// Copyright © SixtyFPS GmbH <info@slint-ui.com>
// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-commercial

use std::cell::RefCell;
use std::pin::Pin;
use std::rc::Rc;

use euclid::approxeq::ApproxEq;
use i_slint_core::graphics::rendering_metrics_collector::RenderingMetrics;
use i_slint_core::graphics::{Image, IntRect, Point, Rect, Size};
use i_slint_core::item_rendering::{ItemCache, ItemRenderer};
use i_slint_core::items::{
    self, Clip, FillRule, ImageFit, ImageRendering, InputType, Item, ItemRc, Layer, Opacity,
    RenderingResult,
};
use i_slint_core::window::WindowRc;
use i_slint_core::{Brush, Color, ImageInner, Property, SharedString};

use crate::event_loop::WinitWindow;
use crate::fonts;
use crate::glwindow::{GLWindow, PASSWORD_CHARACTER};
use crate::images::{CachedImage, Texture, TextureCacheKey};

pub type Canvas = femtovg::Canvas<femtovg::renderer::OpenGl>;
pub type CanvasRc = Rc<RefCell<Canvas>>;

#[derive(Clone)]
pub enum ItemGraphicsCacheEntry {
    Texture(Rc<Texture>),
    ColorizedImage {
        // This original image Rc is kept here to keep the image in the shared image cache, so that
        // changes to the colorization brush will not require re-uploading the image.
        _original_image: Rc<Texture>,
        colorized_image: Rc<Texture>,
    },
}

impl ItemGraphicsCacheEntry {
    fn as_texture(&self) -> &Rc<Texture> {
        match self {
            ItemGraphicsCacheEntry::Texture(image) => image,
            ItemGraphicsCacheEntry::ColorizedImage { colorized_image, .. } => colorized_image,
        }
    }
    fn is_colorized_image(&self) -> bool {
        matches!(self, ItemGraphicsCacheEntry::ColorizedImage { .. })
    }
}

pub type ItemGraphicsCache = ItemCache<Option<ItemGraphicsCacheEntry>>;

const KAPPA90: f32 = 0.55228;

#[derive(Clone)]
struct State {
    scissor: Rect,
    global_alpha: f32,
    current_render_target: femtovg::RenderTarget,
}

pub struct GLItemRenderer {
    pub canvas: CanvasRc,
    // Layers that were scheduled for rendering where we can't delete the femtovg::ImageId yet
    // because that can only happen after calling `flush`. Otherwise femtovg ends up processing
    // `set_render_target` commands with image ids that have been deleted.
    layer_images_to_delete_after_flush: Vec<Rc<crate::images::Texture>>,
    pub graphics_window: Rc<GLWindow>,
    scale_factor: f32,
    /// track the state manually since femtovg don't have accessor for its state
    state: Vec<State>,
    metrics: RenderingMetrics,
}

fn rect_with_radius_to_path(rect: Rect, border_radius: f32) -> femtovg::Path {
    let mut path = femtovg::Path::new();
    let x = rect.origin.x;
    let y = rect.origin.y;
    let width = rect.size.width;
    let height = rect.size.height;
    // If we're drawing a circle, use directly connected bezier curves instead of
    // ones with intermediate LineTo verbs, as `rounded_rect` creates, to avoid
    // rendering artifacts due to those edges.
    if width.approx_eq(&height) && (border_radius * 2.).approx_eq(&width) {
        path.circle(x + border_radius, y + border_radius, border_radius);
    } else {
        path.rounded_rect(x, y, width, height, border_radius);
    }
    path
}

fn rect_to_path(r: Rect) -> femtovg::Path {
    rect_with_radius_to_path(r, 0.)
}

fn adjust_rect_and_border_for_inner_drawing(rect: &mut Rect, border_width: &mut f32) {
    // If the border width exceeds the width, just fill the rectangle.
    *border_width = border_width.min((rect.size.width as f32) / 2.);
    // adjust the size so that the border is drawn within the geometry
    rect.origin.x += *border_width / 2.;
    rect.origin.y += *border_width / 2.;
    rect.size.width -= *border_width;
    rect.size.height -= *border_width;
}

fn item_rect<Item: items::Item>(item: Pin<&Item>, scale_factor: f32) -> Rect {
    let geometry = item.geometry();
    euclid::rect(0., 0., geometry.width() * scale_factor, geometry.height() * scale_factor)
}

fn path_bounding_box(canvas: &CanvasRc, path: &mut femtovg::Path) -> euclid::default::Box2D<f32> {
    // `canvas.path_bbox()` applies the current transform. However we're not interested in that, since
    // we operate in item local coordinates with the `path` parameter as well as the resulting
    // paint.
    let mut canvas = canvas.borrow_mut();
    canvas.save();
    canvas.reset_transform();
    let bounding_box = canvas.path_bbox(path);
    canvas.restore();
    euclid::default::Box2D::new(
        [bounding_box.minx, bounding_box.miny].into(),
        [bounding_box.maxx, bounding_box.maxy].into(),
    )
}

// Return a femtovg::Path (in physical pixels) that represents the clip_rect, radius and border_width (all logical!)
fn clip_path_for_rect_alike_item(
    mut clip_rect: Rect,
    mut radius: f32,
    mut border_width: f32,
    scale_factor: f32,
) -> femtovg::Path {
    // Femtovg renders evenly 50% inside and 50% outside of the border width. The
    // adjust_rect_and_border_for_inner_drawing adjusts the rect so that for drawing it
    // would be entirely an *inner* border. However for clipping we want the rect that's
    // entirely inside, hence the doubling of the width and consequently radius adjustment.
    radius -= border_width * KAPPA90;
    border_width *= 2.;

