par-term 0.49.0

//! macOS-specific NSWindow configuration for translucency.
//!
//! The CAMetalLayer itself is owned by wgpu: every `Surface::configure`
//! rewrites its opacity, display sync, and colorspace from the
//! `SurfaceConfiguration`, so layer properties are set through the renderer
//! (`par_term_render::cell_renderer::surface`), never from here.

use anyhow::Result;

/// Sync the NSWindow background color with the per-pixel translucency setting.
///
/// macOS 27 paints the titlebar from the NSWindow background color when the
/// window is non-opaque. winit's `with_transparent(true)` (required for the
/// runtime opacity feature) sets that color to clear, which turned the
/// titlebar see-through. Setting a real background color restores the standard
/// titlebar, but `NSWindow.backgroundColor` is one alpha floor for the whole
/// window backing store — an opaque floor also greys out the CAMetalLayer's
/// translucent content (measured 2026-09-20, reverted c0f06688). So while
/// translucency is in effect the background stays clear and an opaque backing
/// bar (a borderless filled NSBox in the frame view, pinned under the
/// titlebar) paints the titlebar instead. The CAMetalLayer's per-pixel alpha
/// composites over the clear floor everywhere else, keeping the desktop
/// visible through the content area.
pub fn set_window_background_for_translucency(
    window: &winit::window::Window,
    translucent: bool,
) -> Result<()> {
    #[cfg(target_os = "macos")]
    {
        use objc2::rc::Retained;
        use objc2_app_kit::{NSColor, NSView, NSWindow};
        use raw_window_handle::{HasWindowHandle, RawWindowHandle};

        let window_handle = window.window_handle()?;
        let ns_view_ptr = match window_handle.as_raw() {
            RawWindowHandle::AppKit(handle) => handle.ns_view.as_ptr(),
            _ => anyhow::bail!("Not a macOS AppKit window"),
        };

        if ns_view_ptr.is_null() {
            anyhow::bail!("NSView pointer is null");
        }

        // SAFETY: ns_view_ptr is a non-null NSView pointer obtained from winit's AppKit
        // window handle. winit guarantees it is valid for the lifetime of the window.
        // We are on the main thread (required by AppKit/winit), so the Objective-C
        // message send is safe. The `window` selector is not in the alloc/new/init
        // method family, so the optional retained return is fine; everything after
        // the extraction uses the safe generated objc2-app-kit API.
        unsafe {
            let ns_view = ns_view_ptr as *mut NSView;
            let ns_window: Option<Retained<NSWindow>> = objc2::msg_send![ns_view, window];
            let Some(ns_window) = ns_window else {
                anyhow::bail!("NSView is not installed in an NSWindow");
            };

            let color = if translucent {
                NSColor::clearColor()
            } else {
                NSColor::windowBackgroundColor()
            };
            ns_window.setBackgroundColor(Some(&color));

            if translucent {
                ensure_titlebar_backing_bar(&ns_window)?;
            } else {
                remove_titlebar_backing_bar(&ns_window);
            }

            log::debug!(
                "NSWindow background set to {} (translucent: {}); titlebar bar {}",
                if translucent {
                    "clear"
                } else {
                    "windowBackgroundColor"
                },
                translucent,
                if translucent { "installed" } else { "removed" }
            );
        }
    }

    #[cfg(not(target_os = "macos"))]
    {
        let _ = (window, translucent);
    }

    Ok(())
}

/// Identifier on the titlebar backing bar so repeated config changes can find
/// the existing bar instead of stacking duplicates. `setTag:` is not an option:
/// on modern macOS NSBox no longer inherits NSControl and does not respond to
/// it (measured: NSInvalidArgumentException at window creation), while
/// `setIdentifier:` is available on every NSView.
#[cfg(target_os = "macos")]
const TITLEBAR_BACKING_BAR_ID: &str = "par-term-titlebar-backing-bar";

/// Find the titlebar backing bar previously added to the window's frame view,
/// by identifier. NSView has no `viewWithIdentifier:`, so scan the subviews.
#[cfg(target_os = "macos")]
fn find_titlebar_backing_bar(
    frame_view: &objc2_app_kit::NSView,
) -> Option<objc2::rc::Retained<objc2_app_kit::NSView>> {
    use objc2::rc::Retained;
    use objc2::runtime::AnyObject;
    use objc2_app_kit::NSView;
    use objc2_foundation::NSString;

