Author: Jonas Bilinkevicius

I want my form to snap to the left border of the screen as soon as it gets close 
(Form1.Left<=30) to it. How can I do that?

Answer:

Use the WM_WindowPosChanging message:
1   
2   procedure WMWindowPosChanging(var message: TWMWindowPosChanging);
3     message WM_WindowPosChanging;
4   { ... }
5   
6   procedure TForm1.WMWindowPosChanging(var message: TWMWindowPosChanging);
7   begin
8     inherited;
9     with message.WindowPos^ do
10      if x < 30 then
11        x := 0;
12  end;