    // Convert from logical to physical pixels
    border_width *= scale_factor;
    radius *= scale_factor;
    clip_rect *= scale_factor;

    adjust_rect_and_border_for_inner_drawing(&mut clip_rect, &mut border_width);

    rect_with_radius_to_path(clip_rect, radius)
}

impl ItemRenderer for GLItemRenderer {
    fn draw_rectangle(&mut self, rect: Pin<&items::Rectangle>, _: &ItemRc) {
        let geometry = item_rect(rect, self.scale_factor);
        if geometry.is_empty() {
            return;
        }
        // TODO: cache path in item to avoid re-tesselation
        let mut path = rect_to_path(geometry);
        let paint = match self.brush_to_paint(rect.background(), &mut path) {
            Some(paint) => paint,
            None => return,
        }
        // Since we're filling a straight rectangle with either color or gradient, save
        // the extra stroke triangle strip around the edges
        .with_anti_alias(false);
        self.canvas.borrow_mut().fill_path(&mut path, paint)
    }

    fn draw_border_rectangle(&mut self, rect: Pin<&items::BorderRectangle>, _: &ItemRc) {
        let mut geometry = item_rect(rect, self.scale_factor);
        if geometry.is_empty() {
            return;
        }

        let mut border_width = rect.border_width() * self.scale_factor;
        // In CSS the border is entirely towards the inside of the boundary
        // geometry, while in femtovg the line with for a stroke is 50% in-
        // and 50% outwards. We choose the CSS model, so the inner rectangle
        // is adjusted accordingly.
        adjust_rect_and_border_for_inner_drawing(&mut geometry, &mut border_width);

        let mut path = rect_with_radius_to_path(geometry, rect.border_radius() * self.scale_factor);

        let fill_paint = self.brush_to_paint(rect.background(), &mut path);

        let border_paint = self.brush_to_paint(rect.border_color(), &mut path).map(|mut paint| {
            paint.set_line_width(border_width);
            paint
        });

        let mut canvas = self.canvas.borrow_mut();
        if let Some(paint) = fill_paint {
            canvas.fill_path(&mut path, paint);
        }
        if let Some(border_paint) = border_paint {
            canvas.stroke_path(&mut path, border_paint);
        }
    }

    fn draw_image(&mut self, image: Pin<&items::ImageItem>, item_rc: &ItemRc) {
        self.draw_image_impl(
            item_rc,
            items::ImageItem::FIELD_OFFSETS.source.apply_pin(image),
            IntRect::default(),
            items::ImageItem::FIELD_OFFSETS.width.apply_pin(image),
            items::ImageItem::FIELD_OFFSETS.height.apply_pin(image),
            image.image_fit(),
            None,
            image.image_rendering(),
        );
    }

    fn draw_clipped_image(&mut self, clipped_image: Pin<&items::ClippedImage>, item_rc: &ItemRc) {
        let source_clip_rect = IntRect::new(
            [clipped_image.source_clip_x(), clipped_image.source_clip_y()].into(),
            [clipped_image.source_clip_width(), clipped_image.source_clip_height()].into(),
        );

        self.draw_image_impl(
            item_rc,
            items::ClippedImage::FIELD_OFFSETS.source.apply_pin(clipped_image),
            source_clip_rect,
            items::ClippedImage::FIELD_OFFSETS.width.apply_pin(clipped_image),
            items::ClippedImage::FIELD_OFFSETS.height.apply_pin(clipped_image),
            clipped_image.image_fit(),
            Some(items::ClippedImage::FIELD_OFFSETS.colorize.apply_pin(clipped_image)),
            clipped_image.image_rendering(),
        );
    }

    fn draw_text(&mut self, text: Pin<&items::Text>, _: &ItemRc) {
        let max_width = text.width() * self.scale_factor;
        let max_height = text.height() * self.scale_factor;

        if max_width <= 0. || max_height <= 0. {
            return;
        }

        let string = text.text();
        let string = string.as_str();
        let font = fonts::FONT_CACHE.with(|cache| {
            cache.borrow_mut().font(
                text.unresolved_font_request()
                    .merge(&self.graphics_window.default_font_properties()),
                self.scale_factor,
                &text.text(),
            )
        });

        let paint = match self
            .brush_to_paint(text.color(), &mut rect_to_path(item_rect(text, self.scale_factor)))
        {
            Some(paint) => font.init_paint(text.letter_spacing() * self.scale_factor, paint),
            None => return,
        };

        let mut canvas = self.canvas.borrow_mut();
        fonts::layout_text_lines(
            string,
            &font,
            Size::new(max_width, max_height),
            (text.horizontal_alignment(), text.vertical_alignment()),
            text.wrap(),
            text.overflow(),
            false,
            paint,
            |to_draw, pos, _, _| {
                canvas.fill_text(pos.x, pos.y, to_draw.trim_end(), paint).unwrap();
            },
        );
    }

    fn draw_text_input(&mut self, text_input: Pin<&items::TextInput>, _: &ItemRc) {
        let width = text_input.width() * self.scale_factor;
        let height = text_input.height() * self.scale_factor;
        if width <= 0. || height <= 0. {
            return;
        }

        let font = fonts::FONT_CACHE.with(|cache| {
            cache.borrow_mut().font(
                text_input
                    .unresolved_font_request()
                    .merge(&self.graphics_window.default_font_properties()),
                self.scale_factor,
                &text_input.text(),
            )
        });

        let paint = match self.brush_to_paint(
            text_input.color(),
            &mut rect_to_path(item_rect(text_input, self.scale_factor)),
        ) {
            Some(paint) => font.init_paint(text_input.letter_spacing() * self.scale_factor, paint),
            None => return,
        };

