From 8400c90b5cf8e3df8d86ce81c27b3fa6b299c3e2 Mon Sep 17 00:00:00 2001
From: ffreyer <frederic481994@hotmail.de>
Date: Thu, 28 Dec 2023 16:58:29 +0100
Subject: [PATCH] add stroke and glow

---
 WGLMakie/assets/sprites.frag | 45 +++++++++++++++++++++++++++++++++---
 WGLMakie/assets/sprites.vert | 15 ++++++++++--
 2 files changed, 55 insertions(+), 5 deletions(-)

diff --git a/WGLMakie/assets/sprites.frag b/WGLMakie/assets/sprites.frag
index dd084d8e639..97e04d8fff8 100644
--- a/WGLMakie/assets/sprites.frag
+++ b/WGLMakie/assets/sprites.frag
@@ -64,6 +64,23 @@ void fill(sampler2D image, vec4 fillcolor, vec2 uv, float infill, inout vec4 col
     color = mix(color, im_color, infill);
 }
 
+void stroke(vec4 strokecolor, float signed_distance, float width, inout vec4 color){
+    if (width != 0.0){
+        float t = aastep(min(width, 0.0), max(width, 0.0), signed_distance);
+        vec4 bg_color = mix(color, vec4(strokecolor.rgb, 0), float(signed_distance < 0.5 * width));
+        color = mix(bg_color, strokecolor, t);
+    }
+}
+
+void glow(vec4 glowcolor, float signed_distance, float inside, inout vec4 color){
+    float glow_width = get_glowwidth();
+    float stroke_width = get_strokewidth();
+    if (glow_width > 0.0){
+        float outside = (abs(signed_distance) - stroke_width) / glow_width;
+        float alpha = 1.0 - outside;
+        color = mix(vec4(glowcolor.rgb, glowcolor.a*alpha), color, inside);
+    }
+}
 
 float scaled_distancefield(sampler2D distancefield, vec2 uv){
     // Glyph distance field units are in pixels. Convert to same distance
@@ -94,9 +111,16 @@ void main() {
     int shape = get_shape_type();
     if(shape == CIRCLE)
         signed_distance = circle(frag_uv);
-    else if(shape == DISTANCEFIELD)
+    else if(shape == DISTANCEFIELD) {
         signed_distance = scaled_distancefield(distancefield, tex_uv);
-    else if(shape == ROUNDED_RECTANGLE)
+        if (get_strokewidth() > 0.0 || get_glowwidth() > 0.0) {
+            // Compensate for the clamping of tex_uv by an approximate
+            // extension of the signed distance outside the valid texture
+            // region.
+            vec2 bufuv = frag_uv - clamp(frag_uv, 0.0, 1.0);
+            signed_distance -= length(bufuv);
+        }
+    } else if(shape == ROUNDED_RECTANGLE)
         signed_distance = rounded_rectangle(frag_uv, vec2(0.2), vec2(0.8));
     else if(shape == RECTANGLE)
         signed_distance = 1.0; // rectangle(f_uv);
@@ -104,9 +128,24 @@ void main() {
         signed_distance = triangle(frag_uv);
 
     signed_distance *= frag_uvscale;
-    float inside = aastep(0.0, signed_distance);
+
+
+    float stroke_width = get_strokewidth();
+    float inside_start = max(-stroke_width, 0.0);
+    float inside = aastep(inside_start, signed_distance);
+
     vec4 final_color = vec4(frag_color.xyz, 0);
     fill(image, frag_color, frag_uv, inside, final_color);
+    stroke(get_strokecolor(), signed_distance, -stroke_width, final_color);
+    glow(get_glowcolor(), signed_distance, aastep(-stroke_width, signed_distance), final_color);
+
+    // debug - show background
+    // final_color.a = clamp(final_color.a, 0.0, 1.0);
+    // final_color = vec4(
+    //     vec3(1,0,0) * (1.0 - final_color.a) + final_color.rgb * final_color.a,
+    //     0.4 + 0.6 * final_color.a
+    // );
+
     if (picking) {
         if (final_color.a > 0.1) {
             fragment_color = pack_int(object_id, frag_instance_id);
diff --git a/WGLMakie/assets/sprites.vert b/WGLMakie/assets/sprites.vert
index 2e01298e227..e06dee067e1 100644
--- a/WGLMakie/assets/sprites.vert
+++ b/WGLMakie/assets/sprites.vert
@@ -119,11 +119,22 @@ void main(){
     float sprite_from_u_scale = min(abs(get_markersize().x), abs(get_markersize().y));
     frag_uvscale = viewport_from_sprite_scale * sprite_from_u_scale;
     frag_distancefield_scale = distancefield_scale();
+
+    // add padding for AA, stroke and glow (non native distancefields don't need
+    // AA padding but CIRCLE etc do)
+    vec2 padded_bbox_size = bbox_radius + (
+        ANTIALIAS_RADIUS + max(0.0, get_strokewidth()) + max(0.0, get_glowwidth())
+    ) / viewport_from_sprite_scale;
+    vec2 uv_pad_scale = padded_bbox_size / bbox_radius;
+
     frag_color = tovec4(get_color());
-    frag_uv = get_uv();
     frag_uv_offset_width = get_uv_offset_width();
+    // get_uv() returns (0, 0), (1, 0), (0, 1) or (1, 1)
+    // to accomodate stroke and glowwidth we need to extrude uv's outwards from (0.5, 0.5)
+    frag_uv = vec2(0.5) + (get_uv() - vec2(0.5)) * uv_pad_scale;
+
     // screen space coordinates of the position
-    vec4 quad_vertex = (trans * vec4(2.0 * bbox_radius * get_position(), 0.0, 0.0));
+    vec4 quad_vertex = (trans * vec4(2.0 * padded_bbox_size * get_position(), 0.0, 0.0));
     gl_Position = vclip + quad_vertex;
     gl_Position.z += gl_Position.w * get_depth_shift();