Transparent background

[tobrun]

Feature request to allow setting the background of the render surface to transparent:

Working branch here.

This feature allows to see through the map bounds and see items in the viewhierachy that are behind it (currently this shows a black background). Besides the feature request this also solves the issue of a flashing black background when starting up a mapview.

There are a couple of ways that we could expose this an api:

• expose the variables set with eglconfig chooser
• more limited api with a togle for enabling the transparent background

Before implementing we need to identify what the performance impact will be and if this feature introduces any regressions on older OS verions.

cc @zugaldia @ericdeveloper @kalimar

[tobrun]

Was able to get something working with GLSurfaceView:

While it works, it also doesn't show our logo and attribution icon anymore.
Going to see if I can make this work with TextureView.

[zugaldia]

more limited api with a togle for enabling the transparent background

I like this approach, preferably being opt-in. This enables the usecase while minimizing potential side effects (rendering, or performance).

[tobrun]

To follow up on this, approach mentioned in #10719 (comment) will not be feasible due to needing to move the surface before all the views in the hierarchy, as a result the logo/attribution/compass isn't showing anymore and this would go in against our terms and conditions.

I'm looking now into if a TextureView approach is feasible (as this render component wouldn't require the same changes as GlSurfaceView). TBC.

[tobrun]

Got a POC working with TextureView:

Before

After

TODO

• determine performance impact
• boil current configuration down to minimal changes
• expose as a configurable
• run tests on AWS device farm to verify if devices are unsupported

[tobrun]

Render performance comparison:

Before

After

There is no concrete indication that a translucent surface is adding performance overhead.

[tobrun]

This landed with #11065