        let (mut min_select, mut max_select) = text_input.selection_anchor_and_cursor();
        let cursor_pos = text_input.cursor_position();
        let cursor_visible = cursor_pos >= 0
            && text_input.cursor_visible()
            && text_input.enabled()
            && !text_input.read_only();
        let mut cursor_pos = cursor_pos as usize;
        let mut canvas = self.canvas.borrow_mut();
        let font_height = canvas.measure_font(paint).unwrap().height();
        let mut text = text_input.text();

        if let InputType::password = text_input.input_type() {
            min_select = text[..min_select].chars().count() * PASSWORD_CHARACTER.len();
            max_select = text[..max_select].chars().count() * PASSWORD_CHARACTER.len();
            cursor_pos = text[..cursor_pos].chars().count() * PASSWORD_CHARACTER.len();
            text = SharedString::from(PASSWORD_CHARACTER.repeat(text.chars().count()));
        };

        let mut cursor_point: Option<Point> = None;

        let baseline_y = fonts::layout_text_lines(
            text.as_str(),
            &font,
            Size::new(width, height),
            (text_input.horizontal_alignment(), text_input.vertical_alignment()),
            text_input.wrap(),
            items::TextOverflow::clip,
            text_input.single_line(),
            paint,
            |to_draw, pos, start, metrics| {
                let range = start..(start + to_draw.len());
                if min_select != max_select
                    && (range.contains(&min_select)
                        || range.contains(&max_select)
                        || (min_select..max_select).contains(&start))
                {
                    let mut selection_start_x = 0.;
                    let mut selection_end_x = 0.;
                    let mut after_selection_x = 0.;
                    // Determine the first and last (inclusive) glyph of the selection. The anchor
                    // will always be at the start of a grapheme boundary, so there's at ShapedGlyph
                    // that has a matching byte index. For the selection end we have to look for the
                    // visual end of glyph before the cursor, because due to for example ligatures
                    // (or generally glyph substitution) there may not be a dedicated glyph.
                    // FIXME: in the case of ligature, there is currently no way to know the exact
                    // position of the split. When we know it, we might need to draw in two
                    // steps with clip to draw each part of the ligature in a different color
                    for glyph in &metrics.glyphs {
                        if glyph.byte_index == min_select.saturating_sub(start) {
                            selection_start_x = glyph.x - glyph.bearing_x;
                        }
                        if glyph.byte_index == max_select - start
                            || glyph.byte_index >= to_draw.len()
                        {
                            after_selection_x = glyph.x - glyph.bearing_x;
                            break;
                        }
                        selection_end_x = glyph.x + glyph.advance_x;
                    }

                    let selection_rect = Rect::new(
                        pos + euclid::vec2(selection_start_x, 0.),
                        Size::new(selection_end_x - selection_start_x, font_height),
                    );
                    canvas.fill_path(
                        &mut rect_to_path(selection_rect),
                        femtovg::Paint::color(to_femtovg_color(
                            &text_input.selection_background_color(),
                        )),
                    );
                    let mut selected_paint = paint;
                    selected_paint
                        .set_color(to_femtovg_color(&text_input.selection_foreground_color()));
                    canvas
                        .fill_text(
                            pos.x,
                            pos.y,
                            &to_draw[..min_select.saturating_sub(start)].trim_end(),
                            paint,
                        )
                        .unwrap();
                    canvas
                        .fill_text(
                            pos.x + selection_start_x,
                            pos.y,
                            &to_draw[min_select.saturating_sub(start)
                                ..(max_select - start).min(to_draw.len())]
                                .trim_end(),
                            selected_paint,
                        )
                        .unwrap();
                    canvas
                        .fill_text(
                            pos.x + after_selection_x,
                            pos.y,
                            &to_draw[(max_select - start).min(to_draw.len())..].trim_end(),
                            paint,
                        )
                        .unwrap();
                } else {
                    // no selection on this line
                    canvas.fill_text(pos.x, pos.y, to_draw.trim_end(), paint).unwrap();
                };
                if cursor_visible
                    && (range.contains(&cursor_pos)
                        || (cursor_pos == range.end && cursor_pos == text.len()))
                {
                    let cursor_x = metrics
                        .glyphs
                        .iter()
                        .find_map(|glyph| {
                            if glyph.byte_index == (cursor_pos as usize - start) {
                                Some(glyph.x)
                            } else {
                                None
                            }
                        })
                        .unwrap_or_else(|| metrics.width());
                    cursor_point = Some([pos.x + cursor_x, pos.y].into());
                }
            },
        );

        if let Some(cursor_point) =
            cursor_point.or_else(|| cursor_visible.then(|| [0., baseline_y].into()))
        {
            let mut cursor_rect = femtovg::Path::new();
            cursor_rect.rect(
                cursor_point.x,
                cursor_point.y,
                text_input.text_cursor_width() * self.scale_factor,
                font_height,
            );
            canvas.fill_path(&mut cursor_rect, paint);
        }
    }

    fn draw_path(&mut self, path: Pin<&items::Path>, _: &ItemRc) {
        let elements = path.elements();
        if matches!(elements, i_slint_core::PathData::None) {
            return;
        }

        let (offset, path_events) = path.fitted_path_events();

        let mut femtovg_path = femtovg::Path::new();

