Layout 2020 panics in WebRender with mix-blend-mode over 16k pixels #26463

SimonSapin · 2020-05-07T13:40:23Z

Test case:

<html style="background: green; height: 17000px">
<body style="mix-blend-mode: difference; color: yellow">
Test

Expected result, and actual result in Layout 2013 or Firefox: the page renders

Actual result in Layout 2020: crash with

[2020-05-07T13:24:14Z ERROR webrender::render_task] Attempting to create a render task of size 1024x34000
explicit panic (thread WRRenderBackend#0, at /home/simon/.cargo/git/checkouts/webrender-c3596abe1cf4f320/4ba17a6/webrender/src/render_task.rs:37)
   0: servo::backtrace::print
   1: servo::main::{{closure}}
   2: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:515
   3: std::panicking::begin_panic
   4: webrender::render_task::RenderTask::new_picture
   5: webrender::picture::PicturePrimitive::take_context
   6: webrender::frame_builder::FrameBuilder::build
   7: webrender::render_backend::Document::build_frame
   8: webrender::render_backend::RenderBackend::update_document
   9: webrender::render_backend::RenderBackend::run
  10: std::sys_common::backtrace::__rust_begin_short_backtrace
  11: core::ops::function::FnOnce::call_once{{vtable.shim}}
  12: <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/liballoc/boxed.rs:1008
  13: <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once
             at /rustc/42abbd8878d3b67238f3611b0587c704ba94f39c/src/liballoc/boxed.rs:1008
      std::sys::unix::thread::Thread::new::thread_start
             at src/libstd/sys/unix/thread.rs:87
  14: start_thread
             at /build/glibc-OTsEL5/glibc-2.27/nptl/pthread_create.c:463
  15: __clone
[2020-05-07T13:24:14Z ERROR servo] explicit panic
Stack trace for thread "WRRenderBackend#0"
   0: servo::backtrace::print
   1: servo::install_crash_handler::handler
Segmentation fault (core dumped)

The panic comes from WebRender when the size of a "render task" is more than 16000 device pixels in either dimension:

https://github.com/servo/webrender/blob/4ba17a61580a03b68881ffba7ee22bcf8e1aac72/webrender/src/render_task.rs#L28-L39

jdm added A-layout/2020 A-webrender I-panic labels May 7, 2020

SimonSapin mentioned this issue May 7, 2020

Correctly paint the CSS canvas’ background #26414

Merged

servo / servo

Layout 2020 panics in WebRender with mix-blend-mode over 16k pixels #26463

Layout 2020 panics in WebRender with mix-blend-mode over 16k pixels #26463

SimonSapin commented May 7, 2020

servo / servo

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Layout 2020 panics in WebRender with mix-blend-mode over 16k pixels #26463

Layout 2020 panics in WebRender with mix-blend-mode over 16k pixels #26463

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SimonSapin commented May 7, 2020