    // SAFETY: subviews/identifier are standard AppKit/Foundation messages on
    // live objects owned by the frame view, which the caller keeps alive.
    // objectAtIndex: returns a borrowed reference, so the match is retained
    // before being returned.
    //
    // The comparison is done on a Rust copy, never via isEqualToString: —
    // on macOS 26+ some system subviews carry Swift-backed identifiers
    // (Swift.__StringStorage) whose isEqualToString: registers a legacy 'c'
    // return encoding, and objc4's checked msg_send (debug builds) aborts on
    // objc2's bool/'B' declaration (measured: startup abort 2026-09-22).
    unsafe {
        let subs: Retained<AnyObject> = objc2::msg_send![frame_view, subviews];
        let count: usize = objc2::msg_send![&*subs, count];
        for i in 0..count {
            let sub: *mut AnyObject = objc2::msg_send![&*subs, objectAtIndex: i];
            let ident: *mut AnyObject = objc2::msg_send![sub, identifier];
            if ident.is_null() {
                continue;
            }
            if (&*(ident as *const NSString)).to_string() == TITLEBAR_BACKING_BAR_ID {
                return Retained::retain(sub as *mut NSView);
            }
        }
    }
    None
}

/// The titlebar strip's rect in the frame view's bottom-left coordinates.
///
/// `contentLayoutRect` (window coords, same bottom-left origin) covers the
/// content area ONLY — for a titled window its `origin.y` is 0 and its height
/// is the frame height minus the titlebar. So the strip is derived from the
/// layout's HEIGHT (frame height minus it, pinned at its top), never from its
/// `origin.y`: the first backing-bar port computed `frame.height -
/// layout.origin.y` and `origin.y = layout.origin.y`, which with `origin.y ==
/// 0` drew a bar covering the ENTIRE window and greyed out all content
/// (measured in the isolated AppKit harness /tmp/titlebar-test3, 2026-09-20:
/// shipped formula bar y=0 h=203 vs corrected y=171 h=32 on a 203px frame).
/// Returns None when there is no strip (fullscreen / borderless).
#[cfg(target_os = "macos")]
fn titlebar_strip(
    layout_rect: &objc2_foundation::NSRect,
    frame_bounds: &objc2_foundation::NSRect,
) -> Option<objc2_foundation::NSRect> {
    use objc2_foundation::{NSPoint, NSSize};

    let height = frame_bounds.size.height - layout_rect.size.height;
    if height <= 1.0 {
        return None;
    }
    Some(objc2_foundation::NSRect {
        origin: NSPoint {
            x: 0.0,
            y: layout_rect.size.height,
        },
        size: NSSize {
            width: frame_bounds.size.width,
            height,
        },
    })
}

/// Install or re-show the opaque titlebar backing bar.
///
/// The bar is a borderless, flat-filled NSBox added to the window's frame
/// view (the content view's superview), covering exactly the titlebar strip.
/// On macOS 27 the titlebar's own paint comes from the clear window
/// background, so this bar is what the user sees behind the traffic lights
/// and title text (subviews of the titlebar container; the bar is inserted
/// BELOW that container, never stacked on top of it).
/// A plain NSView without a mouseDown override answers
/// `mouseDownCanMoveWindow` YES, so dragging/double-clicking the titlebar
/// keeps working through it.
#[cfg(target_os = "macos")]
fn ensure_titlebar_backing_bar(ns_window: &objc2_app_kit::NSWindow) -> Result<()> {
    use objc2::MainThreadMarker;
    use objc2_app_kit::{
        NSAutoresizingMaskOptions, NSBox, NSBoxType, NSTitlePosition, NSWindowOrderingMode,
    };
    use objc2_foundation::NSString;

    let Some(frame_view) = ns_window
        .contentView()
        .and_then(|cv| unsafe { cv.superview() })
    else {
        anyhow::bail!("window has no frame view (not a titled window?)");
    };

    if let Some(bar) = find_titlebar_backing_bar(&frame_view) {
        // Re-derive the strip from current geometry so the bar self-corrects
        // after fullscreen exits or a titlebar-thickness change, then refresh
        // the fill so light/dark appearance switches are picked up.
        match titlebar_strip(&ns_window.contentLayoutRect(), &frame_view.bounds()) {
            Some(strip) => {
                bar.setFrame(strip);
                bar.setHidden(false);
                if let Some(b) = bar.downcast_ref::<NSBox>() {
                    b.setFillColor(&objc2_app_kit::NSColor::windowBackgroundColor());
                }
            }
            // Fullscreen / borderless: no strip to back. The Resized-driven
            // sync re-shows it with a fresh frame once a strip exists again.
            None => bar.setHidden(true),
        }
        return Ok(());
    }

    let bar_frame = titlebar_strip(&ns_window.contentLayoutRect(), &frame_view.bounds())
        .ok_or_else(|| anyhow::anyhow!("window has no titlebar strip to back"))?;

