cranpose_render_common/
layer_shadow.rs

1use cranpose_ui_graphics::{GraphicsLayer, Rect};
2
3use crate::layer_transform::layer_uniform_scale;
4
5const MIN_LAYER_SHADOW_SCALE: f32 = 0.1;
6const MIN_LAYER_SHADOW_SPREAD: f32 = 0.8;
7const MIN_AMBIENT_BLUR_RADIUS: f32 = 0.5;
8const MIN_SPOT_BLUR_RADIUS: f32 = 0.5;
9const AMBIENT_SPREAD_FACTOR: f32 = 0.24;
10const SPOT_OFFSET_X_FACTOR: f32 = 0.18;
11const SPOT_OFFSET_Y_FACTOR: f32 = 0.62;
12const AMBIENT_BLUR_FACTOR: f32 = 0.95;
13const SPOT_BLUR_FACTOR: f32 = 0.72;
14const SPOT_SPREAD_FACTOR: f32 = 0.72;
15const AMBIENT_ALPHA_FACTOR: f32 = 0.44;
16const SPOT_ALPHA_FACTOR: f32 = 0.62;
17
18#[derive(Clone, Copy, Debug, PartialEq)]
19pub struct LayerShadowPass {
20    pub rect: Rect,
21    pub blur_radius: f32,
22    pub alpha: f32,
23}
24
25#[derive(Clone, Copy, Debug, Default, PartialEq)]
26pub struct LayerShadowGeometry {
27    pub ambient: Option<LayerShadowPass>,
28    pub spot: Option<LayerShadowPass>,
29}
30
31pub fn layer_shadow_geometry(
32    layer: &GraphicsLayer,
33    transformed_bounds: Rect,
34) -> LayerShadowGeometry {
35    if layer.shadow_elevation <= 0.0 {
36        return LayerShadowGeometry::default();
37    }
38
39    let scale = layer_uniform_scale(layer).max(MIN_LAYER_SHADOW_SCALE);
40    let elevation = layer.shadow_elevation * scale;
41    let spread = (elevation * AMBIENT_SPREAD_FACTOR).max(MIN_LAYER_SHADOW_SPREAD);
42    let ambient_alpha = (layer.ambient_shadow_color.a() * AMBIENT_ALPHA_FACTOR).clamp(0.0, 1.0);
43    let spot_alpha = (layer.spot_shadow_color.a() * SPOT_ALPHA_FACTOR).clamp(0.0, 1.0);
44
45    let ambient = (ambient_alpha > f32::EPSILON).then_some(LayerShadowPass {
46        rect: Rect {
47            x: transformed_bounds.x - spread,
48            y: transformed_bounds.y - spread,
49            width: transformed_bounds.width + spread * 2.0,
50            height: transformed_bounds.height + spread * 2.0,
51        },
52        blur_radius: (elevation * AMBIENT_BLUR_FACTOR).max(MIN_AMBIENT_BLUR_RADIUS),
53        alpha: ambient_alpha,
54    });
55
56    let spot_spread = spread * SPOT_SPREAD_FACTOR;
57    let spot = (spot_alpha > f32::EPSILON).then_some(LayerShadowPass {
58        rect: Rect {
59            x: transformed_bounds.x + elevation * SPOT_OFFSET_X_FACTOR - spot_spread,
60            y: transformed_bounds.y + elevation * SPOT_OFFSET_Y_FACTOR - spot_spread,
61            width: transformed_bounds.width + spot_spread * 2.0,
62            height: transformed_bounds.height + spot_spread * 2.0,
63        },
64        blur_radius: (elevation * SPOT_BLUR_FACTOR).max(MIN_SPOT_BLUR_RADIUS),
65        alpha: spot_alpha,
66    });
67
68    LayerShadowGeometry { ambient, spot }
69}
70
71#[cfg(test)]
72mod tests {
73    use cranpose_ui_graphics::Color;
74
75    use super::*;
76
77    #[test]
78    fn layer_shadow_geometry_returns_none_for_zero_elevation() {
79        let geometry = layer_shadow_geometry(
80            &GraphicsLayer::default(),
81            Rect::from_size(Default::default()),
82        );
83        assert!(geometry.ambient.is_none());
84        assert!(geometry.spot.is_none());
85    }
86
87    #[test]
88    fn layer_shadow_geometry_matches_shadow_model() {
89        let layer = GraphicsLayer {
90            shadow_elevation: 10.0,
91            ambient_shadow_color: Color(0.2, 0.3, 0.4, 0.8),
92            spot_shadow_color: Color(0.7, 0.6, 0.5, 0.9),
93            ..GraphicsLayer::default()
94        };
95        let transformed_bounds = Rect {
96            x: 20.0,
97            y: 30.0,
98            width: 40.0,
99            height: 12.0,
100        };
101        let geometry = layer_shadow_geometry(&layer, transformed_bounds);
102
103        let ambient = geometry.ambient.expect("ambient shadow pass");
104        assert_eq!(
105            ambient.rect,
106            Rect {
107                x: 17.6,
108                y: 27.6,
109                width: 44.8,
110                height: 16.8,
111            }
112        );
113        assert!((ambient.blur_radius - 9.5).abs() < 1e-6);
114        assert!((ambient.alpha - 0.352).abs() < 1e-6);
115
116        let spot = geometry.spot.expect("spot shadow pass");
117        assert_eq!(
118            spot.rect,
119            Rect {
120                x: 20.071999,
121                y: 34.472,
122                width: 43.456,
123                height: 15.455999,
124            }
125        );
126        assert!((spot.blur_radius - 7.2).abs() < 1e-6);
127        assert!((spot.alpha - 0.558).abs() < 1e-6);
128    }
129}
cranpose_render_common/layer_shadow.rs

cranpose_render_common/
layer_shadow.rs
