NEWEST EDIT: A compromise has been added. Enable compatibility mode in the spawn menu options if you really want addons to work, at the cost of having less accurate HL2 movement. (ur_hl2ifier_compatibility 1 in console).

EDIT: The scope of this addon is being reconsidered, so this issue may not apply soon. But as it is currently, it's relevant for knowing why a mod like Super Spammable Sprays may not work with HL2-ifier. Keep in mind that in the original post below, TFA is specifically mentioned but it applies to all mods that need the FinishMove hook to work.

======= ORIGINAL POST =======
TLDR: There is no support planned. HL2-ifier wasn't made with TFA in mind and neither was TFA with HL2-ifier.

Since I've been asked a few times about TFA, I thought a dedicated thread would be appreciated for people wondering about it so the comments can stop getting repetitive about this.

The answer for TFA support is "no" and the reasons are:

1. HL2-ifier hooks onto player movement and defines its own rules on what a jumping and a grounded player is. By design, this overrides GMod behavior to circumvent hardcoded landing friction & jumping behavior in Sandbox mode. I assume TFA was made to expect default hardcoded behavior and rules, and reasonably so.
   
2. With the above in mind, the only "support" I could add would be to disable HL2-ifier automatically for the player holding a TFA weapon. That is stupid and defeats the purpose. By happenstance, this "issue" is really simply an addon conflict that is out of scope for either addon to address.
   
3. I don't use TFA.

There are options here:

• If you want to use TFA *and* have HL2-style movement, I assume TFA would work as expected if you use an addon that comes with its own gamemode and player class with none of the hooks and movement override shenanigans seen here.
  
• Use only TFA or HL2-ifier. Not both.
  
• Double-check TFA's settings to see if there's an option that allows it to work independently of the player's movement state. If it's not already a feature you might be able to suggest it to the TFA devs, but be respectful and don't pester them.

Thanks for reading and understanding.