kui-native 0.1.0-alpha.45

//! The keep-out rect under macOS custom chrome — where the traffic lights
//! are and how tall the OS's own titlebar is — asked of the window rather
//! than assumed.
//!
//! The numbers move with the OS: macOS 26 drew 12 pt buttons in a 28 pt
//! titlebar, macOS 27 draws 14 pt buttons at (9, 9) in a 32 pt one, and a
//! constant measured on one release is what the strip's height was wrong
//! by on the next. AppKit has no public "titlebar height" either, but a
//! window with a full-size content view answers both halves anyway: the
//! `contentLayoutRect` is the part of the frame *under* the titlebar, so
//! the frame's height less its height is the titlebar; and the standard
//! window buttons are views with frames.

use objc2::rc::Retained;
use objc2_app_kit::{NSView, NSWindowButton};
use winit::window::Window;

use crate::Rect;

/// What the runner reported before it measured: gpui's
/// `TRAFFIC_LIGHT_PADDING` under the macOS 26 SDK (78) over the 28 pt
/// titlebar macOS 26 drew. Only the answer when the window has no AppKit
/// view to ask, or its buttons are not there to measure.
const ASSUMED: Rect = Rect {
    x: 0.0,
    y: 0.0,
    w: 78.0,
    h: 28.0,
};

/// The rect `env.window.native_controls` reports for `window`: from the
/// window's origin, as wide as the traffic lights plus the same gap after
/// them that AppKit leaves before them, and as tall as the OS's titlebar.
pub fn native_controls(window: &Window) -> Rect {
    measure(window).unwrap_or(ASSUMED)
}

fn measure(window: &Window) -> Option<Rect> {
    use winit::raw_window_handle::{HasWindowHandle, RawWindowHandle};
    let RawWindowHandle::AppKit(h) = window.window_handle().ok()?.as_raw() else {
        return None;
    };
    // SAFETY: a live winit content view, on the event loop's thread.
    let view = unsafe { Retained::retain(h.ns_view.as_ptr().cast::<NSView>()) }?;
    let ns_window = view.window()?;
    let frame = ns_window.frame();
    // Under a full-size content view the layout rect is what the titlebar
    // leaves; without one the two are the same height and there is no
    // titlebar over the content to keep out of.
    let titlebar = frame.size.height - ns_window.contentLayoutRect().size.height;
    if titlebar <= 0.0 {
        return None;
    }
    // Both buttons in window coordinates: the leading gap is the close
    // button's x, and the same gap follows the zoom button.
    let in_window = |b: NSWindowButton| {
        let button = ns_window.standardWindowButton(b)?;
        // SAFETY: the button's superview is AppKit's titlebar container,
        // retained for as long as the window; read on the main thread.
        let superview = unsafe { button.superview() }?;
        Some(superview.convertRect_toView(button.frame(), None))
    };
    let close = in_window(NSWindowButton::CloseButton)?;
    let zoom = in_window(NSWindowButton::ZoomButton)?;
    let leading = close.origin.x;
    let trailing = zoom.origin.x + zoom.size.width;
    if leading < 0.0 || trailing <= leading {
        return None;
    }
    Some(Rect::new(
        0.0,
        0.0,
        (trailing + leading) as f32,
        titlebar as f32,
    ))
}