nsMsgViewCommandCheckState
the nsmsgviewcommandcheckstate interface contains constants used for command status in thunderbird.

nsIMsgDBView
imsgdbviewcommandupdater acommandupdater); void sort(in nsmsgviewsorttypevalue sorttype, in nsmsgviewsortordervalue sortorder); void docommand(in nsmsgviewcommandtypevalue command); void docommandwithfolder(in nsmsgviewcommandtypevalue command, in nsimsgfolder destfolder); void getcommandstatus(in nsmsgviewcommandtypevalue command, out boolean selectable_p, out nsmsgviewcommandcheckstatevalue selected_p); void viewnavigate(in nsmsgnavigationtypevalue motion, out nsmsgkey resultid, out nsmsgviewindex resultindex, out nsmsgviewindex threadindex, in boolean wrap); boolean navigatestatus(in nsmsgnavigationtypevalue motion); nsmsgkey getkeyat(in nsmsgviewindex index); nsimsgdbhdr getmsghdrat(in nsmsgviewindex index); nsimsgfolder getfolderf...
... void getcommandstatus(in nsmsgviewcommandtypevalue command, out boolean selectable_p, out nsmsgviewcommandcheckstatevalue selected_p); parameters command the nsmsgviewcommandtypevalue to perform.
...defined in the interface: nsmsgviewcommandcheckstate.

Index
for example to move forward a message, you would call: 1261 nsmsgsearchopvalue defined in comm-central/ mailnews/ base/ search/ public/ nsmsgsearchcore.idl 1262 nsmsgviewcommandcheckstate interfaces, xpcom, xpcom api reference, thunderbird the nsmsgviewcommandcheckstate interface contains constants used for command status in thunderbird.

XPCOM reference
for example to move forward a message, you would call:nsmsgsearchopvaluedefined in comm-central/ mailnews/ base/ search/ public/ nsmsgsearchcore.idl nsmsgviewcommandcheckstatethe nsmsgviewcommandcheckstate interface contains constants used for command status in thunderbird.