This bug is for crash report bp-7632e19b-dca5-47cb-8731-50ea90200725.

Top 10 frames of crashing thread:

0 XUL RustMozCrash mozglue/static/rust/wrappers.cpp:17
1 XUL mozglue_static::panic_hook mozglue/static/rust/lib.rs:89
2 XUL core::ops::function::Fn::call src/libcore/ops/function.rs:72
3 XUL std::panicking::rust_panic_with_hook src/libstd/panicking.rs:474
4 XUL rust_begin_unwind src/libstd/panicking.rs:378
5 XUL std::panicking::begin_panic_fmt src/libstd/panicking.rs:332
6 XUL webrender::renderer::Renderer::update_texture_cache gfx/wr/webrender/src/renderer.rs:3911
7 XUL webrender::renderer::Renderer::render_impl gfx/wr/webrender/src/renderer.rs:3391
8 XUL webrender::renderer::Renderer::render gfx/wr/webrender/src/renderer.rs:3183
9 XUL wr_renderer_render gfx/webrender_bindings/src/bindings.rs:606

This crash appears to be macOS-specific and started in buildid 20200708094217. Disregard crashes older than that because they appear to be unrelated problems.

The raw crash reason appears to be something like this:

Unexpected external texture X for the texture cache update of ExternalImageId(Y) 

With X and Y being different numbers in different crashes.

Added a signature

This crash was almost certainly introduced by bug 1536515, which added WebRender support for client storage backed textures.

I don't know if there are different cases mixed up here, but I certainly discovered the case, and it's related to WebGPU support. The following code path on macOS (this OS only, and with specific resolutions) made the presentation broken for WebGPU: https://searchfox.org/mozilla-central/rev/85b84f82489451362a351b144fe5232a8e46c61c/gfx/layers/composite/TextureHost.cpp#590

I'm going to adjust the keywords here accordingly. Please feel free to file another issue if the crash shows up without WebGPU support.

The external texture we create in WebGPU to present the canvas was taking
a different path on macOS with specific resolutions:
https://searchfox.org/mozilla-central/rev/85b84f82489451362a351b144fe5232a8e46c61c/gfx/layers/composite/TextureHost.cpp#590

https://hg.mozilla.org/mozilla-central/rev/44c6059d3345