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// Take a look at the license at the top of the repository in the LICENSE file.

use std::{cell::RefCell, ptr};

use glib::translate::*;

use crate::{prelude::*, DrawingArea};

mod sealed {
    pub trait Sealed {}
    impl<T: super::IsA<super::DrawingArea>> Sealed for T {}
}

// rustdoc-stripper-ignore-next
/// Trait containing manually implemented methods of
/// [`DrawingArea`](crate::DrawingArea).
pub trait DrawingAreaExtManual: sealed::Sealed + IsA<DrawingArea> + 'static {
    #[doc(alias = "gtk_drawing_area_set_draw_func")]
    #[doc(alias = "set_draw_func")]
    fn unset_draw_func(&self) {
        unsafe {
            ffi::gtk_drawing_area_set_draw_func(
                self.as_ref().to_glib_none().0,
                None,
                ptr::null_mut(),
                None,
            )
        }
    }

    /// Setting a draw function is the main thing you want to do when using
    /// a drawing area.
    ///
    /// The draw function is called whenever GTK needs to draw the contents
    /// of the drawing area to the screen.
    ///
    /// The draw function will be called during the drawing stage of GTK.
    /// In the drawing stage it is not allowed to change properties of any
    /// GTK widgets or call any functions that would cause any properties
    /// to be changed. You should restrict yourself exclusively to drawing
    /// your contents in the draw function.
    ///
    /// If what you are drawing does change, call [`WidgetExt::queue_draw()`][crate::prelude::WidgetExt::queue_draw()]
    /// on the drawing area. This will cause a redraw and will call @draw_func again.
    /// ## `draw_func`
    /// callback that lets you draw
    ///   the drawing area's contents
    #[doc(alias = "gtk_drawing_area_set_draw_func")]
    fn set_draw_func<P: FnMut(&DrawingArea, &cairo::Context, i32, i32) + 'static>(
        &self,
        draw_func: P,
    ) {
        unsafe extern "C" fn draw_func_func<
            P: FnMut(&DrawingArea, &cairo::Context, i32, i32) + 'static,
        >(
            drawing_area: *mut ffi::GtkDrawingArea,
            cr: *mut cairo::ffi::cairo_t,
            width: libc::c_int,
            height: libc::c_int,
            user_data: glib::ffi::gpointer,
        ) {
            let drawing_area = from_glib_borrow(drawing_area);
            let cr = from_glib_borrow(cr);
            let callback: &RefCell<P> = &*(user_data as *mut _);
            (callback.borrow_mut())(&drawing_area, &cr, width, height);
        }

        unsafe extern "C" fn destroy_func<
            P: FnMut(&DrawingArea, &cairo::Context, i32, i32) + 'static,
        >(
            data: glib::ffi::gpointer,
        ) {
            let _callback: Box<RefCell<P>> = Box::from_raw(data as *mut _);
        }

        let callback: Box<RefCell<P>> = Box::new(RefCell::new(draw_func));
        unsafe {
            ffi::gtk_drawing_area_set_draw_func(
                self.as_ref().to_glib_none().0,
                Some(draw_func_func::<P> as _),
                Box::into_raw(callback) as *mut _,
                Some(destroy_func::<P> as _),
            );
        }
    }
}
impl<O: IsA<DrawingArea>> DrawingAreaExtManual for O {}