Currently we have OnChangeBounds which gets triggered after the fact.
if one decides it does not like what it has then one could change the size and thus this will of course trigger another event.
Now I know the LCL is processing the WM_WINDOWPOSCHAINGING message and thus if we
could gain access to the WNDOWPOS record so that one could update the record on return to reset the values.
This would then prevent unneeded flickering and slowness of the GUI in many cases when things get busy on the screen..
I am sure the constraints use this message period to limit the size of the form because I see it handles it very well without flicker, so we need this event to be exposed to a common event so the coder can also adjust the sizes..
I have some apps I have always used the WM_SIZING so that I can maintain an aspect ratio of the form without flickering junk on the screen. It works nicely, I can smoothly enlarge and shrink a form there by adjusting the opposite side to maintain the ratio without any junk that takes place because I also have a lot of busy graphics on the form that gets updated.
So a OnChangingBounds with a parameter VAR WINDOWSREC, for example so we can alter it before the LCL does any drawing.