    let mtm = MainThreadMarker::new()
        .ok_or_else(|| anyhow::anyhow!("AppKit calls require the main thread"))?;
    let bar = NSBox::initWithFrame(mtm.alloc(), bar_frame);
    // SAFETY: setIdentifier: is a plain NSView/protocol setter on a live
    // NSBox we just created; the argument is an NSString we own.
    unsafe {
        let ident = NSString::from_str(TITLEBAR_BACKING_BAR_ID);
        let _: () = objc2::msg_send![&*bar, setIdentifier: &*ident];
    }
    bar.setBoxType(NSBoxType::Custom);
    bar.setBorderWidth(0.0);
    bar.setTitlePosition(NSTitlePosition::NoTitle);
    bar.setFillColor(&objc2_app_kit::NSColor::windowBackgroundColor());
    // Follow the frame view's width, stay pinned to its top edge.
    bar.setAutoresizingMask(
        NSAutoresizingMaskOptions::ViewWidthSizable | NSAutoresizingMaskOptions::ViewMinYMargin,
    );
    // Insert ABOVE the content view but BELOW the titlebar container (the
    // sibling holding the traffic lights and title text). A plain
    // `addSubview:` stacks the bar on top of the whole frame view and covers
    // them (user-observed 2026-09-21: buttons and title vanish below 100%
    // opacity); anchoring to the content view backs the strip against
    // translucent content while every system titlebar subview stays above.
    frame_view.addSubview_positioned_relativeTo(
        &bar,
        NSWindowOrderingMode::Above,
        ns_window.contentView().as_deref(),
    );

    // Read back the z-position: this bug class (bar geometry/order) has twice
    // only been caught by introspecting the live hierarchy.
    // SAFETY: subviews/count/indexOfObject: are standard AppKit/Foundation
    // messages on live objects owned by the frame view.
    let (z_index, subview_count) = unsafe {
        let subs: objc2::rc::Retained<objc2::runtime::AnyObject> =
            objc2::msg_send![&frame_view, subviews];
        let count: usize = objc2::msg_send![&*subs, count];
        let idx: usize = objc2::msg_send![&*subs, indexOfObject: &*bar];
        (idx, count)
    };
    log::debug!(
        "Installed opaque titlebar backing bar ({TITLEBAR_BACKING_BAR_ID}) \
         at z-index {z_index} of {subview_count} frame-view subviews"
    );
    Ok(())
}

/// Drop the titlebar backing bar (translucency no longer active; the window
/// background color itself paints an opaque titlebar again).
#[cfg(target_os = "macos")]
fn remove_titlebar_backing_bar(ns_window: &objc2_app_kit::NSWindow) {
    if let Some(frame_view) = ns_window
        .contentView()
        .and_then(|cv| unsafe { cv.superview() })
        && let Some(bar) = find_titlebar_backing_bar(&frame_view)
    {
        bar.removeFromSuperview();
        log::debug!("Removed titlebar backing bar");
    }
}

/// Hide the titlebar backing bar while the window is fullscreen (there is no
/// titlebar there, and a top-pinned bar would paint a strip over content).
/// Call from the Resized event so every transition path — keyboard, menu, the
/// green traffic-light button — is covered without hooking each one.
#[allow(unused_variables)]
pub fn sync_titlebar_backing_bar_visibility(window: &winit::window::Window) -> Result<()> {
    #[cfg(target_os = "macos")]
    {
        use objc2::rc::Retained;
        use objc2_app_kit::{NSView, NSWindow, NSWindowStyleMask};
        use raw_window_handle::{HasWindowHandle, RawWindowHandle};

        let window_handle = window.window_handle()?;
        let ns_view_ptr = match window_handle.as_raw() {
            RawWindowHandle::AppKit(handle) => handle.ns_view.as_ptr(),
            _ => anyhow::bail!("Not a macOS AppKit window"),
        };
        if ns_view_ptr.is_null() {
            anyhow::bail!("NSView pointer is null");
        }

        // SAFETY: Same extraction pattern as set_window_background_for_translucency;
        // the rest is the safe generated objc2-app-kit API.
        unsafe {
            let ns_view = ns_view_ptr as *mut NSView;
            let ns_window: Option<Retained<NSWindow>> = objc2::msg_send![ns_view, window];
            let Some(ns_window) = ns_window else {
                anyhow::bail!("NSView is not installed in an NSWindow");
            };

            let fullscreen = ns_window
                .styleMask()
                .contains(NSWindowStyleMask::FullScreen);
            if let Some(frame_view) = ns_window.contentView().and_then(|cv| cv.superview()) {
                if fullscreen {
                    if let Some(bar) = find_titlebar_backing_bar(&frame_view) {
                        bar.setHidden(true);
                    }
                } else if find_titlebar_backing_bar(&frame_view).is_some() {
                    // Re-derive the strip as well as showing it: a fullscreen
                    // transition can leave the bar with a stale frame. Only
                    // an EXISTING bar is refreshed — this runs on every
                    // Resized, and creating one here would reinstall the bar
                    // at 100% opacity, where the config path removes it.
                    // (If AppKit moved the content view to a fresh frame
                    // view and orphaned the old bar, the next translucency
                    // config change reinstalls a correctly-framed one.)
                    ensure_titlebar_backing_bar(&ns_window)?;
                }
            }
        }
    }

    #[cfg(not(target_os = "macos"))]
    {
        let _ = window;
    }

    Ok(())
}