        /// Contrary to the SVG spec, femtovg does not use the orientation of the path to
        /// know if it needs to fill or not some part, it uses its own Solidity enum.
        /// We must then compute ourself the orientation and set the Solidity accordingly.
        #[derive(Default)]
        struct OrientationCalculator {
            area: f32,
            prev: Point,
        }

        impl OrientationCalculator {
            fn add_point(&mut self, p: Point) {
                self.area += (p.x - self.prev.x) * (p.y + self.prev.y);
                self.prev = p;
            }
        }

        use femtovg::Solidity;

        let mut orient = OrientationCalculator::default();

        for x in path_events.iter() {
            match x {
                lyon_path::Event::Begin { at } => {
                    femtovg_path.solidity(if orient.area < 0. {
                        Solidity::Hole
                    } else {
                        Solidity::Solid
                    });
                    femtovg_path.move_to(at.x * self.scale_factor, at.y * self.scale_factor);
                    orient.area = 0.;
                    orient.prev = at;
                }
                lyon_path::Event::Line { from: _, to } => {
                    femtovg_path.line_to(to.x * self.scale_factor, to.y * self.scale_factor);
                    orient.add_point(to);
                }
                lyon_path::Event::Quadratic { from: _, ctrl, to } => {
                    femtovg_path.quad_to(
                        ctrl.x * self.scale_factor,
                        ctrl.y * self.scale_factor,
                        to.x * self.scale_factor,
                        to.y * self.scale_factor,
                    );
                    orient.add_point(to);
                }

                lyon_path::Event::Cubic { from: _, ctrl1, ctrl2, to } => {
                    femtovg_path.bezier_to(
                        ctrl1.x * self.scale_factor,
                        ctrl1.y * self.scale_factor,
                        ctrl2.x * self.scale_factor,
                        ctrl2.y * self.scale_factor,
                        to.x * self.scale_factor,
                        to.y * self.scale_factor,
                    );
                    orient.add_point(to);
                }
                lyon_path::Event::End { last: _, first: _, close } => {
                    femtovg_path.solidity(if orient.area < 0. {
                        Solidity::Hole
                    } else {
                        Solidity::Solid
                    });
                    if close {
                        femtovg_path.close()
                    }
                }
            }
        }

        let fill_paint =
            self.brush_to_paint(path.fill(), &mut femtovg_path).map(|mut fill_paint| {
                fill_paint.set_fill_rule(match path.fill_rule() {
                    FillRule::nonzero => femtovg::FillRule::NonZero,
                    FillRule::evenodd => femtovg::FillRule::EvenOdd,
                });
                fill_paint
            });

        let border_paint =
            self.brush_to_paint(path.stroke(), &mut femtovg_path).map(|mut paint| {
                paint.set_line_width(path.stroke_width() * self.scale_factor);
                paint
            });

        self.canvas.borrow_mut().save_with(|canvas| {
            canvas.translate(offset.x, offset.y);
            if let Some(fill_paint) = fill_paint {
                canvas.fill_path(&mut femtovg_path, fill_paint);
            }
            if let Some(border_paint) = border_paint {
                canvas.stroke_path(&mut femtovg_path, border_paint);
            }
        })
    }

    /// Draws a rectangular shadow shape, which is usually placed underneath another rectangular shape
    /// with an offset (the drop-shadow-offset-x/y). The algorithm follows the HTML Canvas spec 4.12.5.1.18:
    ///  * Create a new image to cache the shadow rendering
    ///  * Fill the image with transparent "black"
    ///  * Draw the (rounded) rectangle at shadow offset_x/offset_y
    ///  * Blur the image
    ///  * Fill the image with the shadow color and SourceIn as composition mode
    ///  * Draw the shadow image
    fn draw_box_shadow(&mut self, box_shadow: Pin<&items::BoxShadow>, item_rc: &ItemRc) {
        if box_shadow.color().alpha() == 0
            || (box_shadow.blur() == 0.0
                && box_shadow.offset_x() == 0.
                && box_shadow.offset_y() == 0.)
        {
            return;
        }

        let cache_entry =
            self.graphics_window.clone().graphics_cache.get_or_update_cache_entry(item_rc, || {
                ItemGraphicsCacheEntry::Texture({
                    let blur = box_shadow.blur() * self.scale_factor;
                    let width = box_shadow.width() * self.scale_factor;
                    let height = box_shadow.height() * self.scale_factor;
                    let radius = box_shadow.border_radius() * self.scale_factor;

                    let shadow_rect: euclid::Rect<f32, euclid::UnknownUnit> =
                        euclid::rect(0., 0., width + 2. * blur, height + 2. * blur);

                    let shadow_image_width = shadow_rect.width().ceil() as u32;
                    let shadow_image_height = shadow_rect.height().ceil() as u32;

                    let shadow_image = Texture::new_empty_on_gpu(
                        &self.canvas,
                        shadow_image_width,
                        shadow_image_height,
                    )?;

                    {
                        let mut canvas = self.canvas.borrow_mut();
                        canvas.save();

                        canvas.set_render_target(shadow_image.as_render_target());

                        canvas.reset();

                        canvas.clear_rect(
                            0,
                            0,
                            shadow_rect.width().ceil() as u32,
                            shadow_rect.height().ceil() as u32,
                            femtovg::Color::rgba(0, 0, 0, 0),
                        );

                        let mut shadow_path = femtovg::Path::new();
                        shadow_path.rounded_rect(blur, blur, width, height, radius);
                        canvas.fill_path(
                            &mut shadow_path,
                            femtovg::Paint::color(femtovg::Color::rgb(255, 255, 255)),
                        );
                    }

                    let shadow_image = if blur > 0. {
                        let blurred_image = shadow_image
                            .filter(femtovg::ImageFilter::GaussianBlur { sigma: blur / 2. });

                        self.canvas
                            .borrow_mut()
                            .set_render_target(blurred_image.as_render_target());

                        self.layer_images_to_delete_after_flush.push(shadow_image);

                        blurred_image
                    } else {
                        shadow_image
                    };

                    {
                        let mut canvas = self.canvas.borrow_mut();

