detecting auto cast

how? =/

Depends on the ability/situation and other variables. Be more specific please.

Type 1: Single-Target non-attack - This sort of autocast is like Healing(Priests) and can be detected by order Ids(check the spell, or rig a trigger to display the order as it is issued).

Type 2: Attack-type casts - You detect when the unit does damage and if the damaged has the buff.

Type 3: Anything that doesn't fit into those 2

ahh sorry. i just realised.

searing/frost arrows, blood lust and slow.

What are you trying to detect? Whether it's active? When it's auto-cast? Whether an ability has it?

when auto-cast is active and that instance the spell is auto-casted

As far as I know, bloodlust and slow would trigger the normal 'A unit starts the effect of an ability' event. Autocast arrow attacks are a little more difficult, depending on how well you want it to work.

There are orders like "bloodluston" or things like that which can be detected to tell when autocast is on. "bloodluston" might be wrong, but you can find them all in the object editor under the spell.

Did nobody listen to me? Check for issued orders and whatnot, it is foolproof.

let's say when X is auto-casting frost arrows and is shooting one target. just by detecting frostarrowon and/or unit is ordered to cast frost arrows, i can do a function like.. randomly be able to cast a spell on the target (using dummy unit)?

won't the trigger shoots if i'm just afk-ing somewhere and a target is in the trigger's range or something.

Search a lil around in this forum. I've answered this question before... ad the answer was quite long at least for arrow spells.Have a look here @ my first post.For arrowspells look here:http://www.wc3campaigns.net/showthread.php?t=82424
For standard abilities like slow or curse, just detect when the "<order>on" is issued and store it somewhere (this isn't actually required if you wanna do a spell like curse or slow). You always need a trigger that gets executed when the effect of your spell is started,cast,finished etc.

fore fire arrows or the like, just detect when the units order is firearrowson/off or however it goes, that will tell you if it is on or off autocasted