oCastsLeft shows how many times you can cast a spell before you run out of mana. The count appears directly on your action bar.

How it works

By default, no spells are whitelisted. You tell the addon which spells to track by entering partial spell names. For example, entering heal, shock will show counts for Healing Wave, Lesser Healing Wave, Chain Heal, Earth Shock, Flame Shock, and so on. Only spells matching your filter will display a count.

When you have fewer than 3 casts remaining, the number turns red.

Features

Whitelist spells using comma separated partial name matching
Count displayed in your class colour
Red warning when running low on mana
Choose which corner of the button to display the count
Works with default action bars and Bartender4
Lightweight with throttled updates

Usage

Type /ocl to open the settings panel. Enter your spell filters, pick a corner position, and click Save.

Example filters by class:

Class	Filter
Shaman	`heal, shock, lightning, chain`
Priest	`heal, renew, power word`
Paladin	`holy light, flash, holy shock, cons`
Druid	`heal, regrowth, rejuv, swift`
Mage	`blink`

Compatibility

Classic Era, TBC Classic, Wrath Classic, Cataclysm Classic

I made this for myself and use it regularly. Thought I'd share it in case anyone else finds it useful!