                        canvas.global_composite_operation(femtovg::CompositeOperation::SourceIn);

                        let mut shadow_image_rect = femtovg::Path::new();
                        shadow_image_rect.rect(0., 0., shadow_rect.width(), shadow_rect.height());
                        canvas.fill_path(
                            &mut shadow_image_rect,
                            femtovg::Paint::color(to_femtovg_color(&box_shadow.color())),
                        );

                        canvas.restore();

                        canvas.set_render_target(self.current_render_target());
                    }

                    shadow_image
                })
                .into()
            });

        let shadow_image = match &cache_entry {
            Some(cached_shadow_image) => cached_shadow_image.as_texture(),
            None => return, // Zero width or height shadow
        };

        let shadow_image_size = match shadow_image.size() {
            Some(size) => size,
            None => return,
        };

        // On the paint for the box shadow, we don't need anti-aliasing on the fringes,
        // since we are just blitting a texture. This saves a triangle strip for the stroke.
        let shadow_image_paint = shadow_image.as_paint().with_anti_alias(false);

        let mut shadow_image_rect = femtovg::Path::new();
        shadow_image_rect.rect(
            0.,
            0.,
            shadow_image_size.width as f32,
            shadow_image_size.height as f32,
        );

        self.canvas.borrow_mut().save_with(|canvas| {
            let blur = box_shadow.blur() * self.scale_factor;
            let offset_x = box_shadow.offset_x() * self.scale_factor;
            let offset_y = box_shadow.offset_y() * self.scale_factor;
            canvas.translate(offset_x - blur, offset_y - blur);
            canvas.fill_path(&mut shadow_image_rect, shadow_image_paint);
        });
    }

    fn visit_opacity(&mut self, opacity_item: Pin<&Opacity>, item_rc: &ItemRc) -> RenderingResult {
        let opacity = opacity_item.opacity();
        if Opacity::need_layer(item_rc, opacity) {
            self.render_and_blend_layer(opacity, item_rc)
        } else {
            self.apply_opacity(opacity);
            self.graphics_window.graphics_cache.release(item_rc);
            RenderingResult::ContinueRenderingChildren
        }
    }

    fn visit_layer(&mut self, layer_item: Pin<&Layer>, self_rc: &ItemRc) -> RenderingResult {
        if layer_item.cache_rendering_hint() {
            self.render_and_blend_layer(1.0, self_rc)
        } else {
            RenderingResult::ContinueRenderingChildren
        }
    }

    fn visit_clip(&mut self, clip_item: Pin<&Clip>, item_rc: &ItemRc) -> RenderingResult {
        if !clip_item.clip() {
            return RenderingResult::ContinueRenderingChildren;
        }

        let geometry = clip_item.as_ref().geometry();

        // If clipping is enabled but the clip element is outside the visible range, then we don't
        // need to bother doing anything, not even rendering the children.
        if !self.get_current_clip().intersects(&geometry) {
            return RenderingResult::ContinueRenderingWithoutChildren;
        }

        let radius = clip_item.border_radius();
        let border_width = clip_item.border_width();

        if radius > 0. {
            if let Some(layer_image) =
                self.render_layer(item_rc, &|| clip_item.as_ref().geometry().size)
            {
                let layer_image_paint = layer_image.as_paint();

                let mut layer_path = clip_path_for_rect_alike_item(
                    geometry,
                    radius,
                    border_width,
                    self.scale_factor,
                );

                self.canvas.borrow_mut().fill_path(&mut layer_path, layer_image_paint);
            }

            RenderingResult::ContinueRenderingWithoutChildren
        } else {
            self.graphics_window.graphics_cache.release(item_rc);
            self.combine_clip(
                euclid::rect(0., 0., geometry.width(), geometry.height()),
                radius,
                border_width,
            );
            RenderingResult::ContinueRenderingChildren
        }
    }

    fn combine_clip(&mut self, clip_rect: Rect, radius: f32, border_width: f32) {
        let clip = &mut self.state.last_mut().unwrap().scissor;
        match clip.intersection(&clip_rect) {
            Some(r) => {
                *clip = r;
            }
            None => {
                *clip = Rect::default();
            }
        };

        let mut clip_path =
            clip_path_for_rect_alike_item(clip_rect, radius, border_width, self.scale_factor);

        let clip_path_bounds = path_bounding_box(&self.canvas, &mut clip_path);

        self.canvas.borrow_mut().intersect_scissor(
            clip_path_bounds.min.x,
            clip_path_bounds.min.y,
            clip_path_bounds.width(),
            clip_path_bounds.height(),
        );

        // femtovg only supports rectangular clipping. Non-rectangular clips must be handled via `apply_clip`,
        // which can render children into a layer.
        debug_assert!(radius == 0.);
    }

    fn get_current_clip(&self) -> Rect {
        self.state.last().unwrap().scissor
    }

    fn save_state(&mut self) {
        self.canvas.borrow_mut().save();
        self.state.push(self.state.last().unwrap().clone());
    }

    fn restore_state(&mut self) {
        self.state.pop();
        self.canvas.borrow_mut().restore();
    }

    fn scale_factor(&self) -> f32 {
        self.scale_factor
    }

    fn draw_cached_pixmap(
        &mut self,
        item_rc: &ItemRc,
        update_fn: &dyn Fn(&mut dyn FnMut(u32, u32, &[u8])),
    ) {
        let canvas = &self.canvas;

