TListBox - selected scroll speed of an item

Question

I need to change the speed with which the list box scrolls when an item is selected (holding the left mouse button down) and the mouse moves outside the list box. To duplicate behavior, follow these steps:

• Leave the list box on the form (+ - 250 x 200 odd). Do not make it too large, otherwise the scroll bar will not be visible below.
• Set the number of columns to 3.

• Add the following code to the FormCreate form:

  var
    I: Integer;
  begin
    for I := 0 to 200 do
      ListBox1.Items.Add('Item '+IntToStr(I));
  end;
  

• Launch the application and make sure that the scroll bar below is visible. Now click and hold the left mouse button on any of the items in the list. Move the mouse and the selected item will change depending on which item is under the mouse cursor. The problem is that the list box will scroll very quickly when the mouse moves outside the list, which is necessary in my case to select hidden objects. I am trying to slow down the scroll speed.

I understand that this is not normal use of the list and that the behavior may not conform to the standard recommendations of the user interface. This is necessary for a very specific purpose, the problem is that the scroll speed makes it very inconvenient for users.

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Answer 1

, , . , . , ApplicationEvents .

type
  TListBox = class(stdctrls.TListBox)
  protected
    procedure WMMouseMove(var Message: TWMMouseMove); message WM_MOUSEMOVE;
  end;

procedure TListBox.WMMouseMove(var Message: TWMMouseMove);
begin
  if GetCapture = Handle then
    Sleep(250);
  inherited;
end;