Question

I have inherited a Delphi 7 (VisualCLX) application to maintain and I want to filter some windows message like the mouse wheel (WM_MOUSEWHEEL) on the main form(TForm) of the application, is it possible on the Visual CLX ? How ?

I know that is possible on the VCL, but I’m looking for some solutions on the old Cross-Platform (CLX) …

Note

I need to disable the mousewheel event because it keeps changing the active page(TPageControl) and this is very annoying in Delphi with Component Library for Cross-Platform (CLX), so any other workaround that solve the problem is welcome …

Answer 1

Filtering input messages in CLX is not simple. There appears to be nothing like the VCL’s OnMessage.

You can stop mouse wheel events being handled by CLX page controls with a simple interposer. Add this code to your main form, before the declaration of your main form class.

type
  TPageControl = class(QComCtrls.TPageControl)
  protected
    function DoMouseWheel(Shift: TShiftState; WheelDelta: Integer; 
      const MousePos: TPoint): Boolean; override;
  end;

And then in the implementation section of the unit, add this:

function TPageControl.DoMouseWheel(Shift: TShiftState; WheelDelta: Integer; 
  const MousePos: TPoint): Boolean;
begin
  Result := True;
end;

If you have a number of page controls on different forms then you should declare the interposer in a unit that can be shared by all the forms in your app. Or maybe even derive a proper grown-up sub-class.