        let cache_entry =
            self.graphics_window.graphics_cache.get_or_update_cache_entry(item_rc, || {
                let mut cached_image = None;
                update_fn(&mut |width: u32, height: u32, data: &[u8]| {
                    use rgb::FromSlice;
                    let img = imgref::Img::new(data.as_rgba(), width as usize, height as usize);
                    if let Ok(image_id) =
                        canvas.borrow_mut().create_image(img, femtovg::ImageFlags::PREMULTIPLIED)
                    {
                        cached_image =
                            Some(ItemGraphicsCacheEntry::Texture(Texture::adopt(canvas, image_id)))
                    };
                });
                cached_image
            });
        let image_id = match cache_entry {
            Some(ItemGraphicsCacheEntry::Texture(image)) => image.id,
            Some(ItemGraphicsCacheEntry::ColorizedImage { .. }) => unreachable!(),
            None => return,
        };
        let mut canvas = self.canvas.borrow_mut();

        let image_info = canvas.image_info(image_id).unwrap();
        let (width, height) = (image_info.width() as f32, image_info.height() as f32);
        let fill_paint = femtovg::Paint::image(image_id, 0., 0., width, height, 0.0, 1.0);
        let mut path = femtovg::Path::new();
        path.rect(0., 0., width, height);
        canvas.fill_path(&mut path, fill_paint);
    }

    fn draw_string(&mut self, string: &str, color: Color) {
        let font = fonts::FONT_CACHE.with(|cache| {
            cache.borrow_mut().font(
                self.graphics_window.default_font_properties(),
                self.scale_factor,
                string,
            )
        });
        let paint = font.init_paint(0.0, femtovg::Paint::color(to_femtovg_color(&color)));
        let mut canvas = self.canvas.borrow_mut();
        canvas.fill_text(0., 0., string, paint).unwrap();
    }

    fn window(&self) -> WindowRc {
        self.graphics_window.runtime_window()
    }

    fn as_any(&mut self) -> &mut dyn std::any::Any {
        self
    }

    fn translate(&mut self, x: f32, y: f32) {
        self.canvas.borrow_mut().translate(x * self.scale_factor, y * self.scale_factor);
        let clip = &mut self.state.last_mut().unwrap().scissor;
        *clip = clip.translate((-x, -y).into())
    }

    fn rotate(&mut self, angle_in_degrees: f32) {
        let angle_in_radians = angle_in_degrees.to_radians();
        self.canvas.borrow_mut().rotate(angle_in_radians);
        let clip = &mut self.state.last_mut().unwrap().scissor;
        // Compute the bounding box of the rotated rectangle
        let (sin, cos) = angle_in_radians.sin_cos();
        let rotate_point = |p: Point| (p.x * cos - p.y * sin, p.x * sin + p.y * cos);
        let corners = [
            rotate_point(clip.origin),
            rotate_point(clip.origin + euclid::vec2(clip.width(), 0.)),
            rotate_point(clip.origin + euclid::vec2(0., clip.height())),
            rotate_point(clip.origin + clip.size),
        ];
        let origin: Point = (
            corners.iter().fold(f32::MAX, |a, b| b.0.min(a)),
            corners.iter().fold(f32::MAX, |a, b| b.1.min(a)),
        )
            .into();
        let end: Point = (
            corners.iter().fold(f32::MIN, |a, b| b.0.max(a)),
            corners.iter().fold(f32::MIN, |a, b| b.1.max(a)),
        )
            .into();
        *clip = Rect::new(origin, (end - origin).into());
    }

    fn apply_opacity(&mut self, opacity: f32) {
        let state = &mut self.state.last_mut().unwrap().global_alpha;
        *state *= opacity;
        self.canvas.borrow_mut().set_global_alpha(*state);
    }

    fn metrics(&self) -> RenderingMetrics {
        self.metrics.clone()
    }
}

impl GLItemRenderer {
    pub fn new(
        canvas: CanvasRc,
        graphics_window: Rc<GLWindow>,
        scale_factor: f32,
        size: winit::dpi::PhysicalSize<u32>,
    ) -> Self {
        Self {
            canvas,
            layer_images_to_delete_after_flush: Default::default(),
            graphics_window,
            scale_factor,
            state: vec![State {
                scissor: Rect::new(
                    Point::default(),
                    Size::new(size.width as f32, size.height as f32) / scale_factor,
                ),
                global_alpha: 1.,
                current_render_target: femtovg::RenderTarget::Screen,
            }],
            metrics: RenderingMetrics { layers_created: Some(0) },
        }
    }

    fn render_layer(
        &mut self,
        item_rc: &ItemRc,
        layer_logical_size_fn: &dyn Fn() -> Size,
    ) -> Option<Rc<Texture>> {
        let cache_entry =
            self.graphics_window.clone().graphics_cache.get_or_update_cache_entry(item_rc, || {
                ItemGraphicsCacheEntry::Texture({
                    let size = layer_logical_size_fn() * self.scale_factor;

                    let layer_image = Texture::new_empty_on_gpu(
                        &self.canvas,
                        size.width.ceil() as u32,
                        size.height.ceil() as u32,
                    )?;
                    *self.metrics.layers_created.as_mut().unwrap() += 1;

                    let previous_render_target = self.current_render_target();

                    {
                        let mut canvas = self.canvas.borrow_mut();
                        canvas.save();

                        canvas.set_render_target(layer_image.as_render_target());

                        canvas.reset();

                        canvas.clear_rect(
                            0,
                            0,
                            size.width.ceil() as u32,
                            size.height.ceil() as u32,
                            femtovg::Color::rgba(0, 0, 0, 0),
                        );
                    }

                    *self.state.last_mut().unwrap() = State {
                        scissor: Rect::new(
                            Point::default(),
                            Size::new(size.width as f32, size.height as f32),
                        ),
                        global_alpha: 1.,
                        current_render_target: layer_image.as_render_target(),
                    };

                    i_slint_core::item_rendering::render_item_children(
                        self,
                        &item_rc.component(),
                        item_rc.index() as isize,
                    );

