1import bevy_render::view::View;
2import bevy_render::globals::Globals;
3
4@group(0) @binding(0)
5var<uniform> view: View;
6@group(0) @binding(1)
7var<uniform> globals: Globals;
8
9@group(1) @binding(0) var sprite_texture: texture_2d<f32>;
10@group(1) @binding(1) var sprite_sampler: sampler;
11
12struct UiVertexOutput {
13    @location(0) uv: vec2<f32>,
14    @location(1) color: vec4<f32>,
15
16    /// Defines the dividing line that are used to split the texture atlas rect into corner, side and center slices
17    /// The distances are normalized and from the top left corner of the texture atlas rect
18    /// x = distance of the left vertical dividing line
19    /// y = distance of the top horizontal dividing line
20    /// z = distance of the right vertical dividing line
21    /// w = distance of the bottom horizontal dividing line
22    @location(2) @interpolate(flat) texture_slices: vec4<f32>,
23
24    /// Defines the dividing line that are used to split the render target into corner, side and center slices
25    /// The distances are normalized and from the top left corner of the render target
26    /// x = distance of left vertical dividing line
27    /// y = distance of top horizontal dividing line
28    /// z = distance of right vertical dividing line
29    /// w = distance of bottom horizontal dividing line
30    @location(3) @interpolate(flat) target_slices: vec4<f32>,
31
32    /// The number of times the side or center texture slices should be repeated when mapping them to the border slices
33    /// x = number of times to repeat along the horizontal axis for the side textures
34    /// y = number of times to repeat along the vertical axis for the side textures
35    /// z = number of times to repeat along the horizontal axis for the center texture
36    /// w = number of times to repeat along the vertical axis for the center texture
37    @location(4) @interpolate(flat) repeat: vec4<f32>,
38
39    /// normalized texture atlas rect coordinates
40    /// x, y = top, left corner of the atlas rect
41    /// z, w = bottom, right corner of the atlas rect
42    @location(5) @interpolate(flat) atlas_rect: vec4<f32>,
43    @builtin(position) position: vec4<f32>,
44}
45
46@vertex
47fn vertex(
48    @location(0) vertex_position: vec3<f32>,
49    @location(1) vertex_uv: vec2<f32>,
50    @location(2) vertex_color: vec4<f32>,
51    @location(3) texture_slices: vec4<f32>,
52    @location(4) target_slices: vec4<f32>,
53    @location(5) repeat: vec4<f32>,
54    @location(6) atlas_rect: vec4<f32>,
55) -> UiVertexOutput {
56    var out: UiVertexOutput;
57    out.uv = vertex_uv;
58    out.color = vertex_color;
59    out.position = view.clip_from_world * vec4<f32>(vertex_position, 1.0);
60    out.texture_slices = texture_slices;
61    out.target_slices = target_slices;
62    out.repeat = repeat;
63    out.atlas_rect = atlas_rect;
64    return out;
65}
66
67/// maps a point along the axis of the render target to slice coordinates
68/// Arguments:
69///   - p: normalized distance along the axis
70///   - il: target min dividing point
71///   - ih: target max dividing point
72///   - tl: slice min dividing point
73///   - th: slice max dividing point
74///   - r: number of times to repeat the slice for sides and the center
75fn map_axis_with_repeat(
76    p: f32,
77    il: f32,
78    ih: f32,
79    tl: f32,
80    th: f32,
81    r: f32,
82) -> f32 {
83    if p < il {
84        // inside one of the two left (horizontal axis) or top (vertical axis) corners
85        return (p / il) * tl;
86    } else if ih < p {
87        // inside one of the two (horizontal axis) or top (vertical axis) corners
88        return th + ((p - ih) / (1 - ih)) * (1 - th);
89    } else {
90        // not inside a corner, repeat the texture
91        return tl + fract((r * (p - il)) / (ih - il)) * (th - tl);
92    }
93}
94
95fn map_uvs_to_slice(
96    uv: vec2<f32>,
97    target_slices: vec4<f32>,
98    texture_slices: vec4<f32>,
99    repeat: vec4<f32>,
100) -> vec2<f32> {
101    var r: vec2<f32>;
102    if target_slices.x <= uv.x && uv.x <= target_slices.z && target_slices.y <= uv.y && uv.y <= target_slices.w {
103        // use the center repeat values if the uv coords are inside the center slice of the target
104        r = repeat.zw;
105    } else {
106        // use the side repeat values if the uv coords are outside the center slice
107        r = repeat.xy;
108    }
109
110    // map horizontal axis
111    let x = map_axis_with_repeat(uv.x, target_slices.x, target_slices.z, texture_slices.x, texture_slices.z, r.x);
112
113    // map vertical axis
114    let y = map_axis_with_repeat(uv.y, target_slices.y, target_slices.w, texture_slices.y, texture_slices.w, r.y);
115
116    return vec2(x, y);
117}
118
119@fragment
120fn fragment(in: UiVertexOutput) -> @location(0) vec4<f32> {
121    // map the target uvs to slice coords
122    let uv = map_uvs_to_slice(in.uv, in.target_slices, in.texture_slices, in.repeat);
123
124    // map the slice coords to texture coords
125    let atlas_uv = in.atlas_rect.xy + uv * (in.atlas_rect.zw - in.atlas_rect.xy);
126
127    return in.color * textureSample(sprite_texture, sprite_sampler, atlas_uv);
128}