[google_maps_flutter] Disable marker move animation on iOS

[Gibbo97]

Disable the marker move animation google_maps_flutter on iOS. Currently when you update the position it takes some time to move. However, on other platforms; android, web in my testing, the marker move is not animated. Additionally other features like lines being moved is not animated.

Marker move has forced animation on google_maps_flutter iOS.
Issue: flutter/flutter#129826

Behaviour previously, showing lines and markers behaving differently:
https://github.com/user-attachments/assets/d129bbb6-af93-4825-9b05-10befed4fd87

Behaviour now showing markers and lines behaving the same:
https://github.com/user-attachments/assets/3437caf9-628c-489e-ac5d-f0fb55897a6e

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Code Review

This pull request prevents iOS marker position updates from being implicitly animated across multiple google_maps_flutter_ios packages by wrapping the position updates in a CATransaction block with disabled actions. It also adds corresponding unit tests. The review feedback suggests removing the redundant [CATransaction setAnimationDuration:0.0] call since actions are already disabled. Additionally, it is recommended to refactor the unit tests to avoid asserting directly inside the test helper class, instead recording the state on a property and asserting it within the test methods.

[stuartmorgan-g]

This is unconditionally making google_maps_flutter on iOS behave differently from the default behavior of Google Maps SDK on iOS, which is generally not the approach we take. Adding a map-level option to disable implicit animation for markers is fine, but unconditionally changing it may regress other clients.

[Gibbo97]

@stuartmorgan-g Thanks for the prompt reply.

Just so I can get something in which you would be more keen on: are you picturing a new field on PlatformMapConfiguration (defaulting to animated, matching the SDK's native behavior) that, when set to disabled, wraps the marker.position assignment in a CATransaction with actions disabled? So default to the current behaviour, opt in to the standardised behaviour.

Or are you thinking of a bigger change?

A couple other things I'd like to confirm before I sink an afternoon into this:

1. Should the flag be exposed on the cross-platform GoogleMap widget (iOS-only effect, no-op elsewhere) or kept as an iOS-specific option?
2. Any preference on naming/polarity (e.g. markerPositionAnimationsEnabled default-on)?
3. Scope it to position only, or also cover other implicitly animated properties like rotation?

[stuartmorgan-g]

1. Should the flag be exposed on the cross-platform GoogleMap widget (iOS-only effect, no-op elsewhere) or kept as an iOS-specific option?

Do other platforms have APIs that allow toggling animation for these properties? If so we would want to abstract them, if not it should be an iOS-specific option. (I'm not familiar with all of the differences of the Google Maps API surface and behaviors on each platform offhand.)

2. Any preference on naming/polarity (e.g. markerPositionAnimationsEnabled default-on)?

APIs in this package should follow Flutter style guidance.

3. Scope it to position only, or also cover other implicitly animated properties like rotation?

If there are other APIs that this could obviously apply to, it should be designed in such a way that it would be easily extensible to other properties. E.g., a simple data class of animation toggles for various objects.