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Panic when setting canvas width or height #17277

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asajeffrey opened this issue Jun 12, 2017 · 1 comment
Closed

Panic when setting canvas width or height #17277

asajeffrey opened this issue Jun 12, 2017 · 1 comment
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@asajeffrey
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A-content/script A-webrender I-panic

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@asajeffrey
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@asajeffrey asajeffrey commented Jun 12, 2017

Setting the canvas dimensions causes a panic. For example:

<!doctype html>
<html>
    <body>
        <canvas width="50px" height="50px"></canvas>
        <script>
            var canvas = document.getElementsByTagName('canvas')[0];
            var ctx = canvas.getContext('2d');
            ctx.fillStyle = "red";
            ctx.fillRect(0, 0, canvas.width, canvas.height);
            setTimeout(function() {
                canvas.width = 100;
                canvas.height = 100;
                ctx.fillStyle = "green";
                ctx.fillRect(0, 0, canvas.width, canvas.height);
            }, 0);
        </script>
    </body>
</html>

produces:

assertion failed: `(left == right)` (left: `50`, right: `100`) (thread RenderBackend, at /home/ajeffrey/github/asajeffrey/servo/.cargo/git/checkouts/webrender-c3596abe1cf4f320/caec344/webrender/src/resource_cache.rs:298)
stack backtrace:
   0:     0x5595230c1734 - backtrace::backtrace::libunwind::trace
                        at /home/ajeffrey/github/asajeffrey/servo/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.2/src/backtrace/libunwind.rs:53
                         - backtrace::backtrace::trace<closure>
                        at /home/ajeffrey/github/asajeffrey/servo/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.2/src/backtrace/mod.rs:42
   1:     0x5595230b9bdf - backtrace::capture::{{impl}}::new
                        at /home/ajeffrey/github/asajeffrey/servo/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.2/src/capture.rs:64
   2:     0x55951e816446 - servo::main::{{closure}}
                        at /home/ajeffrey/github/asajeffrey/servo/ports/servo/main.rs:129
   3:     0x55952405110a - std::panicking::rust_panic_with_hook
                        at /checkout/src/libstd/panicking.rs:550
   4:     0x559524050fa4 - std::panicking::begin_panic<collections::string::String>
                        at /checkout/src/libstd/panicking.rs:511
   5:     0x559524050ed9 - std::panicking::begin_panic_fmt
                        at /checkout/src/libstd/panicking.rs:495
   6:     0x559521f9d65e - webrender::resource_cache::{{impl}}::update_image_template
                        at /home/ajeffrey/github/asajeffrey/servo/.cargo/git/checkouts/webrender-c3596abe1cf4f320/caec344/webrender/src/resource_cache.rs:298
   7:     0x559521e4452d - webrender::render_backend::{{impl}}::run
                        at /home/ajeffrey/github/asajeffrey/servo/.cargo/git/checkouts/webrender-c3596abe1cf4f320/caec344/webrender/src/render_backend.rs:158
   8:     0x559521d3dd23 - webrender::renderer::{{impl}}::new::{{closure}}
                        at /home/ajeffrey/github/asajeffrey/servo/.cargo/git/checkouts/webrender-c3596abe1cf4f320/caec344/webrender/src/renderer.rs:1136
   9:     0x559521c3aaea - std::sys_common::backtrace::__rust_begin_short_backtrace<closure,()>
                        at /checkout/src/libstd/sys_common/backtrace.rs:136
  10:     0x559521ee4e23 - std::thread::{{impl}}::spawn::{{closure}}::{{closure}}<closure,()>
                        at /checkout/src/libstd/thread/mod.rs:364
  11:     0x559521f6c0da - std::panic::{{impl}}::call_once<(),closure>
                        at /checkout/src/libstd/panic.rs:296
  12:     0x559521ee6409 - std::panicking::try::do_call<std::panic::AssertUnwindSafe<closure>,()>
                        at /checkout/src/libstd/panicking.rs:454
  13:     0x55952405826a - panic_unwind::__rust_maybe_catch_panic
                        at /checkout/src/libpanic_unwind/lib.rs:98
  14:     0x559521ee57ac - std::panicking::try<(),std::panic::AssertUnwindSafe<closure>>
                        at /checkout/src/libstd/panicking.rs:433
  15:     0x559521ee48c5 - std::panic::catch_unwind<std::panic::AssertUnwindSafe<closure>,()>
                        at /checkout/src/libstd/panic.rs:361
  16:     0x559521c6983b - std::thread::{{impl}}::spawn::{{closure}}<closure,()>
                        at /checkout/src/libstd/thread/mod.rs:363
  17:     0x559521c9f0f3 - alloc::boxed::{{impl}}::call_box<(),closure>
                        at /checkout/src/liballoc/boxed.rs:648
  18:     0x55952404fd65 - alloc::boxed::{{impl}}::call_once<(),()>
                        at /checkout/src/liballoc/boxed.rs:658
                         - std::sys_common::thread::start_thread
                        at /checkout/src/libstd/sys_common/thread.rs:21
                         - std::sys::imp::thread::{{impl}}::new::thread_start
                        at /checkout/src/libstd/sys/unix/thread.rs:84
  19:     0x7f53cb8e26a9 - start_thread
  20:     0x7f53cb40113c - __clone
  21:                0x0 - <unknown>
ERROR:servo: assertion failed: `(left == right)` (left: `50`, right: `100`)
@asajeffrey asajeffrey self-assigned this Jun 12, 2017
@asajeffrey
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@asajeffrey asajeffrey commented Jun 12, 2017

IRC conversation with @bzbarsky: http://logs.glob.uno/?c=mozilla%23servo&s=12+Jun+2017&e=12+Jun+2017#c695098

TL;DR we should clear the WR image id when we resize a canvas.
@asajeffrey asajeffrey mentioned this issue Jun 12, 2017
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bors-servo added a commit that referenced this issue Jun 13, 2017
@bors-servo
Auto merge of #17278 - asajeffrey:canvas-clear-webrender-image-key-wh…
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8c2a7d6 
…en-resizing, r=emilio

Clear webrender image id when resizing a canvas.

<!-- Please describe your changes on the following line: -->

Webrender isn't very happy if images change size, so clear the webrender image key when resizing a canvas.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #17277
- [X] There are tests for these changes

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Clear webrender image id when resizing a canvas.
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