Add feature dependency checking

[benloh]

When adding touch, it appears you need to have used addFeature for Costume, then Physics, then Touches, in that order. So it’s a bit of a hassle

[benloh]

Touches

We thought we might be able to just "auto-add" any missing features when using Touches, but the problem is actually rather complex.

A few gotchas:

• Costume has to be added and set before Physics because physics body size is set using the costume size.
• You have to prime Touches with the types of touches you want to use (e.g. 2c2, 2cb, b2b, binb)
• Costume, Physics, and Touches have to be enabled for BOTH the source agent AND the target blueprints.
• Intelligently adding Touches to the target agent would probably require a pre-compile pass to determine target agents needing Touches.
• If we auto-add Costume, Physics, and Touches, we would have to default to some possibly misleading default values. e.g. if costume name wasn't previously set, or the sprite size cannot be determined, we fall back to a default 'padding' size. e.g. if Touch type is not defined, we'd probably want to default to bound-to-bound touching.

A few rules the system should enforce:

• Adding a feature should always go in # PROGRAM DEFINE
• Costume should always be added before Physics
• Physics should always be added before Touches
• Touches should always require both Costume and Physics
• A touch type should be set (e.g. b2b).

Would it be better for the system to:

a) quietly default to values if the user did not set them (leading to mysterious magical behaviors)

or

b) passively show help to the student so they know what they need to do and how to do it

or

c) auto-insert explicit gemscript commands to set default values so that they are visible and can be changed by the student?

Vision

Feature dependency checking for Vision is potentially even more complicated.

For example, for canSeeColorOfAgent to work:

• the target agent must have Costume, Physics, Touches, and Vision features set.
• the background agent that the target agent is on top of also needs to have Costume, Physics, Touches set.

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CONCLUSION

This is probably a 2.0 feature.