skia-canvas 0.2.0

use skia_safe::{
    AlphaType, ColorSpace as SkColorSpace, ColorType, IPoint, ISize, ImageInfo,
    Pixmap, Surface as SkSurface,
};

use crate::{
    backend::{EngineKind, engine_kind_from, resolve_engine},
    color::LinearColorSpace,
    context::page::ExportOptions,
    error::Error,
    image::Image,
    pixels::{
        ExportedPixels, PixelColorSpace, PixelDepth, PixelExportOptions,
        SurfaceOptions,
    },
    recorder::Canvas,
};

pub struct Surface {
    inner: SkSurface,
    color_space: LinearColorSpace,
    /// Cached Skia color-space handle for the working space. Built once
    /// at construction so `with_canvas` can hand it to `Canvas`
    /// without re-resolving on every borrow.
    working_color_space: SkColorSpace,
    /// Which rasterizer the surface ended up using. `Auto` resolves at
    /// construction time, so this is always concrete (`Cpu` or `Gpu`).
    engine: EngineKind,
    width: u32,
    height: u32,
}

impl Surface {
    pub(crate) fn new(
        width: u32,
        height: u32,
        options: SurfaceOptions,
    ) -> Result<Self, Error> {
        if width == 0 || height == 0 {
            return Err(Error::InvalidDimensions {
                width: width as f32,
                height: height as f32,
            });
        }
        let cs = options.color_space.to_skia_color_space()?;
        // Surfaces always composite at RGBAF16 precision in their working
        // color space; readback options control the exported format.
        let info = ImageInfo::new(
            (width as i32, height as i32),
            ColorType::RGBAF16,
            AlphaType::Premul,
            cs.clone(),
        );
        let internal = resolve_engine(options.engine)?;
        let export_options = ExportOptions {
            msaa: options.msaa,
            color_type: ColorType::RGBAF16,
            color_space: cs.clone(),
            ..ExportOptions::default()
        };
        let surface = internal.make_surface(&info, &export_options).map_err(
            |reason| Error::SurfaceCreate {
                reason: format!(
                    "could not allocate {width}x{height} surface: {reason}"
                ),
            },
        )?;
        Ok(Self {
            inner: surface,
            color_space: options.color_space,
            working_color_space: cs,
            engine: engine_kind_from(internal),
            width,
            height,
        })
    }

    pub fn width(&self) -> u32 {
        self.width
    }

    pub fn height(&self) -> u32 {
        self.height
    }

    pub fn color_space(&self) -> LinearColorSpace {
        self.color_space
    }

    /// Which rasterizer ended up backing this surface. With
    /// [`RenderEngine::Auto`] this tells callers whether the GPU path
    /// was selected at construction time.
    ///
    /// [`RenderEngine::Auto`]: crate::RenderEngine::Auto
    pub fn engine(&self) -> EngineKind {
        self.engine
    }

    /// Flush pending Skia work. No-op for CPU surfaces; for GPU
    /// surfaces, submits queued draw commands so that the next
    /// `read_pixels*` reflects them.
    pub fn flush(&mut self) {
        #[cfg(any(feature = "vulkan", feature = "metal"))]
        if self.engine == EngineKind::Gpu {
            crate::gpu::RenderingEngine::GPU.with_direct_context(|ctx| {
                if let Some(ctx) = ctx {
                    ctx.flush_and_submit();
                }
            });
        }
    }

    pub fn snapshot(&mut self) -> Image {
        Image {
            inner: self.inner.image_snapshot(),
        }
    }

    pub fn create_offscreen(
        &mut self,
        width: u32,
        height: u32,
    ) -> Result<Surface, Error> {
        if width == 0 || height == 0 {
            return Err(Error::InvalidDimensions {
                width: width as f32,
                height: height as f32,
            });
        }
        let off = self
            .inner
            .new_surface_with_dimensions(ISize::new(
                width as i32,
                height as i32,
            ))
            .ok_or_else(|| Error::SurfaceCreate {
                reason: format!(
                    "could not allocate {width}x{height} offscreen surface"
                ),
            })?;
        Ok(Surface {
            inner: off,
            color_space: self.color_space,
            working_color_space: self.working_color_space.clone(),
            engine: self.engine,
            width,
            height,
        })
    }

    pub fn with_canvas<R>(
        &mut self,
        f: impl FnOnce(&mut Canvas<'_>) -> R,
    ) -> R {
        // Forward the surface's working color space so canvas methods
        // can tag every `RgbaLinear` value with the right primaries.
        let working_cs = self.working_color_space.clone();
        let canvas = self.inner.canvas();
        let mut nc = Canvas::new(canvas, working_cs);
        f(&mut nc)
    }