                    {
                        let mut canvas = self.canvas.borrow_mut();
                        canvas.restore();

                        canvas.set_render_target(previous_render_target);
                    }

                    layer_image
                })
                .into()
            });

        cache_entry.map(|item_cache_entry| item_cache_entry.as_texture().clone())
    }

    fn render_and_blend_layer(&mut self, alpha_tint: f32, item_rc: &ItemRc) -> RenderingResult {
        let current_clip = self.get_current_clip();
        if let Some((layer_image, layer_size)) = self
            .render_layer(item_rc, &|| {
                // We don't need to include the size of the opacity item itself, since it has no content.
                let children_rect = i_slint_core::properties::evaluate_no_tracking(|| {
                    let self_ref = item_rc.borrow();
                    self_ref.as_ref().geometry().union(
                        &i_slint_core::item_rendering::item_children_bounding_rect(
                            &item_rc.component(),
                            item_rc.index() as isize,
                            &current_clip,
                        ),
                    )
                });
                children_rect.size
            })
            .and_then(|image| image.size().map(|size| (image, size)))
        {
            let mut layer_path = femtovg::Path::new();
            // On the paint for the layer, we don't need anti-aliasing on the fringes,
            // since we are just blitting a texture. This saves a triangle strip for the stroke.
            let layer_image_paint =
                layer_image.as_paint_with_alpha(alpha_tint).with_anti_alias(false);

            layer_path.rect(0., 0., layer_size.width as _, layer_size.height as _);
            self.canvas.borrow_mut().fill_path(&mut layer_path, layer_image_paint);
        }
        RenderingResult::ContinueRenderingWithoutChildren
    }

    fn colorize_image(
        &self,
        original_cache_entry: ItemGraphicsCacheEntry,
        colorize_property: Option<Pin<&Property<Brush>>>,
        scaling: ImageRendering,
    ) -> ItemGraphicsCacheEntry {
        let colorize_brush = colorize_property.map_or(Brush::default(), |prop| prop.get());
        if colorize_brush.is_transparent() {
            return original_cache_entry;
        };
        let original_image = original_cache_entry.as_texture();

        let image_size = match original_image.size() {
            Some(size) => size,
            None => return original_cache_entry,
        };

        let scaling_flags = match scaling {
            ImageRendering::smooth => femtovg::ImageFlags::empty(),
            ImageRendering::pixelated => {
                femtovg::ImageFlags::empty() | femtovg::ImageFlags::NEAREST
            }
        };

        let image_id = original_image.id;
        let colorized_image = self
            .canvas
            .borrow_mut()
            .create_image_empty(
                image_size.width as usize,
                image_size.height as usize,
                femtovg::PixelFormat::Rgba8,
                femtovg::ImageFlags::PREMULTIPLIED | scaling_flags,
            )
            .expect("internal error allocating temporary texture for image colorization");

        let image_size: Size = image_size.cast();

        let mut image_rect = femtovg::Path::new();
        image_rect.rect(0., 0., image_size.width, image_size.height);
        // We fill the entire image, there is no need to apply anti-aliasing around the edges
        let brush_paint =
            self.brush_to_paint(colorize_brush, &mut image_rect).unwrap().with_anti_alias(false);

        self.canvas.borrow_mut().save_with(|canvas| {
            canvas.reset();
            canvas.scale(1., -1.); // Image are rendered upside down
            canvas.translate(0., -image_size.height);
            canvas.set_render_target(femtovg::RenderTarget::Image(colorized_image));

            canvas.global_composite_operation(femtovg::CompositeOperation::Copy);
            canvas.fill_path(
                &mut image_rect,
                femtovg::Paint::image(
                    image_id,
                    0.,
                    0.,
                    image_size.width,
                    image_size.height,
                    0.,
                    1.0,
                ),
            );

            canvas.global_composite_operation(femtovg::CompositeOperation::SourceIn);
            canvas.fill_path(&mut image_rect, brush_paint);

            canvas.set_render_target(self.current_render_target());
        });

        ItemGraphicsCacheEntry::ColorizedImage {
            _original_image: original_image.clone(),
            colorized_image: Texture::adopt(&self.canvas, colorized_image),
        }
    }

    fn draw_image_impl(
        &mut self,
        item_rc: &ItemRc,
        source_property: Pin<&Property<Image>>,
        source_clip_rect: IntRect,
        target_width: Pin<&Property<f32>>,
        target_height: Pin<&Property<f32>>,
        image_fit: ImageFit,
        colorize_property: Option<Pin<&Property<Brush>>>,
        image_rendering: ImageRendering,
    ) {
        let target_w = target_width.get() * self.scale_factor;
        let target_h = target_height.get() * self.scale_factor;

        if target_w <= 0. || target_h <= 0. {
            return;
        }

        let cached_image = loop {
            let image_cache_entry =
                self.graphics_window.graphics_cache.get_or_update_cache_entry(item_rc, || {
                    let image = source_property.get();
                    let image_inner: &ImageInner = (&image).into();

                    let target_size_for_scalable_source = image_inner.is_svg().then(|| {
                        // get the scale factor as a property again, to ensure the cache is invalidated when the scale factor changes
                        let scale_factor = self.window().scale_factor();
                        [
                            (target_width.get() * scale_factor) as u32,
                            (target_height.get() * scale_factor) as u32,
                        ]
                        .into()
                    });

