BUG: Raster and Vector layers desynchronize during map interaction

[UlysselaGlisse]

Bug description

When interacting with the map, there is a desynchronisation between raster and vectors layers.

Where to find this bug

I've found this bug in many applications using MapLibre Native for map rendering across both IOS and Android.
The issue is more prononced on Android: the misalignment triggers immediately upon touching the screen.
On IOS, we have to move the map to see it.

For example :

• CFF (Swiss train company):
  • Android:

CFF-Android.mp4

- IOS:

CFF-IOS.mov

• Mappy:
  • Android:

Mappy-Android.mp4

• IOS:

Mappy-IOS.mov

Proposed fix:

I've found a workaround to avoid this dealignment by deleting this condition:

// src/mbgl/renderer/layers/raster_layer_tweaker.cpp 
// l.97

matrix = getTileMatrix(
        tileID,
        parameters,
        {0.f, 0.f},
        TranslateAnchorType::Viewport,
        false,
        false,
        drawable,
        !parameters.state.isChanging()); // <- That one
        }

[louwers]

Thanks a lot for the detailed report!

Do you feel comfortable making a PR with your fix?

Pinging @mwilsnd authored this particular line of code. 🙂

maplibre-native/src/mbgl/renderer/layers/raster_layer_tweaker.cpp

Lines 97 to 104 in 166593f

	matrix = getTileMatrix(tileID,
	parameters,
	{0.f, 0.f},
	TranslateAnchorType::Viewport,
	false,
	false,
	drawable,
	!parameters.state.isChanging());

[UlysselaGlisse]

Thank you! Yes, i will be happy to submit a PR. I have already tested this fix locally on both Android and iOS using a custom build, and it successfully resolve the desynchronization without any immediate performance regressions. I will prepare the PR shortly.