当为单个元素应用 Flex::SpaceBetween 时, Constraint::Length 不能正常工作

Description

When creating a Layout for an area with a hard length comprising of a single item and applying flex::spacebetween does not properly render the item with fixed length, instead it expands the item to fill the remaining space. Example: let [item] = Layout::horizontal([Constraint::Length(50)]) .flex(Flex::SpaceBetween) .areas(area); =================== Expected behavior ==================== <------------------------------------80 px-------------------------------------> ┌──────50 px───────┐ │ Length(50) │ └──────────────── ┘ ======================Actual behavior ========================= <------------------------------------80 px-------------------------------------> ┌────────────────80 px──────────────────────────┐ │ Length(50) │ └───────────────────────────────────────────── ┘

To Reproduce

Minimal code repo : https://GitHub.com/kb019/ratatui_flex_between

Expected behavior

=================== Expected behavior ==================== <------------------------------------80 px-------------------------------------> ┌──────50 px───────┐ │ Length(50) │ └──────────────── ┘

Screenshots

## Are you willing to contribute a fix?

Yes i am willing to contribute to the fix

• I am willing to open a PR for this bug.
• I can try to investigate, but I will need guidance.
• I am not able to work on a fix right now.

Environment

• OS: Windows
• Terminal Emulator: VS Code Integrated Terminal
• Font:
• Crate version: 0.30.2
• Backend: crossterm

Additional context

Test Case expected to pass

#[test]
fn space_between_single_length_preserves_constraint() {
    let area = Rect::new(0, 0, 80, 1);

    let [item] = Layout::horizontal([Constraint::Length(50)])
        .flex(Flex::SpaceBetween)
        .areas(area);

    assert_eq!(item,
…