Container widget background leaks out of enclosing Pin widget in case of negative offset

[KiraMichiru]

Is your issue REALLY a bug?

• My issue is indeed a bug!
• I am not crazy! I will not fill out this form just to ask a question or request a feature. Pinky promise.

Is there an existing issue for this?

• I have searched the existing issues.

Is this issue related to iced?

• My hardware is compatible and my graphics drivers are up-to-date.

What happened?

Hi,

I was trying to use the new Pin widget to clip the viewport of a contained Container widget with background, depending on the state of some other widget (which seemed easier than writing a new custom widget to do a translated rendering like in Scrollable).

To achieve that, I gave my Pin widget a negative position, and as a consequence, the background of the contained Container was rendered outside the Pin viewport (here is a minimum example of the behavior):

use iced::{Color, Element};
use iced::widget::{Pin, container, text};

pub fn main() -> iced::Result {
    iced::run(ContainerBug::update, ContainerBug::view)
}

#[derive(Default)]
struct ContainerBug{

}

#[derive(Debug, Clone, Copy)]
enum Message {
}

impl ContainerBug {
    fn update(&mut self, message: Message) {
    }

    fn view(&self) -> Element<'_, Message> {

        let text_element = text("Container");

        let inner_container = container(text_element)
        .width(100.0)
        .height(20.0)
        .style(|_| container::Style::default().background(Color::from_rgb(0.7, 0.7, 0.7)));
        
        let pinned_inner = Pin::new(inner_container).x(-50.0);
        
        let outer_container = container(pinned_inner)
        .padding(100.0)
        .width(300.0)
        .height(220.0)
        .style(|_| container::Style::default().background(Color::from_rgb(0.5, 0.5, 0.5)));

        outer_container.into()
    }
}

The output looks like this:

What is the expected behavior?

I would expect the output to not leak the inner container background to the left into the surrounding container. Instead, I would expect the inner container to be clipped, similar to when a positive offset is given (example with 50.0 instead of -50.0):

Version

master

Operating System

Linux

Do you have any log output?

[KiraMichiru]

I haven't worked with iced for a long time yet, but I naively see two ways to solve this:

1. My use of Pin is not how it was intended - and I am aware that the description says "A widget that positions its contents at some fixed coordinates inside of its boundaries". However, as the functionality might be useful nevertheless, it could

• be extended to work with negative offsets or
• the docs could specifically warn from using negative offsets or
• the code could panic! if a negative offset was used.

2. The rendering of Container does not handle this case correctly. If I change
   

   iced/widget/src/container.rs

   Line 352 in 54b5c52

   draw_background(renderer, &style, bounds);

   to
   draw_background(renderer, &style, clipped_viewport);
   my example works as expected - but I'm pretty sure there is a good reason why this line is written like it is.

Any enlightenment would be appreciated :)