renderer does not render paragraphs crated during draw calls because it drops them first

[janWilejan]

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?

creating a custom text widget to render a paragraph of text using renderer.fill_paragraph. the text does not appear.

it seems that the problem is that you're immediately dropping the paragraph of text before queueuing it to be rendered (at line 44 of tiny_skia/src/layer.rs). it seems this is a mistake? surely you would rather drop the text after it has been rendered?

a similar mistake was made on line 63 in Layer::draw_editor.

the relevant part of this SSCCE is the draw() method. the rest is boilerplate.

use iced::advanced::layout::Node;
use iced::advanced::renderer::{self};
use iced::advanced::text::Paragraph as _;
use iced::advanced::text::{self};
use iced::advanced::Widget;
use iced::widget::center;
use iced::{Color, Element, Font, Length, Size};

struct State {
    text: String,
}

impl Default for State {
    fn default() -> Self {
        State {
            text: "Hello, world!".into(),
        }
    }
}

#[derive(Debug)]
enum Message {}

pub fn main() -> iced::Result {
    iced::run("Custom text widget", update, view)
}
fn update(_state: &mut State, _message: Message) {}

fn view(state: &State) -> Element<Message> {
    center(CustomTextWidget::new(&state.text)).into()
}

#[derive(Default)]
pub struct CustomTextWidget<'a> {
    text: &'a str,
}

impl<'a> CustomTextWidget<'a> {
    pub fn new(text: &'a str) -> Self {
        Self { text }
    }
}

impl<'a, Message, Theme, Renderer> Widget<Message, Theme, Renderer> for CustomTextWidget<'a>
where
    Renderer: iced::advanced::Renderer
        + text::Renderer<Paragraph = iced::advanced::graphics::text::Paragraph>,
{
    fn size(&self) -> iced::Size<iced::Length> {
        Size::new(Length::Fill, Length::Fill)
    }

    fn layout(
        &self,
        _tree: &mut iced::advanced::widget::Tree,
        _renderer: &Renderer,
        limits: &iced::advanced::layout::Limits,
    ) -> iced::advanced::layout::Node {
        Node::new(limits.max())
    }

    fn draw(
        &self,
        _tree: &iced::advanced::widget::Tree,
        renderer: &mut Renderer,
        _theme: &Theme,
        _style: &iced::advanced::renderer::Style,
        layout: iced::advanced::Layout<'_>,
        _cursor: iced::advanced::mouse::Cursor,
        _viewport: &iced::Rectangle,
    ) {
        let text = text::Text {
            content: &*self.text,
            bounds: layout.bounds().size(),
            size: iced::Pixels(20.0),
            line_height: text::LineHeight::Relative(1.0),
            font: Font::DEFAULT,
            horizontal_alignment: iced::alignment::Horizontal::Center,
            vertical_alignment: iced::alignment::Vertical::Center,
            shaping: text::Shaping::Advanced,
            wrapping: text::Wrapping::Word,
        };
        let paragraph = Renderer::Paragraph::with_text(text);
        // Uncomment me!
        //std::mem::forget(paragraph.clone());
        renderer.fill_paragraph(
            &paragraph,
            layout.bounds().center(),
            Color::BLACK,
            layout.bounds(),
        );
    }
}

impl<'a, Message, Theme, Renderer> From<CustomTextWidget<'a>>
    for Element<'a, Message, Theme, Renderer>
where
    Renderer: renderer::Renderer
        + iced::advanced::text::Renderer<Paragraph = iced::advanced::graphics::text::Paragraph>,
{
    fn from(value: CustomTextWidget<'a>) -> Self {
        Self::new(value)
    }
}

What is the expected behavior?

Text should appear.

Uncommenting the code that says "Uncomment me!" shows the text properly, by preventing the paragraph from being dropped, by causing a memory leak. This is not ideal.

Version

crates.io release

Operating System

Windows

Do you have any log output?

this error appears unrelated. (issue #2625)

Job 1, 'cargo run' terminated by signal SIGSEGV (Address boundary error)