Author: Jonas Bilinkevicius 

Has anyone found a way to prevent the Paint method from firing when you're in the 
middle of resizing a form? In other words, is there some way to ghost the change 
until the user actually releases the mouse button, instead of redrawing the form 
constantly during the resize?

Answer:

You can revert to the way a window was resized in Win 3.1 - with a sizing frame and 
a redraw only when the user let go of the mouse.

In your forms declaration you place this:
1   
2   private
3   	{Private declarations}
4   	FDragFullWindowState: LongBool;
5   	procedure WMEnterSizeMove(var msg: TMessage); message WM_ENTERSIZEMOVE;
6   	procedure WMExitSizeMove(var msg: TMessage); message WM_EXITSIZEMOVE;


The implementation is like this:
1   
2   private
3   	{Private declarations}
4   	FDragFullWindowState: LongBool;
5   	procedure WMEnterSizeMove(var msg: TMessage); message WM_ENTERSIZEMOVE;
6   	procedure WMExitSizeMove(var msg: TMessage); message WM_EXITSIZEMOVE;


The implementation is like this:

procedure TProdBuilderMainForm.WMEnterSizeMove(var msg: TMessage);
begin
  SystemParametersInfo(SPI_GETDRAGFULLWINDOWS, 0, @FDragFullWindowState, 0);
  if FDragFullWindowState then
    SystemParametersInfo(SPI_SETDRAGFULLWINDOWS, Ord(False), nil, 0);
end;

procedure TProdBuilderMainForm.WMExitSizeMove(var msg: TMessage);
begin
  if FDragFullWindowState then
    SystemParametersInfo(SPI_SETDRAGFULLWINDOWS, Ord(True), nil, 0);
end;