[Engine] Refactor Mana Shield damage handling

[kphoenix137]

Moves reduction to Mana while Mana Shield is active into a Player member function ApplyManaShieldToDamage(), and removes GetManaShieldDamageReduction().

ApplyManaShieldToDamage() takes totalDamage as an argument and reduces the Player's Mana (if applicable), and returns the remaining amount of damage to be dealt to the Player's Life.

[morfidon]

I think the removal condition should use the internal fixed-point mana value, not >> 6. In this engine, damage and mana are both handled in 1/64 units, so whole-mana checks are only a UI-level approximation. The old behavior effectively removed the shield when mana was actually exhausted. Using player._pMana == 0 would be safer and more faithful to how the engine works.

if (&player == MyPlayer) {
    RedrawComponent(PanelDrawComponent::Mana);
    if (manaBefore > 0 && player._pMana == 0)
        NetSendCmd(true, CMD_REMSHIELD);
}

[qndel]

morfidon

if your comment is about certain lines of code, it's best to actually add the comment to them

[StephenCWills]

In this engine, damage and mana are both handled in 1/64 units, so whole-mana checks are only a UI-level approximation.

The thing is, that assessment is actually wrong. Blizzard used (hp >> 6) == 0 checks all over the place inside the game engine so they clearly thought that honoring the UI-level approximation was more important than refunding a few 64ths of a hitpoint.