collision debug doesn't work reliably

[jfirebaugh]

Turning on collision debug option results in some tiles showing it and other tiles not showing it. As you pan and zoom, it turns on and off on a tile-by-tile basis unpredictably.

[brunoabinader]

I've noticed that debug collisions are rendered as expected when using a style with raster layer only:

However, debug collisions are only rendered on the tiles appearing on the bottom right corner for the examples below:

[brunoabinader]

Given the examples above, my suspicion is that somehow the tile size affects the way how the collision debug is rendered.

[brunoabinader]

Given the examples above, my suspicion is that somehow the tile size affects the way how the collision debug is rendered.

Even though we don't always enable stencil test when rendering symbols, we do render collision using the same stencil function. This gets updated on each render call, but only if the bucket needs clipping.

In the cases above, the render result was unpredictable because it used the last stencil function set by the previous bucket that needed clipping.

[jfirebaugh]

Thanks for investigating!

In the cases above, the render result was unpredictable because it used the last stencil function set by the previous bucket that needed clipping.

This means it's a good example of a bug that will be fixed by #6468.