DivideByZero in process_rectangle

[yanshay]

Bug Description

Upgraded an application (ESP32S3) from 1.11.0 .
I use take_screenshot to take screenshot of the display.
With 1.11.0 it work.
Tried 1.13.1 and the latest 1.15.0 as of today and it panic:

====================== PANIC ======================
panicked at /Users/yanshay/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/esp-hal-1.0.0/src/exception_handler/mod.rs:10:5:


Exception occurred on ProCpu 'DivideByZero'
Context { PC: 1112300407, PS: 396848, A0: 2186038766, A1: 1070424944, A2: 0, A3: 1070425464, A4: 1070425436, A5: 2, A6: 383, A7: 65505, A8: 383, A9: 0, A10: 0, A11: 0, A12: 1070429104, A13: 37995, A14: 3276800, A15: 0, SAR: 5, EXCCAUSE: 6, EXCVADDR: 0, LBEG: 1074088944, LEND: 1074088975, LCOUNT: 0, THREADPTR: 0, SCOMPARE1: 1, BR: 0, ACCLO: 0, ACCHI: 0, M0: 0, M1: 0, M2: 0, M3: 0, F64R_LO_CPENABLE: 0, F64R_HI: 0, F64S: 0, FCR: 0, FSR: 1152, F0: 959653562, F1: 1007416904, F2: 868697836, F3: 2991880408, F4: 3225944073, F5: 937178491, F6: 245618435, F7: 261996544, F8: 1136623616, F9: 3338666240, F10: 1112014848, F11: 1191182336, F12: 1127481344, F13: 1136630170, F14: 0, F15: 1112014848 }


Backtrace:

0x42461a6e
core::panicking::panic_fmt
    at /Users/yanshay/.rustup/toolchains/esp1/lib/rustlib/src/rust/library/core/src/panicking.rs:75
0x40378f47
__user_exception
    at /Users/yanshay/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/esp-hal-1.0.0/src/exception_handler/mod.rs:10
0x4037a702
__default_exception
    at /Users/yanshay/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/xtensa-lx-rt-0.21.0/src/exception/context.rs:135
0x403789a8
0x40040000
0x424c5b74
euclid::rect::Rect<T,U>::min_y
    at /Users/yanshay/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/euclid-0.22.11/src/rect.rs:173
0x424c8fe9
<i_slint_renderer_software::RenderToBuffer<B> as i_slint_renderer_software::ProcessScene>::process_rectangle
    at /Users/yanshay/.cargo/git/checkouts/slint-774a37e469fae6bf/854711d/internal/renderers/software/lib.rs:1744
0x424c8c5e
<i_slint_core::partial_renderer::PartialRenderer<T> as i_slint_core::item_rendering::ItemRenderer>::draw_rectangle::{{closure}}
    at /Users/yanshay/.cargo/git/checkouts/slint-774a37e469fae6bf/854711d/internal/core/partial_renderer.rs:628
0x424aae7c
<i_slint_core::items::Rectangle as i_slint_core::items::Item_vtable_mod::Item>::render
    at /Users/yanshay/.cargo/git/checkouts/slint-774a37e469fae6bf/854711d/internal/core/items.rs:380
0x424b9c01
i_slint_core::items::Item_vtable_mod::ItemTO::render
    at /Users/yanshay/.cargo/git/checkouts/slint-774a37e469fae6bf/854711d/internal/core/items.rs:121

It is pretty simple code, I'm just doing:

self.ui_weak.unwrap().window().take_snapshot()

Reproducible Code (if applicable)

Environment Details

• Slint Version: 1.13.1 and 1.15.0
• Platform/OS: ESP32 (develop on Mac)
• Programming Language: Rust
• Backend/Renderer: Software Renderer

Product Impact

No response

[ogoffart]

euclid::rect::Rect<T,U>::min_y
    at /Users/yanshay/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/euclid-0.22.11/src/rect.rs:173
<i_slint_renderer_software::RenderToBuffer<B> as i_slint_renderer_software::ProcessScene>::process_rectangle
    at /Users/yanshay/.cargo/git/checkouts/slint-774a37e469fae6bf/854711d/internal/renderers/software/lib.rs:1744

There is a division per zero, presumably within process_rectangle_impl. But Rect::min_y doesn't do any division. So it must be something else. Not sure what as this function is quite big.
Do you know what kind of rectangle it is drawing? Does it have a gradient or a border radius?

[ogoffart]

The only division in this function that i see is there

slint/internal/renderers/software/lib.rs

Line 1439 in aea3095

255. * h / (h + geom.height())

This could happen for a linear gradient with an angle of 0deg if the height was 0. But we check earlier with the intersects function so the height cannot be zero.
So I'm puzzle as to how to reproduce this.
Could you try a debug build that would have a more complete backtrace?
Would you have a minimal example that reproduces the problem?

[yanshay]

I have there some gradients, not 0deg but there are.
I will try to remove elements from that screen and see when it is working since I see on other screens it does work.
Debug builds don't work with ESP32 esp-hal - it works only in release afaik, or at least whatever doesn't work can be blamed on debug mode.

But another strange issue I see with that. My application scrolls screen up/down by animating y. It's working until I call the take_screenshot. After that, this animation mostly doesn't work at all, and sometimes hangs mid animation. Underneath from a logic perspective it does complete the animation because if I press a location where there is a button (though it doesn't appear there) the button takes effect and new screen displayed on the screen show correctly. It is just that the animation stops in the middle as if it doesn't require my backend to draw. At the same time I have another color animation of some text on the screen, and as long as it is inside the display scroll takes place. Once it goes out and only the y is left animated the drawing stops. Hope I explained this clear enough.

So does take_snapshot have any effect on y (maybe to take a steady screen while taking screenshot)?

[ogoffart]

To be honest, the take_snapshot function was implemented for the purpose of testing. I didn't know one would use it on a micro controller. What are you using this function for?
But there is no reason this shouldn't work.
It does change the RepaintBufferType though, but that might not be a problem.

What is the Window::size() before calling take_snapshot?

It's working until I call the take_screenshot. After that, this animation mostly doesn't work at all

It can't think of a reason why this is happening.

[yanshay]

It's very useful to take screenshot of the application screen and download them (I then convert to png).
Is there another way to do that?

My AppWindow is:

export component AppWindow inherits Window {
    width: 480px;
    height: 320px;

And the screenshot comes out right when it downloads.