1#define_import_path bevy_ui::ui_node
2
3#import bevy_render::view::View
4
5const TEXTURED = 1u;
6const RIGHT_VERTEX = 2u;
7const BOTTOM_VERTEX = 4u;
8// must align with BORDER_* shader_flags from bevy_ui/render/mod.rs
9const BORDER_LEFT: u32 = 256u;
10const BORDER_TOP: u32 = 512u;
11const BORDER_RIGHT: u32 = 1024u;
12const BORDER_BOTTOM: u32 = 2048u;
13const BORDER_ANY: u32 = BORDER_LEFT + BORDER_TOP + BORDER_RIGHT + BORDER_BOTTOM;
14
15fn enabled(flags: u32, mask: u32) -> bool {
16    return (flags & mask) != 0u;
17}
18
19@group(0) @binding(0) var<uniform> view: View;
20
21struct VertexOutput {
22    @location(0) uv: vec2<f32>,
23    @location(1) color: vec4<f32>,
24
25    @location(2) @interpolate(flat) size: vec2<f32>,
26    @location(3) @interpolate(flat) flags: u32,
27    @location(4) @interpolate(flat) radius: vec4<f32>,    
28    @location(5) @interpolate(flat) border: vec4<f32>,    
29
30    // Position relative to the center of the rectangle.
31    @location(6) point: vec2<f32>,
32    @builtin(position) position: vec4<f32>,
33};
34
35@vertex
36fn vertex(
37    @location(0) vertex_position: vec3<f32>,
38    @location(1) vertex_uv: vec2<f32>,
39    @location(2) vertex_color: vec4<f32>,
40    @location(3) flags: u32,
41
42    // x: top left, y: top right, z: bottom right, w: bottom left.
43    @location(4) radius: vec4<f32>,
44
45    // x: left, y: top, z: right, w: bottom.
46    @location(5) border: vec4<f32>,
47    @location(6) size: vec2<f32>,
48    @location(7) point: vec2<f32>,
49) -> VertexOutput {
50    var out: VertexOutput;
51    out.uv = vertex_uv;
52    out.position = view.clip_from_world * vec4(vertex_position, 1.0);
53    out.color = vertex_color;
54    out.flags = flags;
55    out.radius = radius;
56    out.size = size;
57    out.border = border;
58    out.point = point;
59
60    return out;
61}
62
63@group(1) @binding(0) var sprite_texture: texture_2d<f32>;
64@group(1) @binding(1) var sprite_sampler: sampler;
65
66// The returned value is the shortest distance from the given point to the boundary of the rounded 
67// box.
68// 
69// Negative values indicate that the point is inside the rounded box, positive values that the point 
70// is outside, and zero is exactly on the boundary.
71//
72// Arguments: 
73//  - `point`        -> The function will return the distance from this point to the closest point on 
74//                    the boundary.
75//  - `size`         -> The maximum width and height of the box.
76//  - `corner_radii` -> The radius of each rounded corner. Ordered counter clockwise starting 
77//                    top left:
78//                      x: top left, y: top right, z: bottom right, w: bottom left.
79fn sd_rounded_box(point: vec2<f32>, size: vec2<f32>, corner_radii: vec4<f32>) -> f32 {
80    // If 0.0 < y then select bottom left (w) and bottom right corner radius (z).
81    // Else select top left (x) and top right corner radius (y).
82    let rs = select(corner_radii.xy, corner_radii.wz, 0.0 < point.y);
83    // w and z are swapped above so that both pairs are in left to right order, otherwise this second 
84    // select statement would return the incorrect value for the bottom pair.
85    let radius = select(rs.x, rs.y, 0.0 < point.x);
86    // Vector from the corner closest to the point, to the point.
87    let corner_to_point = abs(point) - 0.5 * size;
88    // Vector from the center of the radius circle to the point.
89    let q = corner_to_point + radius;
90    // Length from center of the radius circle to the point, zeros a component if the point is not 
91    // within the quadrant of the radius circle that is part of the curved corner.
92    let l = length(max(q, vec2(0.0)));
93    let m = min(max(q.x, q.y), 0.0);
94    return l + m - radius;
95}
96
97fn sd_inset_rounded_box(point: vec2<f32>, size: vec2<f32>, radius: vec4<f32>, inset: vec4<f32>) -> f32 {
98    let inner_size = size - inset.xy - inset.zw;
99    let inner_center = inset.xy + 0.5 * inner_size - 0.5 * size;
100    let inner_point = point - inner_center;
101
102    var r = radius;
103
104    // Top left corner.
105    r.x = r.x - max(inset.x, inset.y);
106
107    // Top right corner.
108    r.y = r.y - max(inset.z, inset.y);
109
110    // Bottom right corner.
111    r.z = r.z - max(inset.z, inset.w); 
112
113    // Bottom left corner.
