*******************************************************************}
{$IFDEF Win32}
procedure TMainWindow.WndProc(var Message : TMessage);
var
  pt: TPoint;
  i: Integer;
  delta: ShortInt;
  wheel_delta: Word;
  rotation: Double;
begin
  case Message.msg of
    WM_HOTKEY: ExecuteLens(Self);

    WM_MOUSEWHEEL:
    begin
      wheel_delta := HiWord(Message.WParam);
      Move(wheel_delta, delta, SizeOf(Word));
      rotation := delta / WHEEL_DELTA;

      if (rotation > 0.0) then delta := Round(rotation + 0.5)
      else delta := Round(rotation - 0.5);

      for i := 1 to abs(delta) do
      begin
        // Call same code as from VK_ADD, VK_SUBTRACT handlers
        if (delta > 0.0) then
         vConfigurations.iMagnification :=
vConfigurations.iMagnification + 0.5
        else vConfigurations.iMagnification :=
vConfigurations.iMagnification - 0.5;
      end;

      // Hard limits for the magnification
      if vConfigurations.iMagnification < 1.0 then
vConfigurations.iMagnification := 1.0
      else if vConfigurations.iMagnification > 16 then
vConfigurations.iMagnification := 16;

      vGlass.Repaint;
    end;
  else
   
{*******************************************************************
    *  All other messages from the Window are handled by the Component
Library
   
*******************************************************************}
    inherited WndProc(Message);
  end;
end;
{$ENDIF}