bite-gp-engine 1.25.202

gpui_engine — part of the bite-gpui rearchitecture of zed's gpui
Documentation 
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//! Rendering asset identifiers and raster parameters shared by the engine and
//! its platform backends.

use gpui_shared_string::SharedString;
use gpui_types::{DevicePixels, Pixels, Point, Size};
use std::hash::{Hash, Hasher};

/// An opaque identifier for a specific font.
#[derive(Hash, PartialEq, Eq, Clone, Copy, Debug)]
#[repr(C)]
pub struct FontId(pub usize);

/// An identifier for a specific glyph, as returned by the platform text system.
#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
#[repr(C)]
pub struct GlyphId(pub u32);

/// Parameters for rendering a glyph, used as cache keys for raster bounds.
///
/// This struct identifies a specific glyph rendering configuration including
/// font, size, subpixel positioning, and scale factor. It's used to look up
/// cached raster bounds and sprite atlas entries.
#[derive(Clone, Debug, PartialEq)]
#[expect(missing_docs)]
pub struct RenderGlyphParams {
    pub font_id: FontId,
    pub glyph_id: GlyphId,
    pub font_size: Pixels,
    pub subpixel_variant: Point<u8>,
    pub scale_factor: f32,
    pub is_emoji: bool,
    pub subpixel_rendering: bool,
    pub dilation: u8,
}

impl Eq for RenderGlyphParams {}

impl Hash for RenderGlyphParams {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.font_id.0.hash(state);
        self.glyph_id.0.hash(state);
        self.font_size.0.to_bits().hash(state);
        self.subpixel_variant.hash(state);
        self.scale_factor.to_bits().hash(state);
        self.is_emoji.hash(state);
        self.subpixel_rendering.hash(state);
        self.dilation.hash(state);
    }
}

/// A unique identifier for the image cache
#[derive(Copy, Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
pub struct ImageId(pub usize);

#[derive(PartialEq, Eq, Hash, Clone)]
#[expect(missing_docs)]
pub struct RenderImageParams {
    pub image_id: ImageId,
    pub frame_index: usize,
}

#[derive(Clone, PartialEq, Hash, Eq)]
#[expect(missing_docs)]
pub struct RenderSvgParams {
    pub path: SharedString,
    pub size: Size<DevicePixels>,
}

// Adapted from https://github.com/microsoft/terminal/blob/1283c0f5b99a2961673249fa77c6b986efb5086c/src/renderer/atlas/dwrite.cpp
// Copyright (c) Microsoft Corporation.
// Licensed under the MIT license.
/// Compute gamma correction ratios for subpixel text rendering.
#[allow(dead_code)]
pub fn get_gamma_correction_ratios(gamma: f32) -> [f32; 4] {
    const GAMMA_INCORRECT_TARGET_RATIOS: [[f32; 4]; 13] = [
        [0.0000 / 4.0, 0.0000 / 4.0, 0.0000 / 4.0, 0.0000 / 4.0], // gamma = 1.0
        [0.0166 / 4.0, -0.0807 / 4.0, 0.2227 / 4.0, -0.0751 / 4.0], // gamma = 1.1
        [0.0350 / 4.0, -0.1760 / 4.0, 0.4325 / 4.0, -0.1370 / 4.0], // gamma = 1.2
        [0.0543 / 4.0, -0.2821 / 4.0, 0.6302 / 4.0, -0.1876 / 4.0], // gamma = 1.3
        [0.0739 / 4.0, -0.3963 / 4.0, 0.8167 / 4.0, -0.2287 / 4.0], // gamma = 1.4
        [0.0933 / 4.0, -0.5161 / 4.0, 0.9926 / 4.0, -0.2616 / 4.0], // gamma = 1.5
        [0.1121 / 4.0, -0.6395 / 4.0, 1.1588 / 4.0, -0.2877 / 4.0], // gamma = 1.6
        [0.1300 / 4.0, -0.7649 / 4.0, 1.3159 / 4.0, -0.3080 / 4.0], // gamma = 1.7
        [0.1469 / 4.0, -0.8911 / 4.0, 1.4644 / 4.0, -0.3234 / 4.0], // gamma = 1.8
        [0.1627 / 4.0, -1.0170 / 4.0, 1.6051 / 4.0, -0.3347 / 4.0], // gamma = 1.9
        [0.1773 / 4.0, -1.1420 / 4.0, 1.7385 / 4.0, -0.3426 / 4.0], // gamma = 2.0
        [0.1908 / 4.0, -1.2652 / 4.0, 1.8650 / 4.0, -0.3476 / 4.0], // gamma = 2.1
        [0.2031 / 4.0, -1.3864 / 4.0, 1.9851 / 4.0, -0.3501 / 4.0], // gamma = 2.2
    ];

    const NORM13: f32 = ((0x10000 as f64) / (255.0 * 255.0) * 4.0) as f32;
    const NORM24: f32 = ((0x100 as f64) / (255.0) * 4.0) as f32;

    let index = ((gamma * 10.0).round() as usize).clamp(10, 22) - 10;
    let ratios = GAMMA_INCORRECT_TARGET_RATIOS[index];

    [
        ratios[0] * NORM13,
        ratios[1] * NORM24,
        ratios[2] * NORM13,
        ratios[3] * NORM24,
    ]
}