Wrap mouse around screen edges

problem description

I've got a Delphi component. To set a value, you can click and drag.

H开发者_运维知识库owever, when you reach the edge of the screen, you can't go any further. You then need to go back to the component and drag further, which is not very user-friendly.

preferred solution

What I'd like is to have the mouse cursor wrap around the screen if you reach an edge, so you can continue scrolling a value. 3dsmax uses this type of GUI control extensively, and I like how that works.

Alternatively, it would be fine for me if the cursor goes off-screen, but continues to send X/Y coordinates that are out of the screen bounds.

what i have so far

I know that I can get/set the current mouse position via Mouse.CursorPos, and that the screen dimensions are available via Screen.Width and Screen.Height.

The code below does wrap the mousecursor around the way I want to.

procedure TFormXXXX.YYYYMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
var
  LX, LY: Integer;
begin
  LX := Mouse.CursorPos.X;
  if LX < 1 then
    LX := Screen.Width - 1
  else
    if LX>Screen.Width -2 then
      LX := 0;

  LY := Mouse.CursorPos.Y;
  if LY < 1 then
    LY := Screen.Height - 1
  else
    if LY>Screen.Height -2 then
      LY := 0;

  Mouse.CursorPos := Point(LX, LY);
end;

There's still the problem that I have to "manually" keep track of the wraps to obtain a proper offset from the starting point, but I'll find a way to solve that.

I just don't know if this is a proper approach to do this. Maybe somebody has some experience or wise words to say about this...

main question

Is there a tried and tested common approach to this? Does windows provide stuff to do something like this maybe?

some doubts that I have

• How will this behave when there are multiple monitors?
• What happens if the user is connected via a slow (VNC?) connection.. will the cursorposition always reach 0 or the other extreme end of the screen?
• What will happen if the input control is not a mouse, but a sketchpad or a touchscreen?
• Is it bad practice to change the mouse position? I can imagine users don't like my application to mess with their mouse cursor position.

Rather than having a simple linear scale, you could accelerate the change with increasing distance from the control, and have a cutoff where past that it starts incrementing automatically. Basically have it work like dragging to select text does, where the window starts scrolling once the mouse reaches the bottom of a window, even if the mouse stops moving once it reaches that point.