Actually the “o” prefix serves 2 purposes:
Prevent developers from using obsolete commands.
http://doc.4d.com/4Dv15/4D/15/Obsolete-commands-now-hidden.300-2005953.en.htmlo commands are excluded from clairvoyance/auto-complete>.
Help developers identify obsolete commands in converted applications.
but the statement “Ok it still works now, but it has been scheduled to disappear eventually” is just not true.
The http://doc.4d.com/4Dv16R3/4D/16-R3/Deprecated-or-removed-features-in-v16-product-range.200-3269261.en.htmlDeprecated or removed features in…> page lists some commands as “deprecated”, others as “removed”.
Some commands are deprecated because they are at the mercy of external factors, such as the OS.
But as for scheduling commands to disappear, only a handful are given and all with a good reason.
Support for XSLT processing will be removed in future 4D releases.
We plan to remove support for these (QuickTime) specific APIs in the next release.
QuickDraw fonts are now deprecated…The _o_Font number and _o_Font name commands are kept in 4D v15 and higher for compatibility but will be removed in subsequent versions.
We plan to remove ASCII mode in future major versions.
These are the ones that you really need to focus on.
The docs even go as far as to say “we do not plan to remove support for subtables in the near future”.
Deprecated features that are not specifically mentioned with a plan to remove can be given a lower priority.