                    TextureCacheKey::new(
                        image_inner,
                        target_size_for_scalable_source,
                        image_rendering,
                    )
                    .and_then(|cache_key| {
                        self.graphics_window
                            .texture_cache
                            .borrow_mut()
                            .lookup_image_in_cache_or_create(cache_key, || {
                                crate::IMAGE_CACHE
                                    .with(|global_cache| {
                                        global_cache.borrow_mut().load_image_resource(image_inner)
                                    })
                                    .and_then(|image| {
                                        image.upload_to_gpu(
                                            self, // The condition at the entry of the function ensures that width/height are positive
                                            target_size_for_scalable_source,
                                            image_rendering,
                                        )
                                    })
                            })
                    })
                    .or_else(|| {
                        CachedImage::new_from_resource(image_inner).and_then(|image| {
                            image.upload_to_gpu(
                                self,
                                target_size_for_scalable_source,
                                image_rendering,
                            )
                        })
                    })
                    .map(ItemGraphicsCacheEntry::Texture)
                    .map(|cache_entry| {
                        self.colorize_image(cache_entry, colorize_property, image_rendering)
                    })
                });

            // Check if the image in the cache is loaded. If not, don't draw any image and we'll return
            // later when the callback from load_html_image has issued a repaint
            let cached_image = match image_cache_entry {
                Some(entry) if entry.as_texture().size().is_some() => entry,
                _ => {
                    return;
                }
            };

            // It's possible that our item cache contains an image but it's not colorized yet because it was only
            // placed there via the `image_size` function (which doesn't colorize). So we may have to invalidate our
            // item cache and try again.
            if colorize_property.map_or(false, |prop| !prop.get().is_transparent())
                && !cached_image.is_colorized_image()
            {
                self.graphics_window.graphics_cache.release(item_rc);
                continue;
            }

            break cached_image.as_texture().clone();
        };

        let image_id = cached_image.id;
        let image_size = cached_image.size().unwrap_or_default().cast();

        let (source_width, source_height) = if source_clip_rect.is_empty() {
            (image_size.width, image_size.height)
        } else {
            (source_clip_rect.width() as _, source_clip_rect.height() as _)
        };

        let mut source_x = source_clip_rect.min_x() as f32;
        let mut source_y = source_clip_rect.min_y() as f32;

        let mut image_fit_offset = Point::default();

        // The source_to_target scale is applied to the paint that holds the image as well as path
        // begin rendered.
        let (source_to_target_scale_x, source_to_target_scale_y) = match image_fit {
            ImageFit::fill => (target_w / source_width, target_h / source_height),
            ImageFit::cover => {
                let ratio = f32::max(target_w / source_width, target_h / source_height);

                if source_width > target_w / ratio {
                    source_x += (source_width - target_w / ratio) / 2.;
                }
                if source_height > target_h / ratio {
                    source_y += (source_height - target_h / ratio) / 2.
                }

                (ratio, ratio)
            }
            ImageFit::contain => {
                let ratio = f32::min(target_w / source_width, target_h / source_height);

                if source_width < target_w / ratio {
                    image_fit_offset.x = (target_w - source_width * ratio) / 2.;
                }
                if source_height < target_h / ratio {
                    image_fit_offset.y = (target_h - source_height * ratio) / 2.
                }

                (ratio, ratio)
            }
        };

        let fill_paint = femtovg::Paint::image(
            image_id,
            -source_x,
            -source_y,
            image_size.width,
            image_size.height,
            0.0,
            1.0,
        )
        // We preserve the rectangular shape of the image, so there's no need to apply anti-aliasing
        // at the edges
        .with_anti_alias(false);

        let mut path = femtovg::Path::new();
        path.rect(0., 0., source_width, source_height);

        self.canvas.borrow_mut().save_with(|canvas| {
            canvas.translate(image_fit_offset.x, image_fit_offset.y);

            canvas.scale(source_to_target_scale_x, source_to_target_scale_y);

            canvas.fill_path(&mut path, fill_paint);
        })
    }

    fn brush_to_paint(&self, brush: Brush, path: &mut femtovg::Path) -> Option<femtovg::Paint> {
        if brush.is_transparent() {
            return None;
        }
        if self.state.last().unwrap().global_alpha == 0.0 {
            return None;
        }
        Some(match brush {
            Brush::SolidColor(color) => femtovg::Paint::color(to_femtovg_color(&color)),
            Brush::LinearGradient(gradient) => {
                let path_bounds = path_bounding_box(&self.canvas, path);

                let path_width = path_bounds.width();
                let path_height = path_bounds.height();

                let transform = euclid::Transform2D::scale(path_width, path_height)
                    .then_translate(path_bounds.min.to_vector());

                let (start, end) = i_slint_core::graphics::line_for_angle(gradient.angle());

                let start: Point = transform.transform_point(start);
                let end: Point = transform.transform_point(end);

                let stops = gradient
                    .stops()
                    .map(|stop| (stop.position, to_femtovg_color(&stop.color)))
                    .collect::<Vec<_>>();
                femtovg::Paint::linear_gradient_stops(start.x, start.y, end.x, end.y, &stops)
            }
            Brush::RadialGradient(gradient) => {
                let path_bounds = path_bounding_box(&self.canvas, path);

                let path_width = path_bounds.width();
                let path_height = path_bounds.height();

                let stops = gradient
                    .stops()
                    .map(|stop| (stop.position, to_femtovg_color(&stop.color)))
                    .collect::<Vec<_>>();
                femtovg::Paint::radial_gradient_stops(
                    path_width / 2.,
                    path_height / 2.,
                    0.,
                    (path_width + path_height) / 4.,
                    &stops,
                )
            }
            _ => return None,
        })
    }

    fn current_render_target(&self) -> femtovg::RenderTarget {
        self.state.last().unwrap().current_render_target
    }
}

pub fn to_femtovg_color(col: &Color) -> femtovg::Color {
    femtovg::Color::rgba(col.red(), col.green(), col.blue(), col.alpha())
}