From d688ed76f5bcef5ee94a58a0f5510a2ec8216df5 Mon Sep 17 00:00:00 2001
From: Avi Weinstock <aweinstock314@gmail.com>
Date: Mon, 20 Feb 2023 21:21:38 -0500
Subject: [PATCH] Add support for outlined text.

---
 examples/hello.rs     |  2 ++
 src/pipeline.rs       |  3 +++
 src/shader/glyph.wgsl | 23 ++++++++++++++++++++++-
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/examples/hello.rs b/examples/hello.rs
index e656692..03e8efa 100644
--- a/examples/hello.rs
+++ b/examples/hello.rs
@@ -134,6 +134,7 @@ fn main() -> Result<(), Box<dyn Error>> {
                     bounds: (size.width as f32, size.height as f32),
                     text: vec![Text::new("Hello wgpu_glyph!")
                         .with_color([0.0, 0.0, 0.0, 1.0])
+                        .with_outline_color([1.0, 1.0, 1.0, 1.0])
                         .with_scale(40.0)],
                     ..Section::default()
                 });
@@ -143,6 +144,7 @@ fn main() -> Result<(), Box<dyn Error>> {
                     bounds: (size.width as f32, size.height as f32),
                     text: vec![Text::new("Hello wgpu_glyph!")
                         .with_color([1.0, 1.0, 1.0, 1.0])
+                        .with_outline_color([0.0, 0.0, 0.0, 1.0])
                         .with_scale(40.0)],
                     ..Section::default()
                 });
diff --git a/src/pipeline.rs b/src/pipeline.rs
index e2d3daf..b15b7ef 100644
--- a/src/pipeline.rs
+++ b/src/pipeline.rs
@@ -306,6 +306,7 @@ fn build<D>(
                     2 => Float32x2,
                     3 => Float32x2,
                     4 => Float32x4,
+                    5 => Float32x4,
                 ],
             }],
         },
@@ -448,6 +449,7 @@ pub struct Instance {
     tex_left_top: [f32; 2],
     tex_right_bottom: [f32; 2],
     color: [f32; 4],
+    outline_color: [f32; 4],
 }
 
 impl Instance {
@@ -503,6 +505,7 @@ impl Instance {
             tex_left_top: [tex_coords.min.x, tex_coords.max.y],
             tex_right_bottom: [tex_coords.max.x, tex_coords.min.y],
             color: extra.color,
+            outline_color: extra.outline_color,
         }
     }
 }
diff --git a/src/shader/glyph.wgsl b/src/shader/glyph.wgsl
index c8a5910..253ec1c 100644
--- a/src/shader/glyph.wgsl
+++ b/src/shader/glyph.wgsl
@@ -13,12 +13,14 @@ struct VertexInput {
     @location(2) tex_left_top: vec2<f32>,
     @location(3) tex_right_bottom: vec2<f32>,
     @location(4) color: vec4<f32>,
+    @location(5) outline_color: vec4<f32>,
 }
 
 struct VertexOutput {
     @builtin(position) position: vec4<f32>,
     @location(0) f_tex_pos: vec2<f32>,
     @location(1) f_color: vec4<f32>,
+    @location(2) f_outline_color: vec4<f32>,
 }
 
 @vertex
@@ -52,6 +54,7 @@ fn vs_main(input: VertexInput) -> VertexOutput {
     }
 
     out.f_color = input.color;
+    out.f_outline_color = input.outline_color;
     out.position = globals.transform * vec4<f32>(pos, input.left_top.z, 1.0);
 
     return out;
@@ -61,9 +64,27 @@ fn vs_main(input: VertexInput) -> VertexOutput {
 fn fs_main(input: VertexOutput) -> @location(0) vec4<f32> {
     var alpha: f32 = textureSample(font_tex, font_sampler, input.f_tex_pos).r;
 
+    var pixel_size: vec2<f32> = (1.0 / vec2<f32>(textureDimensions(font_tex)));
+
+    var border = false;
+    for(var i = -1; i <= 1 && !border; i += 1) {
+        for(var j = -1; j <= 1 && !border; j += 1) {
+            if i == 0 && j == 0 {
+                continue;
+            }
+            if textureSample(font_tex, font_sampler, input.f_tex_pos + pixel_size*vec2<f32>(f32(i), f32(j))).r <= 0.0 {
+                border = true;
+            }
+        }
+    }
+
     if (alpha <= 0.0) {
         discard;
     }
 
-    return input.f_color * vec4<f32>(1.0, 1.0, 1.0, alpha);
+    if border {
+        return input.f_outline_color * vec4<f32>(1.0, 1.0, 1.0, alpha);
+    } else {
+        return input.f_color * vec4<f32>(1.0, 1.0, 1.0, alpha);
+    }
 }