114    r.w = r.w - max(inset.x, inset.w);
115
116    let half_size = inner_size * 0.5;
117    let min_size = min(half_size.x, half_size.y);
118
119    r = min(max(r, vec4(0.0)), vec4<f32>(min_size));
120
121    return sd_rounded_box(inner_point, inner_size, r);
122}
123
124fn nearest_border_active(point_vs_mid: vec2<f32>, size: vec2<f32>, width: vec4<f32>, flags: u32) -> bool {
125    if (flags & BORDER_ANY) == BORDER_ANY {
126        return true;
127    }
128 
129    // get point vs top left
130    let point = clamp(point_vs_mid + size * 0.49999, vec2(0.0), size);
131 
132    let left = point.x / width.x;
133    let top = point.y / width.y;
134    let right = (size.x - point.x) / width.z;
135    let bottom = (size.y - point.y) / width.w;
136 
137    let min_dist = min(min(left, top), min(right, bottom));
138 
139    return (enabled(flags, BORDER_LEFT) && min_dist == left) ||
140        (enabled(flags, BORDER_TOP) && min_dist == top) || 
141        (enabled(flags, BORDER_RIGHT) && min_dist == right) || 
142        (enabled(flags, BORDER_BOTTOM) && min_dist == bottom);
143}
144
145// get alpha for antialiasing for sdf
146fn antialias(distance: f32) -> f32 {
147    // Using the fwidth(distance) was causing artifacts, so just use the distance.
148    return saturate(0.5 - distance);
149}
150
151fn draw_uinode_border(
152    color: vec4<f32>,
153    point: vec2<f32>,
154    size: vec2<f32>,
155    radius: vec4<f32>,
156    border: vec4<f32>,
157    flags: u32,
158) -> vec4<f32> {
159    // Signed distances. The magnitude is the distance of the point from the edge of the shape.
160    // * Negative values indicate that the point is inside the shape.
161    // * Zero values indicate the point is on the edge of the shape.
162    // * Positive values indicate the point is outside the shape.
163
164    // Signed distance from the exterior boundary.
165    let external_distance = sd_rounded_box(point, size, radius);
166
167    // Signed distance from the border's internal edge (the signed distance is negative if the point 
168    // is inside the rect but not on the border).
169    // If the border size is set to zero, this is the same as the external distance.
170    let internal_distance = sd_inset_rounded_box(point, size, radius, border);
171
172    // Signed distance from the border (the intersection of the rect with its border).
173    // Points inside the border have negative signed distance. Any point outside the border, whether 
174    // outside the outside edge, or inside the inner edge have positive signed distance.
175    let border_distance = max(external_distance, -internal_distance);
176
177    // check if this node should apply color for the nearest border
178    let nearest_border = select(0.0, 1.0, nearest_border_active(point, size, border, flags));
179
180#ifdef ANTI_ALIAS
181    // At external edges with no border, `border_distance` is equal to zero. 
182    // This select statement ensures we only perform anti-aliasing where a non-zero width border 
183    // is present, otherwise an outline about the external boundary would be drawn even without 
184    // a border.
185    let t = select(1.0 - step(0.0, border_distance), antialias(border_distance), external_distance < internal_distance);
186#else
187    let t = 1.0 - step(0.0, border_distance);
188#endif
189
190    // Blend mode ALPHA_BLENDING is used for UI elements, so we don't premultiply alpha here.
191    return vec4(color.rgb, saturate(color.a * t * nearest_border));
192}
193
194fn draw_uinode_background(
195    color: vec4<f32>,
196    point: vec2<f32>,
197    size: vec2<f32>,
198    radius: vec4<f32>,
199    border: vec4<f32>,
200) -> vec4<f32> {
201    // When drawing the background only draw the internal area and not the border.
202    let internal_distance = sd_inset_rounded_box(point, size, radius, border);
203
204#ifdef ANTI_ALIAS
205    let t = antialias(internal_distance);
206#else
207    let t = 1.0 - step(0.0, internal_distance);
208#endif
209
210    return vec4(color.rgb, saturate(color.a * t));
211}
212
213@fragment
214fn fragment(in: VertexOutput) -> @location(0) vec4<f32> {
215    let texture_color = textureSample(sprite_texture, sprite_sampler, in.uv);
216
217    // Only use the color sampled from the texture if the `TEXTURED` flag is enabled. 
218    // This allows us to draw both textured and untextured shapes together in the same batch.
219    let color = select(in.color, in.color * texture_color, enabled(in.flags, TEXTURED));
220
221    if enabled(in.flags, BORDER_ANY) {
222        return draw_uinode_border(color, in.point, in.size, in.radius, in.border, in.flags);
223    } else {
224        return draw_uinode_background(color, in.point, in.size, in.radius, in.border);
225    }
226}