    /// Default readback: tight, sRGB gamma, Uint8, unpremultiplied. Matches
    /// the wire format expected by `HTMLCanvasElement.putImageData`.
    pub fn read_pixels(&mut self) -> Result<ExportedPixels, Error> {
        self.read_pixels_as(PixelExportOptions::default())
    }

    /// Read the surface in its working color space at native precision
    /// (F16, premultiplied). Used when callers need exact internal values.
    pub fn read_pixels_raw(&mut self) -> Result<ExportedPixels, Error> {
        self.read_pixels_as(PixelExportOptions {
            color_space: self.linear_pixel_color_space(),
            depth: PixelDepth::F16,
            premultiplied: true,
        })
    }

    /// Read F32 linear pixels in the surface's working color space.
    pub fn read_pixels_linear(&mut self) -> Result<ExportedPixels, Error> {
        self.read_pixels_as(PixelExportOptions {
            color_space: self.linear_pixel_color_space(),
            depth: PixelDepth::F32,
            premultiplied: true,
        })
    }

    pub fn read_pixels_as(
        &mut self,
        options: PixelExportOptions,
    ) -> Result<ExportedPixels, Error> {
        let dst_cs = options.color_space.to_skia_color_space()?;
        let dst_ct = options.depth.to_skia_color_type();
        let dst_at = if options.premultiplied {
            AlphaType::Premul
        } else {
            AlphaType::Unpremul
        };
        let info = ImageInfo::new(
            (self.width as i32, self.height as i32),
            dst_ct,
            dst_at,
            dst_cs,
        );
        let bpp = options.depth.bytes_per_pixel();
        let stride = (self.width as usize) * bpp;
        let mut buffer: Vec<u8> = vec![0; stride * self.height as usize];
        if !self.inner.read_pixels(
            &info,
            &mut buffer,
            stride,
            IPoint::new(0, 0),
        ) {
            return Err(Error::PixelReadback {
                reason: format!(
                    "read failed for {:?} {:?} premul={}",
                    options.color_space, options.depth, options.premultiplied
                ),
            });
        }
        Ok(ExportedPixels::new(
            self.width,
            self.height,
            stride,
            options.color_space,
            options.depth,
            options.premultiplied,
            buffer,
        ))
    }

    pub fn write_pixels(
        &mut self,
        bytes: &[u8],
        options: PixelExportOptions,
    ) -> Result<(), Error> {
        let dst_cs = options.color_space.to_skia_color_space()?;
        let dst_ct = options.depth.to_skia_color_type();
        let dst_at = if options.premultiplied {
            AlphaType::Premul
        } else {
            AlphaType::Unpremul
        };
        let info = ImageInfo::new(
            (self.width as i32, self.height as i32),
            dst_ct,
            dst_at,
            dst_cs,
        );
        let bpp = options.depth.bytes_per_pixel();
        let stride = (self.width as usize) * bpp;
        let expected = stride * self.height as usize;
        if bytes.len() != expected {
            return Err(Error::InvalidByteLength {
                expected,
                actual: bytes.len(),
            });
        }
        // Pixmap requires `&mut [u8]`; Skia does not modify the source on
        // write, so we copy the caller's slice once. Acceptable cost given
        // write_pixels is not on the per-frame hot path.
        let mut copy = bytes.to_vec();
        let pixmap =
            Pixmap::new(&info, &mut copy, stride).ok_or_else(|| {
                Error::PixelWrite {
                    reason: "pixmap construct failed".to_string(),
                }
            })?;
        self.inner
            .write_pixels_from_pixmap(&pixmap, IPoint::new(0, 0));
        Ok(())
    }

    pub fn write_pixels_linear(&mut self, bytes: &[u8]) -> Result<(), Error> {
        self.write_pixels(
            bytes,
            PixelExportOptions {
                color_space: self.linear_pixel_color_space(),
                depth: PixelDepth::F32,
                premultiplied: true,
            },
        )
    }

    fn linear_pixel_color_space(&self) -> PixelColorSpace {
        match self.color_space {
            LinearColorSpace::Srgb => PixelColorSpace::SrgbLinear,
            LinearColorSpace::DisplayP3 => PixelColorSpace::DisplayP3Linear,
            LinearColorSpace::Rec2020 => PixelColorSpace::Rec2020Linear,
        }
    }
}