Calling wxDialog::EndModal() directly from inside the dialog is a
potential bug if the dialog is shown in the modeless or window modal
(quasi-modal). Use the internal button events where possible and
check for the appropriate mode before calling the correct end dialog
function.
- fix an issue when trying to enter a scale < 1.0: such a scale starts by 0, that was rejected by the filter)
- automatic clamp to user scale limits, to avoid many warnings to users.
- if the user scale is out of bounds, warn the user before trying to print, not when opening the dialog.