addImage support for symbol icons

[tobrun]

We currently don't have a way to set an image to the currently loaded style. Atm we can only reference icon ids of images downloaded as part of the style spritesheet.

[TimothySealy]

I'm currently exploring the idea to add images to a specific folder (for example "assets/symbols") sharing them with the underlying platforms. From there you can reference icons based on the name.

For example if you have an camera icon stored in "assets/symbols/camera.png" then you can add a symbol (with option iconName set to "camera.png") referencing that asset. I have a working iOS implementation on my development branch.

[alfonsodev]

@TimothySealy that sounds great, do you have plans to open a Pull Request here ?

[tobrun]

Flagging here that with the upcoming SDK releases of both iOS as Android (v7.4.0), we are adding a new map change event that is emitted when the style needs a image resource (if not already added). This would simplify integration of suggested approach #44 (comment) more easily + has the benefit of only lazy loading images when needed.

PR of those changes in mapbox/mapbox-gl-native#14302 and mapbox/mapbox-gl-native#14320.

[TimothySealy]

I've created a PR (#79) for tracking the implementation of custom symbols. Currently the legacy API (MGLPointAnnotation) is used for creating the symbols. Will check the recent release of the Mapbox SDKs for the new map change event and how this can be incorporated.

[TimothySealy]

Closed by PR #79.