Implement Platformer Plus Test if Colliding with Wall

[RetrocadeMedia]

Is your feature request related to a problem? Please describe.
In the Platformer plus plug-in you had the ability to test if the player was colliding with a wall like this:

You can try to replace it with this code, however the detection is significantly less reliable than it was in Platformer plus.

Describe the solution you'd like
I would like for the Platformer plus check for wall to be implemented in to Gb Studio

Describe alternatives you've considered
See the above solution

[RetrocadeMedia]

In the previous version of Gb Studio 4.1, I performed the wall check at an interval of 0.02 seconds to help the performance of the game. That 0.02 second wait time was causing the new wall code to work significantly less reliably.

By just letting this code run constantly (while this actor is active anyway, it gets deactivated after the player bounces), the check becomes significantly more reliable without a significant hit to the games performance.
So far, a LOT of issues I've had have been solved by the new performance upgrades in Gb Studio 4.2!

[chrismaltby]

That's definitely odd that the value seems to be less reliable, what you're doing there should be about the same as the "Store Fields in Variable" event. I'd be interested if you had a small example project that shows the issue. I see you had this on an actor's On Update script, I wonder if multiple actors were interfering with each other, especially with how that $player_bounce value is being set.

I tried this

which seemed to work as expected.

Instead of needing a "Platformer Store Fields in Variable" I've been adding things like this as runtime only engine fields, which can be used anywhere that values can be used in scripts

which then also lets you do more complex logic without needing to store a temporary variable

I've realised I didn't expose plat_wall_col this way though so I just need to add it to https://github.com/chrismaltby/gb-studio/blob/fa8a9a743611a5d87f0cbeac6c7e623f6f9fb753/appData/engine/engine.json as something like

    {
      "key": "plat_wall_col",
      "sceneType": "PLATFORM",
      "label": "FIELD_TOUCHING_WALL",
      "description": "FIELD_PLATFORM_TOUCHING_WALL_DESC",
      "group": "GAMETYPE_PLATFORMER",
      "type": "number",
      "cType": "UBYTE",
      "defaultValue": 0,
      "runtimeOnly": true
    },

I'll add this for the next GB Studio release, saves you having to write manual GBVM code.

If you're able to reproduce the original issue in a small sample project please share it here and I'll see if something needs to be fixed.

Thanks!