Check if Mouse LButton is down?

Question

Hi,

How do I check if the Left button of my mouse is currently pressed down/dragging something(I preffer the first possibility).

I tried Mouse.IsDraging,but no result.

NOTE: I handle mouse messages in my application so its no problem if its a WM,just share a way to accomplish my task.

Answer 1

try this

var
  MouseLeftIsDown       : Boolean;


    procedure TForm1.FormMouseDown(Sender: TObject;
       Button: TMouseButton; Shift: TShiftState;
       X, Y: Integer) ;
    begin

    case Button of
      mbLeft :  MouseLeftIsDown := TRUE;
      mbRight:  ;
      mbMiddle: ;
    end;


    end;


procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
    case Button of
      mbLeft :  MouseLeftIsDown := False;
      mbRight:  ;
      mbMiddle: ;
    end;

end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if MouseLeftIsDown then
  begin
   //your code

  end;
end;

Answer 2

There is a Windows API function GetAsyncKeyState(), which despite its name is also usable to get the state of the mouse buttons. The linked documentation directly contains the answer to your question:

The GetAsyncKeyState function works with mouse buttons. However, it checks on the state of the physical mouse buttons, not on the logical mouse buttons that the physical buttons are mapped to. For example, the call GetAsyncKeyState(VK_LBUTTON) always returns the state of the left physical mouse button, regardless of whether it is mapped to the left or right logical mouse button. You can determine the system's current mapping of physical mouse buttons to logical mouse buttons by calling GetSystemMetrics(SM_SWAPBUTTON) which returns TRUE if the mouse buttons have been swapped.

The result type is short, to check for the most significant bit just test whether the value is negative.